Multicentre Radial Artery Patency Study: Results of Patency Beyond 5 Years After Coronary Artery Bypass Surgery

Multicentre Radial Artery Patency Study: Results of Patency Beyond 5 Years After Coronary Artery Bypass Surgery

Bypass surgery is often required to treat severe coronary heart disease. Either arteries or veins can be used as bypass grafts. We wish to compare the long-term durability of the saphenous vein from the leg to that of the radial artery from the fore-arm when used as bypass grafts. We are examining how many of these grafts are still functioning beyond 5 years after bypass surgery by performing a coronary angiogram. After 1-year, we found that radial arteries were more likely to be functioning than saphenous veins. We hypothesize that radial arteries will continue to be superior beyond 5 years.

The multi-centre Radial Artery Patency Study, (RAPS) is a series of longitudinal graft patency studies designed to compare the long-term patency of the radial artery to the saphenous vein. Between 1996 and 2001, 561 patients were intraoperatively randomized to undergo surgery according to one of two strategies: radial-artery grafting to the circumflex territory and saphenous-vein grafting to the right coronary artery or radial-artery grafting to the right coronary artery and saphenous-vein grafting to the circumflex territory. The first study compared the 8-12 month angiographic patency of the radial artery with that of the saphenous vein as a conduit for coronary artery bypass and found that radial arteries were superior. The primary objective of this current study is to determine the beyond 5-year angiographic patency of the radial artery compared with a saphenous vein coronary bypass graft.

HYPOTHESES

1. The angiographic patency of radial artery grafts studied beyond 5 years following surgery exceeds that of saphenous vein grafts.
2. Radial artery conduits studied beyond 5 years postoperatively have less graft disease than saphenous veins.

SAMPLE SIZE We expect to study 350 patients, which will allow us to test for a 35% risk reduction from 23% occlusion rate in saphenous veins to 15% in radial arteries, assuming a 5% within-patient correlation, with 80% power for a 2-tailed alpha of 0.05.

Inclusion Criteria:

The patient population consists of patients who were enroled into the original Multicentre Radial Artery Patency Study between November 1996 and January 2001. These included patients undergoing isolated coronary artery bypass surgery less than 80 years of age with 3 vessel coronary disease and left ventricular ejection fraction greater than 35%.

Exclusion Criteria:

Exclusion criteria included 1: Inability to use the radial artery or saphenous vein conduits: a)nonpalpable ulnar arteries or a positive Allen's test, b) an abnormal Doppler study or ultrasonographic study of the arms, c) a history of vasculitis or Raynaud's syndrome, bilateral varicose veins or vein stripping. 2: Conditions that affected the safety of follow-up angiography: a)renal insufficiency (creatinine > 180 umol/L) b)severe peripheral vascular disease precluding femoral access b)coagulopathy or obligatory uninterrupted use of anticoagulants c) known allergy to radiographic contrast media d) women of childbearing potential e) comorbid illness which precludes the use of follow up angiography f) geographically inaccessible for follow up angiography.