What is the cause of sudden death? How to prevent and first aid?

What is the cause of sudden death?  How to prevent and first aid?

In the European Cup group game on June 13, Danish player Eriksson suddenly fell to the ground due to a cardiac arrest. 37 seconds later, the medical staff rushed into the venue with the AED to perform first aid, and successfully pulled Eriksson back from the god of death. The entire rescue process was also broadcast live and popularized the “golden 4 minutes” of sudden death first aid for global audiences.

On November 27, 2019, an actor suddenly suffered a cardiac arrest and fell to the ground while running on a recording program. He failed to defibrillate and CPR in time on the spot. After more than 2 hours of rescue at the hospital, he was ineffective, and eventually died of sudden cardiac death. Both of these news events received widespread attention at the time, and words such as “sudden cardiac death”, “AED”, and “CPR” were brought into the public view for a while. The results of the two cases of sudden death to rescue the public are completely different, and the thinking on the prevention and treatment of sudden death is not only the “golden 4 minutes” point.

According to the “China Cardiovascular Disease Report” estimates, nearly 600,000 people die every year in my country, and one person suddenly falls to the ground due to cardiac arrest every minute, but the rescue success rate is only 1%. To save the huge population at high risk of sudden death, we still have a lot to do.

1. Sudden death and survival rate

1. What is sudden death

Sudden death accounts for 5%-15% of the total mortality in industrialized countries, but the exact incidence of sudden death in China or the United States and Europe is relatively vague. Sudden cardiac death in the United States accounts for 5.6% of the annual deaths. In 1999, the estimated number of sudden cardiac death in the United States was 450,000, and the incidence of cardiac arrest was estimated to be more than 180,000-450,000. In North America and Europe, the estimated incidence in the general population is 50-100 per 100,000 people.

Among them, two-thirds of cardiac arrest patients tried resuscitation, and the survival conditions were quite different-the survival rate in out-of-hospital cases was 1%-6%; among the out-of-hospital cardiac arrest patients’ discharge survival rate, after emergency treatment The survival rate of patients is 5%-10%; and when the underlying arrhythmia of the patient is ventricular fibrillation, the survival rate is 15%.

According to the “China Cardiovascular Disease Report” issued by the National Cardiovascular Disease Center, it is estimated that 544,000 people die from sudden cardiac death each year in China.

The Fuwai Cardiovascular Hospital of the Chinese Academy of Medical Sciences followed up more than 670,000 people in four cities in the eastern, central and western regions from 2005 to 2006. A total of 284 cases of sudden cardiac death occurred in one year. It is inferred that the incidence of sudden cardiac death in China is 41.8 100,000 people, of which the incidence of sudden cardiac death is 44.6 per 100,000 men and 39 per 100,000 women.

Current media reports of “sudden death” or “sudden cardiac death” is a general description that includes the cardiac arrest (sudden cardiac arrest, SCA) and sudden cardiac death (sudden Cardiac Death, SCD) , both Refers to the sudden stop of the mechanical activity of the heart, accompanied by hemodynamic failure, resulting in the patient’s unresponsiveness, no normal breathing, and no circulatory signs. If it is not corrected quickly, it will develop into sudden death. Is usually caused by sustained ventricular tachycardia (the VT) / ventricular fibrillation (VF) to cause (Fig. 1) . Most patients with cardiac arrest will lose consciousness within seconds to minutes due to insufficient cerebral blood flow.

What is the cause of sudden death? How to prevent and first aid?

Figure 1. Normal ECG on the left, ECG with ventricular fibrillation on the right

As shown in the figure above, the regular electrocardiographic rhythm of the left heart causes the myocardium to contract regularly and pump blood normally. When ventricular fibrillation occurs, the electrical activity of the myocardium on the right side is disturbed, the myocardium of the ventricle twitches, and the heart chamber cannot effectively contract (the mechanical of the heart). Sudden stagnation of activity) , pumping blood, causing instantaneous blood flow stagnation throughout the body, insufficient cerebral blood flow, loss of consciousness, and instant fall to the ground.

Usually emergency intervention methods include cardiopulmonary resuscitation (CPR) and/or defibrillation, cardioversion ; cardiac pacing , if intervention or spontaneous reversal to restore circulation, called cardiac arrest (or attempted cardiac death) ; if the patient dies It is called sudden cardiac death. It is difficult to distinguish between out-of-hospital cardiac arrest and sudden cardiac death, because only 2/3 of sudden deaths have witnesses, and it is unknown whether the heart rhythm of many patients is ventricular fibrillation at the time of onset.

There are often “early warning” symptoms before the cardiac arrest event , and the time of occurrence ranges from 1 hour to 1 month before the cardiac arrest: 51% of patients have early warning symptoms within 4 weeks before the cardiac arrest, 80% and 34% Of patients had symptoms at least 1 hour and 24 hours before the onset of cardiac arrest, respectively.

Among them, chest pain (46%) and dyspnea (18%) are the most common symptoms, and dyspnea is more common than chest pain in women (31% vs 24%) . However, because most of the symptoms are non-specific and may not appear before the onset, and the causal or temporal relationship between symptoms and sudden death has not been determined, it is of little significance in prevention. 49% of sudden cardiac deaths occur during daily activities, 23% occur during sleep, and 23% are related to exercise.

2. External and internal factors of survival rate

Despite the advancement of first aid measures in recent years, the outcome of cardiac arrest patients is still poor. Only 1/3 of patients with out-of-hospital cardiac arrest succeeded in resuscitation, and only about 10% of all patients were discharged from the hospital. Many of them had neurological impairment. . There are many factors that affect the outcome: delayed bystander cardiopulmonary resuscitation (CPR), delayed cardiac defibrillation, old age, reduced proportion of patients with ventricular fibrillation (VF) , etc., among them, from onset to effective resuscitation (that is, effective pulse establishment) The time interval may be the most critical.

(1) External cause: the time interval from onset to effective resuscitation

①Availability of first aid system

Even in foreign countries with more mature emergency systems, emergency resuscitation training has become more mature in recent years, the proportion of patients receiving eyewitness cardiopulmonary resuscitation (CPR) has increased, and the interval between onset and defibrillation has been shortened. However, with population growth and urbanization, basic The time required for basic life support (BLS) and advanced life support (ALS) services to arrive on site is still increasing. Foreign studies have shown that there are obvious regional differences in the incidence and outcome of cardiac arrest, and emphasize the importance of emergency systems in various regions for the outcome of cardiac arrest.

② Duration of ventricular fibrillation

The survival of patients with cardiac arrest depends on whether effective CPR is implemented quickly. Electrical defibrillation is the only treatment method to re-establish regular electrical activity and myocardial contraction.

Increased duration of ventricular fibrillation will cause two main adverse reactions: ① reduce the possibility of terminating the arrhythmia; ② if VF lasts for more than 4 minutes, the central nervous system and other organs begin to suffer irreversible damage-the origin of the “golden 4 minutes”. The longer the duration of cardiac arrest, the lower the likelihood of resuscitation or survival.

Studies have shown that in the absence of CPR, the survival rate of cardiac arrest caused by VF is reduced by about 10% for every 1 minute delay in defibrillation; after 12 minutes without CPR, the survival rate is only 2%-5% .

(2) Internal cause: cause of disease

There is a correlation between the mechanism of cardiac arrest and the outcome of initial resuscitation, and the survival rate of patients with cardiac arrest caused by ventricular tachyarrhythmia is often higher.

①Ventricular tachyarrhythmia: good outcome

The most common cause of sudden death is ventricular fibrillation . When the initial heart rhythm is continuous ventricular tachyarrhythmia (such as ventricular fibrillation, ventricular tachycardia, etc.) , the patient’s outcome will be relatively good.

Ventricular fibrillation (VF) : 25%-40% of patients with cardiac arrest caused by VF can survive. 38% of cardiac arrest patients treated abroad are VF witnessed by bystanders. VF patients with bystander witnesses are significantly more likely to survive discharge from the hospital (34% vs 6%) compared with other cardiac arrest patients . Acute myocardial infarction or myocardial ischemia is the main potential cause of VF. About 47%-51% of surviving patients have acute myocardial infarction.

