Stress test just as good as pricier options, heart study finds

Researchers looked at 2012 data on almost 19,000 Ontario adults

An old, cheaper test for heart disease is just as effective as newer, costlier ones, Ontario researchers have found.

Their work, published Thursday in the Journal of the American Heart Association, suggests that health systems could save money by using the decades-old exercise stress test as a first-line diagnostic tool to identify coronary artery disease.

“With healthcare budgets rising sharply in many high-income countries and with cardiac diagnostic testing and medical imaging contributing substantively to these costs, the assessment of comparative clinical effectiveness is important to assess the real-world impact of these modalities,” the study states.

The paper compares four different noninvasive tests for coronary artery disease, the second leading cause of death in Canada, after cancer.

The oldest of these tests, in existence for more than half a century, is the exercise stress test. Also known as a graded exer- cise test (GXT), it shows how the heart responds to increasing levels of stress on a treadmill or stationary bike and reveals whether there are blockages in arteries. Three newer tests studied include: Stress echocardiography, or stress echo. This is similar to a GXT, but also involves taking ultrasound images of the heart.

Myocardial profusion imaging (MPI), also known as a nuclear stress test. It assesses blood flow through the heart and uses the intravenous injection of a small amount of a radioactive blood flow marker.

“No one knows what the best approach is because there is disagreement among the guideline writers.” DR. IDAN ROIFMAN LEAD AUTHOR

Coronary computed tomography angiography (CCTA). A CT scanner is used to look at the structures and blood vessels of the heart after a patient is injected with an intravenous dye. Contemporary MPI technology was first used in1988. Stress echo and CCTA are newer tests for which OHIP billing codes were introduced in 2011. All tests have undergone many iterations and improvements over time.

Lead author Dr. Idan Roifman, an adjunct scientist at the Institute for Clinical Evaluative Sciences and staff cardiologist at the Schulich Heart Centre at Sunnybrook Hospital, said there has been an international debate among cardiologists about which test to use first on patients suspected of having coronary artery disease.

U.S. guidelines recommend the exercise stress test, but European guidelines suggest that an MPI or stress echo may be preferable. There are no Canadian guidelines. “No one knows what the best approach is because there is disagreement among the guideline writers, and in clinical practice people do whatever they feel is better,” Roifman explained.

Over the past five years, cardiologists have been increasingly using the three newer tests, which provide more information on heart structure and/or function than the GXT, he noted.

“Physicians do it because they honestly think it’s better since they are getting more information,” he explained.

In an attempt to get some clarity, Ontario researchers did a retrospective study, looking at administrative and clinical data for 18,819 Ontario adults who had undergone some form of non-invasive diagnostic testing in 2012.

Within six months, these patients also underwent invasive angiograms, considered the gold standard in diagnostic testing for coronary artery disease. This test can tell a physician what percentage of an artery is blocked, but is used more sparingly because it comes with higher risks.

It involves inserting a catheter into an artery, typically in the groin region, and threading it up through the femoral artery to the heart. Contrast dye is injected into the coronary arteries.

In comparing the four initial tests, Ontario researchers planned to rank them by assessing their ability to detect coronary artery disease and their association with improved clinical outcomes. For outcomes, researchers looked at rates of heart attacks and deaths.

Roifman said they were surprised by what they found. They expected one of the three newer tests to show superior results, given that they are being used more and provide more information.

But there was no significant difference between the newer tests and the “plain old stress test,” he said.

The oldest, least expensive test performed just as well as the newer, costlier ones, the study found.

“The angiograms didn’t show heart disease more often in the patients who had the fancy tests, the nonGXT tests. And, more importantly, there was no difference in clinical outcomes down the road,” Roifman said.

The study did not draw any conclusions about potential cost savings.

Roifman said that’s the next step and his team is now working on a cost analysis. Between 2011 and 2014, physicians billed for more than 2.2 million non-invasive cardiac diagnostic tests in Ontario.

An exercise stress test (including professional and technical fees) costs OHIP $105 while a nuclear stress test (including multiple component fees) costs about $600. The other two tests fall in between.

The study says that more research is necessary to assess outcomes related to all patients who undergo non-invasive cardiac testing in Ontario, not just those who have subsequent invasive angiograms.

The paper emphasizes that about 20 per cent of patients requiring non-invasive cardiac testing are ineligible for exercise stress tests. As well, a certain subpopulation may benefit from initial non-GXT tests, something else the researchers continue to study.