PATency assessmENt of Grafts by Computerized tomographY in CORONARY Patients: the PATENCY-CORONARY Trial

Background: As Coronary Artery Bypass Grafting (CABG) aims to restore adequate blood supply to the ischemic heart, the success of the operation should depend mainly on the patency of the bypass grafts. Graft failure has consequences similar to those of native coronary artery disease: recurrent angina, myocardial infarct (MI), additional revascularization procedures, and premature death. CABG is generally performed using cardiopulmonary bypass (CPB) with cardioplegic arrest allowing the surgeon to complete the delicate coronary anastomoses on a still heart in a bloodless field. Off-pump CABG surgery using specially designed heart stabilizer systems has been proposed as a less invasive approach to CABG avoiding the CPB circuit itself. The benefits of off-pump CABG compared with conventional on-pump CABG are still intensively debated. Multislice spiral computed tomography angiography (CTA) represents a non-invasive method as compared to conventional coronary angiography allowing a comprehensive and objective imaging of bypass grafts and native coronaries with elevated diagnostic accuracy.

Rationale: CORONARY trial (NCT00463294) is a large, international, prospective, CIHR-funded, randomized controlled trial assessing both the short and long-term clinical outcomes of 4,700 patients undergoing on-pump or off-pump CABG. However, angiographic evaluation of coronary graft patency was not intended in CORONARY.

Objectives: PATENCY-CORONARY is a new prospective trial of a consecutive subset of 1,200 CORONARY patients reaching their one-year follow-up who will undergo graft patency assessment using CTA and 3D reconstructions. This trial will determine whether off-pump compared to on-pump CABG surgery is associated with lower CABG patency when performed by experienced surgeons and if there is an association between graft failure assessed by CTA, and the occurrence of CORONARY primary outcomes (composite of death, angina, MI, stroke, renal failure and new coronary revascularization [CABG or PCI]).

Primary outcome: CABG patency index (i.e. the percentage of patent [non-occluded] distal anastomoses out of the total number of distal anastomoses for all patients) at 1 year after CABG surgery by experienced surgeons; Secondary outcomes: 1) graft lesion severity on a 3-point scale at 1 year (mimicking the FitzGibbon grading ABO); and 2) percentage of patients with at least one occluded bypass graft at 1 year; Tertiary outcome: correlation between CTA findings (compromised grafts) with CORONARY primary outcomes(composite of death, angina, MI, stroke, renal failure and new coronary revascularization [CABG or PCI]), at one and five-year of follow-up post-CABG.

Methods: All CORONARY patients reaching their one-year follow-up will be included consecutively in the PATENCY-CORONARY trial until the target of 1,200 CTA is reached and reasons for exclusion will be noted prospectively to prevent selection bias. Amount of contrast agent used, radiation dose and potential morbidities during this imaging procedure will be recorded. Each CTA examination will be assessed by two experienced and blinded radiologists and each graft will be classified according to conduit type and portions: body of the graft, anastomoses and the distal native coronary bed. In addition of PATENCY-CORONARY outcome analyses, patients undergoing CTA will be compared to excluded patients (no CTA) and the overall cohort of patients.