Low Diagnostic Yield of Elective Coronary Angiography

Reference: Patel MR, Peterson ED, Dai D. New England Journal of Medicine 2010 Mar 11;362:886-895.

ABSTRACT

Background Guidelines for triaging patients for cardiac catheterization recommend a risk assessment and noninvasive testing. We determined patterns of noninvasive testing and the diagnostic yield of catheterization among patients with suspected coronary artery disease in a contemporary national sample.

Methods From January 2004 through April 2008, at 663 hospitals in the American College of Cardiology National CardiovascularData Registry, we identified patients without known coronary artery disease who were undergoing elective catheterization.The patients’ demographic characteristics, risk factors, and symptoms and the results of noninvasive testing were correlated with the presence of obstructive coronary artery disease, which was defined as stenosis of 50% or more of the diameter of the left main coronary artery or stenosis of 70% or more of the diameter of a major epicardial vessel.

Results A total of 398,978 patients were included in the study.The median age was 61 years; 52.7% of the patients were men,26.0% had diabetes, and 69.6% had hypertension. Noninvasive testing was performed in 83.9% of the patients. At catheterization,149,739 patients (37.6%) had obstructive coronary artery disease.No coronary artery disease (defined as <20% stenosis in all vessels) was reported in 39.2% of the patients. [Non-obstructive coronary artery disease was reported in 23.2% of the patients. A total of 60.8% of the patients had coronary artery disease with >20% stenosis in one or more vessels.—M Crouch comment] Independent predictors of obstructive coronary artery disease included male sex (odds ratio, 2.70; 95% confidence interval [CI], 2.64 to2.76), older age (odds ratio per 5-year increment, 1.29; 95%CI, 1.28 to 1.30), presence of insulin-dependent diabetes (odds ratio, 2.14; 95% CI, 2.07 to 2.21), and presence of dyslipidemia (odds ratio, 1.62; 95% CI, 1.57 to 1.67). Patients with a positive result on a noninvasive test were moderately more likely to have obstructive coronary artery disease than those who didnot undergo any testing (41.0% vs. 35.0%; P<0.001; adjusted odds ratio, 1.28; 95% CI, 1.19 to 1.37).

Conclusions In this study, slightly more than one third of patients without known disease who underwent elective cardiac catheterization had obstructive coronary artery disease. [Almost two-thirds of the patients had significant coronary artery disease with >20% stenosis in one or more coronary artery segments.—MC comment] Better strategies for risk stratification are needed to inform decisions and to increase the diagnostic yield of cardiac catheterization in routine clinical practice. [dubious conclusion—MC comment]

Source Information: From the Duke Clinical Research Institute, Duke University, Durham, NC (M.R.P., E.D.P., D.D., J.M.B., P.S.D.); University of California at San Francisco, San Francisco (R.F.R., R.G.B.); and the University of Texas Health Science Center, Houston (H.V.A.). Address reprint requests to Dr. Patel at the Duke Clinical Research Institute, DukeUniversityMedicalCenter, P.O. Box 17969, Durham, NC27715

The problem with Patel et al’s interpretation of the elective coronary angiography data in the March NEJM article, is that it ignores the 23.2% of patients found to have non-obstructive CAD (20-49% left main or 20-69% other coronary stenosis). These patients are also at high risk for myocardial infarction (and stroke, since they are likely to have concomitant carotid artery disease). Aggressive medical management of their reversible risk factors is advisable to reduce their cardiovascular event risk. If they are like my patients, many of them are reluctant to take statins unless they think they “have to.” Finding out that they have clinically significant coronary artery disease breaks through their denial of their high-risk status. Knowing that they have coronary artery disease makes many of them more receptive to starting and continuing statin therapy.

So detecting those with sub-critical CAD can prevent some heart attacks and save some lives. If the non-obstructive CAD cases are added to the obstructive CAD, that makes the diagnostic yield 60.8%. Patel et al’s “glass half empty” conclusion is that a little over one-third of the patients had obstructive coronary disease. My “glass half full” conclusion is that almost two-thirds of the patients had clinically significant coronary artery disease. It seems to me that 60.8% is a very acceptable diagnostic yield for a condition that is still the leading cause of death each year in the U.S. (see above).

My opinion is that Patel et al’s conclusion that “Better strategies for risk stratification are needed to inform decisions and to increase the diagnostic yield of cardiac catheterization in routine clinical practice” is not a valid conclusion.

Michael Crouch, MD, MSPH   5/28/10

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