Doctors with private financial conflicts of interest dominated some of the panels that wrote guidelines on cardiovascular health in recent years, according to a medical journal study released on Monday.

The guideline panels are the select groups of experts who are assigned to evaluate science independently and issue their advice to other doctors on what to do in clinical practice. The guidelines influence medical care, product choice, insurance coverage, government policy and malpractice cases.

The study, published in the Archives of Internal Medicine, found that conflicts of interest were reported by 56 percent of 498 people who helped write 17 guidelines for the American Heart Association and American College of Cardiology, from 2003 through 2008.

Of people who led those groups, an even higher rate — 81 percent — had personal financial interests in companies affected by their guidelines, the study found.