B Vitamins and Restenosis after Coronary Angioplasty

To the Editor: Schnyder et al. (Nov. 29 issue) 1 suggest that a combination of B vitamins lowers plasma homocysteine levels, which, in turn, reduces the rate of restenosis after coronary angioplasty. This effect is interpreted as evidence of a causal role of hyperhomocysteinemia in the progression of atherosclerotic disease. Observational studies and clinical trials have been unable to rule out the alternative hypothesis that serum folate, vitamin B 12 , or pyridoxine may have an independent inhibitory effect on atherosclerosis, with a secondary effect on the homocysteine level. Indeed, observational data from large, prospective studies, such as the Atherosclerosis Risk . . .