Myocardial performance after cardiopulmonary bypass and cardioplegic arrest:: Impact of Na+/H+ exchanger inhibition

This study was designed to determine if pretreatment with a sodium/hydrogen exchange inhibitor (EMD 96 785) improves myocardial performance and reduces myocardial edema after cardioplegic arrest (CPA) and cardiopulmonary bypass (CPB). Anesthetized canines (n = 18) were instrumented with vascular catheters, myocardial ultrasonic crystals, and left ventricle (LV) micromanometer to measure preload recruitable stroke work (PRSW), +dP/dt(max), and cardiac output. Serial myocardial tissue water content (MWC) was determined from sequential biopsy. After baseline measurements, hypothermic (28degreesC) cardiopulmonary bypass was initiated. CPA was maintained for 2 h, followed by reperfusion/rewarming and separation from CPB. PRSW and myocardial tissue water were measured at 30, 60, and 120 min after CPB. EMD 96 785 (3 mg/kg) was given 15 min prior to CPB. Controls received the same volume of saline vehicle. It was found that MWC increased from baseline in both EMD 96 785 and controls with CPB/CPA. PRSW decreased from baseline at 30 and 60 min post CPB/CPA in controls; PRSW did not decrease from baseline with EMD 96 785, and was statistically greater at 30 and 60 min post CPB/CPA compared to controls. Thus, Na+/H+ exchanger inhibition with EMD 96 785 (3 mg/kg) pretreatment improves post-CPB/CPA myocardial performance without reducing myocardial edema. Na+/H+ exchanger inhibition during cardiac procedures using CPB/CPA may be a useful adjunct to improve immediate post-CPB/CPA myocardial performance.