A new triple-drug treatment has dramatically decreased cholesterol in 22 patients with severe cholesterol problems, dropping the levels of the life-threatening substance to below the national average, according to a San Francisco study. The treatment by doctors at San Francisco's Cardiovascular Research Institute included a new anti-cholesterol drug, lovastatin, combined with long-accepted cholesterol therapy using niacin and colestipol. The patients suffer from a severe form of familial hypercholsterolemia, an inherited disease which causes high cholesterol and frequently leads to clogged arteries and heart attacks by middle age. Although the disease occurs in one of every 500 people, few people realize that they have it. Doctors reported that the 22 patients had an average cholesterol level of 420 milligrams per 10 liters of blood, which decreased after therapy to 184 to 190 milligrams per 10 liters of blood after treatment--a level lower than the national average of about 200.