Prediction of cardiac events after uncomplicated myocardial infarction: a prospective study comparing predischarge exercise thallium-201 scintigraphy and coronary angiography.

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Abstract
The ability of predischarge quantitative exercise 201Tl scintigraphy to predict future cardiac events was evaluated prospectively in 140 consecutive patients with uncomplicated acute myocardial infarction; the results were compared with those of submaximal exercise treadmill testing and coronary angiography. High risk was assigned if scintigrapohy detected 201Tl defects in more than 1 discrete vascular region, redistribution or increased lung uptake, if exercise testing caused ST segment depression .gtoreq. 1 mm or angina or if angiography revealed multivessel disease. Low risk was designated if scintigraphy detected a single-region defect, no redistribution, or no increase in lung uptake, if exercise testing caused no ST segment depression or angina or if angiography revealed single-vessel disease or no disease. By 15 .+-. 12 mo., 50 patients had experienced a cardiac event; 7 died (5 suddenly), 9 suffered recurrent myocardial infarction and 34 developed severe class III or IV angina pectoris. Compared with that of patients at low risk, the cumulative probability of a cardiac event was greater in high-risk patients identified by scintigraphy (P < 0.001), exercise testing (P = 0.011) or angiography (P = 0.007). Scintigraphy predicted low-risk status better than exercise testing (P = 0.01) or angiography (P = 0.05). Each predicted mortality with equal accuracy. However, scintigraphy was more sensitive in detecting patients who experienced reinfarction or who developed class III or IV angina. When all 50 patients with events were combined, scintigraphy identified 47 high risk patients (94%), whereas exercise-induced ST segment depression or angina detected only 28 (56%) (P < 0.001). The presence of multivessel disease as assessed by angiography identified 9 more patients with events than exercise testing (P = 0.06). However, the overall sensitivity of angiography was lower than that of scintigraphy (71% vs. 94%; P < .01) because 3 patients who experienced reinfarction and 10 who developed class III or IV angina had single-vessel disease. Importantly, 12 (92%) of these 13 patients with single-vessel disease who had an event exhibited redistribution on scintigraphy. Apparently, submaximal exercise 201Tl scintigraphy can distinguish high- and low-risk groups after uncomplicated acute myocardial infarction before hospital discharge; 201Tl defects in > 1 discrete vascular region, presence of delayed redistribution, or increased lung thallium uptake are more sensitive predictors of subsequent cardiac events than ST segment depression, angina or extent of angiographic disease; and low-risk patients are best identified by a single-region 201Tl defect without redistribution and no increased lung uptake.