An investigation in patients with previous myocardial infarction who present with chest pain.

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Abstract
Patients [35] who presented with chest pain underwent mapping of the ECG with exercise and angiocardiography. 81mKr was used to assess regional myocardial perfusion before, during and after atrial pacing. Twelve of the 35 patients had negative exercise tests. Eight of these 12 had normal coronary arteries and 4 had .ltoreq. 50% stenosis of at least 1 major coronary artery. All 12 patients had uniform increases in regional myocardial perfusion (98 .+-. 14.0%) during atrial pacing. Thirteen of the 35 patients had a history of myocardial infarction and precordial areas of Q waves. During exercise, all 13 patients complained of chest pain and showed precordial areas of both ST-segment elevation and depression. These 13 patients had .gtoreq. 70% stenosis of at least 1 major coronary artery. Myocardial blood flow studies showed fixed defects of perfusion corresponding to the Q waves and ST-segment elevation. There were separate transient decreases of regional myocardial perfusion (70 .+-. 9.0%) during atrial pacing corresponding to ST-segment depression and chest pain. Ten of the 35 patients had a history of myocardial infarction and precordial areas of Q waves. During exercise, only 2 of these 10 complained of chest discomfort and all showed precordial areas of significant ST-segment elevation alone. All these patients had .gtoreq. 70% stenosis of one or more major coronary arteries. Myocardial blood flow studies showed fixed defects of perfusion that corresponded to Q waves. These areas showed no changes during atrial pacing. All the patients showed at least 1 remote region of myocardium that increased perfusion (74 .+-. 170%) throughout pacing. Patients with a history of myocardial infarction may present with chest pain. ST-segment elevation during an exercise ECG was not associated with chest pain or detectable myocardial ischemia. Regional perfusion in infarcted segments of myocardium did not change with atrial pacing. Separate precordial areas of ST-segment depression during exercise were associated with angina during exercise and pacing. ST-segment depression was also associated with the presence of a separate region of myocardium showing reversible disturbances of perfusion during pacing.