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Adrenergic beta receptor blocking agents, or beta blockers, are routinely used in the treatment of patients with chronic obstruction of the arteries that supply blood to the heart muscle (coronary arteries). The use of this class of drugs in patients suffering acute bouts of coronary artery blockage (myocardial ischemia) is less well established. Although preliminary results indicate that beta blocker treatment may be beneficial in some cases, the drugs' side effects are poorly characterized, and more studies are required to fully evaluate the effects of beta blockers in acute ischemia. Percutaneous transluminal coronary angioplasty (PTCA), a technique of opening blocked coronary arteries by means of an inflatable balloon at the end of a catheter inserted into the artery, offers a model of temporary coronary artery blockage (which happens when the arterial balloon is inflated). This model was therefore used to evaluate the effects of the ultrashort-acting beta blocker esmolol in 16 patients (11 men and 5 women, ranging in age from 39 to 67 years). Ultrasound and electrocardiographic monitoring of heart function were performed continuously before, during, and after balloon inflation in patients during both drug-free and esmolol-treated conditions. An indicator of myocardial ischemia visible on an electrocardiogram, which is a graphic record of the heart's electrical conduction, is a prolongation and exaggeration of part of the wave known as the ST segment. This was seen in both control and drug-treated condition, but the change was greatly reduced (both in magnitude and duration) by drug treatment. Similarly, the decrease in ejection fraction (the percent of blood ejected from the ventricle during maximal contraction) seen during balloon occlusion was moderated by esmolol treatment, and the abnormalities of cardiac wall motion were delayed. Hence, treatment with esmolol diminishes the extent and delays the onset of myocardial ischemia during acute occlusion of the coronary arteries. (Consumer Summary produced by Reliance Medical Information, Inc.)