Prediction of Ventricular Arrhythmias in Patients at Risk of Sudden Cardiac Death

Abstract

Sudden cardiac deaths remain the major cause of mortality in the western world. Ventricular arrhythmia due to ischemic heart disease is the most frequent cause of sudden cardiac death. In patients >35 years of age, ischemic heart disease is the most frequent cause of ventricular arrhythmias. In patients <35 years of age, inherited cardiac diseases play a significant role in sudden cardiac death. Prediction of who will experience a life-threatening ventricular arrhythmia is a major challenge in current cardiology. An implantable cardioverter defibrillator (ICD) provides efficient preventive treatment for ventricular arrhythmias and sudden death and is implanted in patients at risk. However, risk stratification of ventricular arrhythmias is insufficient and the majority of patients dying suddenly have not been evaluated for ICD therapy. Patients after myocardial infarction are at high risk for cardiac arrhythmic events and sudden cardiac death (Zipes, 2006). Currently, LV ejection fraction (EF) is the primary parameter used to select patients for ICD therapy after a myocardial infarction. Impaired EF is shown to be a marker of increased cardiovascular mortality and sudden cardiac death. However, EF has relatively low sensitivity to detect arrhythmic risk (Buxton, 2007). A number of other diagnostic tests have been proposed to improve the accuracy for selection of patients for ICD therapy. Currently available data, however, are not adequate to routinely recommend additional risk-stratification methods for selection of patients for ICD therapy (Passman, 2007). The presence of myocardial scar forms the substrate for malignant arrhythmias (Zipes, 1998). Heterogeneity in scar tissue may create areas of slow conduction that generate the substrate for ventricular arrhythmia post-myocardial infarction (Verma, 2005). Electrical dispersion, including both activation time and refractoriness, in infarcted tissue is a known arrhythmogenic factor, (Endresen, 1987; Han, 1964; Janse, 1989; Vassallo, 1988). Electrical abnormalities may lead to distorted myocardial function (Nagueh, 2008). Therefore, regional differences in electrical properties may cause heterogeneity of myocardial contraction which can be recognized as myocardial dyssynchrony (Yu, 2003). In this report, a novel echocardiographic method will be presented in order to evaluate the cardiac contractility pattern in patients at increased risk of life-threatening arrhythmias.