In vivo assessment of left ventricular wall and chamber dynamics during transient myocardial ischemia using prospectively ECG-gated computerized transmission tomography.

Abstract

Seven dogs were evaluated with prospective ECG-gated computerized transmission tomography (CTT) to analyze left ventricular (LV) wall thickness and cross-sectional chamber area after acute occlusion of the left anterior descending coronary artery (LAD). ECG-gated CTT scanning during i.v. administration of contrast material was performed over the mid-left ventricle at rest, after acute occlusion of the LAD and 30 minutes after release. The extent of systolic wall thickening (EWTh) of the anterior (potentially ischemic) segment was 39.8 +/- 8.8% (SEM) in the control state and -26.0 +/- 4.7% during LAD occlusion (p less than 0.01). The nonischemic septum demonstrated a compensatory increase in EWTh, from 28.6 +/- 3.5% to 46.4 +/- 6.1% during LAD occlusion (p less than 0.05). The end-diastolic LV luminal area (LVA) increased from 17.4 +/- 0.8 cm2 in the control state to 21.0 +/- 1.1 cm2 during LAD occlusion (p less than 0.01). End-systolic LVA also increased, from 11.0 +/- 0.9 to 15.2 +/- 1.1 cm2 (p less than 0.01). In addition, the percent change in LVA from end-diastole to end-systole declined from 37.4 +/- 3.8% during control to 28.0 +/- 2.6% during LAD occlusion (p less than 0.02). In conclusion, gated CTT demonstrates that the alterations in acute ischemia are characterized by changes in regional wall thickening dynamics, consisting of wall thinning during systole in the jeopardized segment and compensatory increase in the extent of systolic thickening in the normal segment, and changes in global LV function, consisting of an increase in the LVA and a decrease in the percent change of LVA during systole. Gated CTT may be useful for monitoring regional and global effects of ischemia when subjects can be studied in the supine position and with respiration suspended for 45 seconds.