Can a baseline heart-rhythm measurement help identify which heart failure patients might benefit from dofetilide?

Details

A prolonged QTc interval is considered a contraindication for class III antiarrhythmic drugs. However, how a normal or slightly increased baseline QTc interval affects the risks or benefits of these drugs has not been sufficiently clarified.

This prospectively defined substudy included 703 patients enrolled in the Danish Investigations of Arrhythmia and Mortality on Dofetilide-Congestive Heart Failure (DIAMOND-CHF) study. The patients had moderate to severe congestive heart failure (CHF) and reduced left ventricular systolic function. Baseline QTc interval was measured before randomization to either dofetilide, a new class III antiarrhythmic drug, or placebo.

During a median follow-up of 18 months, with a minimum of 1 year, 285 patients (41%) died. Baseline QTc interval had no prognostic value for survival in placebo-treated patients. In dofetilide-treated patients, a baseline QTc interval <429 ms was associated with a significant reduction in mortality risk (risk ratio 0.4, 95% confidence interval 0.3 to 0.8). As QTc interval increased, risk rose gradually; for QTc interval >479 ms, the risk ratio was 1.3 (0.8 to 1.9).

The researchers concluded that a baseline QTc interval within normal limits was associated with markedly reduced mortality in patients with CHF and left ventricular systolic dysfunction treated with dofetilide. They described this as a potentially important indication of which patients with CHF might benefit from prophylactic treatment with an antiarrhythmic drug.