Background: Saphenous vein grafts (SVG) remain the most widely used conduit for CABG. However, contemporary patency rates at one-year post CABG remain poor, despite optimal medical therapy. Recent trials (PREVENT IV) demonstrate that up to 45% of all patients have one or more SVG occluded at angiography one year post-CABG; up to 25% of all SVG are occluded at one year post-CABG angiography. Furthermore, patients with at least one SVG occluded had twice the incidence of perioperative MI, and thirteen times the composite endpoint of death, late MI or repeat revascularization at 12-18 months.
The proposed SUPERIOR SVG Trial is a prospective, international, multi-centre randomized controlled clinical trial (RCT). It utilizes a factorial design to elucidate the benefits of two interventions, one surgical and the other pharmacological, to improve saphenous vein graft patency after coronary artery bypass grafting surgery (CABG):
Surgical Arm: Does a novel atraumatic ("no touch") technique of pedicled saphenous vein graft (SVG) harvesting result in improved angiographic patency and clinical outcomes at 1 year, compared to conventional SVG harvesting techniques, in patients undergoing CABG.
Rationale: A Swedish cardiac surgical centre has published numerous studies demonstrating that harvesting the SVG with a cushion of surrounding fat and without vein graft distension, "no touch" technique, improved surrogate markers of vein preservation in operative specimens. Graft patency was superior in a single small RCT (8.5 year patency: "no touch" 90% vs. conventional 76%, p=0.01, adjusted OR 3.7, 95% CI 1.4-9.6, p=0.007).
Pharmacological Arm: Does N-3 polyunsaturated fatty acid (fish oil) oral supplementation result in improved angiographic patency and clinical outcomes at 1 year, compared to placebo, in patients undergoing CABG.
Rationale: In vivo studies showed levels of N-3 polyunsaturated fatty acids (PUFA; fish-oils) inversely correlate with the risk of coronary disease. Several large RCTs (more than 40,000 patients in aggregate) performed in diverse cardiovascular populations, have demonstrated moderate mortality benefits. A single RCT from the 90's found that that SVG patency was enhanced with fish oils.
Methods: Each patient will be randomized to a SVG harvested in the conventional fashion (open or endoscopic) or using the "no touch" technique (single-blinded). The pharmacological arm of the factorial design will have patients also randomized to fish-oil or placebo (double-blinded) starting prior to surgery and continuing for 1 year. The primary outcomes (Surgical Arm: proportion of study SVG grafts occluded; Pharmacological Arm: proportion of patients with ≥1 graft occluded) at 1 year CT angiography (window 9-15 months) will be compared between the treatment and control groups. Secondary endpoints include incidence of 50-99% study SVG stenosis at 1 year, adverse events and perioperative and 1 year clinical events (mortality, non-fatal MI, repeat revascularization).
A sample size of 615 patients/arm will provide adequate statistical power (Surgical Arm, Primary Outcome: study SVG graft occlusion, control event rate = 20%, no-touch event rate = 14%, RRR = 0.30, β = 0.2; Pharmacological Arm, Primary Outcome: patients with at least 1 graft occlusion, control event rate = 30%, fish oils event rate 22.5%, RRR = 0.25, β= 0.15). The total sample size has been increased 25% to 1550 patients as approximately 20% of recruited patients in angiographic trials fail to undergo follow-up angiography. Study patients will be enrolled over 39 months at 50 centers. Pilot funding has been secured from CIHR-CANNeCTIN to assess feasibility in 50 patients from 15 sites. A single interim analysis will be performed following completion of 50% of the CT angiograms, p\<0.001.
