[Determination of myocardial risk on basis of the outcome of previous myocardial infarcts. Advantages of myocardial tomoscintigraphy using thallium with dipyridamole].

Exercise stress test, 24-hour-ambulatory electrocardiographic monitoring and myocardial perfusion 201-Thallium single photon emission computerized tomography (SPECT) with dipyridamole pharmacological stress probably have different sensitivities and specificities for the identification of residual ischemia after an acute myocardial infarction. Their clinical value is still a matter of debate. To comparatively evaluate various non-invasive methods, we studied 63 patients with previous myocardial infarction consecutively referred to our Nuclear Medicine Department to undergo myocardial dipyridamole (0.56 mg/kg) Thallium SPECT, by comparing scintigraphic results with those of the exercise stress test and Holter monitoring. In basal conditions, heart rate was 67 +/- 14 beats per minute; systolic and diastolic arterial pressures were 139 +/- 24 and 86 +/- 12 mmHg, respectively. Following intravenous dipyridamole, heart rate rose to 84 +/- 15 beats per minute (p < 0.0001), while systolic and diastolic pressures dropped to 133 +/- 26 and 79 +/- 13 mmHg, respectively (p < 0.0001; p < 0.0001). In only one patient with a non-Q wave myocardial infarction we did not observe any myocardial perfusion defect. Of 62 patients with stress perfusion defects, 53 (85.5%) showed reversible defects and 9 (14.5%) persistent defects. Of 53 patients with reversible defects, 29 (55%) showed defects at the infarct site, 6 (11%) had defects outside the infarct site and 18 (34%) had defects at as well as outside the infarct site. Forty-two patients were examined by both exercise stress test and myocardial SPECT imaging: SPECT demonstrated reversible perfusion defects in 34 (81%) of them, whereas exercise stress test showed evidence of residual ischemia in 24 (57%) (p < 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)