Doctors in Ontario used a diagnostic heart test before scientific evidence emerged on its effectiveness, researchers have found.

Coronary angiography, also called cardiac catheterization, uses X-rays to study the inside of the heart and blood vessels. By looking at blood flow, the test helps identify blocked vessels that may be treated with angioplasty, in which a tiny balloon is inflated to open an artery from the inside to restore circulation.

Dr. David Alter of the Institute for Clinical Evaluative Sciences in Toronto and his colleagues looked at the adoption rates for angiographies and statin drugs for heart attack patients aged 65 and older who were admitted to hospital in Ontario between 1992 and 2004.

The introduction of angiographies in Ontario peaked in September 1998, 11 months before the first randomized controlled trial showing benefits of the test for heart attack patients, the study's authors report in Monday's issue of the Archives of Internal Medicine.

"The proliferation of cardiac catheterization in Ontario is attributable to factors other than the emergence of published scientific evidence," the researchers concluded.

The findings were the same regardless of whether hospitals had catheterization labs or the severity of illness.

The opposite was true for statins, where ample evidence from clinical trials suggested survival benefits, but it took four years from the first trial being published before the drugs were widely used, the team found.

In the case of angiography, evidence now suggests certain risk groups should get the test after a heart attack, but it was gamble, Alter said, before the evidence was found. 

Allure of technology

Other technologies that took off without established evidence of benefits include the introduction of balloon-tipped right heart catheters in the 1970s, and increased use of MRIs and CT scans to assess acute low back pain in the U.S., the researchers said.

Several possible reasons may explain the mismatch between the use of diagnostic technology and evidence of benefits, the researchers said. Doctors may accept new devices more quickly than new drugs partly because of the allure of technology, Alter said.

Also, regulatory approval of devices does not require the same set of evidence that drugs do, said Alter, who suggested raising Health Canada's bar for approval of technologies. Historically, scientific evidence of diagnostic technologies has focused on accuracy, the study's authors noted.

Side-effects of drugs are commonly reported, while those of technology may not be, Alter added.

A previous U.S. study also suggested that doctors on health policy committees tend to "accept interventions without critical assessment when the proponents are prestigious and prominent and the interventions well remunerated," the study's authors wrote.