Comparison between M-mode echocardiography and 201thallium myocardial scintigraphy for diagnosis of transient myocardial ischemia

Purpose of this study was to evaluate the capability of M-mode echocardiography (M-mode) and of 201Thallium myocardial scintigraphy (201T1) to detect transient myocardial ischemia at rest in man. Fourteen male patients (pts) were studied by the two techniques under basal conditions and during episodes of angina at rest. Data were obtained in 2 pts in rapid succession during the same episode, in the remaining 12 pts in different episodes with electrocardiographic changes similar in site, type, entity and duration. Echocardiographic criteria of transient ischemia (reversible asynergies and transient reduction of systolic thickening) were present in 9/11 pts during episodes of ST segment elevation; the scintigraphic ones (reversible perfusion defects) in 10/11 pts. In 3 pts during episodes of ST segment depression M-mode was positive in 2, 201T1 in all three. The poor acoustic window in 2 pts and the involvement in one of left ventricular lateral wall not seen by M-mode on parasternal approach, may account for the 3 false negatives of M-mode. The single false negative of 201T1 can be related to the short duration (1') of the episode. A complete correspondence of site of ischemia, detected by ECG, M-mode and T1, was observed. In conclusion, M-mode appears a reliable technique for detecting transient ischemic episodes, being the main limits the acoustic window and the incapacity in exploring all ventricular walls and the main advantage the high temporal resolution, which permits to study continuously the full sequence of the ischemic event. On the other hand 201T1 does not allow detection of episodes of short duration. This two techniques, when combined in anginal patients, provide complementary information on perfusion and contraction respectively. The reliability of these techniques in the assessment of transient myocardial ischemia is the basis for their possible diagnostic use in pts with transient specific ECG changes or with typical anginal pain without ECG evidence of ischemia.