Wide Variability Seen in Hospitals' Rates of Discovering CAD During Angiography

August 16, 2011—In the Journal of the American College of Cardiology, Pamela S. Douglas, MD, et al published findings from a study with the purpose to describe hospital variability in the rate of finding obstructive coronary artery disease (CAD) during elective coronary angiography (2011;58:801–809).

According to the American College of Cardiology (ACC), the study found that hospitals vary markedly in regard to the rate at which diagnostic coronary angiography actually finds obstructive CAD in patients without known heart disease. Although some hospitals in the United States report that 100% of patients undergoing this procedure were found to have CAD, other hospitals had rates as low as 23%, meaning that the majority of patients who were selected for elective catheterization did not have blockages. The investigators stated that these findings warrant further efforts to improve the patient selection and decision-making processes used by institutions to limit exposure to costly, invasive procedures when they are not needed. 


“This procedure has associated costs, and it's not without risk,” commented Dr. Douglas. “This study is an important step in assessing quality of care and is integral to efforts to improve it. Our findings indicate that there may be an opportunity to increase the likelihood of finding CAD at catheterization and perhaps reduce the number of procedures that don't find disease.”
 

The ACC stated that the study is a follow-up to the investigators' 2010 study. It is the first to investigate the degree to which hospitals differ in the rate of discovering CAD with coronary angiography and the factors that might predict this. The investigators reported that hospital-level variability appears to be predictable based on differing patterns of patient selection and precatheterization evaluation, testing, and treatment. 
 

Dr. Douglas explained, “Because hospitals maintained a similar rate of finding disease relative to other hospitals year in and year out and these rates are also related to patient characteristics, it suggests that decision-making processes and clinical practice patterns are a highly influential factor guiding the use of diagnostic coronary angiography and could be a target for quality-improvement efforts.”

The study was not able to capture all of the reasons for performing angiography, but its findings suggest that some procedures might be avoided if decisions about whether to perform cardiac catheterization in the hospitals with the lowest rates of finding CAD were more similar to those hospitals with the highest rates. Hospitals with lower rates of finding CAD by catheterization were more likely to perform the procedures on younger patients, women, and those with a lower likelihood of disease (as indicated by a low Framingham or Diamond and Forrester risk score) who presented with atypical symptoms and had negative noninvasive diagnostic testing done prior to angiography. Patients who are at higher risk of being diagnosed with obstructive CAD were more likely to have hypertension, diabetes, and other expected risk factors. In general, the size and type of hospital (eg, teaching hospital, public vs private) and setting did not change the findings. 


The investigators identified 565,504 patients without known heart disease who underwent elective cardiac catheterization at 691 hospitals nationwide during a 3-year period to evaluate the rate of finding obstructive CAD. The investigators defined CAD as any major epicardial vessel stenosis at 50% or higher, but similar patterns remained even when alternate definitions were applied.

“The decision to perform catheterization should be selective and ideally limited to patients with moderate-to-high pretest probability for CAD,” stated Dr. Douglas, who also cautioned that there are other valid reasons to perform catheterization besides the expectation of finding obstructive CAD, such as patient reassurance. 
 

The ACC advised that to provide additional guidance to cardiologists, it is currently working on appropriate-use criteria for ordering invasive diagnostic coronary angiography, with release expected this winter. In the meantime, the ACC noted that Dr. Douglas advocates for closer consideration of those clinical factors that are known to be most strongly associated with CAD, including advancing age, risk factors, and typical symptoms. A careful assessment of patients' risk and presenting symptoms, as well as results of any stress and other noninvasive tests, should be considered.