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We found reductions in heart rate and cardiac conduction and loss-of-function mutations in SCN5A in patients with idiopathic ventricular fibrillation associated with early repolarization. These findings support the hypothesis that decreased sodium current enhances ventricular fibrillation susceptibility.

SUMMARYTachycardia-induced cardiomyopathy is characterized by ventricular systolic dysfunction and congestive heart failure resulting from persistent or highly frequent tachyarrhythmias with uncontrolled heart rate. While reversible and often considered benign, few studies have examined the outcome of the disorder.The clinical characteristics, treatment, and long-term outcomes of 12 consecutive patients with tachycardia-induced cardiomyopathy (9 men, age, 51.9 ± 17.6 years) were studied. The mean period between the occurrence of tachyarrhythmias and the development of congestive heart failure was 26.0 ± 34.3 days. The mean heart rate on admission was 156.3 ± 28.7 beats/min. All patients had severe heart failure with a NYHA functional class of 2.3 ± 0.5, left ventricular ejection fraction of 0.32 ± 0.10, and brain natriuretic peptide level of 505.7 ± 449.1 pg/mL. In all patients, cardiac dysfunction recovered after 53.5 ± 61.3 days. During the follow-up of 53 ± 24 months, 2 patients had a recurrence of heart failure with uncontrolled tachyarrhythmia and 1 patient died suddenly.In tachycardia-induced cardiomyopathy, recurrent heart failure with uncontrollable tachyarrhythmia and sudden death were observed after recovery from cardiac dysfunction. A substrate for heart failure and/or life-threatening arrhythmia might persist, and careful, long-term follow-up seems required. (Int Heart J 2008; 49: 39-47)

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