Failure of intra-aortic balloon pumping to reduce experimental myocardial infarct size in swine.

Although intra-aortic balloon pumping (IABP) is reported to reduce myocardial infarct size in dogs, this phenomenon may be due to pre-existing collaterals in this species. Pigs more closely approximate human coronary anatomy, having poor inherent collateralization. This study evaluates hemodynamic changes and quantitates myocardial infarct size 24 hours after coronary occlusion in swine, with and without IABP. Eighteen pigs underwent ligation of the left anterior descending coronary artery distal to the first diagonal branch: Nine were treated with IABP beginning 45 minutes after coronary occlusion and nine served as control subjects. Three in each group died prior to completion of the study. In both groups myocardial infarction resulted in a significant (p less than 0.05) decrease of cardiac output (28.5%) and mean aortic pressure (p less than 0.05) improvement of mean aortic pressure (4 to 7%) during the switch on period. After 24 hours, mean aortic pressure in IABP-treated animals (105 +/- 20 mm Hg) was significantly (p less than 0.01) higher than in control pigs (73 +/- 12 mm Hg). Myocardial infarct size as detected by staining with nitroblue tetrazolium was 22.7 +/- 4.9 gm infarct/100 gm left ventricular and septal mass in control pigs and 19.4 +/- 5.9 gm infarct/100 gm left ventricular and septal mass in treated animals (p less than 0.3). In conclusion, IABP, despite significantly improving circulatory parameters, does not significantly reduce the size of an acute myocardial infarction after coronary ligation in swine.