Left atrium-to-femoral artery bypass: effectiveness in reduction of acute experimental myocardial infarction.

The effects of prompt institution of left atrium-to-femoral artery (LA-FA) bypass on myocardial infarct area (AI) as a percentage of myocardial area at risk for infarction (AR) during a 4 hour period following ligation of the left anterior descending coronary artery (LAD) were studied in 26 dogs. Following LAD ligation, baseline measurements of myocardial tension-time index (TTI) and regional myocardial blood flow (RMBF) were obtained. Group I (controls, n = 16) received no further support. Group II (LA-FA bypass, n = 10) underwent left ventricular unloading via LA-FA bypass beginning 15 minutes after coronary occlusion. Four hours after LAD occlusion, measurements of TTI and RMBF were repeated in both groups. Just before sacrifice, gentian violet was injected into the aortic root to delineate the AR. The hearts were then removed and sectioned transversely through the left ventricle (LV) and septum. The AR (that ventricular area not perfused by gentian violet) was measured by planimetry and compared to the AI as identified by incubation of heart slices in triphenyltetrazolium chloride dye. In comparisons of control versus LA-FA bypass groups, both AI/LV (21.6% versus 10.4%) and AI/AR ratios (73.7% versus 21.8%) were significantly reduced in the bypass group (p less than 0.005). Mortality in the control group (5/16, 31.2%) was significantly greater (p less than 0.005) than in the bypass group (0/10, 0%). Mean TTI over the 4 hour ischemic period was essentially unchanged in the control group as compared to a reduction of 62.8% in the bypass group (p less than 0.005). Furthermore, RMBF at 4 hours was significantly improved in all regions of the LV in hearts undergoing LA-FA bypass when compared with control hearts (p = 0.025). These results demonstrate by a consistent method that prompt institution of LA-FA bypass significantly reduces the mortality associated with acute coronary artery occlusion, as well as the total AI and AI/AR. The protective mechanisms provided by LA-FA bypass probably include the highly significant reduction of LV work and the opening of new bridge collateral blood vessels with redistribution of blood flow to the ischemic region.