Prediction of life-threatening arrhythmias--still an unresolved problem.

A major challenge in current cardiology is to predict who will die suddenly from ventricular arrhythmias. Ventricular arrhythmias are the most common cause of sudden cardiac death, occurring in about 1-2:1,000 inhabitants yearly, and is most frequently due to coronary artery disease. Patients with increased risk of ventricular arrhythmias can be offered medical treatment and ultimately an implantable cardioverter defibrillator (ICD). Left ventricular ejection fraction (EF) is currently the main risk stratification tool used to select patients for ICD therapy. However, EF is insufficient in predicting arrhythmic risk. A number of techniques have been presented to improve arrhythmic risk stratification without having reached clinical utility. Conduction abnormalities and dispersion of action potential duration forms the substrate for malignant ventricular arrhythmias in infarcted tissue as in several cardiomyopathies. The ability to assess electrical dispersion in patients noninvasively has been limited. Myocardial strain by echocardiography has been presented as an accurate tool for assessing myocardial function and timing. Inhomogeneous and dispersed myocardial contraction has been related to the occurrence of ventricular arrhythmias and seems to be a promising tool in risk stratification. This review focuses on arrhythmia mechanisms and novel echocardiographic tools for assessing risk of ventricular arrhythmias.