Objectives: We sought to determine the effect of multivessel as opposed to single-vessel coronary artery stenosis on myocardial contrast defects observed with intermittent harmonic imaging and intravenous perfluorocarbon-exposed sonicated dextrose albumin contrast injection.
Background: Intermittent harmonic imaging has permitted the detection of myocardial perfusion abnormalities with an intravenous ultrasound contrast agent. The effect of multivessel disease on inducibility of these perfusion abnormalities is unknown.
Methods: In 10 dogs, intravenous injections of contrast agent were given at rest and during dobutamine stress echocardiography when a single coronary artery stenosis was present (> or = 50% diameter by quantitative angiography) and again when a second stenosis (range 44% to 92% diameter) was present in the vessel supplying the adjacent perfusion bed. The peak myocardial contrast was visually and quantitatively assessed in the mid and lateral regions of the perfusion bed of the first stenosis (original stenosis zone) in the presence of one- and two-vessel stenosis.
Results: Peak myocardial contrast defects in both the mid and lateral segments of the original stenosis zone during dobutamine stress echocardiography was significantly lower when two-vessel stenosis was present (p = 0.015), especially in the lateral segment. The spatial extent of the perfusion defect in the original stenosis zone risk area increased significantly when two-vessel stenosis was present, and correlated closely with actual risk area (r = 0.99). Previous total occlusion followed by reperfusion of the vessel supplying the original stenosis zone significantly increased the amount of collateral activity between perfusion beds.
Conclusions: Collateral flow limits the spatial extent of inducible ischemia within the risk area of single-vessel stenosis. Restoring blood flow to one perfusion bed reduces the extent of a perfusion abnormality that can be induced in an adjacent stenosed bed.