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Can You Afford Not to Measure Coronary Artery Bypass Graft (CABG) Flow?

By Susan Eymann, MS16 Sep 2015

cabg-flow-measurementImproved medical therapy and percutaneous stenting have caused a rapid decline in the total number of open chest CABG surgeries. Nevertheless, there are still well over 500,000 CABG surgeries performed annually throughout the world. During CABG surgery, measuring bypass graft flow intraoperatively is one quality measure to assess bypass patency.

Transit-time ultrasound flow measurement is one of the most widely accepted methods of intraoperative CABG quality assessment and has gained wide acceptance, especially in Europe, where graft patency assessment is included in the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) European Guidelines for Myocardial Revascularization.

The 2010 Guidelines state: “Graft flow measurement, related to graft type, vessel size, degree of stenosis, quality of anastomosis, and outflow area, is useful at the end of surgery. Flow < 20 mL/min and pulsatility index >5 predict technically inadequate grafts, mandating graft revision before leaving the operating theatre.” 1

The 2014 Guidelines elaborate, “Graft flow measurement may be useful in confirming or excluding a technical graft problem indicated by haemodynamic instability or inability to wean the patient from cardiopulmonary bypass, new regional wall motion abnormalities on transoesophageal echocardiography, or ventricular arrhythmias. It has also been shown to reduce the rate of adverse events and graft failure, although interpretation can be challenging in sequential grafts and T-grafts.”2

Cardiothoracic societies in the United States have not, as yet, followed the lead of their European counterparts and established similar guidelines. In reviewing intraoperative coronary graft assessment, cardiothoracic surgeon Michael Mack, M.D. from Division of Cardiothoracic Surgery, Baylor Healthcare System, The Heart Hospital, Plano, TX notes, “Coronary artery bypass grafting (CABG) is the only major vascular procedure currently performed that does not routinely undergo an assessment of patency at the end of the procedure.3 He notes that this is based on a false assumption that a large majority of grafts produce good clinical outcomes, but data from the PREVENT IV trial of 22,400 saphenous vein grafts showed a suboptimal rate of failure at one year of 25% after on- and off-pump CABG.4 Furthermore, a meta-analysis reported a failure rate of approximately 5% and 25% at three and 12 months, respectively. Mack comments, “It is appropriate to presume that a large portion of those grafts fail early in the postoperative period. It also stands to reason that a significant number of these failures could be corrected by an intraoperative assessment of graft patency with immediate revision of the graft, if stenosed or occluded.”3

In this era of the Affordable Care Act where quality, performance and accountability are mandated in the provision of health care, a quick, simple intraoperative test of the patency of a bypass graft provides the proof of performance required for best surgical practices. If it was worth taking your time to construct a graft, then it is also worth taking the time to measure flow in the graft to make sure that it is patent to ensure the best possible outcome for your patient. Can you afford to wait any longer to measure bypass flow?

1 The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) “2010 Guidelines on Myocardial Revascularization,” “Eur J CardiothoracSurg 2010; 38, S1 S52.
2The Task Force on Myocardial Revascularization of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) 2014 ESC/EACTS Guidelines on myocardial revascularization: Eur J Cardiothorac Surg. 2014 Oct;46(4):517-92.
3Magee MJ, Mack MJ, et al, PREVENT IV Investigators. “Coronary artery bypass graft failure after on-pump and off-pump coronary artery bypass: findings from PREVENT IV,” Ann Thorac Surg 2008; 85(2): 494-9.
4Mack, MJ, “Intraoperative Coronary Graft Assessment,” Current Opinion in Cardiology 2008, 23: 568-572.

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