Ventricular tachycardia (VT) : The survival rate of patients with hemodynamic instability VT is about 65%-70%. The prognosis of patients with monomorphic VT may be better because such arrhythmias are more regular and there may be a certain degree of systemic perfusion. Moreover, the incidence of myocardial infarction in patients with VT is lower than that in patients with ventricular fibrillation, and the heart function is better (the ejection fraction is often higher) .

②Asystole: poor outcome

When the initially observed heart rhythm is asystole (even if it was VT or VF before the heart is stopped ) or the patient whose ventricular spontaneous rhythm is very slow and causes bradycardia, the probability of successful resuscitation is low. Only 10% of patients with out-of-hospital arrest and initial cardiac arrest survive to hospital admission, and less than 5% of patients survive to discharge with good neurological function. The poor outcome of such patients may be due to the long duration of cardiac arrest (usually more than 4 minutes) and severe and irreversible myocardial damage.

③ Pulseless electrical activity: poor outcome

Pulseless electrical activity (pulseless electrical activity, PEA) also referred to cardiac electromechanical dissociation, resulting in cardiac arrest patient outcome is poor. Patients who were resuscitated and survived on admission accounted for 23%, and only 11% of patients survived on discharge.

④Non-cardiogenic cardiac arrest: poor outcome

One-third of cardiac arrests are non-cardiogenic. Trauma, non-traumatic hemorrhage, poisoning, near drowning and pulmonary embolism are the most common. 40% were successfully resuscitated and hospitalized, only 11% were discharged, and 6% were neurologically intact.

2. “Catch up” to solve external causes-the race of seconds between public health and sudden death

Based on the above analysis, the key to improving the rescue success rate of patients with sudden cardiac death is to implement effective rescue as soon as possible. There is a high probability that CPR and defibrillation can save the patient within the “golden 4 minutes” of the best rescue time. Very few people can be rescued back after 10 minutes.

Since 87.7% of sudden deaths in our country occur outside the hospital, first cardiopulmonary resuscitation by witnesses is the most timely method, which can buy time for medical staff to go to the scene for rescue. Eyewitness first aid is very important-compared with the professional treatment of emergency centers, the use of automated external defibrillator (AED) early defibrillation by non-professional first rescuers can increase the survival rate of patients to 2 Times. If defibrillation is given within 3 minutes of fainting, 74% of ventricular fibrillation patients with witnesses can survive. For every minute delay in the interval from sudden arrest to defibrillation, the survival rate will decrease by about 5%-10%. Eyewitness cardiopulmonary resuscitation can reach 60% in Europe, but the popularity rate of cardiopulmonary resuscitation in the public in my country is very low. It is very rare for witnesses to perform cardiopulmonary resuscitation, and the quality of resuscitation is even more difficult to guarantee.

1. The key to survival-time window and quality of resuscitation

Basic resuscitation, including CPR and AED defibrillation. The key to survival after cardiac arrest is early recognition and treatment. The patient’s survival rate mainly depends on whether to initiate high-quality CPR and early defibrillation immediately.

The key points emphasized by the current resuscitation guidelines are: ①Identify cardiac arrest immediately by observing unresponsiveness or no breathing/wheezing breathing; ②Immediately implement high-quality CPR (appropriate force + rapid compression) , and continue to pay attention to the chest External compression quality and ventilation frequency; ③Minimize the interruption of CPR; ④For medical professional rescuers, the time to check for pulse should not exceed 10 seconds; ⑤For untrained single rescuers, encourage them to implement High-quality simple chest compression CPR (CO-CPR) ; ⑥ If there is AED, apply it as soon as possible; ⑦ Call the emergency center as soon as possible.

(1) Time window

The time window for resuscitation is mainly divided into three stages: immediate defibrillation is required for the first 4-5 minutes, chest compression + defibrillation for 4-10 minutes, and few patients survive after 10 minutes. This is mainly related to the progression mechanism of cardiac arrest:

① Electrical phase : within 4-5 minutes of cardiac arrest caused by ventricular fibrillation. At this time, immediate defibrillation is required to increase the survival rate of these patients as much as possible. High-quality chest compressions during the preparation of the defibrillator will also improve survival.

② Hemodynamic phase (circulation phase) : 4-10 minutes after cardiac arrest, during this period the patient may still have ventricular fibrillation, and early defibrillation is still critical to the survival of patients found to have ventricular fibrillation. Once a cardiac arrest is determined, high-quality chest compressions should be started immediately and continued until defibrillation is implemented. In practice, the defibrillator should be charged during the effective compression period. Compression should be suspended only when the rhythm is confirmed and the shock is given, and CPR should be restarted immediately after the shock. Patients in the hemodynamic phase will benefit from high-quality chest compressions that produce adequate cerebral and coronary perfusion and immediate defibrillation.

③ Metabolic stage : 10 minutes after the pulse disappears, few patients survive this stage. Its treatment is mainly based on post-resuscitation measures, such as hypothermia. If patients at this stage cannot quickly return to a perfused heart rhythm, they usually cannot survive.

(2) Quality of recovery

① Identification

Rapid identification of cardiac arrest is the first essential step for successful resuscitation. When a rescuer witnesses a sudden fall or encounters a person who seems unresponsive, he should ensure that the area is safe before approaching the patient, and then pat his shoulder and shout loudly to confirm whether there is no response. If no response is confirmed, the rescuer should immediately start chest compressions and call the emergency center. It should be noted that even professionals are difficult to determine whether there is a pulse or whether breathing is adequate. Witnesses should not try to assess the pulse but should assume that the patient has stopped breathing. Even if the carotid pulse is checked, it should not exceed 10 seconds. The key principle is not to delay CPR.


The most important part of CPR is chest compressions  , because coronary perfusion and return of spontaneous circulation (ROSC) are both related to compressions. Key indicators: ①Frequency: The speed of chest compressions is maintained at 100-120 times per minute. Insufficient chest compressions will reduce the possibility of ROSC and survival after cardiac arrest and the nervous system is intact; ②Depth: the depth of each chest compression is at least 5cm, but not more than 6cm; ③Rebound: each compression After the chest, let the rib cage fully recover. Rebound will reduce the intrathoracic pressure, thereby increasing the preload of the heart and achieving a higher coronary perfusion pressure; ④Continued: The frequency and duration of any interruptions should be minimized.

Minimize interruptions: If chest compressions are interrupted during CPR (no matter how short the time is) , it will cause the coronary artery and brain perfusion pressure to drop and further make the patient’s outcome worse.


When non-professional witnesses are rescued, chest compression CPR (CO-CPR) may be better than chest compression plus ventilation. The current guidelines advocate the compression-airway-breathing (CAB) method for cardiac arrest. The principle is that the alveoli are likely to contain sufficient levels of oxygen in the early stage of cardiac arrest, and the pulmonary blood vessels and heart may A sufficient amount of oxygenated blood can meet the body’s significantly reduced oxygen demand. Starting high-quality chest compressions is the first step to improve oxygen delivery to the tissues. At this time, chest compressions are more important than ventilation.

However, in patients with cardiac arrest accompanied by hypoxia, their oxygen reserves may have been exhausted. At this time , high-quality ventilated CPR is required . As the disappearance of the pulse continues, proper ventilation becomes more and more important. Key indicators: ①If the patient has not established a high-level airway, ventilate twice after every 30 chest compressions; ②The duration of each ventilation does not exceed 1 second; ③The tidal volume given is only enough to observe the rise of the chest ( 500-600mL) .

④ Defibrillation

Early defibrillation is critical to the survival rate of patients with ventricular fibrillation. For adults, it is recommended to use the maximum energy level available for defibrillation, do not stop compressions before the AED is fully charged, and resume chest compressions immediately after giving an electric shock to the AED.

