Although post-imaging use of cardiac catheterization and medical therapy increased in proportion to the degree of abnormality findings, noninvasive testing had only a modest impact on clinical management of patients referred for clinical testing, according to the SPARC trial published in the Jan. 31 issue of the Journal of the American College of Cardiology .
Noninvasive cardiac imaging is widely used in coronary artery disease, but its effects on subsequent patient management are “unclear,” according to Rory Hachamovitch, MD, MSc, of The Cleveland Clinic Foundation, and colleagues.
Thus, the SPARC [Study of Perfusion and Anatomy's Role in Coronary Artery] researchers assessed the 90-day post-test rates of catheterization and medication changes in a prospective registry of 1,703 patients without a documented history of coronary artery disease and an intermediate to high likelihood of coronary artery disease undergoing cardiac SPECT, PET or 64-slice coronary CT angiography (CCTA).
Baseline medication use was relatively infrequent. At 90 days, 9.6 percent of patients underwent catheterization, Hachamovitch et al wrote. The rates of catheterization and medication changes increased in proportion to test abnormality findings. Among patients with the most severe test result findings, 38 to 61 percent were not referred to catheterization, 20 to 30 percent were not receiving aspirin, 35 to 44 percent were not receiving a beta-blocker, and 20 to 25 percent were not receiving a lipid-lowering agent at 90 days after the index test, they found.
The researchers wrote that the risk-adjusted analyses revealed that compared with stress SPECT or PET, changes in aspirin and lipid-lowering agent use was greater after CCTA, as was the 90-day catheterization referral rate in the setting of normal/nonobstructive and mildly abnormal test results.
The study authors reported that the frequency of catheterization and medication change suggests possible under-treatment of higher risk patients. Patients were more likely to undergo cardiac catheterization after CCTA than after SPECT or PET after normal/nonobstructive and mildly abnormal study findings.
Compared with stress myocardial perfussion imaging, they found that catheterization referral rates and subsequent need for revascularization are greater after CCTA, but the rates of medication use are similar.
“In light of the enormous costs associated with cardiovascular imaging, efforts have been made to improve the appropriate use of medical imaging,” wrote Hachamovitch and colleagues. “Many justify the use of these tests on grounds that they play a central role in patient management and, although an unproven hypothesis, improve patient outcomes. The assumed paradigm is that in the setting of abnormal study results—particularly high-risk results—patients undergo intervention. The relatively limited changes in management after abnormal study results, especially high-risk findings, undermine this paradigm, especially because in our diagnostic cohort, these abnormalities represented a de novo CAD [coronary artery disease] diagnosis.”