Effect of metoprolol and diltiazem on the total ischaemic burden in patients with chronic stable angina: a randomized controlled trial.

We conducted a randomised controlled trial to study the effects of metoprolol and diltiazem on the total ischaemic burden--sum of symptomatic and silent myocardial ischaemia, in 146 patients with stable angina pectoris. One-hundred thirty-four completed the study protocol. Sixty-eight patients received metoprolol (100 mg twice daily, n = 52, 50 mg twice daily, n = 16) while 66 received diltiazem (90 mg three times daily, n = 50, 60 mg three times daily, n = 16). The drugs were given for 4 weeks. The primary outcome variables were frequency and duration of total ischaemic burden, silent and symptomatic myocardial ischaemia. These were measured on 48 h of Holter monitoring. The reductions in duration and frequency of total ischaemic burden by metoprolol, 76% and 40%, respectively, were significantly higher than by diltiazem, 43% and 24%, respectively (P < 0.01 and P < 0.02). The frequency and duration of silent myocardial ischaemia, which constituted more than 80% of the total ischaemic burden in the two groups showed similar results. However, the reduction in frequency of symptomatic myocardial ischaemia only was significantly greater by metoprolol (63% than diltiazem (24%) as the difference in reduction of duration of symptomatic ischaemia was insignificant (85% vs. 75%; P > 0.05). Whether a greater reduction of total ischaemic burden by metoprolol as compared to diltiazem has any implications for prognosis in patients with chronic stable angina remains to be established.