Reduction of "No-Reflow" phenomenon by intra-aortic batloon counterpulsation in a randomized magnetic resonance Imaging experimental study

OBJECTIVES. Intra-aortic balloon counterpulsation (IABC) can improve post-myocardial infarction (MI) outcomes, but the mechanisms of such effect remain unclear. We hypothesized that IABC augmentation reduces the extent of microvascular obstruction after acute infarction. BACKGROUND Microvascular obstruction or "no-reflow" (MO) has been shown to negatively influence left ventricular (LV) remodeling after myocardial infarction (MI). METHODS Seventeen dogs underwent 90 min of coronary artery occlusion followed by reperfusion. Animals were then randomized to either IABC (n = 9) or control (n = 8); IABC augmentation was performed for 24 h after MI. Microvascular obstruction and infarct size by first-pass and delayed contrast-enhanced magnetic resonance imaging (MRI) were measured at 1 and 24 h after reperfusion and compared with postmortem infarct size and MO by microspheres. RESULTS Microvascular obstruction by MRI, expressed as percent LV mass, decreased significantly in IABC (4.9 +/- 2.2% to 3.6 +/- 1.5%) and increased in controls (3.4 +/- 0.5% to 4.9 +/- 1.1% from 1 to 24 h, respectively; p < 0.001). Similar results were found for MO defined by microspheres. In the control group, MO increased significantly, during 24 h of study (from 8.8 +/- 1.7% to 43.2 +/- 11.1% of infarcted myocardium; p < 0.05), whereas not important change was observed in the IABC group (from 21.3 +/- 7.1% to 25.8 +/- 14.7%; p < 0.05 vs. control at 24 h). Infarct size, measured by MRI, increased in both groups (13.2 +/- 1.8 to 15.5 +/- 2.1 from 1 to 24 h, respectively, p < 0.05). CONCLUSIONS Intra-aortic balloon counterpulsation augmentation performed after reperfusion improves myocardial perfusion at the tissue level, and reduces the extent,of no reflow caused by microvascular obstruction. (C) 2004 by the American College of Cardiology Foundation.