When a patient undergoes an angioplasty, a balloonlike device is inserted through a catheter into a clogged artery. By expanding this device while it is inside the artery, the atherosclerotic plaque that has accumulated is compressed against the vessel wall. However, up to 40% of patients then develop restenosis, necessitating an other angioplasty or even bypass surgery.

Guido Schnyder, a visiting cardiologist at UCSD from Switzerland and lead author of the study, explains that hundreds of thousands of angioplasties are performed each year, and given the high risk of restenosis, repeat procedures are common. Schnyder and his colleagues at the Swiss Cardiovascular Center had previously observed that patients with high levels of homocysteine are more likely to develop restenosis. Homocysteine is a protein-derived amino acid that can build up in the blood and block the arteries, increasing the risk of heart disease. Previous studies had shown that a daily dose of at least 500 µg of folic acid in combination with vitamins B12 and B6 could lower homocysteine levels by 25–30%.

In Schnyder’s study, 105 patients were given 400 µg of vitamin B12 and 10 mg of vitamin B6, while 100 patients were given a placebo for 6 months after successful coronary angioplasty. Of the patients who took the vitamins, only 19.6% developed restenosis (N. Engl. J. Med. 2001, 345, 1593–1600). In comparison, 37.6% of those given the placebo had repeat blockage.

“No real drug has been found to treat restenosis,” says Schnyder. “By administering this vitamin B combination, we can lower the rate of restenosis at an extremely low cost without inducing side effects, which is unusual in medicine.”