Slightly more than one-third of patients without known disease, who underwent elective cardiac catheterization, had obstructive coronary artery disease (CAD) out of nearly 400,000 patients at 663 sites, based on study findings published March 11 in the New England Journal of Medicine. However, in an interview, Timothy D. Henry, MD, from Minneapolis Heart Institute, said that when reviewing the study’s data in its entirety, it appears that most practices are performing these procedures properly.

Evaluating the complete ACC-NCDR database, which the study authors used to gather their data, about 1.99 million patients at these 663 sites underwent cardiac catheterization between January 2004 and April 2008.

“To start with, 80 percent of the patients had known coronary disease, acute coronary syndromes, cardiogenic shock or another clear indication for the procedure,” explained Henry, who is the director of research at Minneapolis Heart. “Of the remaining 20 percent without known CAD, 35 percent were found to have significant CAD, leaving only about 12 percent of the overall patient population with ‘normal’ coronaries.”

He said, “This study is quite important, especially if taken in the proper context, and I do not believe it suggests that clinical practices are inappropriately performing invasive procedures on their patients.”

Based on their findings, the researchers, led by Manesh R. Patel, MD, from the Duke Clinical Research Institute at Duke University in Durham, N.C., said that better strategies for risk stratification are needed to inform decisions and to increase the diagnostic yield of cardiac catheterization in routine clinical practice in patients without known CAD.

They wrote that the “threshold for invasive angiography may need to be higher in asymptomatic patients, for whom the potential benefits remain uncertain.”

Conversely, Henry said, “It is hard to be critical of these practices because 84 percent of these patients underwent a noninvasive procedure prior to coronary angiography, which means they are following best practice protocols.”

In fact, noninvasive testing (which included electrocardiography, echocardiography, CT or a stress test) was performed in 83.9 percent of the patients before invasive angiography. The researchers found that patients with a positive result on a noninvasive test were moderately more likely to have obstructive CAD than those who did not undergo any testing (41 vs. 35 percent).

Patel and colleagues noted that they could not evaluate the performance of noninvasive testing because they did not have any information on those patients who underwent noninvasive testing but were not referred for catheterization. Also, the specific noninvasive test used was unknown, among the “broad range of tests” that could have been used, according to the authors.

In the accompanying commentary, David J. Brenner, MD, from Columbia University Medical Center in New York City, wrote: “Patel and colleagues rightly suggest that we need to optimize the application of gatekeeper tests such as myocardial perfusion scintigraphy, in order to decrease the disturbingly large proportion of invasive coronary angiographic procedures that yield negative results.”

He suggested that “a better gatekeeper test” may be another imaging technique, specifically multidetector-row CT angiography, adding that this “very promising gatekeeper test” is currently undergoing clinical trials for this purpose.

Henry concurred that with contemporary dose-lowering techniques, CT angiography can inform clinical decision making without exposing the patients to unnecessary radiation risks in those without known CAD, who have indeterminate risk or non-diagnostic tests.

The study was supported by unrestricted funding from the American College of Cardiology’s National Cardiovascular Data Registry CathPCI Registry.