Abstract 1100: A Novel Hybrid Of On-Pump Beating Heart Coronary Artery Bypass Grafting Results Produces Significant Myocardial Injury Compared to Conventional Cardioplegic Arrest

Abstract

Beating heart coronary artery bypass grafting (CABG) improves early post-operative cardiac function in patients with at least moderate ventricular function but its effects in patients with significantly impaired ventricular function is uncertain. We compared a novel hybrid technique of on-pump beating heart (ONBEAT) to conventional cardioplegic arrest (ONSTOP) in CABG patients with impaired ventricular function using cardiac magnetic resonance (CMR) and biochemical markers. In a single centre randomized trial, 50 patients with impaired ventricular function undergoing CABG were randomly assigned to ONBEAT or ONSTOP. Patients underwent CMR assessment for function and delayed hyperenhancement (HE) for irreversible injury pre-operatively and early post operatively; in addition serum was taken for cTn I and CKMB (0,1,6,24,48 and 120 hours) after surgery. Forty-five patients completed surgery with follow up imaging. Pre-operative characteristics were well matched except for a higher incidence of renal impairment in ONBEAT patients (glomerular filtration rate 58 versus 68 ml.min−1, p=0.02). Mean ± SD cardiac index (CI): ONBEAT 2.85±0.53 and ONSTOP 2.62±0.59L.min−1.m−2. After surgery both groups sustained minor changes to CI (4% reduction ONBEAT, p = 0.43 versus 1% increase ONSTOP, p = 0.97) without significant inter-group difference. The incidence of new HE was significantly higher in the ONBEAT group (p = 0.04) with 6/17 patients (35%) sustaining 8.2 ± 5.2 g of new HE each compared with 2/23 patients (9%) in the ONSTOP group each with 9.8 ± 9.0 g of new HE, p = 0.86. Furthermore serum markers of myocardial injury were higher in ONBEAT patients; median AUC for Troponin I 461[226 – 1141]μg/L versus 160[98 – 357]μg/L, p=0.002 and CKMB 862[499 – 1768]ng/mL versus 549[447–704]ng/mL p=0.004. The incidence of new irreversible myocardial injury was significantly higher in ONBEAT patients, although there was no effect on global cardiac function. Inadequate coronary perfusion in patients with severe proximal coronary disease and low cardiac output may render distal coronary territories ischemic in the absence of formal myocardial protection.