Detection of Regional Myocardial Dysfunction During Ischemia with Computerized Tomography Documentation and Physiologic Basis

Abstract

Cross-sectional imaging techniques have the potential for measuring left ventricular (LV) wall thickness (WTh) dynamics. This proposition was assessed in a canine experimental model, using prospectively gated computed tomography (CT) scans before and after occlusion of a coronary artery. Gated CT scans detected loss of wall thickening in the LV anterior segment immediately after occlusion of the left anterior descending coronary artery in two dogs. After demonstrating the feasibility of using gated CT scans to demonstrate ischemic functional abnormalities by monitoring wall thickness changes, we assessed the relationship between regional wall thickening dynamics and coronary blood flow in eight anesthetized dogs. Graded circumflex (Cx) coronary artery stenosis (CAS) was produced while sonomicrometer crystals continuously recorded LV WTh and extent of wall thickening (EWTh) in the anterior descending and the Cx distributions. The first significant change in EWTh in the ischemic segment occurred at 33% decrease in CBF (P less than .05) which corresponded to an 80% CAS. At 33% decrease in CBF, there was a concomitant increase in EWTh in the normal segment. In conclusion, we have demonstrated the feasibility of using gated CT to detect myocardial ischemia by monitoring WTh dynamics. Physiologic studies document a close relationship between regional wall thickening dynamics and coronary blood flow and should provide a basis for interpretation of dynamic cross-sectional images of the left ventricle in ischemic heart disease.