Cardiomyopathies and their role in sudden death.

Frequent ventricular premature complexes, complex ventricular ectopic activity and asymptomatic ventricular tachycardia are common to both hypertrophic and dilated cardiomyopathy; in both conditions, sudden death is a common occurrence. Asymptomatic young patients with hypertrophic cardiomyopathy who have a family history and a high incidence of ventricular arrhythmias have a particularly high incidence of sudden death. In patients with hypertrophic cardiomyopathy, efforts to attribute sudden death to the cardiac index, left ventricular end-diastolic pressure, left ventricular outflow obstruction, ejection fraction, age, symptomatic state and septal thickness have been unrewarding. Myocardial hypertrophy and disordered myocardial cell arrangement are the likely substrates for the development of ventricular arrhythmias in hypertrophic cardiomyopathy. Ventricular fibrillation preceded by ventricular tachycardia appears to be the terminal event in most patients who die suddenly. In some patients, cardiac asystole is the terminal event. Additional factors playing a role in the development of the substrate for sudden death in patients with hypertrophic cardiomyopathy vary in importance on an individual basis. These factors include narrowing of septal arteries and the artery to the atrioventricular node, preservation of fetal anatomy with dispersion in the atrioventricular node and His bundle, fibrosis of the sinus node, clefts in the septum, multiple atrioventricular pathways and massive myocardial infarction. Patients with dilated cardiomyopathy appear to have the highest incidence of ventricular arrhythmias of any disease yet studied. The substrate for the development of ventricular arrhythmias in these patients appears to be myocardial hypertrophy and myocardial fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)