Experts call for improved risk stratification strategies before elective angiography
MedWire News: Only around one third of patients without known coronary artery disease (CAD)who underwent elective coronary angiography were found to have obstructive disease in a large, representative US registry, report researchers in the New England Journal of Medicine.
They say better strategies for clinical risk assessment and noninvasive testing are needed to limit unnecessary referrals for invasive testing.
Of 397,954 patients without known CAD who underwent elective cardiac catheterization and were included in the American College of Cardiology National Cardiovascular Data Registry between 2004 and 2008, only 149,739 (37.6%) were diagnosed with obstructive CAD, report Manesh Patel (Duke University Medical Center, Durham, North Carolina) and colleagues.
Obstructive CAD was defined as stenosis of 50% or more of the diameter of the left main artery or stenosis of 70% or more of the diameter of a major epicardial or branch vessel more than 2.0 mm in diameter.
Broadening the definition to include stenosis of 50% or more in any coronary vessel increased the prevalence to 41%.
In contrast, 39.2% of patients had no coronary artery disease (less than 20% stenosis in all vessels).
Overall, 83.9% of patients in the study underwent some form of noninvasive testing, which included any of a range of tests such as resting electrocardiography, computed tomography, or stress testing, before cardiac catheterization.
But, at odds with guidelines, noninvasive testing was performed more often in patients with higher Framingham risk scores, according to Patel and team. They report that noninvasive testing was not performed in 17.1% of low-risk, 15.9% of intermediate-risk, and 15.0% of high-risk patients (p<0.001).
Of information gather prior to angiography, the strongest predictors of obstructive CAD were the traditional risk factors, such as older age, male gender, use of tobacco, and presence of diabetes, dyslipidemia, or hypertension.
Symptoms also independently predicted obstructive CAD, and slightly improved predictive ability, from a C-statistic of 0.7417 to 0.7609.
However, although a positive result on a noninvasive test was also independently associated with obstructive CAD, this had a limited effect on predictive ability.
The authors comment: “Our results suggest that greater focus should be placed on the 30.0% of patients who were noted to have no symptoms, including no angina. Presumably the decision to proceed with invasive catheterization in the case of these patients was driven by clinical assessment of risk, testing for ischemia, or both.
“Given that the primary benefit of invasive treatment for obstructive CAD is relief of symptoms, we think that the threshold for invasive angiography may need to be higher in asymptomatic patients, for whom the potential benefits remain uncertain.”
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By Caroline Price