Two case studies from Brody School of Medicine at East Carolina State University in Greenville, N.C., highlight the importance of checking for competitive flow by occluding the native coronary artery during intraoperative assessment of graft patency. The clinicians recognized that preoperative coronary angiography doesn’t adequately inform about competitive flow.
In newly released follow-up data, Dr. Robert Michler, et al. found there was no significant benefit in patients with moderate ischemic mitral regurgitation who underwent coronary-artery bypass grafting (CABG) with combined CABG and mitral-valve repair.
According to the study, “Patients with CABG and mitral-valve repair had an early hazard of longer hospital stay post-surgery, a higher incidence of postoperative supraventricular arrhythmias and higher rate of serious neurological events than those with CABG alone. There was a threefold higher incidence of persistent mitral regurgitation in this same group without evidence of higher mortality or adverse clinical events.”
Measurement of blood flow during coronary artery bypass grafting (CABG) is not new.
Since the 1970s, electromagnetic blood flow meters have been available to surgeons. However, their use was problematic. Within the surgical suite, other OR apparatus or ambient electrical noise interfered with operation of the flow meters. To measure flow, electromagnetic flow probes had to have a tight (constrictive) contact around the vessel which could heat up vessels and also cause vasospasm. Also, they were not able to measure flow in internal mammary arteries that were becoming the first choices for a bypass grafts. Because of these problems with electromagnetic flowmeters, blood flow measurement during surgery fell into disfavor.
Saphenous veins are used for coronary artery bypass grafting (CABG) surgery. However, progressive neointimal hyperplasia contributes to considerable vein graft failure. Dr. J.H. Alexander, from Duke Clinical Research Institute, sought to assess the efficacy and safety of pretreating vein grafts with edifoligide for patients undergoing CABG in order to determine if it may prevent neointimal hyperplasia and vein graft failure.
A phase 3 randomized, double-blind, placebo-controlled trial at 107 U.S. sites with 3,014 patients undergoing primary CABG surgery with at least two planned saphenous vein grafts was conducted.
Dr. Matija Jelenc, a leading Slovenian surgeon, recognized that low mean bypass graft flow and a high pulsatility index measured by the transit-time flow measurement (TTFM) method are not specific for anastomotic stenosis, but also occur in the presence of competitive flow and poor coronary run-off.
He hypothesized that graft compliance is responsible for these changes and that flow measured at the proximal end of the coronary bypass can be viewed as a sum of the graft capacitive flow and the flow that passes through the distal anastomosis.
In a 2015 study that included 345 CABG patients who had had 982 intraoperative graft flow measurements, Copenhagen University surgeons sought to determine if transit-time flow measurement can be used to predict graft patency at one year post-op.
Beijing surgeons achieved total arterial myocardial revascularization in 208 patients through evaluation of the early outcome of off-pump coronary artery bypass grafting (OPCAB) with a bilateral internal mammary artery (BIMA) Y-configuration graft. The patients ranged from 33 to 78 years old. The average age was 56. Of the total, 80.2% had triple-vessel disease; 15.9% cases had left coronary disease, and 3.9% had double-vessel disease.
University of Toronto clinicians studied coronary artery graft patency one year after CABG surgery.
They also investigated any major adverse cardiac events such as death, myocardial infarction or repeat revascularization during that time frame.
A short eight-page article by Dr. David Taggart, one of 25 ECS/EACTS Myocardial Revascularization Guidelines authors, provides an excellent overview of current treatment for coronary artery disease (CAD), the findings of various randomized trials, and the implication of current data for the need for multi-disciplinary heart teams to ensure the best avenue for treatment for their CAD patients.
The publication points out that, despite a decline in the number of CABG surgeries due to improved medical therapy and percutaneous stenting, more than 500,000 patients worldwide undergo CABG annually with excellent results and an estimated mortality of about 1%. Heart teams must establish whether a proposed intervention (stenting or surgery) is planned for symptomatic and/or prognostic reasons, or justified by significant ischaemia (>10% of myocardial mass).
A common complication following implantation of a ventricular assist device (VAD) is acute right heart failure. To manage this complication effectively, left ventricular preload and contractility must be estimated reliably.
A 66-year-old female with end-stage heart failure was implanted with a HeartAssist 5 (from Micromed Cardiovascular Inc. of Houston) with a custom Transonic® Flowprobe on the VAD’s outflow graft to continuously measure real-time pump blood flow. On days one and two post-op, mean flow through the graft was 4.8 L/min. On day three post-op, real-time flow began a progressive decline that was accompanied by an increase in central venous pressure and progressive renal failure.