Abstract
The role of calcium channel blockers in acute myocardial infarction (MI) remains controversial, but increasingly these agents are being employed in the management of postinfarction angina and for prophylaxis against reinfarction. Few studies have examined systematically the effect of calcium channel blockers on left ventricular (LV) function during the early course of acute MI. We studied changes in global and regional LV function in a subset of patients from the multicenter, prospective Diltiazem Reinfarction Study of non-Q wave MI. Seventy-four patients who were randomized to diltiazem (360 mg/day) or placebo within 24-72 h of MB-creatine kinase confirmed non-Q wave MI underwent sequential multigated radionuclide ventriculography before and after treatment group assignment. LV ejection fraction (EF) using standard count volume techniques and regional wall motion were analyzed by group consensus (dividing the LV into 11 segments) and was assessed by: (a) summing the number of asynergic LV segments, and (b) calculating a 'regional wall motion score' as the sum of all segments, using a nonordinal 5-point semiquantitative scale ranging from hyperkinetic (-1) to dyskinetic (+4). The baseline (early) and follow-up (predischarge) radionuclide ventriculograms (RVGs) were obtained 50.5 ± 12.8 h and 10 ± 2 days after onset of non-Q wave MI, respectively. All patients were permitted to have concurrent treatment with standard medical therapy during the randomized study; 67% of the study group were receiving beta-blockers, and 91% were taking long-acting nitrates. Early and late mean LVEF values for the diltiazem subgroup (n = 39) were 49 ± 15 and 51 ± 13% versus 53 ± 9 and 55 ± 9% for the placebo subgroup (n = 35), respectively. There were no significant between-group differences in regional function when mean values for the number of asynergic LV segments or regional wall motion scores were compared for early versus late RVGs during diltiazem or placebo treatment. However, when regional wall motion score from the late RVG was compared to the early RVG, 24 patients (32%) exhibited improvement (13 on diltiazem, 11 on placebo), 16 patients (22%) showed worsening (8 on diltiazem, 8 on placebo) and 34 patients (46%) showed no significant change (18 on diltiazem, 16 on placebo). Only 1 of the 39 patients assigned to diltiazem experienced clinical congestive heart failure as an adverse drug effect during the study period, and in none of the 16 patients whose EF deteriorated between the early and late RVG did heart failure develop. We conclude that global and regional LV function is not adversely affected by high-dose (360 mg/day) diltiazem treatment for non-Q wave MI, despite use of concurrent nitrate and beta-blocker therapy in 91 and 67% of the group, respectively. These data indicate that diltiazem is safe and apparently devoid of clinically significant negative inotropic effects in the early (2- to 14-day) post-non-Q wave MI period.