Researchers find older and cheaper test for heart disease just as effective as newer tests

An older and less expensive non-invasive diagnostic test called the graded exercise stress test (GXT), that measures for blockages in the heart arteries, is as effective as the newer, more expensive cardiac tests according to a new study from the Institute for Clinical Evaluative Sciences (ICES).

Physicians use diagnostic imaging and testing to determine the cause of coronary artery disease (CAD), the second leading cause of death in Canada.

The study published today in the Journal of the American Heart Association looked at all patients in Ontario, 20 years of age or older who underwent a non-invasive diagnostic test and received coronary angiography from January 1, 2012 to December 31, 2012.

“Diagnostic imaging and testing has been under the microscope recently due to the large growth in utilization. We have multiple testing options that have been developed over the past few years. There isn’t consensus on which testing option should initially be used for the evaluation of patients with stable CAD.  The evidence behind using one testing strategy over the other is currently not very strong,” says Dr. Idan Roifman, an adjunct scientist at ICES, staff cardiologist at Schulich Heart Centre and lead author of the study.

Currently there are four tests used in Ontario for CAD:

• exercise stress test (GXT)
• myocardial perfusion imaging (MPI),
• coronary computed tomography angiography (CCTA)
• stress echocardiography (stress echo)

“There is a trend to do tests other than GXT as first line tests with the thought being that they provide more information about heart structure and/or function. We therefore expected clinical outcomes to be better for those patients who had one of the non-GXT tests as their initial testing strategy. Instead, we found that none of the other tests performed better at identifying patients with significant coronary disease than the oldest and least expensive one, the GXT,” adds Roifman.

The researchers stress that not all patients would be eligible to undergo GXT as the first line test. Approximately 20 per cent of patients cannot undergo a GXT because it would be uninterpretable due to other contraindications.

“But often times, physicians were ordering the other tests as first line tests even in those who could undergo GXT. We do see this in Europe as the guidelines there recommend MPI or stress echo as preferable to GXT in most cases as a first line test,” says Dr. Jack Tu, a senior scientist at ICES, staff cardiologist at Schulich Heart Centre and senior author of the study.

Previous data shows that in 2011-2014 there were 2,166,371 total non-invasive cardiac diagnostic tests billed for in Ontario.

The researchers add that the results of their study shows that in a large contemporary real-world population-based cohort, an initial non-invasive diagnostic strategy with a CCTA, stress echo, or MPI failed to result in a higher yield of obstructive CAD compared with an initial strategy with a GXT.

“These findings highlight the need for future research to explore the reasons for the discrepancy between our real-world findings and those of clinical efficacy studies,” adds Tu.

“Comparison of anatomic and clinical outcomes in patients undergoing alternative initial noninvasive testing strategies for the diagnosis of stable coronary artery disease,” was published today in Journal of the American Heart Association.

Author block: Idan Roifman, Harindra C. Wijeysundera, Peter C. Austin, Mohammad R. Rezai, Graham A. Wright and Jack V. Tu.

The Institute for Clinical Evaluative Sciences (ICES) is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

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