TREATMENT OF CHRONIC MYOCARDIAL-ISCHEMIA - RATIONALE AND TREATMENT OPTIONS

A rational approach to the treatment of chronic myocardial ischemia re quires an appreciation of the pathophysiology of coronary artery disea se and the treatment options available. Any factor that causes an imba lance between myocardial oxygen supply and demand can provoke ischemia . Myocardial oxygen requirements rise with increases in heart rate, co ntractility, or left ventricular wall stress. Myocardial oxygen supply is determined by coronary artery flow and myocardial oxygen extractio n. Anti-anginal medications are the mainstay of anti-ischemic manageme nt and act to correct the balance between myocardial supply and demand by increasing coronary blood flow, reducing myocardial oxygen require ments, or both. These medications include nitrates (which act principa lly by venous vasodilation, but also probably by coronary dilation), b etablockers (which act mainly by reducing heart rate and cardiac contr actility), and calcium channel blockers (which act principally by arte rial and coronary vasodilation). The choice of therapy and its effecti veness depend on the underlying cause of ischemia. The complimentary m echanisms of action of these drug classes suggest that their use in co mbination may result in a greater reduction in myocardial oxygen deman d than that achieved with monotherapy. In addition, the pharmacologica l actions of some of these drugs may serve to offset the undesirable s ide effects associated with others, for example, the reflex tachycardi a produced by some calcium channel blockers may be offset by beta-bloc ker therapy. Finally, aspirin and lipid-lowering drugs and the potenti al role for anti-oxidants must also be considered in combination thera py. Invasive techniques for myocardial ischemic management, such as co ronary artery bypass and coronary angioplasty, improve myocardial oxyg en supply by relieving or circumventing the atherosclerotic obstructio n responsible for ischemia. Surgery is the preferred technique in pati ents with certain medical conditions, for example, those with triple-v essel disease, but is not recommended in patients with mild angina unl ess left main artery disease is present.