Genetic Risk Assessment of Defibrillator Events

Arrhythmias remain a major health problem, causing at least 250,000 deaths annually in the United States. Pharmacological treatments often do more harm than good, and device therapies are limited by high cost and effects on quality of life. Ion channel mutations cause rare inherited arrhythmopathies, but account for only a small fraction of patients with life- threatening arrhythmias and sudden death. Most arrhythmias occur during myocardial ischemia, following myocardial infarction, and in patients with poor left ventricular (LV) function of any etiology. Aside from ejection fraction (EF), few clinically useful indicators to stratify the risk of sudden death have been identified. The role of subtle difference in ion channel expression and/or structure in predisposing patients to arrhythmias and modulating the risk of sudden death is unknown. In this study, we are prospectively testing whether polymorphisms in ion channels and ion channel modifying genes are associated with arrhythmias in a population with internal cardioverter-defibrillators (ICDs) and poor LV function. We will test the hypothesis that functional polymorphisms in the coding sequences and promoter regions of cardiac genes (e.g. ion channels, beta-adrenergic receptors) predispose individuals to arrhythmias and /or heart failure progression. We hope to identify genetic predictors for the common forms of sudden cardiac death. This would allow the identification of a subpopulation of heart failure patients that would benefit most from ICD placement.