Beta-blockers for the treatment of angina pectoris: indications in relation to pathophysiological mechanisms.
In patients with ischaemic heart disease, therapeutic options should be selected on the basis of pathophysiological considerations. Classically, whereas calcium channel blockers and nitrates should be used in patients whose symptoms are more likely to result from coronary vasoconstriction, beta-blockers and revascularisation procedures should be considered when coronary flow reserve is severely limited by "fixed" atheroma. However, recent studies from our laboratory indicate that in patients with "mixed" angina whose symptoms are thought to be at least partially consequent to coronary vasoconstriction superimposed on atheromatous lesions of different severity, beta-blockers can also be effective in preventing episodes of myocardial ischaemia which occur during everyday life. Although most of these episodes are not apparently caused by an excessive increase in cardiac work, their number, severity, and duration are markedly reduced by beta-blocking agents. From these observations it is argued that, in patients with "mixed" angina, most ischaemic events are likely to be caused by transient reduction of regional myocardial perfusion, occurring for different levels of cardiac metabolic demand. The higher the latter, the more likely the former will be to precipitate clinical ischaemia.