Influence of Calcium Channel Antagonist Therapy on the Ischemic Response to Acute Coronary Occlusion in Humans

The effects of calcium channel blockers on myocardial ischemia in humans can be evaluated in studies reporting changes during coronary angioplasty. These studies indicate that the extent and duration of myocardial ischemia in most patients with single vessel coronary artery disease can be improved somewhat by calcium channel blockers. The anti-ischemic effects of intravenous diltiazem, nifedipine, nisoldipine, and nicardipine are discussed. Intravenous diltiazem produces effects similar to intracoronary, but not systemic, nifedipine. Intracoronary nifedipine and nicardipine produce similar degrees of cardioplegia in most studies. Nicardipine and nisoldipine also reduce signs of myocardial ischemia, although different mechanisms are postulated to be involved. Although clinically beneficial in some patients, data indicate that the cardioprotective effect of calcium channel blockers during supply-side ischemia is less potent than reperfusion with blood. For the most part, calcium channel antagonists function through reduction of myocardial oxygen demand with rare agents favorably influencing collateral flow or providing direct myocardial protection. The potential myocardial cellular effects of calcium channel blockers on supply-side ischemia merit further investigation.