Functional Testing vs. CT Angiography in Stable CAD
How does use of stress testing or coronary computed tomography angiography (CCTA) affect downstream treatment, costs, and clinical outcomes in stable coronary artery disease (CAD) patients?
The investigators retrospectively analyzed national health insurance and registry data from Denmark. Baseline comorbidities, downstream catheterization, revascularization, and medications were assessed from insurance and registry data. Adjusted analyses were performed using the Cox proportional hazard regression model to adjust for age, sex, year, echocardiography during preceding year, medical therapy, and clinical comorbidities. Additionally, a weighted causal inference model was used to control for confounding in a sensitivity analysis.
A total of 86,705 patients were included (exercise electrocardiogram, n = 42,659; nuclear stress testing, n = 11,085; CCTA, n = 32,961). Overall function and CCTA groups had similar age, although women more commonly underwent CCTA. Use of testing declined over time with a shift toward CCTA. Patients undergoing CCTA were more commonly treated medically, although the functional testing group generally had higher burden of comorbidities.
Statin and aspirin therapy were more often changed (started or stopped) with CCTA compared to functional testing (statins: hazard ratio [HR], 1.42; 95% confidence interval [CI], 1.39-1.46; aspirin: HR, 1.36; 95% CI, 1.32-1.40). Although downstream noninvasive testing was less common with CCTA (5.9% vs. 10.5%, p < 0.001), cardiac catheterization and revascularization were more common with CCTA (catheterization: 12.9% vs. 8.0%, p < 0.001, percutaneous coronary intervention: 3.8% vs. 2.2%, p < 0.001, coronary artery bypass grafting: 1.3% vs. 1.0%, p < 0.001). Overall, downstream costs were higher with CCTA ($995 vs. $718, p < 0.001).
Over a median follow-up of 3.6 years, on an unadjusted basis, there were fewer deaths with CCTA (2.1% vs 4.0%, p < 0.001) and fewer myocardial infarctions (MIs) (0.8% vs. 1.5%, p < 0.001). However, after adjusting for risk factors, there was no significant difference in mortality, although a difference in MI risk persisted (HR, 0.71; 95% CI, 0.61-0.82).
Among stable CAD patients, CCTA resulted in greater use of medical and invasive therapies compared to functional testing, and was associated with a lower risk of MI, but not death.
This important study adds to a growing body of literature comparing CCTA and functional testing. This observational, retrospective study evaluated patients with stable CAD, similar to the PROMISE study. Consistently across these studies, CCTA has been associated with somewhat higher costs, but also frequently with lower rates of MI, possibly due to increased use of medical therapy. The failure to see decreased mortality is unlikely due to power, but may be due to: 1) limitations of medical therapy to reduce mortality in relatively low-risk stable populations, 2) counterbalancing downstream complications from additional revascularization, or 3) other counterbalancing risks of medical therapy.
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