2. For the time window-AED configuration density and radius

Cardiac arrest occur with high frequency in special places, including public transport, shopping centers, sports stadiums and other public before emergency personnel arrive by witnesses AED defibrillator use of these places, this is the ” public defibrillation ” (public Access at defibrillation, PAD) , greatly expanding the group of potential rescuers who can provide early defibrillation.

(1) AED configuration directly affects the survival rate of sudden death

Public defibrillation can effectively improve the survival rate and neurological outcome after cardiac arrest . Foreign studies have shown that the survival rate of patients with cardiac arrest in public places who are equipped with AED (23.4%) is significantly higher than that without AED (14.0%) , and the proportion of survivors with normal nervous system function is higher (50% vs 14%) ). Japan widely deployed AEDs in public places across the country from 2005 to 2013, and the proportion of non-professionals using AEDs to shock VF arrests with witnesses rose from 1.1% to 16.5%. With the increase in defibrillation initiated by the public, the time from arrest to electric shock was shortened from 3.7 minutes to 2.2 minutes, and the survival rate with good nervous system function was significantly increased by 2 times (from 18.2% to 38.5%) .

(2) Further shorten the reach of AED

The golden rescue time for sudden cardiac death is to start cardiopulmonary resuscitation and defibrillation within 4 minutes. It is calculated based on the running distance of a normal person and the existing AED coverage rate. At present, China’s AED is still in the “ existent but unreachable” stage. .

The coverage efficiency of the active AED is 6 times that of the fixed AED. Taking this European Cup as an example, the speed and efficiency of the emergency team’s AED entry is a model of a mobile AED- 0 seconds , the athlete falls to the ground without contact; 5 Seconds , the referee greets the medical staff to enter the field; 13 seconds , the team doctor arrives on the scene; 37 seconds , the medical staff carrying the first aid equipment AED rushes into the field; 52 seconds , the AED starts to work; 1 minute 36 seconds , the medical staff starts CPR. If the AED is placed in a fixed position in the stadium, it is impossible to complete first aid at such a speed. The direction of action of the mobile AED is one-way, and the coverage area is 4 times that of the fixed AED (the one-way running distance is twice the distance of the two-way running back and forth) ; at the same time, a series of operations such as judgment, search and retrieval are saved. The responsible person has clear tasks and clear division of labor. Studies have shown that the rescue coverage efficiency of mobile AEDs is about 6 times that of fixed AEDs, which greatly increases the potential range of AEDs.

(3) China’s AED popularization lags behind, and it will start to catch up in 2020

At present, there is still a big gap between the popularization of AED and the use of related science education in my country. The deployment rate of AEDs in China is only 0.2 units per 100,000, while the US has reached 317 units per 100,000 in 2017, 394 units per 100,000 in Japan, and 695 units per 100,000 in the Netherlands. Correspondingly, the success rate of treatment for sudden death outside hospital in China is only 1% , while the success rate of treatment in the United States is close to 40%.

In recent years, with the frequent occurrence of sudden deaths of public figures, AED has gradually gained attention and attention, and the government has gradually accelerated the popularization of AED in public places. In 2006, China officially launched AEDs. Beijing Capital Airport was the first public place to introduce AEDs in China, and 11 units were installed in the T2 terminal. The 2008 Beijing Olympics brought the popularity of AED to a small climax in China, but after the Olympics ended, it cooled down again. In 2019, the “Healthy China Action (2019-2030) ” promulgated by the State Council clearly put forward the requirements for the proportion of CPR training personnel, and pointed out that the standards for first aid facilities and equipment in public places should be improved. Port passenger terminals, large shopping malls, movie theaters and other crowded places are equipped with emergency medicines, equipment and facilities, and equipped with AEDs.

The 15th meeting of the Standing Committee of the 13th National People’s Congress passed the review of the Basic Medical Hygiene and Health Promotion Law of the People’s Republic of China, which added the corresponding provisions of the AED: public places should be equipped with necessary first aid equipment and facilities in accordance with the regulations. It is hoped that on the basis of comprehensive conditions such as scale, personnel situation, and willingness to set up, AEDs will be deployed in public places in a reasonable manner to gradually form a network.

2020 is a key node for the popularization of AEDs. Many cities across the country have begun to deploy or increase AEDs in public places, especially transportation hubs, marking a big step in the popularization of AEDs in China. Many cities across the country are promoting the launch of AEDs. In order to accelerate the implementation of AED popularization, AED configuration plans have been formulated.

The earlier action was Shenzhen, which currently has the largest AED coverage rate in the country. In 2017, Shenzhen has launched a plan to equip public places with AEDs. As of March 2021, Shenzhen has deployed more than 5,500 AEDs in public places and equipped with “AED navigation” systems. In the next 5-10 years, it will strive to reach 100 units per 100,000 people. Internationally recommended standards for rates.

In December 2020, three cities completed the scale-up of AEDs at the same time: Dongguan Metro Line 2 achieved full site coverage of AEDs, the first batch of 59 AEDs piloted by the Guangzhou Metro completed the installation and use, and Kunming put 1,100 AEDs in subway stations and large shopping malls. Supermarkets, scenic spots, airports and other public places. Beginning in 2016, in some cities in China, AEDs have already played a role in public places. On October 27, 2020, AED entered Beijing’s subway station for the first time. As of the end of December 2020, 58 AEDs have been installed on the Beijing Metro, on Line 1, Line 2, and Line 13.

At the same time, cities are continuing to specify future deployment plans: Nanjing has formulated a plan to deploy 1,000 AEDs by 2021, and subway stations will be fully covered by AEDs; Beijing announced that key public places (rail transit stations) will be fully covered by AED facilities by the end of 2022. Coverage; Hangzhou plans to deploy 4,200 AEDs in public places in the city by 2022; Yunnan will deploy 4,800 AEDs throughout the province.

In October 2020, the “Administrative Measures for Automated External Defibrillators in Public Places in Hangzhou” was passed, and will be implemented on January 1, 2021, becoming the country’s first local legislation to regulate the configuration of AED (automated external defibrillators) in public places . And the city used. At the same time, it is planned to increase 3596 AEDs in the city within 3 years, guaranteeing a configuration rate of 42 units per 100,000 people.

With the popularization of AEDs, there have been many news reports of successful AED rescues due to sudden subway deaths in the first half of this year, and the domestic public defibrillation rescues have had a gratifying start.

3. Reach out-the burden of the “bystander” most likely to save lives is relieved

The reason for the unsuccessful promotion of AED in the country at the beginning was also the public’s concern. If a person with cardiac arrest suddenly falls to the ground in a public place, surrounding onlookers are afraid of legal risks and seldom come forward to rescue. Due to some widely circulated unfavorable cases, many people worry about legal disputes with patients or family members afterwards. Concerns about civil liability after life-saving are not only for individuals, but also for management departments in many public places. Although Article 184 of the Civil Code of the People’s Republic of China stipulates that the victim shall not bear civil liability for the damage caused by the voluntary implementation of emergency relief. However, in reality, it will take a long time to change the public’s fear of rescue. However, with the implementation of relevant policies and permits, more and more successful cases of rescue in public are publicized. “The burden will gradually decrease.

4. For the quality of resuscitation-CPR training

In addition to the AED configuration density and the legal liability of bystanders, the low rate of first aid penetration in my country is also the main reason for the low rate of emergency rescue in cardiac arrest. It is also a problem that many witnesses cannot or dare not CPR at the scene of sudden death. They can only dial 120 and miss the “golden 4 minutes” rescue time. The coverage rate of first aid training in developed countries is very high. The penetration rate of first aid training in France is 40% of its total population, 80% in Germany, and 30% in the United States. However, the rate of first aid training in my country is only 1%. At present, there are institutional arrangements for popularizing first aid knowledge. The “Healthy China Action (2019-2030) ” encourages and supports the Red Cross and other social organizations and first-aid centers and other medical institutions to carry out mass first-aid training, popularize the first-aid knowledge of the whole people, and make The public has the basic knowledge and skills of cardiopulmonary resuscitation and other emergency self-rescue and mutual rescue.

