FAQ on Sudden Death and Myocarditis
Written By Monte Willis MD, PhD, FASCP, FCAP
What is sudden death?
A: Sudden death is the sudden, unexpected death, caused by a loss of heart function. It occurs most often as a result of sustained abnormal electrical activity in the heart. This can result from structural problems in the heart and as a result of heart attacks. But the causes of sudden cardiac death are diverse.
How does it present clinically?
A: Sudden cardiac death is responsible for up to one half of heart disease deaths. It is not a specific disease itself, but results from a number of very common heart diseases including heart attacks and myocarditis. It might be best recognized from media reports featuring apparently health young athletes that die during physical activities. Many times these young athletes have an underlying genetic heart disease that results in death despite their athletic training. Similarly, myocarditis can occur in athletes following an infection (see FAQ on viruses and bacteria that cause myocarditis).
What are the known causes of sudden death?
A: There are multiple causes of sudden death. As many as 70% of sudden death cases have been attributed to coronary heart disease, including heart attacks and heart failure 1. The actual incidence of sudden death due to myocarditis is not known, but in routine autopsies, 1-9% of patients demonstrate evidence of cardiac inflammation; in young adults up to 20% of sudden death cases have been reported to be due to myocarditis 2. Up to 50% of patients with HIV have evidence of myocarditis on autopsy 3.
Other acquired and hereditary causes, including left ventricular hypertrophy (enlarged heart usually due to high blood pressure), hypertrophic cardiomyopathy (due to genetic mutations in heart proteins), arrhythmogenic right ventricular cardiomyopathy (also due to genetic mutations in heart proteins), mitral valve prolapse (mainly secondary to infections), and congenital coronary artery anomalies (due to inherited defects) have been reported. Another 10-12% of cases under the age of 45 (~5% in those older) occur without structural heart disease1.
Are there factors that increase ones risk of sudden death?
A: Several factors are associated with an increased risk of sudden death, including high blood pressure, high cholesterol (High LDL, low HDL), cigarette smoking, physical inactivity, obesity, diabetes mellitus, and a family history of premature death (sudden death) 4-9.
Can exercise put susceptible people at risk of sudden death?
A: The risk of sudden death increases during exercise and for 30 minutes after strenuous exercise 7,10. However, the actual risk during any one episode is extremely low (1 per 1.5+ million hours of exercise) 10. The transient increase in risk is lower among those who regularly exercise 7,10. And this small increase in risk is far outweighed by the benefits of reducing the risk of sudden cardiac death by exercising 9,11. The exception to this is in people with inherited heart diseases, which put them a higher risk of sudden during exercise, including hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, long QT syndrome subtypes, and myocarditis 12,13.
Can caffeine increase risk of sudden death?
A: Caffeine has been studied as a potientiator of sudden death risk 14. No associations have been found in the limited data collected so far.
Can sudden death be predicted?
A: Generally, sudden death cannot be predicted, which makes the disease so insidious. But people at risk can be screened (e.g. stress testing and ECG monitoring) and may benefit from specific interventions if issues are identified.
Can risk factors be reduced?
A: Primary interventions: Maybe. Effective treatment of high cholesterol, high blood pressure, the adoption of a heart-healthy diet, regular exercise, smoking cessation, moderation of alcohol consumption, and diabetes treatment/management may decrease the risk of sudden death. While studies have demonstrated that interventions to reduce risk factors reduces coronary heart disease, the most common cause of sudden death, risk factor reduction on sudden death itself has not been extensively studied 1.
Secondary interventions: Implantable cardioverter-defibrillator (ICD) devices are the preferred modality of survivors of sudden death 1. ICDs can detect abnormal electrical signals in the heart which dont allow the heart to pump blood, and correct them with a shock. While ICDs do not prevent malignant arrhythmias (abnormal electrical signals), it terminates them when they (rarely) happen so the heart can continue pumping. Anti-arrhythmic drugs can also be given to prevent these abnormal electrical signals in the heart.
- Siscovick DS, Podrid PJ, eds. Overview of sudden cardiac arrest and sudden cardiac death. Waltham, MA: Wolters Kluwer Health; 2012.
- Feldman AM, McNamara D. Myocarditis. The New England journal of medicine 2000;343:1388-98.
- Cooper LT, Jr. Myocarditis. The New England journal of medicine 2009;360:1526-38.
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- Siscovick DS, Raghunathan TE, King I, et al. Dietary intake and cell membrane levels of long-chain n-3 polyunsaturated fatty acids and the risk of primary cardiac arrest. JAMA : the journal of the American Medical Association 1995;274:1363-7.
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- Maron BJ, Carney KP, Lever HM, et al. Relationship of race to sudden cardiac death in competitive athletes with hypertrophic cardiomyopathy. Journal of the American College of Cardiology 2003;41:974-80.
- Corrado D, Basso C, Schiavon M, Thiene G. Screening for hypertrophic cardiomyopathy in young athletes. The New England journal of medicine 1998;339:364-9.
- Weinmann S, Siscovick DS, Raghunathan TE, et al. Caffeine intake in relation to the risk of primary cardiac arrest. Epidemiology 1997;8:505-8.