Collateral perfusion through overlapping vessels reduces canine right ventricular ischemic injury from positive end-expiratory pressure

OBJECTIVETo test, in a canine model of right ventricular ischemia with 15 cm H2O positive end-expiratory pressure, whether collateral perfusion through overlapping vessels from the left ventricle to the right ventricular free wall can reduce infarct size. DESIGNRandomized, prospective, controlled, experimental study in dogs. SETTINGAnesthesia research laboratory of an academic medical center. SUBJECTSTwenty microfilaria-free mongrel dogs. INTERVENTIONSAnesthetized, closed-chest dogs were managed with the application of 15 cm H2O positive end-expiratory pressure. The right coronary artery was ligated (90 mins) with occlusion (n = 10) and without occlusion (n = 10) of overlapping vessels. MEASUREMENTS AND MAIN RESULTSMyocardial blood flow (using radioactive microspheres) was measured in the area at risk (gentian violet) and in the area of necrosis (triphenyltetrazolium chloride). With right coronary and overlapping vessel occlusion, blood flow in the area at risk decreased from 80.1 ± 14.0 to 9.0 ± 1.7 mL/min/100 g after 5 mins of ischemia (p = .0001) and remained depressed at 8.7 ± 1.8 mL/min/100 g after 75 mins of ischemia. With right coronary occlusion alone, blood flow decreased after 5 mins of ischemia from 64.8 ± 5.4 to 14.3 ± 1.9 mL/min/100 g (p = .0001 compared with baseline), which was 60% greater than the group with occluded collateral vessels (p = .0055). Moreover, after 75 mins of ischemia, blood flow in the area at risk increased further to 28.9 ± 5.4 mL/min/100 g with patent overlapping vessels (p = .0001 compared with 5-min value). The patency of overlapping vessels during right ventricular free wall ischemia reduced the area at risk from 68.5 ± 2.4% to 38.6 ± 5.1% (p = .0001) and the area of necrosis/area at risk from 58.1 ± 8.4% to 16.9 ± 3.6% (p = .0007). CONCLUSIONSDespite 15 cm H2O positive end-expiratory pressure, perfusion through overlapping vessels improved peri-ischemic blood flow in the area at risk, thereby reducing the size of the risk area and the amount of right ventricular free wall necrosis. (Crit Care Med 1993; 21:721–732)