Blood pressure drugs beta-blockers can help keep arteries from clogging up, researchers said on Monday in a report that helps explain how the drugs prevent heart attack and sudden heart death.

The drugs are cheap and most are generically available, although studies show they are not prescribed as often as recommended.

Dr. Steven Nissen and colleagues at the Cleveland Clinic in Ohio pooled the results of four trials involving 1,500 patients to see if beta-blockers help slow the clogging of arteries.

They said 1,100 of the patients took beta-blockers. Most of the patients also got a cocktail of heart drugs including aspirin, ACE inhibitors, calcium-channel blockers, nitrates and statins.

Part of the study involved teasing out the effects of the beta-blockers versus the other drugs.

At the beginning, the patients given beta-blockers had similarly clogged arteries as those not given the drugs, Nissen's team reported in the Annals of Internal Medicine.

But when the patients were followed up, those given beta blockers had smaller blockages, while those who did not get the drugs did not, on average, show any change.

Cholesterol-lowering drugs called statins also, as would be expected, helped clean out arteries. But the beta-blockers had the effect independent of statin use, Nissen's team found.

"Beta blockers probably slow progression of coronary atherosclerosis," the researchers wrote.

The finding is a little surprising because beta-blockers are not designed to affect the cholesterol and inflammation that are usually blamed for causing atherosclerosis, or clogged arteries.

In fact, they can worsen some type of cholesterol measurements, lowering HDL or "good" cholesterol and raising triglyceride levels.

Beta-blockers work by blocking message-carrying chemicals such as epinephrine, adrenaline and norepinephrine, involved in stress.

They regulate heart rate but can often cause patients to complain of fuzzy thinking and sexual dysfunction.

Nissen's team said the findings support the continued use of beta-blockers, as recommended by several expert panels.