Treatment of acute myocardial infarction: a cardiologist's perspective

The treatment of acute myocardial infarction can generally be organized along three pathways. First, interventions directed toward alleviating acute myocardial ischemia include oxygen, sublingual nitroglycerin, morphine, aspirin, heparin, and intravenous nitroglycerin. Appropriate patients may also benefit from beta-adrenergic blockers, thrombolytic agents, intra-aortic balloon counterpulsation, and revascularization with either coronary angioplasty or bypass graft surgery. Second, interventions directed toward assessing and treating acute left ventricular dysfunction include invasive hemodynamic monitoring and echocardiography; maximizing preload; correcting blood gas, serum electrolyte, acid-base, or hemoglobin abnormalities; controlling heart rate; and maintaining AV conduction. Pharmacological agents to consider include diuretics, nitroglycerin, nitroprusside, dobutamine, dopamine, norepinephrine, and amrinone. Support devices, coronary angioplasty, and cardiac surgery are also occasionally needed. Third, interventions directed toward preventing or treating arrhythmias and conduction disturbances include atropine, isoproterenol, beta-blockers, verapamil, digitalis, adenosine, lidocaine, procainamide, bretylium, amiodarone, countershock, and cardiac pacing. All of the above information has been drawn from studies in nonsurgical patients. Unfortunately, there is little in the cardiology literature about treatment of patients with perioperative MI [17]. It is of interest to note that most perioperative MI occurs in the postsurgical period, not intraoperatively, and is often painless. As discussed throughout this volume, controlling postoperative stresses--including surgical complications, pulmonary complications, fluid and electrolyte abnormalities, and heart rate and blood pressure responses--is probably important. Serial cardiac enzymes and electrocardiograms improve the diagnostic yield. Treatment options are limited by the fact that many events are non-Q wave infarctions. Also, the increased risk of bleeding from the operative site precludes use of antiplatelet, anticoagulation, and thrombolytic agents. Hemodynamically or electrically unstable patients should be referred for emergency cardiac catheterization and probable coronary angioplasty. Patients at risk for large Q wave MI, heralded by ST-segment elevation in several electrocardiographic leads, should also be considered for invasive treatment. Further clinical investigation of the natural history, diagnosis, and treatment of perioperative MI is sorely needed.