Let's wait for US trial results before recommending drug-eluting stents to patients

I refer to the letter by Dr Tan Soon Kiam (Online forum, Feb 26), 'Drug-eluting stems - benefits outweigh the risks.'

The writer seeks to espouse chelation therapy for the treatment of coronary artery disease.

We would like to provide a balanced view on this subject on the basis of evidence-based practice. Chelation therapy involves administering intravenous EDTA (a man-made amino acid) infusion over 2-4 hours, given weekly for a total of 30 or more treatments.

The aim of this therapy is to reduce the amount of calcium in atheromatous coronary arteries, hence possibly reducing the arterial narrowings.

There have also been many alternative explanations as to why chelation therapy might work.

Reports of beneficial effects of drugs or devices could be due to subjective and biased reporting, unless they are tested in double blind randomised placebo controlled trials, with an adequate number of patient subjects.

In a 2005 review of the chelation literature by a group of authors from Canada, they found five such randomised trials (see website www.biomedcentral.com/1471-2261-5-32). After going through these trial results, they concluded that the best available evidence does not support the therapeutic use of EDTA chelation therapy in the treatment of atherosclerotic cardiovascular disease. The American Heart Association, American College of Cardiology and the American Food and Drug Administration (FDA), among many other medical organisations, also similarly do not recommend chelation therapy for this indication.

These trials were, however, underpowered for detecting differences in clinical outcomes, as the numbers recruited were too small. Hence, a large US/Canadian multicentre randomised placebo controlled clinical trial, focusing on major clinical outcome endpoints, is currently being carried out by the National Institute of Health, US. The trial is expected to recruit around 2,000 patients, and be completed by June 2010. As the cost of conducting such a trial is at least US$30 million, the National Heart Centre will not be in a position to perform such a trial, given its prohibitive cost.

We should therefore await the results of this NIH-sponsored trial before recommending such unproven therapy to our patients. This is especially so when there are already very effective proven therapy for atherosclerotic cardiovascular disease, in terms of drugs, bypass surgery and coronary stenting.

Chelation therapy has also been reported to have rare side-effects of sudden blood pressure drop, abnormally low calcium levels in the blood and kidney damage and it may affect blood cell production.

For more information on this subject, please access the American Heart Association website: http://www.americanheart.org/presenter.jhtml?identifier=4493

A/Prof Koh Tian Hai

Medical Director

National Heart Centre