Studies of controlled reperfusion after ischemia. XVII. Reperfusion conditions: controlled reperfusion through an internal mammary artery graft--a new technique emphasizing fixed pressure versus fixed flow.

Abstract

This study tests the usefulness of delivering a controlled reperfusate through an internal mammary graft after acute ischemia by applying a percutaneous technique of mammary artery cannulation and compares reperfusion at fixed pressure versus fixed flow. Twenty-one dogs underwent 2 hours of ligation of the left anterior descending coronary artery followed by regional controlled revascularization on total vented bypass. A reperfusion catheter was introduced percutaneously from the brachial artery into the internal mammary artery. Five dogs received normal blood reperfusion at 50 mm Hg pressure, and eight dogs received a regional blood cardioplegic reperfusate at 50 mm Hg before reperfusion with normal blood. Eight additional dogs received regional cardioplegia at 30 ml/min for 20 minutes. Coronary vascular resistance, segmental shortening (ultrasonic crystals), tissue water content, and histochemical damage (triphenyltetrazolium chloride stain) were assessed. Reperfusion with normal blood increased coronary vascular resistance progressively to 62% above initial values (p less than 0.05) and failed to restore regional contractility (9% +/- 6% systolic shortening, p less than 0.05). In contrast, coronary resistance remained low throughout blood cardioplegic reperfusion at fixed pressure and the reperfused muscle recovered immediate contractility (73% systolic shortening, p less than 0.05). Controlled reperfusion at a fixed flow rate resulted in pressure that ranged from 30 to 80 mm Hg, slightly less recovery of systolic shortening (57%), and less return of contractile reserve (81% versus 114%, p less than 0.05). Regional blood cardioplegic reperfusion limited edema formation (79.5 versus 82% water content, p less than 0.05) and histochemical damage (11% versus 50% area of necrosis/area at risk, p less than 0.05). An internal mammary artery graft can be used effectively in the setting of acute ischemia if a controlled blood cardioplegic reperfusate is delivered through it to ensure limitation of histochemical damage, low reflow phenomenon, and restoration of immediate segmental contractility. Controlled-pressure reperfusion seems superior to fixed-flow reperfusion. A technique is described that may allow preoperative insertion of the reperfusion catheter in the internal mammary artery in the catheterization laboratory.