Detection of myocardial ischemia by electron beam CT. Experimental studies

To determine if contrast-enhanced electron beam CT (EBCT) can detect areas of acute myocardial ischemia, and if pharmacological stress testing improves the diagnostic accuracy of EBCT.

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. administration of 0.6 mg/kg dipyridamole before and after LAD occlusion.

At rest, the contrast agent increased myocardial density by 28+/-2 HU, corresponding to a myocardial perfusion estimate of 67+/-7 ml/min/100 g. After dipyridamole, myocardial density increased by 29+/-4 HU. Following occlusion of the LAD, anteroseptal myocardium displayed 10+/-4 HU density increase. The area of non-enhancement corresponded to ischemic myocardium in stained pathologic sections.

Contrast-enhanced stress EBCT can be used to detect areas of myocardial ischemia, and EBCT stress perfusion imaging may be necessary to consistently differentiate ischemic from non-ischemic myocardial tissue.