[Radionuclide ventriculographic evaluation of left ventricular systolic function in acute myocardial infarction]

Within 18 hours of acute myocardial infarction, global left ventricular (LV) function was evaluated by radionuclide ventriculography for 127 patients. Ejection fraction (EF) was calculated using a variable region of interest counts method. LV end-diastolic volume index (EDVI) was calculated from the LV outlines in the anterior and LAO projections using the area-length method. To validate the determination of EDV by the area-length method, the radionuclide EDV correlated with that derived from direct contrast angiography in 44 other patients who had both studies within two weeks, with an overall correlation coefficient of 0.84. To minimize any potential problems with the geometric ellipsoid model, the end-systolic volume index (ESVI) was calculated from EF and EDVI. Peak systolic blood pressure (PSP) was recorded with a cuff during imaging and the PSP/ESV calculated as a measure of LV contractile function. The regional wall motion of five segments in both the anterior and LAO projections were each scored on a scale, from 4 (= normal) to 0 (= dyskinesis). The wall motion index (WMI) derived from the sum of the 10 segment scores represented an overall index of wall motion (maximum = 40). In addition, the more widely used % abnormally contracting segments (%ACS) was calculated. The severity of wall motion abnormalities were associated with significant increases in heart rate and ESVI, whereas EDVI began to increase under more severe damage to the myocardium. Our data are consistent with those of Klein who found that the LV enlarges only when 20 to 25% of the surface area is rendered akinetic. There were significant decreases in EF and PSP/ESV with moderate reduction in wall motion, and the relation between EF and PSP/ESV was curvilinear. Information about ventricular volume and systolic blood pressure might be of additional value to EF for a more complete understanding of the changes in the functional state of the LV. Global LV function was compared between anterior and inferior myocardial infarcts. The size of %ACS was larger in anterior than in inferior infarction and a greater decrease in WMI in the former suggested larger infarct size in anterior infarction. As a result, ESVI was significantly larger in anterior infraction than in anterior infraction. However, an increase in EDVI was not significantly different between the two groups. EF was reduced to a greater extent in anterior than in inferior infarction. The overall data indicate that patients with anterior infarction have more severe impairment of left ventricular global function than do those with inferior infarction.