QTc interval as a guide to select those patients with congestive heart failure and reduced left ventricular systolic function who will benefit from antiarrhythmic treatment with dofetilide

Background-A prolonged QTc interval is considered a contraindication for cl ass III antiarrhythmic drugs, but the influence of a normal or a slightly i ncreased baseline QTc interval on the risk or benefit of treatment with a c lass III antiarrhythmic drug is not sufficiently clarified. Methods and Results-This prospectively defined substudy included 703 patien ts enrolled in the Danish Investigations of Arrhythmia and Mortality on Dof etilide-Congestive Heart Failure (DIAMOND-CHF) study. Patients included had moderate to severe CHF and reduced left ventricular systolic function, Bas eline 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 (minimum 1 year), 285 patients (41%) died. Baseline QTc interv al had no prognostic value on survival in placebo-treated patients. In dofe tilide-treated patients, a baseline QTc interval <429 ms was associated wit h a significant risk reduction (risk ratio 0.4, 95% CI 0.3 to 0.8). With in creasing QTc interval, the risk increased gradually, and for QTc interval > 479 ms, risk ratio was 1.3 (0.8 to 1.9). Conclusions-A baseline QTc interval within normal limits is associated with a marked reduction of mortality in patients with CHF and left ventricular systolic dysfunction treated with dofetilide, This is a potentially importa nt indication of which patients with CHF might benefit from prophylactic tr eatment with an antiarrhythmic drug.