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Abstract

Thank you for the opportunity to respond to Dr Magarakis and colleagues’ letter [1Magarakis M. Macias A.E. Salerno T.A. Off-pump versus on-pump: should graft flow confirmation at time of surgery become standard of care? (letter).Ann Thorac Surg. 2019; 108: 1265Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] on our article [2Shroyer A.L.W. Quin J.A. Wagner T.H. et al.Off-pump versus on-pump impact: diabetic patient 5-year coronary artery bypass clinical outcomes.Ann Thorac Surg. 2019; 107: 92-98Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar] regarding the utility of transit time flow meters (TTFMs) to assess coronary artery bypass grafting (CABG) intraoperative graft patency—particularly for higher-risk patients, such as diabetics. Although the ROOBY (Randomized On/Off-Bypass) trial’s recent manuscript describing the 5-year follow-up for diabetic patients did not report TTFM or graft patency data [2Shroyer A.L.W. Quin J.A. Wagner T.H. et al.Off-pump versus on-pump impact: diabetic patient 5-year coronary artery bypass clinical outcomes.Ann Thorac Surg. 2019; 107: 92-98Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar], the ROOBY trial’s intraoperative TTFM data and 1-year graft patency rates have been published previously [3Quin J. Lucke J. Hattler B. et al.Surgeon judgment and utility of transit time flow probes in coronary artery bypass grafting surgery.JAMA Surg. 2014; 149: 1182-1187Crossref PubMed Scopus (12) Google Scholar, 4Hattler B. Messenger J.C. Shroyer A.L. et al.Off-pump coronary artery bypass surgery is associated with poorer arterial and saphenous vein graft patency and less effective revascularization: results from the Veterans Affairs Randomized On/Off Bypass (ROOBY) trial.Circulation. 2012; 125: 2827-2835Crossref PubMed Scopus (172) Google Scholar, 5Shroyer A.L.W. Hattler B. Wagner T.H. et al.Comparing off-pump and on-pump clinical outcomes and costs for diabetic cardiac surgery patients.Ann Thorac Surg. 2014; 98: 38-45Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar]. In the ROOBY trial, TTFM was used in 68.7% of off-pump and 67.4% of on-pump cases (p = 0.58). Correspondingly, TTFM use appeared similar between diabetics (66.3%) and nondiabetics (69.4%) (p = 0.19). Despite comparable rates of TTFM use between on-pump and off-pump groups, 1-year graft patency was significantly higher with the on-pump approach for both all patients and the diabetic patient subgroup [4Hattler B. Messenger J.C. Shroyer A.L. et al.Off-pump coronary artery bypass surgery is associated with poorer arterial and saphenous vein graft patency and less effective revascularization: results from the Veterans Affairs Randomized On/Off Bypass (ROOBY) trial.Circulation. 2012; 125: 2827-2835Crossref PubMed Scopus (172) Google Scholar, 5Shroyer A.L.W. Hattler B. Wagner T.H. et al.Comparing off-pump and on-pump clinical outcomes and costs for diabetic cardiac surgery patients.Ann Thorac Surg. 2014; 98: 38-45Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar]. Adhering to randomized, controlled trial intention-to-treat principles, the ROOBY trial’s differential 5-year clinical outcomes for off-pump vs on-pump patients should not be adjusted based on TTFM. Worse off-pump graft flow may be related to inherent anastomotic technical challenges, explaining lower 1-year off-pump graft patency [4Hattler B. Messenger J.C. Shroyer A.L. et al.Off-pump coronary artery bypass surgery is associated with poorer arterial and saphenous vein graft patency and less effective revascularization: results from the Veterans Affairs Randomized On/Off Bypass (ROOBY) trial.Circulation. 2012; 125: 2827-2835Crossref PubMed Scopus (172) Google Scholar, 5Shroyer A.L.W. Hattler B. Wagner T.H. et al.Comparing off-pump and on-pump clinical outcomes and costs for diabetic cardiac surgery patients.Ann Thorac Surg. 2014; 98: 38-45Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar]. As the ROOBY trial documented, low TTFM graft flow was a poor predictor of 1-year graft occlusion rates (ie, positive predictive value was 23%). When TTFM was used, moreover, ROOBY surgeons’ graft revision decisions did not appear to be exclusively based on TTFM flow or pulsatility index metrics. Based on these ROOBY trial findings, there does not yet appear to be adequate data-driven evidence to recommend that cardiac surgeons utilize TTFM uniformly for all CABG patients. In summary, TTFM appears to be useful as part of a CABG surgeon’s armamentarium. Further research appears warranted to evaluate the association between TTFM findings with subsequent clinical outcomes [6Thuijs D.J.F.M. Bekker M.W.A. Taggart D.P. et al.Improving coronary artery bypass grafting: a systematic review and meta-analysis on the impact of adopting transit-time flow measurement.Eur J Cardiothorac Surg. 2019 March 25; ([Epub ahead of print])Crossref Scopus (35) Google Scholar]. Off-Pump Versus On-Pump: Should Graft Flow Confirmation at Time of Surgery Become Standard of Care?The Annals of Thoracic SurgeryVol. 108Issue 4PreviewShroyer and colleagues [1] compared off-pump and on-pump coronary artery bypass graft surgery (CABG) in patients with diabetes. Five-year, all-cause mortality among patients undergoing off-pump CABG was reportedly higher compared with the on-pump group (20.2% versus 14.1%, respectively; p = 0.0198). Full-Text PDF