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Beyond the numbers

May 7, 2014

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By Alisa Kim

The Canadian Institutes of Health Research Institute of Health Services and Policy Research has named a study led by Dr. Dennis Ko, a scientist in the Schulich Heart Research Program at Sunnybrook Research Institute, its article of the year.

The award recognizes publications that have advanced the field of health services and policy research. The paper, “Prevalence and extent of obstructive coronary artery disease among patients undergoing elective coronary catheterization in New York State and Ontario,” was published in 2013 in the Journal of the American Medical Association.

In the study, Ko and colleagues compared rates of coronary angiography in the two regions between 2008 and 2011. Coronary angiography is a test in which doctors study blood flow patterns by injecting an X-ray dye into the arteries and heart using a catheter. It is the gold standard for diagnosing heart disease—narrowing of the coronary arteries that reduces or halts blood flow to the heart—which is the leading cause of death worldwide.

A large U.S. study found the majority of patients who had the test done did not have significant blockages, suggesting the procedure is overused and that patients are often exposed to associated risks and costs unnecessarily. The researchers wanted to understand the reasons behind overuse of the procedure.

Despite greater use of coronary angiography in New York, the researchers found that the likelihood of diagnosing obstructive heart disease among people who had the test done was higher in Ontario. “The rate of [disease] detection was lower in New York State by about 15%. In fact, we found the main reason a lot patients didn’t have coronary artery disease was because they were low risk. The chance of detecting something was low, yet they were still getting the procedure done,” says Ko, who is also an interventional cardiologist at Sunnybrook Health Sciences Centre.

Interestingly, the percentage of patients with left main disease (narrowing of at least 50% of the left main coronary artery) or significant narrowing of multiple vessels on the heart’s surface was much lower in New York compared with Ontario. This, says Ko, suggests doctors are not under-detecting heart disease in this province. “There’s no evidence that the way Ontario selects people for angiography is associated with greater harm,” he says.

The researchers noted the findings underscore differences in practice between the two regions. For example, most of the patients in the study did an exercise “stress test” prior to the angiogram to evaluate whether blood supply was reduced in coronary arteries. Of these, only 5% of patients in New York had high-risk findings, whereas in Ontario, high-risk findings were found in one-half of the patients.

Ko notes there are about 50,000 coronary angiograms done each year in Ontario at an estimated cost of $3,000 each. An implication of the study is that more selective use of the test could save millions of dollars, he says.

He also points out that the higher diagnostic yield of coronary angiograms in Ontario does not mean there isn’t room for improvement. “We used Ontario as a comparison. That’s not to say our way of testing is perfect. It’s definitely not,” says Ko.

The ultimate goal of his research is to improve patient outcomes and use of health care resources. “As patients get older, there are more comorbidities. The money that needs to be spent on health care is increasing. We need to be more efficient and minimize things that will not benefit patients. That’s what we [try to] do.”

Dr. Ko