TUESDAY, Feb. 6 (HealthDay News) -- Scientists have shown for the first time that raising "good" cholesterol levels is almost as important as lowering levels of "bad" cholesterol in reducing heart-threatening plaque in arteries.

But it's unclear at this stage whether the strategy will translate into fewer heart attacks and other cardiovascular events.

"A little bit of HDL [high-density lipoprotein, or "good" cholesterol] goes a long way. A small increase in HDL produces nearly as much of a benefit as LDL [low-density lipoprotein or "bad" cholesterol] reduction," said Dr. Steve Nissen, senior author of the study and chairman of cardiovascular medicine at the Cleveland Clinic. "In general, when we've found a therapy that slowed progression of disease, that translated into major clinical benefits. This makes a lot of sense."

Dr. Gregory Dehmer, professor of internal medicine at Texas A&M Health Science Center College of Medicine and director of the cardiology division at Scott & White Hospital, added: "It's almost been the holy grail to treat LDL in patients, and most take statins for that. Many clinicians stop with LDL and don't continue to aggressively attack HDL. This points up the need to aggressively address HDL and to not give up the cause."

The challenge now is to find safe ways to elevate HDL even more than is currently possible with the widely used drugs called statins.

Pfizer recently halted a trial of torcetrapib, an experimental drug that raised HDL levels, due to an increased mortality rate.

The value of lowering LDL is well known. But scientists have been unsure about the merits of raising HDL when it comes to atherosclerosis, or the accumulation of plaque in the lining of the arteries.

"We've always known that statins were very good at lowering LDL, and we knew that they increased HDL a little bit, about 7 to 8 percent," Nissen said. "That seemed to most of us to be fairly trivial, so we've already attributed the benefit of statins primarily to the lowering of bad cholesterol. But, we've always wondered whether that little bit of an increase in HDL was important as well."

For the new study, published in the Feb. 7 issue of the Journal of the American Medical Association, the researchers revisited four previously conducted studies involving 1,455 participants.

All patients had coronary artery disease and were taking statins. They underwent two ultrasound exams 18 moths to 24 months apart to determine changes in the amount of plaque in a coronary artery.

All four studies were sponsored by pharmaceutical companies.

Participants who both raised their good cholesterol levels and achieved very low bad cholesterol levels showed evidence of the most plaque removal.

"People were concerned about the HDL hypothesis, but this shows the hypothesis is sound," Nissen said. "This helps to nail down the fact that at least with respect to progression of disease, the HDL-raising properties of the statins are important."

Other experts sounded a cautionary note, pointing out that reducing plaque build-up has not been shown to reduce cardiovascular events, even though lowering LDL cholesterol has.

"For a long time now, we've understood that events go way down with therapy, even though plaques don't seem to get a lot smaller," said Dr. Kirk Garratt, clinical director of interventional cardiovascular research at Lenox Hill Hospital in New York City. "The more important thing is not shrinkage but plaque stability and less blood clot formation."

"The current study corroborates that," Garratt continued. "There were no important differences in clinical events between those patients with little/no plaque regression compared with those who had a lot of plaque regression. This is because statins lower events through plaque stabilization more than plaque regression and likely also work through other mechanisms like lowering inflammation."

More information

For more on atherosclerosis, visit the American Heart Association.