How much do you know about sudden cardiac death？

Original Zhu Xinpu Yun Dan Gongbu Zhu Xinpu Stroke Prevention Science Popularization

Sudden cardiac death (SCD) is an unpredictable natural death caused by heart, accounting for about 80% of sudden death. The main manifestations are acute onset, with more males than females. A variety of heart diseases can lead to sudden death, especially those with organic basic cardiovascular diseases or related risk factors. Patients may have a history of heart disease or heart disease in the past. At present, it is recognized that most of the deaths within one hour of onset are sudden cardiac death.

According to the China Cardiovascular Disease Report released in 2019, there are 544,000 cases of sudden cardiac death in China every year.

1. Coronary artery disease

It mainly includes coronary heart disease (coronary atherosclerotic heart disease), acute myocardial infarction, coronary thrombosis, embolism or spasm, coronary arteritis, congenital coronary artery dysplasia, etc., among which coronary heart disease is the most common.

As the most common cause of sudden death, coronary heart disease is seen in acute coronary syndrome (including acute myocardial infarction and unstable angina pectoris). According to the American Heart Association, 25% of patients with coronary heart disease take sudden cardiac death as the first clinical manifestation. According to the domestic literature, 80% of adult deaths from sudden cardiac death are related to acute coronary syndrome. These patients died of acute myocardial ischemia.

The etiological basis of coronary heart disease is atherosclerosis, which leads to the decrease of coronary blood flow and myocardial perfusion. Under the inducement, acute coronary spasm or microcirculation embolism can occur, causing acute myocardial ischemia, causing electrophysiological disorder, leading to malignant arrhythmia and even sudden cardiac death.

2.cardiomyopathy

Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in cardiomyopathy. Hypertrophic cardiomyopathy (HCM) is a complex hereditary cardiomyopathy characterized by thickening of left ventricular wall, which has various clinical and genetic manifestations. It is a common cause of sudden death in adolescents, with a high missed diagnosis rate and 50% family history.

The research shows that the risk of sudden cardiac death such as having a history of ventricular tachycardia attack, severe left ventricular wall hypertrophy (≥30mm), unexplained syncope, family history of sudden cardiac death and exercise-related hypotension is obviously increased. It is suggested that all patients with family history of sudden death should be screened by echocardiography.

3. valvular disease

Cardiac valvular disease is also one of the risk factors of sudden cardiac death, including mitral stenosis and/or insufficiency, aortic stenosis and/or insufficiency, infective endocarditis, mitral valve prolapse (MVP) or chordae tendineae rupture. For example, severe aortic stenosis can cause a serious decrease in blood flow into the aorta and cardiac output, leading to sudden cardiac death.

In China, the incidence of valvular heart disease is high, which is mainly caused by rheumatic diseases, trauma, degeneration, congenital malformation, inflammation and other reasons. The structural function of one or more valves is abnormal, resulting in stenosis and/or insufficiency of the valve orifice.

4. Structural heart disease

Structural heart disease is a general term for a large class of diseases caused by abnormal heart structure, which mainly includes: congenital heart structure abnormality, valve abnormality, coronary artery dysplasia, acquired valve disease and so on.

Congenital cardiovascular diseases mainly include atrial septal defect, ventricular septal defect, patent ductus arteriosus, coarctation of aorta, congenital aortic or pulmonary valve stenosis, tetralogy of Fallot and so on. Such diseases increase the risk of sudden cardiac death. In particular, patients with left-to-right shunt congenital heart disease who develop to Eisenmenger syndrome and complex congenital heart disease are more prone to sudden cardiac death.

Abnormal coronary artery is the main cause of sudden death in young people. Especially after strenuous exercise. The clinical manifestations are angina pectoris, arrhythmia, syncope and even sudden cardiac death after strenuous exercise. Therefore, for special people who have uncomfortable symptoms after exercise, athletes and so on, congenital coronary artery dysplasia should be screened out.

5. Aortic disease

Aortic disease is one of the important factors leading to sudden cardiac death, and its main pathogenesis is fatal ischemia of target organs caused by aortic rupture and involvement of important branches. Among them, Stanford A aortic dissection is the most dangerous, and the main causes of sudden cardiac death include: aortic rupture, pericardial tamponade, dissection involving coronary artery leading to large-scale myocardial infarction, and involvement of brachiocephalic artery leading to cerebral infarction.

6. Pulmonary embolism

Pulmonary thromboembolism is a common emergency in cardio-pulmonary vascular diseases, and its incidence and mortality are extremely high.

The embolus source of pulmonary embolism can be endogenous or exogenous, and the embolic site is mainly in the trunk or main branch of pulmonary artery. Clinically, pulmonary embolism thrombus mainly comes from venous system or right atrial appendage. When patients have pulmonary embolism, pulmonary circulation disorder can occur in a short time, and sudden cardiac death can occur in severe cases.

In daily life, sudden cardiac death caused by pulmonary embolism is most common in "economy class syndrome", that is, the lower limbs are in a state of braking for a long time, which leads to venous thrombosis. Once a large thrombus falls off, it will lead to acute pulmonary embolism, and then sudden cardiac death can occur.

In addition, a considerable number of patients’ thrombi come from the right atrial appendage, mainly due to atrial fibrillation, so for such patients, it is also necessary to be alert to the occurrence of sudden cardiac death caused by pulmonary embolism.

7. Abnormal cardiac electrophysiological activity

Abnormal primary ECG or abnormal ion channels can induce sudden cardiac death, such as sinoatrial node lesions and abnormal cardiac conduction system (Lenegre disease or Lev disease, WPW syndrome, Q-T interval extension syndrome). This is an important cause of sudden death of teenagers.

Once the cardiac electrophysiological abnormality occurs, it may induce cardiac pacing conduction disorder, eventually leading to complete atrioventricular block, and even fatal arrhythmia such as ventricular tachycardia and ventricular fibrillation may occur, which may lead to insufficient blood output from the heart to brain tissue and the whole body, resulting in shock and syncope. If cardiac arrest lasts for 5 minutes, it can cause irreversible brain tissue damage and death, which will eventually lead to sudden cardiac death.

Sometimes, viral infection and other diseases may also involve the cardiac electrical conduction system, which increases the risk of sudden death of patients.

8. Explosive myocarditis

Early mortality is extremely high, which is another important cause of sudden cardiac death in children and young adults. The early symptoms of myocarditis are very similar to the common cold, only "a little uncomfortable", which is difficult to attract attention.

9. Kawasaki disease

The etiology is not clear yet. At present, it is considered that some patients are immune-mediated systemic vasculitis triggered by various infectious pathogens (viruses, bacteria, etc.). Kawasaki disease mostly occurs in children, which is one of the main causes of sudden death of children. Having Kawasaki disease in childhood can also cause myocardial infarction in adults.

10. Others

Other causes of sudden cardiac death mainly include: acute pericardial tamponade, intracardiac thrombosis, electrolyte disorder, sleep apnea and gene correlation.

Original title: How much do you know about sudden cardiac death? 》

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