Sudden Cardiac Death (SCD) refers to an unexpected death from a cardiovascular cause in an individual with or without pre-existing heart disease according to Dr. Steven Reisman, a Manhattan Cardiologist. This usually is a death occurring within one hour of an acute change in clinical status or an unexpected death that occurred within the previous 24 hours.
In the United States the incidence of sudden cardiac death varies between an 180,000 to 450,000 deaths per year. SCD still accounts for greater than 50 percent of all coronary heart disease (CHD) deaths, and approximately 15-20 percent of all deaths in the United States.
The incidents of SCD increases with age regardless of race or sex. Women, at any age have a lower incidence in SCD than men. Approximately two-thirds of women who present with SCD have no known history of heart disease compared with 50 percent of men.
A variety of risk factors have been proposed for the pathophysiology of SCD. CHD is the most common underlying disease associated with SCD in the western world being responsible for approximately 75 percent of SCD. Cardiomyopathies such as dilated and hypertrophic along with primary electrical disorders are responsible for the remainder. CHD in relation to SCD occurs in three settings including acute myocardial infarction, ischemia without infarction, and structural alteration such as scar formation with ventricular dilatation. The mechanism of SCD in cases without acute myocardial infarction is likely an electrical event due to a ventricular arrhythmia which is a caused by ischemia or other arrhythmogenic stimuli in a chronically diseased heart. It is suggested that approximately 90 percent of deaths that occur within one hour of symptom onset are arrhythmic in nature.
Coronary heart disease or congestive heart failure significantly increases SCD risk of the population. SCD risk factors may be similar to CHD risk factors. Risk factors for sudden cardiac death include smoking, diabetes mellitus, and hypertension. There are certain measurements on the standard resting electrocardiogram that may serve as risk factors for SCD including an elevated resting heart rate, prolonged QT interval and prolonged QRS duration. Some studies have suggested early repolarization as a risk factor for sudden cardiac death.
Certain nutritional patterns may provide protection for the risk of SCD. In some studies consuming fish one to two times per week was associated with approximately a 50 percent reduction in SCD risk. Light to moderate levels of alcohol consumption may be associated with reduced risk of SCD. In some studies it is suggested that an increase in plasma magnesium levels may provide protection for SCD. In addition, a mediterranean diet appears to provide some protection for SCD.
There are certain triggers that may be associated with SCD. There may be a certain diurnal variation to SCD with the greatest incidence occurring in the morning hours from 6am to noon. Certain studies have suggested the highest risk of out of hospital arrest may be on Mondays. These patterns may suggest activity with psychological exposure playing a role in triggering SCD. Although there are long term benefits of exercise, it is also suggested that SCD occurs with a higher than average frequency during or shortly after vigorous exertion. Chronic habitual exertion may result in increase cardiac electrical stability but transient vigorous exercise may have an increased risk for SCD. Both depression and acute mental stress may trigger SCD and acute increases have been seen in situations such as populations experiencing disaster such as earthquake along with life stresses such as the death of a spouse or loss of a job.
The New York Cardiac Diagnostic Center along with Dr. Steven Reisman, a cardiology doctor in NYC, promotes early diagnosis of heart disease and strategies to increase both awareness and prevention of triggers and risk factors related to both coronary heart disease and sudden cardiac death.