The results of a small but important study showed that intravenous doses of a synthetic component of high-density lipoprotein (HDL) cholesterol ("good" cholesterol) may help reduce the number of deaths from heart disease. The treatment used a laboratory-produced version of an unusually effective form of HDL. The results of the study stem from a discovery 25 years ago in the village of Limone sul Garda in Italy. The researchers found that 40 residents there had very low HDL levels, yet they had low rates of coronary artery disease. Laboratory tests showed a likely explanation: All the residents had a gene variation in a key protein component of HDL. The variation contributed to larger-than-normal HDL particles, which are thought to make HDL cholesterol especially efficient at removing plaque. The scientists made a synthetic form of the protein, which rapidly showed a reduction of plaque buildups in mice and rabbits. In the study of 47 participants, 36 patients who had heart attacks or severe chest pain received weekly intravenous infusion of the synthetic protein for 5 weeks, and 11 patients received placebo treatments. At 6 weeks, imaging tests indicated that the patients receiving the synthetic protein had a 4% reduction in plaque buildup in their coronary arteries, compared with no significant change in the placebo group. The findings were published in the Journal of the American Medical Association (November 3, 2003).