Preserved autoregulation of coronary flow after off-pump coronary artery bypass grafting: retrospective assessment of intraoperative transit time flowmetry with and without intra-aortic balloon counterpulsation

Abstract

BackgroundIntra-aortic balloon pumping (IABP) markedly increases graft flow after coronary artery bypass grafting (CABG) with cardiopulmonary bypass. We sought to delineate the effects of IABP on graft flow after off-pump CABG (OPCAB).MethodsThe clinical records of 32 patients (25 male, 7 female; mean age: 70 ± 9 years) who underwent OPCAB with IABP between January 2011 and May 2015 were retrospectively reviewed. Thirteen patients (41%) had a history of myocardial infarction, and 13 patients (41%) had a history of percutaneous coronary intervention. In total, there were 76 bypass grafts with 102 distal anastomoses. These included 50 in situ or pedicled grafts and 26 aortocoronary grafts. After completion of the anastomoses, the heart was positioned normally, and graft flow with IABP was measured using transit-time flowmetry under stable circulation. Then, IABP was turned off for 30 s to a few minutes, until graft flow was constant, for measurement of flow off IABP.ResultsThe angiographic patency rate was 100% (47/47). Overall, graft flow was 55 ± 36 ml/min on IABP and 53 ± 36 ml/min off IABP (p = 0.37). The pulsatility index was 4.1 ± 2.1 on IABP and 2.7 ± 1.5 off IABP (p < 0.001). There was no significant difference in graft flow between on and off IABP for aortocoronary bypass or in situ grafts. Graft flow was 57 ± 36 ml/min on IABP and 55 ± 37 ml/min off IABP (p = 0.41) in in situ grafts and 52 ± 34 ml/min on IABP and 49 ± 35 off IABP (p = 0.41) in aortocoronary grafts. Graft flow on IABP was more than 5 ml/min greater in 28 (37%) bypass grafts, and more than 5 ml/min lower in 20 (26%) bypass grafts.ConclusionIn contrast to previous reports for conventional CABG, graft flow after OPCAB was not necessarily increased by IABP, regardless of elevated diastolic arterial pressure. It is suggested that preserved autoregulation of coronary flow contributes to a lower impact on the heart and early functional recovery, and consequently, greater perioperative safety of OPCAB.

Roles of Transit-Time Flow Measurement for Coronary Artery Bypass Surgery

“…In contrast to these studies, Nakajima et al 49 reported no significant difference in graft flow between on IABP and off IABP after OPCAB. They suggested that autoregulation may be preserved or minimally damaged during OPCAB, in contrast to ONCAB.…”

On-pump beating heart versus off-pump myocardial revascularization—a propensity-matched comparison

“…With a decrease in coronary perfusion pressure, there is a progressive redistribution of blood flow away from the subendocardium [31]. In OPCAB surgery, subendocardial ischemia to a large extent is prevented by auto-regulation [32]. In OP-BH surgery, the cardiac workload is reduced in an empty beating heart; however, the bypassed beating heart is completely dependent on the perfusion pressure and a drop in perfusion pressure below 50 mm of Hg leads to significant subendocardial ischemia [33,34].…”

Current mechanisms of low graft flow and conduit choice for the right coronary artery based on the severity of native coronary stenosis and myocardial flow demand

“…In the present study, we assessed native coronary stenosis using the MLD, a simple structural and functional parameter of the native coronary artery. Moreover, TTFM is reliable in off-pump CABG [19] rather than in on-pump CABG because cardiopulmonary bypass can induce a hyperaemic state, creating a major bias in flow measurement [20]. Furthermore, to assess the impact of the size and status of the RCA area, only an individual bypass graft created as a sole bypass graft in the RCA area.…”