MYOCARDIAL PROTECTION WITH CALCIUM-CHANNEL BLOCKERS DURING ISCHEMIA AND REPERFUSION BY PTCA

The effects of calcium channel blockers on acute myocardial ischaemia have been evaluated over the past two decades. A number of experimental studies have demonstrated that calcium antagonists protect the myocardium when administered before or during PTCA. Intracoronary verapamil prior to the second inflation attenuates the severity of ischaemic ST-segment changes and anginal pain. Heart rate and blood pressure are not influenced by verapamil or placebo. Similarly, there are multiple clinical and biological data suggesting that intracoronary nifedipine, diltiazem or bepridil, and intracoronary or intravenous nicardipine might result in a reduced incidence of myocardial ischaemia during PTCA. The beneficial effect of these drugs can be explained by a direct cardioprotective effect or by an enhanced collateral flow and haemodynamic improvement. During early reperfusion in acute myocardial infarction (AMI) administration of calcium channel blockers or agents that inhibit calcium release from the sarcoplasmic reticulum can protect hearts from stunning and can decrease the no-reflow phenomenon. The most recent explanation relates this observation to decreased sensitivity of the myofibrils to calcium. Further clinical and experimental studies are necessary to clarify the protective role in reperfusion injury. To summarize, therefore, administration of calcium channel blockers can decrease ischaemia during elective PTCA and can reduce reperfusion injury during early PTCA in AMI.