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Drugs taken by more than 1.5 million North Americans to control heart rhythm offer no medical benefits and increase the risk of death, a major Canadian-led study has concluded.

"Anti-arrhythmic drugs have been a decade and a half of disappointment, basically," said study chairman Dr. D. George Wyse, a University of Calgary professor of cardiology.

Published today in the New England Journal of Medicine, this is the second study in 2002 to reveal the dangers of drugs in widespread use for heart protection. In July, a U.S. Women's Health Initiative found hormone replacement does more harm than good, causing small increases in breast cancer, heart attacks, strokes and blood clots. Neither approach was properly tested in clinical trials, experts say.

For patients who take anti-arrhythmic drugs, the news is stunning.

"My doctor said millions of patients take it so it's safe," said Eric Freeman, a retired Victoria accountant.

"As far as I'm concerned, I've taken my last pill."

The study suggests the simpler and less expensive regimen of blood thinners and drugs that slow the heart rate is safer and more effective.

At least 200,000 Canadians suffer from atrial fibrillation, a number expected to grow to 600,000 patients by 2010. The condition occurs when electrical signals in the heart's upper chambers begin to fire in a fast, chaotic manner. Since blood in the chambers no longer moves well, it can stagnate and clot. "If a piece of clot breaks off, it can go to the brain and cause a stroke," said Dr. Wyse, a leading international authority on the condition.

The electrical chaos in the atria can also cause the heart's main pumping chambers, the ventricles, to pump erratically, causing fatigue, palpitations and shortness of breath.

About 75% of atrial fibrillation patients across North America take drugs to control heart rhythm.

In the past 12 months, Canadian pharmacies dispensed 1.5 million prescriptions for such drugs, which include sotalol, amiodarone, propafenone, according to the research firm IMS Health.

The conventional wisdom among cardiologists is that rhythm control prevents strokes and other complications. "It makes sense that people would feel better in normal rhythm," Dr. Wyse said.

"But the benefits that we expected to see we didn't really see."

Indeed, anti-arrhythmia drugs have failed to deliver on their promise from the start.

In 1989, a U.S. study using the drugs to treat patients who previously suffered a heart attack was halted when preliminary results showed the risk of death for treated patients was 2 1/2 times greater than those who took a placebo.

Concerned about such poor results, Dr. Wyse lobbied the U.S. National Heart, Lung and Blood Institute (NHLBI) for funds to compare rhythm control with heart rate control in non-heart attack patients.

The study, which lasted from 1995 until late 2001, followed 4,060 atrial fibrillation patients across North America. The patients were older than 65 and also suffered high blood pressure, diabetes or congestive heart failure.

Patients received either anti-arrhythmic drugs or drugs that slow and strengthen the heart rate, such as digoxin, beta blockers and calcium channel blockers.

Both groups also received blood thinners to reduce the risk of clotting and strokes.

At the conclusion, 356 patients who took rhythm-control drugs had died, compared to 310 in the rate control group. During the study, 1,374 patients in the rhythm-control group were hospitalized compared to 1,220 in the rate control group.

"It appears that the preferred therapy for many patients with atrial fibrillation may be a strategy to control the heart rate," said Dr. Claude Lenfant, director of the NHLBI.

A European study, published today in the same journal, largely came to the same conclusion. However, it also found female patients who received rhythm control faced a higher risk of heart failure, stroke and other events than males.

"For many patients, [these studies] should fundamentally alter their approach to treatment," said Dr. Michael Domanski, head of the NHLBI's clinical trials group.

However, Dr. Domanski said younger patients who have fewer risk factors, such as high blood pressure, may be at less risk than older patients. He urged patients not to stop taking their medications until they consulted their doctors.

Dr. Wyse said these findings may shift the spotlight to non-drug-based methods of controlling atrial fibrillation, such as implantable defibrillators.

bevenson@nationalpost.com