Author + information
- Joanna Chikwe, MD∗ (, )@IcahnMountSinai@SUNY,
- Timothy Lee, MD,
- Shinobu Itagaki, MD, MSc,
- David H. Adams, MD and
- Natalia N. Egorova, PhD
- ↵∗Department of Cardiovascular Surgery, Icahn School of Medicine at Mount Sinai, 1190 Fifth Avenue, New York, New York 10029
In their responses to our comparison of on-pump versus off-pump coronary bypass surgery, both Dr. Vallely and colleagues and Dr. Balacumaraswami and colleagues focus on the impact of surgeon experience (1). We agree that surgical expertise is central to any analysis of off-pump versus on-pump surgery; including surgeons without substantial off-pump experience biases such comparisons in favor of on-pump surgery because of the greater technical challenges of reliably performing hand-sewn coronary anastomoses on the perfused, beating heart, compared with the more reproducible on-pump technique.
Our study specifically addressed this differential expertise bias in several ways (1). First, we excluded inexperienced surgeons by adopting the same surgeon inclusion criteria as the CORONARY (Coronary Artery Bypass Surgery (CABG) Off or On Pump Revascularization Study) trial (2), the multicenter randomized trial with the highest qualifying criteria for surgeon eligibility, specifying a minimum of 100 off-pump cases for inclusion in our analysis (1). Dr. Balacumaraswami and colleagues appear to have misinterpreted this minimum case requirement as the average case experience of surgeons in our study. Contrary to their incorrect assertions, surgeons in our study had performed on average 497 off-pump coronary bypass cases (the median was 438 and the maximum was 1,926 off-pump cases) before the index cases. This substantial prior experience suggests that the poorer outcomes we observed with off-pump surgery were not attributable to surgeon inexperience. Further, as Dr. Vallely and colleagues note, low rates of intraoperative conversion from off-pump to on-pump surgery may be a hallmark off-pump surgeon expertise. The 3.6% intraoperative conversion rate in our overall off-pump cohort compares favorably to the rates of 7.7% reported by the CORONARY trial (2), 9.7% in the GOPCABE (German Off Pump Coronary Artery Bypass in Elderly Study) (3), and 3% described by Dr. Vallely and colleagues in “expert” groups, underlining the substantial off-pump expertise of our study surgeons (1).
Additionally, we controlled for differential surgeon expertise in multivariate and propensity-matched analysis. First, after adjusting for individual surgeon case experience, off-pump surgery was associated with significantly worse mortality in multivariate Cox analysis (hazard ratio [HR]: 1.1; 95% confidence interval [CI]: 1.04 to 1.18). Second, in propensity-matched patients with surgeon case experience as a covariate, 10-year mortality was worse with off-pump surgery (HR: 1.19; 95% CI: 1.08 to 1.30). Third, 10-year mortality was worse after off-pump surgery in the subgroups of patients operated on by surgeons performing >80% of their cases off-pump (HR: 1.16; 95% CI: 1.03 to 1.39) and in the subgroup of surgeons with <3% conversion rates (HR: 1.1; 95% CI: 1.10 to 1.19).
Dr. Vallely and colleagues cite individual endpoints for incomplete revascularization and mortality from the CORONARY trial, which was not powered for those individual endpoints. One of the key strengths of our population-based analysis is that it had sufficient power to compare these important individual endpoints in contemporary, real-world practice by experienced surgeons.
In summary, even when off-pump surgery is performed by experienced off-pump surgeons averaging around 500 prior off-pump cases and performing >80% of their cases off-pump, rates of incomplete revascularization and late mortality are significantly worse with off-pump surgery compared with on-pump coronary bypass. These data support the conclusion that, for most patients without contraindications to cardiopulmonary bypass undergoing surgical revascularization, on-pump coronary bypass remains the appropriate choice.
Please note: The Icahn School of Medicine at Mount Sinai receives royalty payments from Edwards Lifesciences for intellectual property related to the development of 2 mitral valve repair rings, and from Medtronic for intellectual property related to the development of a tricuspid valve repair ring. Dr. Chikwe has received speaker honoraria from Edwards Lifesciences. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.