WENBIT - Western Norway B Vitamin Intervention Trial

PURPOSE OF STUDY Observational studies have demonstrated that elevated levels of plasma total homocysteine is a risk factor for cardiovascular disease. The purpose of this trial is to evaluate the clinical effects of homocysteine lowering treatment with B vitamins during 3-5 years follow-up of patients undergoing cardiac catheterization for suspected coronary artery disease (CAD). Special attention will be given to complication rates among patients needing subsequent percutaneous transluminal coronary angioplasty (PCI) or coronary artery by-pass grafting (CABG). HYPOTHESIS The primary hypothesis of this study is that, among patients with CAD, a daily supplement with B vitamins will reduce the risk for cardiovascular mortality and serious cardiovascular events with at least 20%. The secondary hypothesis of this study is that, among patients with CAD, a daily supplement with B vitamins will reduce the risk for total mortality, coronary events, cerebrovascular events and other cardiovascular events. The hypothesis will be tested for an effect of any of the treatments (folic acid / vitamin B12 or B6), and the effect will be evaluated according to initial total homocysteine levels and B vitamin levels as well as to the change in these levels after 1 and 6 months. The sample size has been calculated to 3088 patients using a two-sided chi-square test with significance 0.05 and at an 80% power level, presumed event rate of 22% over 4 years, and event rate reduction of 20%, adjusted for non-compliance/drop-out of 20%. STUDY DESIGN This is a controlled, double-blind two-centre trial with 3090 included men and women who underwent coronary angiography at Haukeland University Hospital or Stavanger University Hospital between April 1999 and April 2004. At baseline about 1300 patients underwent PCI and 600 underwent CABG. The patients were randomized into 4 groups in a 2 x 2 factorial design to receive one of the following four treatments: A, folic acid 0.8 mg plus vitamin B12 0