Doubt has been cast over a recent study which suggests that heparin in high doses can aid coronary arteries and make angioplasty unnecessary in some patients with heart attacks.

A leading US investigator disputes the claims of the HEAP (Heparin in Early Patency) report as invalid and potentially dangerous.

The investigator, Eric Topol of the Cleveland Clinic in Ohio, says he has "heaps of doubt" about the small study since results weren't confirmed by a larger main study conducted later. More over, Topol believes high dose heparin is likely to cause significant bleeding complications when used with angioplasty or stents (devices used to open up arteries).

The pilot study monitored 108 patients with acute heart attacks who were eligible for angioplasty and given a high dose of heparin in the emergency room. The report states that at 90 minutes, 51 per cent of the patients had a clear coronary artery, more than in control groups.

The study's author, Freek Verheugt of University Hospital Nijmegen, Netherlands, had said that high doses of heparin can safely open up arterial vessels, making angioplasty unnecessary in certain patients (Lancet, 1998; 351: 421).