Arrange for the National Health Commission to take the lead, and the Ministry of Education, the Ministry of Finance, and the General Committee of the Red Cross Society of China will be responsible according to the division of responsibilities. And clearly put forward the health promotion actions of primary and secondary schools, including students’ health knowledge, first aid knowledge, especially cardiopulmonary resuscitation, into the content of the examination, and the mastery of health knowledge, first aid knowledge and physical fitness test conditions as the first evaluation of school students, graduation assessment and An important indicator for further studies.

In the end, how to implement it still requires the guidance of the health administration department, the training of the education department, and the cooperation of non-profit organizations. The multi-link connection can make up for the current shortcomings of public services, and ultimately effectively improve the survival rate of sudden death in our country.

5. Further improve the quality of life-ECPR

At present, the good rate of neurological function after routine CPR resuscitation for out-of-hospital cardiac arrest is only 5%~10%. Patients often lose the chance of good neurological prognosis because they cannot get timely and efficient rescue measures. Although conventional CPR is still the basic method of cardiopulmonary resuscitation widely promoted because of its convenience and speed, its circulatory support effect is relatively weak.

After cardiac arrest, the body is in blood flow stagnation and vital organs are in a state of non-perfusion. Conventional CPR is actually in a low blood flow state under high-quality compression (cardiac output can reach 30% to 40% of that before cardiac arrest, and coronary artery The perfusion pressure reaches 20-25 mmHg) , which can meet certain requirements for the recovery of spontaneous circulation. However, if the patient fails to maintain spontaneous circulation for more than 30 minutes in a cardiac arrest, it is called refractory cardiac arrest. Such patients have a lower probability of good neurological prognosis due to long-term insufficient perfusion of vital organs (brain, kidneys, etc.) .

What is the cause of sudden death? How to prevent and first aid?

Figure 2. Cardiac output under conventional CPR is 30%-40% of normal. However, if the spontaneous circulation cannot be maintained continuously for more than 30 minutes in a cardiac arrest, ECMO should be used immediately for emergency circulation and oxygenation support to maintain the circulatory perfusion of vital organs

Extracorporeal cardiopulmonary resuscitation (ECPR) refers to rapid extracorporeal cardiopulmonary resuscitation (ECPR) for patients with selected causes of cardiac respiratory arrest and those who have been unable to recover their spontaneous heart rhythm using traditional cardiopulmonary resuscitation, providing temporary circulation and breathing. Supported technologies.

ECPR is a newly developed resuscitation technology in recent years, which can shorten the time of low blood flow after cardiac arrest, and make the neurological function of patients with refractory cardiac arrest reach 30%-40%. The 2015 American Heart Association cardiopulmonary resuscitation guidelines proposed that ECPR can be considered for specific cardiac arrest patients, but there must be a fast and professional team. The International Extracorporeal Life Support Organization (ELSO) report shows that adult ECPR has grown rapidly in the past 10 years. In 2018, the overall survival rate of 1197 cases reached 29.5%, and the overall survival rate of ECPR in China was 26%.

According to reports from some centers, among ECPR patients, the prognosis rate of patients with good neurological function in ECPR patients whose duration of CPR is less than 60 minutes to establish an ECMO cycle reaches 50%, and the prognosis rate of patients with good neurological function of more than 60 minutes is 23.1%.

The success of ECPR depends on timely CPR, a strong ECMO team and follow-up ICU intensive treatment. The current emergency system in my country and the critical clinical linkage need to be further strengthened:

(1) System: Emergency network linkage and ECPR response area coverage

It should be noted that ECPR also has an obvious rescue time window-when CPR continues for more than 15 minutes without regaining the spontaneous heartbeat, ECMO should be used immediately for emergency circulation and oxygenation support. If you want to apply ECMO in a timely manner within 15 minutes for patients with out-of-hospital cardiac arrest, you must rely on the existing emergency system. In the pre-hospital link, when witnesses call for help at 120, they should also notify the ECPR team of the hospital in the area to prepare in advance. After emergency personnel arrive at the scene, they will evaluate the patient and inform the ECPR team of the hospital where the patient is about to be delivered. Then the ECPR team will immediately set off with the equipment.

When transferring 120, it is necessary to consider the transportation radius and time of hospitals that are feasible for ECPR, which is directly related to the success rate of ECPR. After entering the hospital, the ECPR green channel is provided in the hospital, and patients can enter the ECPR clinical path in time. The resuscitation room for ECPR requires the necessary equipment and items to be complete.

(2) Personnel: ECPR technology and ECMO training

Since ECPR time is extremely important, the distance should not be too far. If the distance permits, the patient can be transferred to a regional ECPR center with strong comprehensive treatment capabilities for multidisciplinary collaborative treatment. In order to further shorten the transfer radius, it is imperative to establish ECPR sub-centers to cover different areas to ensure timely treatment of patients with cardiac arrest. ECPR should be further carried out on a large scale, involving ECMO training, and relying on local experienced regional ECPR centers to provide technical guidance to ensure the quality of resuscitation and ECPR skills.

(3) Equipment and site ECPR: mobile ECMO shortens cycle recovery time

The traditional method of transporting to the hospital while resuscitation will inevitably encounter a decline in the quality of resuscitation during transport. At present, some pre-hospital emergency systems in Europe and the United States directly carry ECMO equipment to the site to implement ECPR, which shortens the low blood perfusion time and increases the recovery of spontaneous circulation. rate. However, my country’s emergency system and resources are still limited, and on-site ECPR is at an early stage of development. In recent years, with the improvement of first aid awareness, my country’s high-end emergency vehicles have begun to be equipped with ECMO equipment.

Because the environment during the transfer is different from the ICU environment, the ECMO performance for emergency transfer has special requirements-it can withstand the bumps in the transfer and require portability. Due to the high technical barriers, yet domestic production, domestic ECMO are imported, mainly Maquet (Maike Wei) , Medtronic (Medtronic) , LivaNova (Li Connaught enamel) and other import manufacturers occupy. Among them, ECMO used for emergency transport due to high performance requirements, currently only Maquet exclusive product Cardiohelp, as a high-end product line priced at nearly 3 million yuan has not yet been deployed on a large scale. The current domestic companies that develop emergency ECMO include Suzhou Xinqing Medical and so on.

3. “Beyond” to solve the internal cause-one step forward, the important task of clinical prevention

The onset of sudden cardiac death is sudden and unpredictable, most of which occur outside the hospital. Although AED can be effectively rescued, it requires bystanders to apply and operate. According to statistics, only 50% of cardiac arrests are witnessed. When there are no witnesses around the patients with cardiac arrest, it is impossible to provide effective rescue. Therefore, at the group level, it is too late to save lives after sudden cardiac death. The key to reducing the mortality rate of sudden cardiac death lies in the effectiveness of the prevention and treatment of sudden cardiac death.

1. The “upstream” of sudden death-the progress of chronic cardiovascular disease

(1) Principle of sudden death: abnormal “structure” of myocardium→”electrical short circuit”→”power” stop

Cardiac arrest often occurs in patients with certain underlying organic heart diseases, the most important being coronary heart disease (coronary heart disease) , 70% of cardiac arrests can be attributed to coronary heart disease. In patients with coronary heart disease, cardiac arrest can be seen not only during acute coronary syndrome (ACS) , but also in patients with chronic stable coronary heart disease. Patients with chronic coronary heart disease usually have previous myocardial damage and myocardial scars that may induce cardiac arrest.

