Operative risks and mid-term outcomes following offpump coronary artery bypass grafting at Christchurch Hospital

Abstract

Introduction: Various randomised and non-randomised studies have been conducted to compare offpump versus standard onpump coronary artery bypass grafting (CABG). However a definitive conclusion regarding the relative merits of both surgical strategies is difficult to reach due to the nature of the study design, influenced by factors such as patient selection and the relative experience of surgeons performing offpump CABG. At Christchurch Hospital, two out of three surgeons perform isolated CABG using offpump techniques routinely in all patients. Our study sought to review the clinical outcomes of patients undergoing offpump CABG from an “all-comers” registry. Methods: All patients receiving offpump CABG at the Christchurch Hospital between January 2009 and March 2014 were identified. Baseline demographics, intra-operative data and clinical outcomes were reviewed. Results: Between January2009andMarch2014, 499patients underwent offpump CABG. Eighty-one percent of patients were male. The mean age was 70 years. The mean pre-operative New York Heart Association (NYHA) and Canadian Cardiovascular Society (CCS) class were 1.4 and 2.8 respectively. Sixty-one patients (12%) had ejection fraction less than 35% and 195 (39%) had left main coronary stenosis >50%. The urgency of the operation were as follows: 19% (95/499) elective, 79.4% urgent (396/499) and 1.6% (8/499) emergency. The average number of grafts (distal anastomosis) performed was 3.6 and the average number of proximal anastomosis performed was 1.5. There was a higher rate of conversion to onpumpwith patients who had >50% left main disease (2.5% vs 0.3%, P<0.05). The conversion however is not associatedwith increased 30-daymortality andmorbidity nor themid-termmortality.Operativemortality analysis using the Society of Thoracic Surgeons (STS) predicted risk of mortality revealed a relatively low operative mortality even in moderately high risk patient group at our centre. Thirty-day outcomes are as shown in Table 1. At the latest follow-up (mean follow-up of 40 months), 469/499 (94%) patients are alive. Discussion: Offpump CABG at our centre is associated with low operative risks. The higher rate of conversion to onpump may be due to the nature of cardiac instability during manipulation; it is however not associated with increased mortality or morbidity. The low operative mortality in patients with high STS predicted risk of mortality suggest that offpump CABG at our centre has past the learning curve. It may also imply that offpump CABG may be better and safer for high risk patients.