Background: Evidence is arising that calcium antagonists in idiopathic dilated cardiomyopathy (IDC) may have beneficial effects on virus-induced cardiopathology, alcohol toxicity, micro-circulatory disorders, and impaired calcium cycling, all possibly involved in the pathogenesis of the disease. Thus, the effect of adjunct diltiazem (60 to 90 mg TID) on standard treatment was investigated.
Methods and results: The Diltiazem in Dilated Cardiomyopathy (DiDi) trial was a randomized, double-blind, placebo-controlled, multicenter trial of 186 patients (92 receiving diltiazem, 94 receiving placebo) with IDC diagnosed by coronary angiography, catheterization of the left side of the heart, and a left ventricular ejection fraction of < 0.50 (mean, 0.34 +/- 0.11). The effect of adjunct diltiazem treatment on transplant listing-free survival, hemodynamics, exercise capacity, and subjective status was investigated. During the 24-month study period, 33 patients dropped out of the study; 153 patients finished the study protocol. Twenty-seven patients died or had a listing for heart transplantation: 16 in the placebo group and 11 in the diltiazem group. The transplant listing-free survival rate was 85% for diltiazem and 80% for placebo recipients (P = .444). After 24 months, only diltiazem significantly increased cardiac index at rest (P = .01) and under a workload (P = .02), systolic and diastolic pressures (P = .003 and P = .004), stroke volume index (P = .003), and stroke work index (P = .000) and decreased both pulmonary artery pressure under workload (P = .007) and heart rate (P = .001). Diltiazem also increased exercise capacity (P = .002) and subjective well-being (P = .01). Adverse reactions were minor and evenly distributed in both groups, except for an increase in the PQ interval in the diltiazem group.
Conclusions: In patients with IDC, the adjunct therapy of diltiazem improves cardiac function, exercise capacity, and subjective status without deleterious effects on transplant listing-free survival.