So how does myocardial injury affect electrical conduction, leading to cardiac arrest? Among the arrhythmia types that can cause sudden cardiac death, 25%-35% are caused by ventricular fibrillation and pulseless ventricular tachycardia, and 25% are caused by PEA. The electrical conductivity after the occurrence of ventricular fibrillation and ventricular tachycardia myocardial ischemia or myocardial infarction caused by abnormal scar has a great relationship :

The mechanism of ventricular fibrillation (VF) -myocardial heterogeneity: the rotating spiral wave is the most likely mechanism, and it almost always occurs in the usually diffuse underlying cardiomyopathy (Figure 3) , leading to heterogeneity of depolarization The discrete trend of sex and repolarization. This inconsistency of electrophysiological properties is a prerequisite for reentry. Multiple local ECG micro-reentrant areas cause ventricular fibrillation, and there is no orderly electrical activity during ventricular fibrillation. The difference in conduction and repolarization parameters (myocardial heterogeneity) causes the impulse to fragment during the process of conduction through the myocardium, thereby forming multiple local reentrant areas or multiple myocardial activation spiral wavelets. Because there is no orderly electrical activity and myocardial depolarization, there is no uniform ventricular contraction, which prevents the heart from producing cardiac output.

The mechanism of ventricular tachycardia (VT) : In about 80% of VT/VF patients, persistent ventricular arrhythmia will have increased ventricular ectopic pacing and repetitive ventricular arrhythmia, especially if multiple non-sustained arrhythmias occur. VT, these spontaneous arrhythmias have different durations before the occurrence of VT/VF. Persistent polymorphic VT can progress to VF, which is most often caused by underlying ischemia. VF can also be the primary event of sudden cardiac death.

What is the cause of sudden death? How to prevent and first aid?

Figure 3. The relationship between sudden death and coronary heart disease (an example of a common mechanism of arrhythmia after infarction): myocardial injury or myocardial scar caused by ischemia → myocardial heterogeneity → inconsistency of electrophysiological characteristics → reentry → multiple regional hearts Electrical micro-reentry area → ventricular fibrillation → no orderly electrical activity → cardiac arrest (a. Normal electrical conduction system; b. The distal myocardial ischemia due to vascular obstruction (black circle), the area supplied by blood vessels Myocardial infarction (gray area); c. Infarct area (dark red area); d. ECG reentry at the border of normal myocardium (pale pink) and infarcted myocardium (dark red), leading to ventricular fibrillation.)

(2) A huge group of potential patients—coronary heart disease and heart failure patients in the process of chronic disease

Causes of sudden death

The cause of sudden cardiac death is related to age and population: 73% of sudden cardiac death patients under 40 years old (no underlying heart disease) are cardiogenic, and 15% are non-cardiac (most often intracranial hemorrhage) . Those under 35 are more likely to be non-coronary heart disease causes. The incidence of sudden death in both sexes increases with age, but men are more likely to die suddenly than women-men are 2-3 times more likely than women.

Whether there is underlying heart disease, the risk of cardiac arrest is also significantly different: the risk of cardiac arrest increases to 6-10 times when there is a heart disease, and the risk of cardiac arrest increases to 2-4 times when there are risk factors for coronary heart disease. Among them, the main causes of sudden death include:

① Coronary heart disease: The most common cause, 70% of cardiac arrests can be attributed to coronary heart disease (58% in patients over 30 years old, 22% in patients under 30 years old) . In patients with coronary heart disease, cardiac arrest can be seen not only during acute coronary syndrome (ACS) , but also in patients with chronic stable coronary heart disease (usually there is previous myocardial damage and scars that may induce cardiac arrest) . In fact, sudden cardiac death is more common in patients with no recognizable acute cardiac events, and more than 50% of cardiac arrests are the first manifestations of previously unknown or unrecognized cardiac diseases.

②Other organic heart disease: account for 10% of out-of-hospital cardiac arrest cases. ① Heart failure (heart failure) and cardiomyopathy, about 1/3 of deaths are caused by sudden cardiac death. ②Left ventricular hypertrophy caused by hypertension or other reasons (Myocardial hypertrophy caused by hypertension is usually accompanied by myocardial fibrosis, which may create conditions for ventricular arrhythmia); ③Myocarditis; ④Hypertrophic cardiomyopathy (for patients under 30 years old) 13%) ; ⑤ arrhythmogenic right ventricular cardiomyopathy; ⑥ congenital coronary artery abnormalities; ⑦ mitral valve prolapse.

③No organic heart disease: 10%-12% of cardiac arrest cases under 45 years old. ① Brugada syndrome; ② idiopathic VF; ③ long QT syndrome; ④ familial polymorphic VT; ⑤ unexplained familial sudden cardiac death; ⑥ WPW syndrome; ⑦ heart concussion.

Among them, two major patient groups need attention:

① Coronary heart disease

65%-70% of sudden cardiac deaths can be attributed to coronary heart disease, and 30%-50% of coronary deaths are caused by sudden cardiac death. Coronary angiography showed that 71% of cardiac arrest survivors had meaningful coronary stenosis (48% of them had coronary artery occlusion) , and the remaining patients could not rule out acute coronary syndrome or myocardial ischemia. About 24% of sudden cardiac death cases under the age of 30-40 are caused by coronary heart disease. The incidence of sudden cardiac death is related to the clinical manifestations of coronary heart disease: it is the highest in patients with previous myocardial infarction, and it is middle in patients with angina pectoris without previous myocardial infarction. However, sudden cardiac death can occur in patients with asymptomatic ischemia and can be the initial manifestation of coronary heart disease.

Acute myocardial infarction: In patients with acute myocardial infarction rather than sudden cardiac death, the incidence of VF varies with the type and time of the infarction: the overall incidence of VT/VF in acute ST-segment elevation myocardial infarction is 10.2 %, 80%-85% of such arrhythmias occur in the first 48 hours. The overall incidence of VT/VF in non-ST-elevation acute coronary syndromes was 2.1%. The median time to arrhythmia was 78h (interquartile range 16h and 7d) .

Multiple studies have shown that the peak of VF in the first 48 hours after acute myocardial infarction may be caused by ischemia, and the subsequent VF may be related to the healing of the infarction and the formation of scars (and the increased risk of monomorphic VT) , and It can increase the risk of late-onset sudden cardiac death. Late-onset sudden cardiac death most often occurs in the first year, most of which occur within the first few months, and are caused by ventricular tachyarrhythmias. The risk of late-onset VT/VF seems to be the same in patients with ST-elevation and non-ST-elevation infarctions. These data do not include sudden cardiac death patients who have died before admission. It is estimated that more than 50% of deaths caused by acute myocardial infarction occur outside the hospital, and most occur within 1 hour of the onset of symptoms.

Myocardial ischemia: There are unstable coronary artery lesions, which may cause acute ischemic events (without infarction) and may lead to unstable electrical activity. 76% of patients with cardiac arrest have obvious coronary artery disease, spasm or unstable lesions, and nearly one-half of patients have coronary artery occlusion. Patients who are not in the acute phase of myocardial infarction may continue to have a higher risk of VT/VF recurrence even after successful revascularization.

②Heart failure

Heart failure is a relatively common cause of sudden cardiac death. 30%-50% of deaths in patients with heart failure are caused by sudden cardiac death, and the incidence of sudden cardiac death increases during the exacerbation of heart failure symptoms. The incidence of sudden cardiac death in patients with heart failure is 5 times that of patients without heart failure, and the absolute risk of female patients is 1/3 of that of male patients.

What is the cause of sudden death? How to prevent and first aid?

Figure 4. The progression of heart failure is related to the incidence of sudden cardiac death: as the heart failure progresses from the initial stage (A, B or NYHA II) to the middle and terminal stages (C, D or NYHA III, IV) sudden death Incidence and probability are getting higher and higher (the red arrow below indicates the frequency of sudden death)

Among the causes of death in patients with heart failure, progressive pump failure, unexpected sudden cardiac death (usually caused by ventricular tachyarrhythmia, sometimes caused by cardiac arrest and pulseless electrical activity) and during the onset of clinical worsening of heart failure Sudden cardiac deaths accounted for about 1/3 of the total number of heart failure deaths. 39% of the sudden deaths in patients with heart failure are considered to be caused by arrhythmia. The development of VT to VF is the most common cause of sudden cardiac death, 5%-33% The case is caused by bradyarrhythmia or PEA. Acute coronary events may be the cause of sudden death in some patients with heart failure. Among patients with heart failure who had significant coronary artery disease, 54% of sudden death patients and 32% of patients who died of heart failure had acute coronary artery disease.

