[Left ventricular volume decrease during isovolumic relaxation period in gated blood pool scintigraphy: observations in patients with old myocardial infarction].

We studied left ventricular (LV) volume decrease, namely, the downward displacement of the LV volume curve, during the isovolumic relaxation period on the time-activity curves obtained from gated blood pool scintigraphy in patients with old myocardial infarction (OMI). To evaluate the mechanism and clinical significance of this phenomenon, 113 consecutive patients with OMI undergoing gated blood pool scintigraphy, left ventriculography, and Doppler echocardiography were studied. 1. This phenomenon was observed only in patients with anterior OMI (13 of 51 patients: 25%). Presence (Group I) or absence (Group II) of this phenomenon was examined. 2. On left ventriculography, dyskinetic or aneurysmal wall motion was observed in the anterior or apical region more frequently in Group I (11 of 13 patients: 85%) than in Group II (20 of 51 patients: 39%) (p < 0.001). 3. Doppler echocardiography showed that the presence of abnormal LV reversed flow over 20 cm/sec from the apex to the base during the isovolumic relaxation period is more frequent in Group I (7 of 13: 54%) than in Group II (4 of 51: 8%) (p < 0.001). These results suggested that this blood shift in the left ventricle is attributed to asynchronous LV relaxation occurring simultaneously with LV volume decrease on gated blood pool scintigraphy. In conclusion, this phenomenon suggests the presence of asynchronous LV relaxation.