In vivo estimation of myocardial infarct size and left ventricular function by prospectively gated computerized transmission tomography.

Abstract

Eleven dogs were evaluated using computerized transmission tomography (CTT), 8 were studied after coronary occlusion and 3 served as sham controls. Ungated scans (1 cm deep) of the left ventricle (LV) were obtained from LV apex to base to determine infarct size (IS). At the middle LV level, prospectively gated scans were obtained to determine LV function. In all infarct dogs, contrast medium enhancement of the entire infarct or the periphery of the infarct occurred. Autopsy IS was compared with the IS by CTT using either the inner (IM) or outer margin (OM) of the contrast-enhanced periphery of the infarcts as the border of the infarct. IS by both CTT techniques correlated with well autopsy IS (r = 0.89 for IM; r = 0.93 or OM). The estimate using OM (26.5 .+-. 12 g) gave IS sizes similar to autopsy values (25.5 .+-. 11.7 g), but IS derived using IM (14.1 .+-. 8.0 g) underestimate autopsy values by .apprx. 45% (P < 0.01). From the prospectively gated CTT images, mid-LV end-diastolic (EDA) and end-systolic areas (ESA) were calculated as well as percent area change before and after coronary occlusion. EDA increased from 17.0 .+-. 5.3 cm2 to 23.7 .+-. 7.6 cm2 (P < 0.05). ESA increased from 12.1 .+-. 4.1 cm2 to 18.6 .+-. 7.2 cm2 (P < 0.05) and percent area change decreased from 29.3 .+-. 5.0% to 21.7 .+-. 9.9% (P < 0.05). Apparently, CTT imaging can reliably estimate IS, particularly when the area of rim enhancement of the infarct is included within the presumed infarct region. Estimates of chamber function can be made from gated CTT scans. Anterior myocardial infarctions produce left ventricular dilatation with reduced chamber function, which can be detected by gated CTT scans.