Using Intraoperative Coronary Bypass Graft Imaging to Improve Graft Patency (GRIIP)

• 50-99% graft stenosis on postoperative graft angiography [ Time Frame: 4 day to 4 months postoperatively ] [ Designated as safety issue: No ]
• Mortality, myocardial infarction, low output syndrome [ Time Frame: Perioperatively ] [ Designated as safety issue: No ]
• Major cardiac adverse events [ Time Frame: 1 year postoperatively ] [ Designated as safety issue: No ]

• 1. presence of 50-99% stenoses, 6-12 weeks on angiography;
• 2. perioperative myocardial infarction (MI), low-output syndrome, or all-cause mortality;
• 3. 1-year major adverse cardiac events (MACE) defined as late MI, cardiac mortality or repeat revascularization.

The primary objective of the proposed study is to determine if a strategy of intraoperative patency assessment and graft revision can decrease the rate of graft occlusion or significant stenosis (>50%) at 6-12 weeks after coronary artery bypass grafting (CABG) versus traditional operative management without routine intraoperative patency assessment. Patency will be assessed with a new fluorescence angiography technique as well as ultrasonic transit-time flow measurement. We hypothesize that the strategy of intraoperative patency assessment and graft revision will significantly reduce the frequency of graft occlusion at 6-12 weeks in comparison to patients who do not have intraoperative patency assessment. We also hypothesize that the strategy of intraoperative patency assessment and graft revision will significantly reduce the frequency of 50-99% stenoses at 6-12 weeks in comparison to patients who do not have intraoperative patency assessment. We expect both groups will experience similar perioperative outcomes but hypothesize that patients receiving a strategy of intraoperative patency assessment and graft revision will experience improved long-term graft patency and freedom from late clinical events at 5-6 years post-operatively.

The immediate and long term success of coronary surgery is dependent on the construction of a high quality anastomosis with a durable conduit to an appropriate target coronary vessel. Significant advances in medical therapy including early post-operative aspirin administration and increased use of arterial grafting have improved early, midterm and late graft patency. However, modern coronary bypass series continue to report perioperative graft occlusions rates as high as 11%. These very early graft failures have been predominantly ascribed to technical problems at graft anastomosis sites and may be preventable. New intraoperative graft assessment technologies have recently become available which can identify technical problems such that they can be repaired in the operating room. However, these techniques increase the length of the bypass operation and may have false positives, which may lead to unnecessary and potentially damaging graft revisions. The primary objective of the proposed study is to determine if a strategy of intraoperative patency assessment and graft revision can decrease the rate of graft occlusion or significant stenosis(>50%) at 6-12 weeks after coronary artery bypass grafting (CABG) versus traditional operative management without routine intraoperative patency assessment.

• No Intervention: 1
  Graft patency assessment by routine clinical assessment with/without intraluminal coronary probe
• Experimental: 2
  Graft patency assessment by indocyanine green angiography and transit-time flowmetry
  Intervention: Procedure: Indocyanine green intraoperative angiogram and transit-time flowmetry

Inclusion Criteria:

• isolated aortocoronary bypass surgery
• left ventricular ejection fraction >20%
• expect at least 2 bypass grafts

Exclusion Criteria:

• renal insufficiency (creatinine >180 umol/L)
• known allergy to indocyanine green contrast dye
• severe peripheral vascular disease precluding femoral access
• known allergy to radiographic contrast media
• women of childbearing potential
• co-morbid illness which precludes the use of follow-up angiography
• geographically inaccessible for follow-up angiography