The more severe the heart failure, the higher the overall mortality and the absolute incidence of sudden cardiac death (Figure 4) . The mortality rate and mode of patients with heart failure vary with the level of heart failure and the type of cardiomyopathy. The mode of death of patients with NYHA Ⅱ or Ⅲ heart failure is more likely to be “sudden” sudden death, while the death of patients with NYHA Ⅳ heart failure The method is more likely to be related to “pump” failure (Figure 5) , where VT and VF are still the most common arrhythmias that cause sudden cardiac death. The MERIT-HF study showed that the higher the level of heart failure (NYHA II, III and IV) , the higher the chance of sudden cardiac death at 1 year (6.3%, 10.5%, and 18.6% , respectively) , but attributable sudden cardiac death in proportion to the total proportion of deaths there the drop (respectively 64%, 59% and 33%) .

What is the cause of sudden death? How to prevent and first aid?

Figure 5. The cause of death in patients with heart failure is related to the degree of heart failure. Sudden death is the main cause in the early and mid-term (NYHA II and III)

“Trigger”-an acute trigger

In addition to basic organic heart disease, some short-lived or reversible causes may induce arrhythmia and sudden cardiac death. Identifying these causes is essential for treating underlying diseases and judging the recurrence probability of sudden cardiac death. Possible reversible triggers of sudden cardiac death include : ①Acute cardiac ischemia and myocardial infarction: Coronary heart disease is the most common cause of sudden cardiac death, so all survivors of sudden cardiac death should consider acute coronary ischemia; ②Heart failure: During the worsening of heart failure symptoms, the incidence of sudden cardiac death may increase; ③Autonomic nervous system excitement, especially sympathetic nerves, such as sudden emotional agitation; ④Other: antiarrhythmic drugs, toxins, electrolyte abnormalities, acidosis, Severe hypoxemia.

2. “Save” is never too late, “Prevention” can run ahead of death

Based on the above, all kinds of heart diseases have the possibility of sudden cardiac death, and even many patients with coronary heart disease have sudden death as the first manifestation. It is particularly important to prevent the huge number of patients with high risk of sudden cardiovascular death. According to the guidelines for the prevention and treatment of cardiovascular diseases, China already has primary and secondary prevention standards and measures for sudden cardiac death .

Primary prevention is through clinical diagnosis, finding patients with high risk factors and implanting a cardioverter defibrillator (ICD) as soon as possible . Secondary prevention is to prevent sudden cardiac death in patients who have experienced sudden cardiac death, and prevent sudden cardiac death by implanting ICD. However, secondary prevention measures are only for patients who have experienced sudden cardiac death, and it is difficult to cover the entire high-risk population of sudden cardiac death. At present, primary prevention is generally accepted and used in Europe and the United States, that is, prevention for high-risk populations who have not experienced sudden cardiac death.

(1) Indication dimension: Stratification strategy and logic

Although ICD is very effective in the treatment of ventricular tachyarrhythmias and the prevention of sudden cardiac death, it is expensive, requires continuous follow-up, and has many risks during implantation and during the life of the device (eg, bleeding, pneumothorax, perforation, and infection , Device and wire failure, etc.) , and only some patients with cardiomyopathy have sustained ventricular tachyarrhythmia or sudden cardiac death. Therefore, patients should be risk stratified before ICD treatment, to provide treatment to patients at the highest risk of sudden cardiac death, and to minimize the number of ICD implants for patients who are unlikely to benefit . The main indicators for stratifying the risk of sudden cardiac death for the primary prevention of ICD implantation include: ① the etiology of left ventricular dysfunction; ② left ventricular ejection fraction (LVEF) ; ③ heart failure symptom classification; ④ life expectancy more than 1 year ⑤ Inducible persistent ventricular tachycardia; ⑥ ECG monitoring showed non-sustained ventricular tachycardia.

The main indicators involve two aspects: ①The risk of patients with significantly reduced LVEF seems to be the greatest, and the benefits that can be obtained from the primary prevention of ICD implantation are also the greatest; ②The risk factors for sudden cardiac death after acute myocardial infarction include: left ventricular dysfunction or LVEF Reduce; heart failure symptoms and degree of heart failure; left ventricular aneurysm; Q wave on the surface electrocardiogram; indoor conduction delay, etc.

The patients who recommend ICD implantation for primary prevention of sudden cardiac death are as follows (Figure 6) :

What is the cause of sudden death? How to prevent and first aid?

Figure 6. A simple matrix of screening criteria for patients with primary prevention of sudden cardiac death: On the basis of primary diseases such as cardiomyopathy and heart failure caused by myocardial ischemia in coronary heart disease, cardiac function (EF is the pumping capacity of the heart, NYHA is Patients with poor cardiac function ratings from the perspective of symptoms are at high risk of sudden death (CHD: coronary heart disease or ischemic cardiomyopathy, HF: heart failure, MI: myocardial infarction, VT: ventricular tachycardia)

①Patients with cardiomyopathy caused by ischemic heart disease, LVEF≤35%, and NYHA grade Ⅱ or Ⅲ heart failure, at least 40 days after myocardial infarction and after revascularization and drug treatment in accordance with the guidelines3 Accept ICD assessment for more than one month.

②Patients with cardiomyopathy caused by ischemic heart disease, LVEF≤30%, and NYHA class I status, receive ICD assessment at least 40 days after myocardial infarction and more than 3 months after revascularization and drug treatment as guided by the guidelines .

③Patients with previous myocardial infarction-related NSVT, LVEF≤40%, and patients who can induce persistent VT or VF during electrophysiological examination (EPS) . The patient should be in the acute phase of myocardial infarction and be treated with the medications as directed by the guidelines, and the expected survival period is at least 1 year. Patients with reduced LVEF due to myocardial infarction have an increased risk of sudden cardiac death, most often due to ventricular tachyarrhythmia. For certain patients with ischemic cardiomyopathy, preventive implantation of ICD for primary prevention of sudden cardiac death can reduce mortality.

④For patients with non-ischemic dilated cardiomyopathy, LVEF≤35%, and NYHA grade Ⅱ or Ⅲ heart failure, ICD can very effectively reduce the total mortality and the mortality caused by sudden cardiac death. All patients receiving ICD as primary prevention of sudden cardiac death should undergo guideline-based drug therapy for at least 3 months before ICD implantation.

⑤For patients with LVEF ≤ 35%, NYHA Ⅲ or Ⅳ heart failure and QRS interval ≥ 120 milliseconds, it is recommended to implant CRT-D combined device (biventricular pacing combined with ICD) instead of simply implanting ICD. For patients with left bundle branch block (LBBB) QRS, patients with QRS interval ≥ 150 milliseconds, and patients who rely on ventricular pacing due to atrioventricular block, CRT should be considered the most.

(2) Primary prevention: prevent people who have not died suddenly

①General population: risk stratification and reduction of risk factors

Screening and risk stratification: For people with known increased risk of cardiac arrest (such as previous myocardial infarction) , further risk stratification can be performed to identify patients who can benefit from ICD. For the general population without known cardiovascular disease, the guidelines recommend screening for risk factors for cardiovascular disease, and screening for coronary heart disease in some patients as appropriate.

Lifestyle intervention: Many traditional risk factors related to coronary heart disease are also related to cardiac arrest, so targeted interventions on these risk factors can also reduce the incidence of cardiac arrest. Intervention measures include: effective treatment of hypercholesterolemia and hypertension; adopting a heart-healthy diet; regular exercise; quitting smoking; drinking moderately; effective treatment of diabetes. Although there is no definite evidence that reducing risk factors in the general population can reduce the incidence of cardiac arrest, since most coronary heart disease deaths are caused by sudden cardiac death, studies have confirmed that interventions to reduce risk factors can reduce cardiovascular and coronary Arterial-related total mortality, thereby reducing the incidence of cardiac arrest.

