The long-awaited results of a study gauging the benefits of a controversial heart disease therapy have once more pitted the alternative medicine community against mainstream cardiologists.
A clinical trial that cost taxpayers $30 million and took researchers more than a decade to complete suggests that chelation -- the removal of heavy metals from the body -- may offer some benefits to patients who have suffered a heart attack.
But those findings were immediately discounted by the editors of the influential journal that published the study's findings. The findings were also set upon by a leading cardiologist, who charged that the study was poorly designed and executed and should not be seen as justification for a practice that diverts heart patients from therapies with clearer evidence of benefit.
For more than half a century, a growing number of physicians treating heart attack survivors have taken to ordering an infusion of disodium EDTA -- a chelating agent that treats heavy metal toxicity.
In recent decades, a small but growing minority of physicians have joined with practitioners of alternative medicine in believing that chelation can prevent a repeat heart attack and many other dangers lying in wait for someone with heart disease. Advocates of the controversial therapy believe that by drawing down the body's stores of calcium, magnesium, lead, zinc, iron, aluminum and copper, chelation softens plaque buildup in the arteries, improves blood flow, decreases the formation of free-radicals, and improves cell membrane function. Many practitioners also offer chelation in treatment of arthritis, multiple sclerosis, Parkinson's disease and Alzheimer's.
About 550 members of the American College for Advancement in Medicine indicate that they practice chelation therapy, in which patients are infused with disodium EDTA between one and three times a week at a cost of between $75 and $125 per treatment. Researchers estimate that by 2007, 111,000 heart attack patients had undergone chelation treatment.
But having a long history and a growing following does not mean a medical procedure offers real benefits: In modern medicine, the benefits of a treatment are expected to have been shown in rigorous clinical trials, in which a given therapy is compared head to head to an inactive look-alike therapy.
The TACT trial -- short for Trial to Assess Chelation Therapy -- was to have served that purpose. Researchers led by Dr. Gervasio A. Lamas of Columbia University's Mt. Sinai Medical Center enrolled 1,708 patients aged 50 or older who'd had a heart attack in recent months at 134 sites across the United States and Canada. Roughly half the group got 40 infusions of the chelation agent over roughly a year, and were followed on average for about five years after that. The other half got infusions of a sham solution.
In the follow-up period, researchers found that those who got the chelation were slightly less likely to require revascularization procedures or hospitalization for angina. But they were not significantly less likely to have another heart attack, to suffer a stroke, or to die of either a stroke or heart attack.
"A bad trial can be worse than none at all," said Cleveland Clinic cardiologist Dr. Steven Nissen. During the trial, a higher-than-expected number of subjects dropped out of the trial's placebo arm, undermining the statistical reliability of its findings, Nissen charged. He suggested that some of the investigators who were advocates for chelation therapy may have tipped their hands to patients who were not getting chelation, prompting them to drop out.
The editors of JAMA concluded chelation is a far-from-proven way to avert a second heart attack, a stroke, death, or the need for additional invasive vascular procedures such as stenting or coronary bypass.
"The possible benefit of chelation therapy, if there is any, is small," wrote a group of editorialists. "This evidence and information should serve to dissuade responsible practitioners from providing or recommending chelation for patients with coronary disease and should discourage patients with previous myocardial infarction from seeking this therapy with the hope of preventing subsequent cardiovascular events."
A single study rarely is powerful enough proof to change clinical practice by itself, the editorialists wrote. But even with significant flaws in design and execution, this study is one of those, they added: "These findings do not support the routine use of chelation therapy."