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Ontario’s method of selection of patients for cardiac catheterization is more efficient than that in New York State: ICES study

July 9, 2013 Toronto

Doing more cardiac imaging procedures is expensive and does not result in healthier patients according to new research conducted at the Institute for Clinical Evaluative Sciences (ICES) and the Cardiac Care Network (CCN) of Ontario. Researchers compared the use and outcomes of cardiac catheterization in Ontario and New York State.

Cardiac catheterization is a medical procedure used to diagnose and treat patients with blockages of their heart arteries. A long, thin, flexible tube called a catheter is put into a blood vessel in the arm, groin or neck and threaded to the heart. Through the catheter, a doctor can inject contrast for x-rays to outline the arteries, or carry our treatment procedures, such as cardiac stents.

“Prior studies have shown that New York State performs twice as many cardiac catheterizations per capita as Ontario for stable patients with suspected coronary artery disease. We wanted to know what the implication was in terms of detecting heart blockages under these two different systems,” says Dr. Dennis Ko, lead author of the study, a senior scientist at ICES and an interventional cardiologist at the Schulich Heart Centre at Sunnybrook Health Sciences Centre.

The study, published today in JAMA, found substantially more cardiac catheterizations are being performed on low risk patients with a small chance of having heart blockages in New York State, when compared to Ontario. As a result, the detection rate of the procedure is low, which implies that too many cardiac catheterizations are being performed New York State, with both a financial and a human cost.

“The higher use of cardiac catheterization in New York State was primarily due to selecting patients at low risk of obstructive coronary artery disease. The Ontario approach of selecting patients with a higher probability of having coronary disease for cardiac catheterization is associated with improved diagnostic yield of the procedure,” says Ko.

In the past, there was concern that not performing cardiac catheterization may lead to under-detection of critical heart blockages. However, this is not the case in contemporary practice.

The observational study was conducted using data from New York State and Ontario. Patients without a history of cardiac disease who underwent elective cardiac catheterization between October 1, 2008 and September 30, 2011 were included in the analysis. Obstructive coronary artery disease was defined as diameter stenosis of 50 per cent or more in the left main coronary artery or stenosis of 70 per cent or more in a major coronary vessel. Findings include:

  • The diagnostic yield of cardiac catheterization rate (angiogram) to detect obstructive coronary artery disease (or heart blockage) is low in New York State and Ontario.
  • The rate of detecting any blockages was significantly lower in New York State at 30.4 per cent vs. 44.8 per cent in Ontario.
  • The rate of detecting critical blockages was also significantly lower in New York State at 7 per cent vs. 13 per cent in Ontario.
  • The poor detection rate of coronary artery disease in New York State is primarily driven by the selection of low risk patients.
  • New York State could potentially save $100 million per year if it adopted Ontario’s method of selection of patients for cardiac catheterization.

“Most importantly, this research indicates that the rates of subsequent death and heart attacks in Ontario patients is not higher because of lower rates of angiography in this province compared to New York State,” says Ko.

The study “Prevalence and extent of obstructive coronary artery disease among patients undergoing elective coronary catheterization in New York State and Ontario,” was published today in JAMA.

Authors: Dennis T. Ko, Jack V. Tu, Peter C. Austin, Harindra C. Wijeysundera, Zaza Samadashvili, Helen Guo, Warren J. Cantor and Edward L. Hannan.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care 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.

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