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

We evaluated 11 dogs using computerized transmission tomography (CTT); eight were studied after coronary occlusion and three 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 well with autopsy IS (r = 0.89 for IM; r = 0.93 for 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) underestimated autopsy values by approximately 45% (p<0.01). From the prospectively gated CTT images, we calculated mid-LV end-diastolic (EDA) and end-systolic areas (ESA) 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). We conclude that 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.