Effect of a residual stenosis by quantitative angiography on the myocardial contrast defect observed following coronary reperfusion using intermittent harmonic ultrasound imaging and intravenous perfluorocarbon ultrasound contrast

Intermittent harmonic imaging following intravenously injected perfluorocar bon-containing microbubbles can detect myocardial perfusion, abnormalities caused by ischemia. It is unknown whether this technique can. differentiate viable, ischemic myocardium from infarcted myocardium immediately followin g coronary reperfusion. The objective of this paper was to determine whethe r intermittent harmonic imaging with intravenous microbubbles could define myocardial perfusion abnormalities following reperfusion. In 26 dogs, a pro longed total coronary occlusion. (mean occlusion time 2.1 +/- 0.4 hours) wa s followed by coronary reperfusion. Wall thickening (WT) and peak myocardia l video intensity (PMVI) within and outside the risk area (PMVI ratio) were measured following intravenous perfluorocarbon microbubbles under resting conditions and during a 5 mu g/kg per minute dobutamine [low dose dobutamin e (LDD)] infusion in the presence and absence of a greater than or equal to 50% diameter stenosis in the reperfused vessel. Infarct size was determine d postmortem. The resting contrast defect in all dogs correlated closely (r = 0.93) with infarct size when no residual stenosis was present but correl ated more closely with risk area (r = 0.88) when a greater than or equal to 50% diameter residual stenosis was present. In dogs with infarction involv ing > 50% of the risk area, the PMVI ratio was lower under resting conditio ns (0.51 +/- 0.27) than in dogs with no or partial infarction when no resid ual stenosis was present. However, in dogs with no or partial infarction, t he PMVI ratio fell significantly when. a greater than or equal to 50% diame ter stenosis was present, both under resting conditions and during LDD. We conclude that the myocardial contrast defect observed with intermittent har monic imaging and intravenous ultrasound contrast is affected by both the i nfarct size and the presence of a significant residual stenosis.