Sudden cardiac death: role of left ventricular dysfunction.

Abstract

Early studies from the Coronary Drug Project of sudden cardiac death in patients surviving an episode of myocardial infarction called attention to the importance of ventricular ectopic beats.' In that study, complex ventricular ectopic beats recorded on a 12-hour Holter electrocardiogram were found to be associated with an excessive risk of sudden cardiac death. When the relationship was examined between complex ventricular ectopic beats and other risk factors, such as age, number of prior infarctions, angina pectoris, hypertension, serum cholesterol, glucose intolerance, cardiomegaly seen on chest X-ray films, and cigarette-smoking, complex ventricular ectopic beats were found to be independent risk factors with respect to sudden cardiac death. The importance of ventricular ectopic beats as a predictor of sudden cardiac death during the convalescent or late hospital phase of acute myocardial infarction in this and other studies has led to the use of prophylactic antiarrhythmic therapy in an attempt to prevent or reduce these ectopic beats and hence to prevent sudden cardiac death. In a subsequent study by Schulze et al. patients surviving an episode of acute myocardial infarction underwent 24-hour Holter electrocardiographic recording and gated radionuclide left ventricular angiography prior to discharge from the hospital.? Several important findings emerged from this study: It was noted that 26 of 29 (90%) patients with complex ventricular arrhythmias (Lown Class 111-V) on Holter electrocardiographic recording had a left ventricular ejection fraction of <40% compared with only 19 of 52 (37%) without complex ventricular arrhythmias. During a mean follow-up period of 7 months, eight patients had documented ventricular fibrillation. All eight patients who suffered sudden death were in the subset of patients with complex late hospital phase ventricular arrhythmias and a left ventricular ejection fraction of <40%. This study was one of the first to call attention to the role of ventricular dysfunction in patients with sudden cardiac death after an episode of acute myocardial infarction. The failure of left ventricular dysfunction to be recognized as an important predictor of sudden death after myocardial infarction in the Coronary Drug Project and in other previous studies may be related to the use of the cardiothoracic (CT) ratio on chest X-ray film as an index of left ventricular function. Subsequent studies have pointed out that the CT ratio is a poor index of left ventricular function and that the correlation between the CT ratio and left ventricular ejection fraction is poor. Schulze et al. also found that the left ventricular ejection fraction and the percent of left ventricular akinesia on gated blood pool imaging were significantly better predictors of subsequent sudden cardiac death than was peak creatine phosphokinase (CPK) determined during the episode of acute infarction. Patients who subsequently died suddenly had