Detection of myocardial ischemia by electron beam CT - Experimental studies

Purpose. To determine if contrast-enhanced electron beam CT (EBCT) can dete ct areas of acute myocardial ischemia, and if pharmacological stress testin g improves the diagnostic accuracy of EBCT. Material and Methods. We injected 0.5 ml/kg and 1.0 ml/kg b.w. of iopromide at a rate of 4 ml/s into the right atrium of 5 ventilated female minipigs at rest and after occlusion of the left anterior descending (LAD) coronary artery. Both ventricles were examined at six short axis levels with an EBCT unit. Myocardial perfusion was calculated from the time-density curves of four left ventricular myocardial segments and the aorta. We also tested the effect of the contrast agent on myocardial density after i.v. administrati on of 0.6 mg/kg dipyridamole before and after LAD occlusion. Results: At rest, the contrast agent increased myocardial density by 28 +/- 2 HU, corresponding to a myocardial perfusion estimate of 67 +/-7 ml/min/10 0 g. After dipyridamole, myocardial density increased by 29 +/-4 HU. Follow ing occlusion of the LAD, anteroseptal myocardium displayed 10 +/-4 HU dens ity increase. The area of non-enhancement corresponded to ischemic myocardi um in stained pathologic sections. Conclusion. Contrast-enhanced stress EBCT can be used to detect areas of my ocardial ischemia, and EBCT stress perfusion imaging may be necessary to co nsistently differentiate ischemic from non-ischemic myocardial tissue.