Previous findings from the Swiss Heart Study show that lowering homocysteine levels through the use of vitamin supplements decreases the occurrence of restenosis after coronary angioplasty. A continuation of this study, published in a recent issue of the Journal of the American Medical Association, examines whether the benefits of using B vitamins to lower homocysteine hold over time.

The Swiss Heart Study is a prospective study involving 553 people who had undergone angioplasty of at least one significant coronary stenosis (>/=50%). After the procedure they were randomly assigned to receive either a daily supplement that included folic acid (1 mg/day), vitamin B12 (400 µg/day), and vitamin B6 (10 mg/day), or a placebo, for 6 months.

Fasting total plasma homocysteine levels were measured at baseline and after 6 months using a liquid chromatographic assay. A noninvasive stress test and resting electrocardiogram were performed at 6 months and 1 year, or earlier if symptoms were present. Endpoints were cardiac death, nonfatal myocardial infarction, need for repeat revascularization, and total cardiac events.

B vitamin benefits

One year after the study began (6 months after supplementation was stopped) the vitamin supplement group needed significantly fewer target lesion revascularizations than the placebo group (9.9% vs. 16%, RR=0.62; 95% CI, 0.40-0.97; p=0.03). This effect remained after controlling for other risk factors including age, sex, and other variables that would influence the need for the procedure (stent use, vessel size, target lesion location, treatment of re-stenosed lesions).

The incidence of total cardiac events was significantly lower in patients receiving the vitamin therapy at both 6 months (11.4% vs. 18.9%; RR=0.60; 95% CI, 0.40-0.91; p=0.02) and 1 year (15.4% vs 22.8%; RR=0.68; 95% CI, 0.48-0.96; p=0.03). The benefit of vitamin supplementation was most evident in patients with the highest total and LDL cholesterol levels. Those in the lower cholesterol (total and LDL) tertiles did not benefit significantly from the supplement.

Therapeutic vitamin levels

This study adds to evidence of the long-range beneficial effects of folate, B12, and B6 therapy. It is not clear, though, if each of the vitamins played an equal role in reducing the occurrence of restenosis, or if the benefits seen in this study were the result of something other than lowered homocysteine levels.

The levels of folic acid and vitamins B6 and B12 were chosen for maximum benefit with a minimal chance of side effects. These doses are higher than one would get from a typical multivitamin/mineral supplement. In fact, the amount of folic acid (1 mg) is the Upper Tolerable Limit as determined by the U.S. Committee on the Scientific Evaluation of Dietary Reference Intakes.

Other studies are currently underway to further evaluate the independent effects of folate, B12, and B6 vitamin therapy and its use in improving outcome after coronary angioplasty.