② ischemic heart disease (CHD) patients

Patients with ischemic heart disease are at increased risk of cardiac arrest, especially those with a history of myocardial infarction. The risk of cardiac arrest after myocardial infarction is significantly increased due to a number of factors. Methods to prevent cardiac arrest in such patients: ①Standard drug treatment. Beta blockers and angiotensin converting enzyme inhibitors can reduce the overall mortality after myocardial infarction and can be used routinely. These drugs can also reduce the incidence of sudden cardiac death. ②Risk stratification should be carried out to identify patients with the highest risk of cardiac arrest. ③ICD implanted in selected patients.

Studies on the primary prevention of ICD implantation in ischemic cardiomyopathy have shown that ICD can significantly improve survival: The MADIT-I trial (Multicenter Automatic Defibrillator Implantation Trial) is to confirm that ICD is effective in certain high-risk, asymptomatic patients. The first clinical study where the primary prevention of sudden death is effective. These patients had previous myocardial infarction with reduced LVEF (≤35%) , ECG monitoring showed NSVT, and inducible persistent monomorphic VT during EPS (which can also be induced after intravenous procainamide). Compared with patients in the drug treatment group, the overall mortality, cardiac mortality, and arrhythmia deaths in the ICD treatment group were significantly reduced (Figure 7 left panel) . MADIT-II test: Patients with previous myocardial infarction and LVEF decreased (≤30%) more than 30 days before enrollment . Compared with the drug treatment group, the ICD group had a lower all-cause mortality rate (ICD group 14.2% vs. conventional treatment group 19.8%, HR 0.65, 95% CI 0.51-0.93) (Figure 7 right panel) .

What is the cause of sudden death? How to prevent and first aid?

Figure 7. The MADIT-I trial on the left and the MADIT-II trial on the right showed that patients at high risk of sudden death have a significant increase in survival after the application of ICD for primary prevention.

③Patients with heart failure and cardiomyopathy

The risk of sudden cardiac death increases with the severity of left ventricular systolic dysfunction and clinical heart failure. Regardless of the cause, patients with heart failure and left ventricular systolic dysfunction have an increased risk of cardiac arrest. For patients with heart failure and cardiomyopathy, the role of ICD in the primary prevention of sudden cardiac death depends on several factors: the severity of left ventricular systolic dysfunction; the severity of clinical heart failure; the etiology of left ventricular dysfunction (ischemia) Sexual vs non-ischemic cardiomyopathy) ; Competitive co-existing diseases (chronic kidney disease, chronic obstructive pulmonary disease, etc.) that affect life span and risk of ICD complications . At the same time, the risk of death from other causes (progressive heart failure) will also increase with heart failure and deterioration of left ventricular systolic function, so it is extremely important to select patients appropriately before implanting ICD primary prevention.

④ Congenital diseases related to increased risk of cardiac arrest (such as Brugada syndrome, congenital long QT syndrome and WPW) .

(3) 1.5-level prevention: the target population under China’s national conditions is sufficient and necessary to intervene

As there are significantly more patients eligible for primary prevention indications than secondary prevention patients in my country, there are fewer patients who use preventive devices to prevent sudden cardiac death. At present, the implantation rate of ICDs in my country is only 1.4 per million people, and the current rate of ICD implantation is only 1.4 per million people. Medical resources are difficult to meet the primary prevention needs of patients with sudden cardiac death under the huge population base. Medical insurance policies, lack of evidence-based medicine data, patients’ ignorance or fear of implantable ICDs, and many patients’ refusal to accept ICD implantation are all reasons why primary prevention is difficult to implement.

In order to further improve patients and doctors’ awareness of ICD therapy to prevent sudden cardiac death, and to strengthen the prevention of sudden death in extremely high-risk patients, the Chinese Medical Association Electrophysiology and Pacing Branch proposed a 1.5-level prevention for Chinese patients , On the basis of the international first-level prevention indications, one of the four high-risk factors is further added-LVEF <30%, frequent ventricular premature, non-sustained ventricular tachycardia, syncope, and syncope precursors. The concept of level 1.5 prevention is of practical significance to promote the prevention and treatment of sudden cardiac death. The population involved in level 1.5 prevention is the population that is fully necessary for ICD implantation. Compared with the scope of primary prevention, it is narrower, more targeted and necessary. , Which indirectly reduces the burden on medical insurance and patients.

3. Prevention time window

What is the cause of sudden death? How to prevent and first aid?

Figure 8. After the risk stratification of patients with high risk of sudden death, the prevention time window is divided into 3 months, divided into short-term and long-term sudden death risks, and different sudden death prevention programs can be matched accordingly

At present, the time window for primary prevention of sudden death (as above) is only 3 months after the patient’s revascularization is evaluated and considered for ICD implantation, and the patient is still at a high-risk period within 3 months, according to the large national cardiovascular data registry in the United States Research (NCDR) and the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database research show that patients with left ventricular insufficiency (such as LVEF≤30%) have significantly higher mortality rates in the early postoperative period after PCI or CABG. The mortality of patients with significant left ventricular dysfunction at 30 days after CABG is significantly higher than that of patients with normal left ventricular function. These patients not only have an increased risk of sudden cardiac death due to ventricular arrhythmia, but also have an increased risk of death due to non-arrhythmic events. Will increase.

At the same time, in actual clinical practice, both domestic and foreign have encountered the challenge of ICD implantation to prevent sudden death in the short and medium term: the US reimbursement does not cover the cost of ICD implantation for primary prevention within 3 months after CABG or PCI. In China, due to the implantability and cost of ICDs, clinicians often spend a long time convincing patients that this time span is likely to be longer than the time window for high-risk patients. How to prevent sudden death within 3 months in a way that is easy for patients (non-invasive and affordable) is the key.

For temporary treatment of high-risk patients with sudden cardiac death, WCD can be used as an alternative measure to prevent sudden cardiac death. Wearable cardioverter-defibrillator (WCD) is an external vest-type defibrillation device that can automatically detect ventricular tachycardia (VT) , ventricular fibrillation (VF) and non- invasive defibrillation. Among the recommendations of the 2016 American Heart Association (AHA) scientific recommendations, the American Heart Rhythm Society (HRS) and the 2017 AHA/ American College of Cardiology (ACC) /HRS guidelines, the following Patients may benefit from temporary use of WCD:

① LVEF≤35% within 40 days after myocardial infarction: Active patients with NYHAⅡ-Ⅲ or LVEF<30%, NYHAⅠclass use WCD, because such patients may need ICD implantation after 40 days. The LVEF should be reassessed 1-3 months after myocardial infarction. If the LVEF is still ≤35% after the appropriate drug treatment is given, the patient needs to be implanted with an ICD, which should be considered.

②LVEF≤35%, coronary artery bypass surgery (CABG) revascularization in the past 3 months : WCD is used as the primary prevention of sudden cardiac death. At the same time, LVEF should be reassessed 3 months after CABG. If persistent ventricular tachyarrhythmia occurs, or LVEF is still ≤35%, ICD implantation is usually required.

③Newly diagnosed non-ischemic cardiomyopathy: For patients with partially severe but potentially reversible cardiomyopathy, such as tachycardia or myocarditis-related cardiomyopathy, WCD may help while waiting for the improvement of left ventricular function and ICD implantation Or, if necessary, to prevent sudden cardiac death caused by ventricular arrhythmia during heart transplantation.

④ Transition to heart transplantation: Patients with severe heart failure waiting for heart transplantation have a particularly high risk of sudden cardiac death, and ICD implantation is generally recommended. WCD may be a reasonable non-invasive alternative, especially for patients who have not yet been implanted with an ICD and are expected to have a short waiting time.

⑤Bridge to indicated or interrupted ICD treatment: Some patients with indications for ICD implantation may need to delay ICD implantation due to coexisting diseases (such as infection, postoperative recovery, lack of vascular access) . In addition, some patients with ICDs need to remove the device due to infection. For these patients, WCD can combat ventricular tachyarrhythmia until the patient can implant or re-implant the ICD.

4. Outlook

1. Closer cooperation between public health and clinics, the whole system linkage from first-line emergency to front-end prevention

What is the cause of sudden death? How to prevent and first aid?

