title: Transit-time flow predicts outcomes in coronary artery bypass graft patients: a series of 1000 consecutive arterial grafts.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Cardiac Sciences, LIBIN Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada. t.kieserprieur@ucalgary.ca
authors.forename: Teresa Mary
authors.initials: TM
authors.lastname: Kieser
authors.forename: Sarah
authors.initials: S
authors.lastname: Rose
authors.forename: Ryszard
authors.initials: R
authors.lastname: Kowalewski
authors.forename: Israel
authors.initials: I
authors.lastname: Belenkie
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001783:Blood Flow Velocity / Q000502:physiology; D001026:Coronary Artery Bypass / Q000009:adverse effects; D005260:Female; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011673:Pulsatile Flow / Q000502:physiology; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome; D014654:Vascular Patency / Q000502:physiology