Dying Suddenly - Sudden Cardiac Death
People at Risk
- Individuals who have coronary artery disease, especially those who have suffered myocardial infarctions ("heart attacks") in the past
- Individuals who have congestive heart failure of any cause
- Individuals with intrinsic heart muscle disease such as hypertrophic cardiomyopathy, idiopathic dilated cardiomyopathy, and arrhythmogenic right ventricular dysplasia
- Individuals with family history of heart muscle disease and SCD
- Individuals with syncope of unknown cause
- Individuals who abuse cocaine or heroin
Coronary artery disease is the underlying heart disease in 70 to 90% of individuals who succumb to SCD. Although many episodes of SCD are called "heart attacks," most of them, in fact, do not represent new myocardial infarctions. The arrhythmias that occur originate in previously damaged regions of the heart, and no new heart damage is necessary to start the arrhythmias.
Patients with congestive heart failure are at high risk of SCD. As left ventricular ejection fraction falls, the risk of SCD increases regardless of the underlying cause of the heart disease. Ironically, CHF patients who receive certain types of antiarrhythmic drugs are particularly prone to suffer proarrhythmic side effects of the medications because of interactions between the medications and the diseased tissue. Some non-antiarrhythmic medications, the beta blockers and angiotensin-converting enzyme inhibitors, have been shown to decrease the risk of SCD in CHF patients, but the degree of risk is still much higher than that of a normal healthy person.
SCD is frequently seen in individuals with heart diseases where the primary problem lies with the heart muscle cells themselves; these diseases are called cardiomyopathies. Different cardiomyopathies are caused by different cellular defects, but most of the cardiomyopathies are associated at one time or another with congestive heart failure and the formation of scar tissue in the ventricles. Since many cardiomyopathies are genetically transmitted, individuals in families that exhibit cardiomyopathy who have family members that have died suddenly appear to be more prone to SCD than those without a family history of SCD.
Syncope is spontaneous loss of consciousness. Since arrhythmias may cause syncope and may also be the first and only manifestation of heart disease, thorough cardiac evaluation following an episode of syncope is very important. Although the most common causes of syncope are relatively benign, "aborted" SCD should be considered as a possible cause of syncope, especially in a patient who has not been evaluated. If no heart disease is found after thorough evaluation and the history suggests a simple drop in blood pressure in the absence of arrhythmias, one can be reassured that the likelihood of life-threatening disease is low.
Many drugs have been associated with serious arrhythmias. Antiarrhythmic medications, when administered to patients with heart disease, can have proarrhythmic effects as noted above. Cocaine has been noted to cause spasm of the coronary arteries and, in large repeated doses, to have a direct toxic effect on the heart muscle. The cocaine-induced cardiomyopathy shows the same tendency toward arrhythmias as other cardiomyopathies. In addition, cocaine increases adrenaline and catecholamine levels in the bloodstream that further stresses the heart and exacerbates the tendency toward arrhythmias.