Figure 9. Emergency-treatment-prevention of sudden cardiac death involves the linkage of different departments, and each link requires close cooperation between public health and clinical practice to achieve the best results.

(1) First-line first aid-bystander CPR and AED

The population density of our country is large, and the number of people who died suddenly is relatively large. The most effective way to solve first-line first aid problems is the “public defibrillation” method-AEDs are equipped in public transportation facilities, shopping malls, public sports venues and other places. Before emergency personnel arrive, witnesses can use AED defibrillation, which expands the ability to provide The group of potential rescuers for early defibrillation can solve the first aid problem of potential sudden death patients under the population base of our country to the greatest extent. At the same time, due to the unfavorable precedents that have been widely circulated by public opinion in history, such as courage to see righteousness, the Chinese public has special civil liability concerns. To relieve the burden of “bystanders” requires more positive public opinion propaganda.

In cardiac arrest, defibrillation alone is not enough to restore the patient’s spontaneous circulation. Effective and high-quality CPR is the key to resuscitation, and corresponding emergency training needs to be strengthened urgently. How to implement first aid training still needs the guidance of the health administrative department, the training of the education department, and the multi-sectoral collaboration and multi-link connection with the cooperation of public welfare organizations to make up for the current shortcomings of public services, maximize the use of public health resources, and ultimately make my country’s sudden death treatment. The survival rate is effectively improved.

(2) Advanced life support-ECPR

When cardiac arrest exceeds 30 minutes and cannot continue to maintain spontaneous circulation, in order to shorten the time of low blood flow after cardiac arrest and reduce the complications caused by insufficient perfusion of vital organs after resuscitation, patients need extracorporeal cardiopulmonary resuscitation (ECPR) to give full circulation Perfusion effectively protects important organs (brain, kidney, liver, etc.), especially key nerve functions. However, the success of ECPR relies on a strong ECMO team and subsequent ICU treatment. my country’s current emergency system and critical clinical linkages need to be further strengthened: on the one hand, through the improvement of the emergency network linkage and ECPR response area coverage, and the strengthening of the professional team’s ECPR technology With ECMO training, if conditions permit, further on-site ECPR can be promoted through mobile ECMO to minimize the reach.

(3) Solving the primary disease-construction of chest pain center and syncope center

Since nearly 70% of sudden cardiac deaths are caused by coronary heart disease, and sudden death is the first manifestation of many coronary heart diseases, it is particularly important to treat both resuscitation and the treatment of the original disease in the emergency treatment of sudden death. At present, in order to improve the early diagnosis and treatment of patients with acute chest pain, my country has established a national chest pain center system. Since its establishment in 2015, there have been thousands of institutions nationwide. The chest pain center has an emergency green channel, which can complete fast and accurate diagnosis, risk assessment and treatment. The catheterization laboratory can be open 365 days/24 hours, and emergency PCI treatment can be performed at any time, effectively reducing the mortality of chest pain patients.

In addition, in the symptoms of cardiac arrest survivors, syncope may appear as an early warning signal . Syncope is a disorder of consciousness caused by insufficient blood supply to the brain. The causes mainly include cardiogenic syncope, nerve-mediated reflex syncope, and orthostatic syncope. Since the diagnosis of syncope involves multidisciplinary fields such as cardiovascular and neurology, it is difficult to accurately diagnose. The lack of standardized management has a low diagnosis rate and a high misdiagnosis rate. For this reason, experts recommend setting up a syncope center in a tertiary hospital to open a syncope clinic to centrally and standardize management of patients with transient loss of consciousness. In 2019, the first batch of 72 hospitals in my country launched the construction of syncope centers, which are fully responsible by trained doctors and nurses, unified diagnostic standards and processing procedures, responsible for patient management and follow-up, emphasized risk stratification of syncope patients, and actively treated heart diseases , Prevent the occurrence of malignant arrhythmia.

(4) Sudden death prevention-high-risk stratification and ICD

Primary prevention relies on relevant sub-specialty cardiovascular doctors to stratify the risk of patients. Secondary prevention relies on intervention as soon as possible after detailed evaluation in outpatient clinics or syncope clinics.

Primary prevention emphasizes the screening and management of coronary heart disease risk factors for the general population without known heart disease, and pays attention to lifestyle adjustment and intervention. For heart disease patients with an increased risk of cardiac arrest, such as previous myocardial infarction, cardiomyopathy or heart failure, the main preventive measure is standard drug treatment. After determining the risk of cardiac arrest, the selected patients will be implanted with an ICD. Patients with short-term risks may consider non-implantable WCD.

When cardiac arrest occurs, it has entered the category of secondary prevention of sudden death, focusing on comprehensive assessment and secondary prevention for survivors of cardiac arrest. After cardiopulmonary resuscitation, survivors of cardiac arrest need to identify and treat acute reversible causes, assess for organic heart disease and/or primary ECG disease, assess the nervous system, and assess family members for specific cases. The secondary prevention of sudden cardiac death is usually ICD, which is suitable for most survivors of cardiac arrest.

2. Technology trends for clinical needs

(1) AED accessibility

Movable AED shortens the radius: In addition to increasing the AED deployment density, the AED coverage efficiency within 4 minutes can be further improved by the mobile AED. The rescue coverage efficiency of the latter is 6 times that of the fixed AED, which can significantly expand the potential treatment range of the AED .

APP monitors cardiac arrest patients and informs nearby volunteers of nearby emergency treatment: consider developing a mobile phone APP application to sense the patients with cardiac arrest and automatically notify the 120 emergency system, and the emergency center will assign the nearby distance events of the cardiac arrest patients Volunteers who can move within 4 minutes of the location of the occurrence will go to the patient’s location for rescue according to the APP-related map location. For some patients with arrest in public areas and at home, this approach may increase early CPR and survival rates.

AED configuration at home: Since about 3/4 of cardiac arrests occur at home, the configuration of AED for home use may reduce mortality.

(2) ECPR accessibility

Unlike AED, ECMO is not suitable for conventional public area configuration, so it is impossible to increase configuration density through large-scale regional deployment. At present, ECPR still relies on regional central hospitals to provide technical support. If you want to improve the accessibility of ECPR, one of the important directions is the mobility and miniaturization of ECMO equipment. The portable ECMO is smaller and lighter than the ECMO in the conventional ICU, and it can be easily held on a helicopter or ambulance by one person. Taking into account the special circumstances of long-distance transportation, the product needs to take into account the characteristics of high stability, anti-collision protection and long-term battery life in the transportation at the same time.

(3) Minimally invasive and non-invasive defibrillation: WCD and SICD

ICD is currently the first choice for the prevention of sudden cardiac death. The traditional ICD implantation delivers electrodes to the right ventricle through the peripheral vein, and the pulse generator chain structure is buried under the skin of the left chest. Although ICD is commonly used, its complications have always plagued the clinic, especially complications related to intravenous catheters. Due to frequent failures of the defibrillation electrode leads and many complications related to intravenous implantation, S-ICD has begun to be used in clinical practice in recent years. The leads and pulse generators are located under the skin, and the defibrillation leads do not directly contact the heart and Veins, well solve the long-term sudden death prevention needs.

Despite this, there are still some patients with high risk of SCD who do not meet the indications for implantation in the existing guidelines, and most of the patients are in a short-term high-risk state after discharge from the hospital for myocardial ischemia and related revascularization surgery. The need for sudden death prevention is stronger, requiring non-invasive defibrillation. Because WCD is non-invasive and easy to wear, it solves the above-mentioned problem of SCD prevention in patients.

About the author: Dr. Chen Yang is responsible for innovative medical device investment at Northern Light Venture Capital. He has more than ten years of clinical work and early medical investment experience. He holds a master’s degree and doctorate degree from Peking Union Medical College and a bachelor’s degree in clinical medicine from Shanghai Jiaotong University School of Medicine.

Posted by:CoinYuppie,Reprinted with attribution to:https://coinyuppie.com/what-is-the-cause-of-sudden-death-how-to-prevent-and-first-aid/
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