Mechanisms of arrhythmias in heart failure.

The diagnosis of heart failure infers a bad prognosis. Mortality is high and many patients die suddenly. Ventricular arrhythmias, commonly observed in patients with heart failure, are thought to underlie at least some of these sudden deaths. The mechanism of arrhythmias occurring in the setting of heart failure is still unclear. Experimental evidence points to a higher tendency for failing myocardium to develop delayed and early afterdepolarization-induced triggered activity and automaticity. Conditions favoring reentry also have been described in failing hearts. Modulating factors such as sympathetic activation, electrolyte disturbances, and chronic stretch are present in the setting of heart failure and may favor all of the mentioned mechanisms of arrhythmias. Clinical evaluation of arrhythmias in patients and animals with heart failure and the effects of pharmacologic treatment of ventricular arrhythmias in patients with depressed left ventricular function further accentuate that more than one mechanism of arrhythmia may be operating in heart failure and underscore the importance of modulating factors such as sympathetic activation and stretch.