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Compared with clinicians in Ontario, doctors in New York ordered more cardiac catheterizations that ultimately proved to be negative, researchers found.
The observed rate of obstructive CAD in those who underwent a cardiac cath was significantly lower in New York state than in Ontario (30.4% versus 44.8%, P<0.001), according to Dennis Ko, MD, MSc, of the Institute for Clinical Evaluative Sciences in Toronto, and colleagues.
The New York cohort also had an overall lower predicted probability of detecting obstructive CAD than the Ontario group (19.3% versus 41%), researchers wrote in the study published in the July 10 issue of JAMA.
Specifically, when the predicted probability of detecting obstructive CAD was less than 15%, the New York cohort had more than double the percentage of patients who underwent angiography than the Ontario group (15.1% versus 6.9%).
Conversely, when the predicted probability was greater than 75%, the New York group had a lower proportion of patients who received diagnostic angiography compared with the Ontario group (1.4% versus 7.9%).
In each of the remaining four categories comprising low probability of obstructive CAD (from 15% to 55%), New York outpaced Ontario in catheter exams. And in each of the two remaining categories comprising high probability (from 55% to 75%), the reverse was true -- New York patients received fewer angiograms.
"According to these findings, one might reasonably conclude that a more selective use of cardiac catheterization should be implemented to reduce its associated cost and to improve its diagnostic efficiency," researchers wrote.
They suggested that a more selective approach could result in a $75 million per year savings for New York.
In a 2010 study, Manesh Patel, MD, from Duke University, and colleagues found that 38% of patients referred to a cath lab had obstructive CAD.
"The findings in the current study -- 30% versus 44% of observed obstructive CAD -- are directly intermediate of Patel's finding of 38%, and still relatively low," Ajay Kirtane, MD, an associate professor of medicine at Columbia University Medical Center in New York City, told MedPage Today.
Kirtane, who was not involved in the current study, also cautioned against being too restrictive in ordering cath exams, due to the potential of overlooking those who need the exam.
Ko and colleagues addressed this issue and found that "a more restrictive approach in selecting higher-risk patients for cardiac catheterization was associated with improved detection of patients with single-vessel as well as multivessel CAD ... and did not lead to substantial underdetection."
This is not the first time that the U.S. and Canada showed differences in health outcomes. The researchers cited two studies, also led by Ko, that examined care and outcomes in older acute myocardial infarction patients (Circulation 2007; 115: 196-203) and older heart failure patients (Arch Intern Med 2005; 165: 2486-2492) that favored Canada.
"Given the increasing focus on how best to use scarce healthcare resources, it is important to understand the reasons underlying the different utilization patterns and their associated implications," they explained.
They therefore conducted the current study, which included patients without a history of cardiac disease who underwent elective cardiac catheterization between October 2008 and September 2011. A total of 18,114 patients from New York and 54,933 from Ontario were included.
They found significantly lower rates of observed obstructive disease in New York versus Ontario when they examined specific coronary regions (all P<0.001):
- Left main stenosis: 2.5% versus 5%
- Three-vessel CAD: 5.2% versus 9.8%
- Left main or three-vessel disease: 7% versus 13%
The researchers also found that at 30 days, crude mortality for patients undergoing cardiac catheterization was slightly higher in New York at 0.65% versus 0.38% in Ontario.
"However, this difference was driven primarily by higher mortality for patients without obstructive CAD in New York at 0.62% versus 0.27% in Ontario," they noted.
There were also some significant individual factors between the two regions that could have contributed to the differences, the authors pointed out. A majority of the New York cohort (58%) did not have typical chest pain as categorized by the Canadian Cardiovascular Society classification.
Also, although the majority of patients in both cohorts (75% New York versus 63% Ontario) had noninvasive coronary evaluation such as SPECT imaging, only 5% of the New York group had high-risk findings compared with 50% for Ontario.
The large discrepancy could be a result of differences in how "physicians interpret high-risk findings on noninvasive stress testing in each region," the authors offered.
They also suggested using the obstructive CAD rate as a potential quality indicator to enhance efficiency and improve quality.
A limitation of the study included not being able to calculate the effect of race, body mass index, or physician characteristics. Also, they could not assess the appropriateness of cardiac caths in Ontario, because data is lacking in Canada to create appropriate-use criteria.
From the American Heart Association:
The study was supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-term Care. The analysis of the study was supported by a grant from the Canadian Institutes of Health Research. The Heart and Stroke Foundation of Ontario also provided support to some authors.
The authors reported no conflicts of interest.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner
Journal of the American Medical AssociationSource Reference: Ko DT, et al "Prevalence and extent of obstructive coronary artery disease among patients undergoing elective coronary catheterization in New York state and Ontario" JAMA 2013; 310: 163-169.