Radial Artery Patency Study - RAPS: 5-Year Outcomes

Description:

The goal of the trial was to evaluate the angiographic patency of radial-artery grafts compared with saphenous-vein grafts at 1 year, and again at 5 years, in patients undergoing coronary artery bypass grafting (CABG).

Hypothesis:

Radial-arterial grafts would be superior to saphenous-venous grafts at 1 year in patients undergoing CABG.

Study Design

  • Randomized

Patients Enrolled: 561
Mean Follow Up: 1 year, 5 years
Mean Patient Age: 61 years
Female: 13%

Patient Populations:

  • Age <80 years
  • Undergoing primary, isolated nonemergency coronary bypass surgery with graftable triple-vessel disease and estimated left ventricular ejection fraction >35%
  • Target coronary vessel's left circumflex or right coronary arteries that were ≥1.5 mm in diameter, with proximal lesions causing narrowing ≥70% of the diameter

Exclusions:

  • Nonpalpable ulnar arteries or a positive Allen's test
  • Abnormal Doppler study or ultrasonographic study of the arms
  • History of vasculitis or Raynaud's syndrome, bilateral varicose veins or vein stripping, or conditions that affected the safety of follow-up angiography

Primary Endpoints:

  • Proportion of radial-artery and saphenous-vein grafts completely occluded at 1 year

Secondary Endpoints:

  • Perfect graft patency (TIMI flow grade 3)
  • Angiographic stenosis of any degree on visual assessment
  • Presence of diffuse graft narrowing to <1 mm in diameter, but with a TIMI flow grade of at least 1 (the angiographic "string sign")

Drug/Procedures Used:

Patients were randomized in the operating room to undergo surgery according to one of two strategies: 1) radial-artery grafting to the circumflex territory and saphenous-vein grafting to the right coronary artery, or 2) radial-artery grafting to the right coronary artery and saphenous-vein grafting to the circumflex territory. Each patient served as his or her own control because the randomization was conducted within each patient. The internal thoracic artery was used to bypass the left anterior descending coronary artery. Follow-up angiography was performed at 1 year, and was repeated in a subgroup at 5 years.

Concomitant Medications:

Aspirin (325 mg) postoperatively and continued indefinitely, intravenous nitroglycerin for 24 hours postoperatively, and calcium channel blockade starting on postoperative day one and continued for 6 months

Principal Findings:

A total of 561 patients were enrolled, of which 529 had clinical follow-up, and 501 had angiographic follow-up. Study grafts were not placed in 17 patients and these patients were excluded from the analysis as prespecified. Crossover of randomized strategy was performed in 24 patients, but these patients were analyzed by the intent-to-treat. Harvesting of the radial artery was well tolerated, with only one patient requiring readmission due to infection at the radial artery harvest site. Duration of cardiopulmonary bypass was 97 minutes, with a cross-clamp time of 73 minutes. Patients received an average of 3.8 distal anastomoses. Angiography was performed in 440 patients at 1-year follow-up.

The primary endpoint of graft occlusion was higher in saphenous-vein grafts compared with radial-artery grafts (13.6% vs. 8.2%, p = 0.009), a relative risk reduction of 40%. Diffuse narrowing of the graft (i.e., the angiographic "string sign") was more frequent in radial-artery grafts than saphenous-vein grafts (7.0% vs. 0.9%, p = 0.001). In an analysis restricted to patients with patent study grafts, presence of some angiographic stenosis at the proximal anastomosis was higher in radial-artery grafts compared with saphenous-vein grafts (21.4% vs. 11.1%, p < 0.001), but presence of stenosis in the graft body was lower in radial-artery grafts (5.7% vs. 12.3%, p = 0.003), with no difference in presence of stenosis at the distal anastomosis (14.0% for radial-artery grafts vs. 17.7% for saphenous-vein grafts). There was no difference in perfect graft patency (i.e., TIMI flow grade 3) by graft type (87.7% for radial vs. 85.7% for saphenous).

Survival at 1 year was 98.6%. Perioperative myocardial infarction occurred in the region of the radial-artery graft in 3.2% of patients and in the region of the saphenous-vein graft in 3.0%.

Five-year angiographic follow-up was available for 269 patients. In this subgroup, functional graft occlusion (TIMI grade flow 0-2) was still lower in the radial-artery grafts compared with the saphenous-vein grafts (12.0% vs. 18.8%, odds ratio [OR] 0.64, 95% confidence interval [CI] 0.41-0.98, p = 0.05), as was total graft occlusion (TIMI grade flow 0) (8.9% vs. 17.8%, OR 0.50, 95% CI 0.32-0.80, p = 0.004). There was no difference in proximal or distal anastomotic stenosis between the two grafts, but stenosis in the body of the graft was more common with saphenous-vein grafts (15.2% vs. 6.7%, p = 0.02). Mortality was 0.4% within 30 days, and totally 10% over the period of follow-up. Only 0.4% of patients required redo-CABG, while 4.5% required PCI.

Interpretation:

Among patients undergoing CABG, the rate of graft occlusion at 1 year was lower in radial-artery grafts compared with saphenous-vein grafts. This benefit appeared to be sustained at 5 years, at least in the subgroup that underwent repeat angiography.

Prior studies have demonstrated the internal thoracic artery to be superior to saphenous-vein grafts, but data from randomized trials comparing radial-artery grafts to saphenous-vein grafts are mixed. The recently published VA Cooperative Study comparing radial grafts to saphenous-vein grafts noted no difference in outcomes at 1 year, whereas the RSVP trial demonstrated higher graft patency with radial-artery grafts.

The current trial, with 5-year follow-up, seems to suggest that radial-artery grafts may indeed have better long-term patency compared with saphenous-vein grafts. Translational studies suggest that one reason for this is that radial-artery grafts demonstrate flow-mediated vasodilation, whereas saphenous-vein grafts do not. Differences in patency and vasoreactivity based on gender and diabetes status will need to be further investigated.

References:

Presented by Dr. Stephen Fremes at the ACC.11/i2 Summit, New Orleans, LA, April 4, 2011.

Desai ND, Cohen EA, Naylor CD, Fremes SE, for the Radial Artery Patency Study Investigators. A randomized comparison of radial-artery and saphenous-vein coronary bypass grafts. N Engl J Med 2004;351:2302-9.

Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Atherosclerotic Disease (CAD/PAD), Cardiac Surgery and Heart Failure, Interventions and Coronary Artery Disease

Keywords: Odds Ratio, Risk, Coronary Artery Disease, Myocardial Infarction, Operating Rooms, Vasodilation, Follow-Up Studies, Radial Artery, Human Rights, Constriction, Pathologic, Mammary Arteries, Stroke Volume, Cardiopulmonary Bypass, Confidence Intervals, Coronary Artery Bypass, Diabetes Mellitus


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