This study was undertaken to evaluate transit-time flow (TTF) as a tool to detect technical errors in arterial bypass grafts intra-operatively and predict outcomes. TTF's three parameters, pulsatility index (PI, index of resistance), flow (cc min(-1)) and diastolic filling (DF, proportion of diastole with coronary flow), were measured in 990/1000 (99%) of arterial grafts in 336 consecutive patients, prospectively enrolled in a database. Grafts were revised when TTF findings supported the otherwise suspected graft malfunction. If no other signs/suspicion of graft malfunction existed (normal electrocardiogram (EKG), stable haemodynamics and unchanged ventricular function on trans-oesophageal echocardiography (TEE)), and the PI was >5, grafts were not revised. Major adverse cardiac events (MACEs: recurrent angina, perioperative myocardial infarction, postoperative angioplasty, re-operation and/or perioperative death) were related to TTF measurements. The average number of grafts per patient was 3.02, of which 99% were arterial. Satisfactory grafts were achieved in 916/990 (93%) of the grafts, with flows from 34 to 61 cc min(-1), PI < or =5 and DF of 62-85%. Fourteen conduits, 20 grafts (2%) suspected to be problematic, were revised. Patients were divided into two groups: 277 (82%) with at least one graft with PI < or =5 and 59 (18%) with a PI >5. MACE occurred in 25 (7.4%) patients--15/277 patients with a PI < or =5 (5.4%) and 10/59 with a PI >5 (17%, p=0.005). Mortality following non-emergent surgery was significantly higher in patients with a PI >5 (5/54, 9%) than in patients with a PI < or =5 (5/250, 2%, p=0.02). Flow and DF were not predictive of outcomes. A high PI predicts technically inadequate arterial grafts during surgery--even if all other intra-operative assessments indicate good grafts; it also predicts outcomes, particularly mortality.

Transit time flow measurement (TTFM) allows quality control in coronary artery bypass grafting but remains largely underused, probably because of limited information and the lack of standardization. We performed a systematic review of the evidence on TTFM and other methods for quality control in coronary artery bypass grafting following PRISMA standards and elaborated expert recommendations by using a structured process. A panel of 19 experts took part in the consensus process using a 3-step modified Delphi method that consisted of 2 rounds of electronic voting and a final face-to-face virtual meeting. Eighty percent agreement was required for acceptance of the statements. A 2-level scale (strong, moderate) was used to grade the statements based on the perceived likelihood of a clinical benefit. The existing evidence supports an association between TTFM readings and graft patency and postoperative clinical outcomes, although there is high methodological heterogeneity among the published series. The evidence is more robust for arterial, rather than venous, grafts and for grafts to the left anterior descending artery. Although TTFM use increases the duration and the cost of surgery, there are no data to quantify this effect. Based on the systematic review, 10 expert statements for TTFM use in clinical practice were formulated. Six were approved at the first round of voting, 3 at the second round, and 1 at the virtual meeting. In conclusion, although TTFM use may increase the costs and duration of the procedure and requires a learning curve, its cost/benefit ratio seems largely favorable, in view of the potential clinical consequences of graft dysfunction. These consensus statements will help to standardize the use of TTFM in clinical practice and provide guidance in clinical decision-making.

Quality assurance (QA) in medicine is the practice of the prevention of errors and avoiding problems when delivering care in the form of medical therapy, both in terms of non-invasive and invasive procedures. It is rightly expected by patients. Up until the last 10 years, verification of intraoperative bypass graft patency was limited to a stable hemodynamic status, lack of electrocardiographic evidence of myocardial infarction and, if available, no new regional wall motion abnormalities on transesophageal echo. This perspective outlines two technologies for QA during coronary artery bypass graft (CABG) surgery: transit-time flow measurement (TTFM) for functional assessment of coronary grafts and anatomical evaluation with epicardial ultrasound (ECUS). TTFM is a seasoned technology, used since the late 1990s. ECUS is relatively new, used since 2012. TTFM alone, although useful for intraoperative bypass graft assessment, is not enough; 10–15% of graft values are ambiguous as to the efficacy of graft function. Therefore, although newer, ECUS is already being established as an indispensable tool for quality assessment in coronary surgery. The two modalities combined are vital for ‘state of the art’ intraoperative bypass graft assessment.