Weak Evidence Backs Most Heart Guidelines, Report Finds

Experts agree that field needs more rigorous trials to aid doctors

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By Ed Edelson
HealthDay Reporter

TUESDAY, Feb. 24 (HealthDay News) -- A majority of the guidelines for cardiac care issued by the American Heart Association and the American College of Cardiology are not supported by the kind of gold-standard evidence that doctors respect most, a new study finds.

That conclusion does not come from heretics crying in the wilderness. One author of the report, published in the Journal of the American Medical Association, is Dr. Sidney Smith, a professor of medicine at the University of North Carolina, a past president of the heart association and former chairman of the AHA/ACC Guidelines Task Force.

The findings were quickly endorsed by Dr. Timothy J. Gardner, current AHA president.

"There are many situations we encounter where we don't have as strong evidence for the guidelines as we would like to have," said Gardner, who is medical director of the Center for Heart & Vascular Health at the Christiana Care Health System in Delaware. "There haven't been enough randomized trials."

And too many of the carefully controlled trials now being done are financed by pharmaceutical companies, said Dr. Pierluigi Tricoci, a cardiologist at the Duke Heart Center and another member of the team that did the study.

"Most major clinical trials are sponsored by the pharmaceutical industry, because they want to bring products to market," Tricoci said. "We don't have a source of funding for those situations that the pharmaceutical industry might not be interested in. We should not be surprised that the pharmaceutical industry is not interested in trials from which they might not make money."

Tricoci was an originator of the project that looked at the evidence supporting cardiac care guidelines, which have multiplied in number in recent years. The project investigators examined 53 guidelines on 22 topics, with a total of 7,196 recommendations.

The evidence for those recommendations was graded A to C. A recommendation got an A if its evidence came from multiple controlled trials, a B if evidence came from one randomized trial or non-randomized trials, and a C if the recommendation was based on clinical judgment, with little or no scientific evidence.

Just 12 percent of current recommendations -- 314 of the 7,196 -- got a grade of A, and 45 percent earned a C.

Those grades have been dropping in recent years, the study found. Though the number of recommendations increased by 48 percent over the 24 years covered by the study, there has been a steady shift toward lower levels of supporting evidence.

The lack of evidence is greatest in treating disorders of the heart valves, Tricoci said. "This is the area with the highest number of level C recommendations," he said.

The findings do not mean that cardiologists should ignore the guidelines, Tricoci said. "What the paper says is that cardiologists in daily practice face several situations where there is not scientific evidence and not a consensus about the best approach," he said. "This quantifies the gap in knowledge that I'm sure every cardiologist is familiar with every day."

One example of the uncertainty they face is the recommendation for prescribing the clot-preventing drug Plavix for someone who has had a stent implanted after an artery-opening procedure such as angioplasty, Tricoci said.

"That is uncertain even in the guideline," he said. "It says, 'for at least a year,' but there is no trial that shows how long Plavix should be given."

"There are lots of issues raised by this discussion," Gardner said. "To us, it is a validation of the usefulness of guidelines, plus pointing out that we don't have as many multi-center randomized trials as we would like to have."

But existing guidelines, Gardner said, are basically the best that can be set at this time. "As we get into more areas of medical science and patient care, sometimes we get into areas where there are not primary clinical trials," he said. "When guidelines are based on clinical trials, which is as good evidence as can be obtained, they can be trusted quite enthusiastically. When we are forced to rely on expert opinion, we need to respect the fact that future trials may provide further information."