Compared to stress testing, patients who undergo CT angiography more likely to undergo subsequent invasive, more costly cardiac procedures

"Technologic advances in computed tomography have facilitated the development of coronary computed tomography angiography (CCTA) as a noninvasive diagnostic test to evaluate patients with suspected coronary artery disease (CAD). The anatomical information provided by CCTA is distinctly different from the functional information provided by stress testing using electrocardiography (ECG), echocardiography, or myocardial perfusion scintigraphy [MPS; diagnostic imaging technique using a radioactive tracer that is administered within the myocardial capillary system] to assess myocardial ischemia [insufficient blood flow to the heart muscle]," according to background information in the article. The number of CCTA procedures among Medicare beneficiaries has increased steadily since the procedure was first reimbursed. The association of CCTA with subsequent use of cardiac tests and procedures and with clinical outcomes is not well established. CCTA may detect atherosclerotic plaques that are not hemodynamically (affecting blood circulation) significant and lead to additional tests and procedures, such as coronary catheterization and revascularization, that would not otherwise have been performed, thereby increasing expenditures, the authors write.

Jacqueline Baras Shreibati, M.D., of the Stanford University School of Medicine, Stanford, Calif., and colleagues compared health care utilization and Medicare expenditures of beneficiaries who underwent initial diagnostic evaluation for CAD in the outpatient setting, using either CCTA or stress testing (MPS, stress echocardiography, or exercise ECG). The researchers used claims data from a 20 percent random sample of 2005-2008 Medicare fee-for-service beneficiaries 66 years or older with no claims for CAD in the preceding year, who received non-emergent, noninvasive testing for CAD (n = 282,830).

The researchers found that patients who underwent CCTA were about twice as likely to undergo subsequent cardiac catheterization (22.9 percent vs. 12.1 percent), more than two times as likely to undergo a percutaneous coronary intervention (procedures such as balloon angioplasty or stent placement used to open narrowed coronary arteries) (7.8 percent vs. 3.4 percent), and about three times as likely to undergo coronary artery bypass graft surgery (3.7 percent vs. 1.3 percent), compared to patients who underwent MPS.

Patients undergoing CCTA had a slightly lower likelihood of hospitalization for acute heart attack (0.19 percent vs. 0.43 percent) than patients undergoing MPS at 180 days. Patients undergoing CCTA had a similar likelihood of all-cause mortality (1.05 percent vs. 1.28 percent) than patients undergoing MPS.

Regarding spending, average total spending ($29,719) and CAD-related spending ($14,943) in the subsequent 180 days was significantly higher among patients undergoing CCTA, who had nearly 50 percent higher CAD-related average expenditures than patients undergoing MPS. Compared with MPS, there was lower associated spending with stress echocardiography (-$4,981) and exercise electrocardiography (-$7,449).

The researchers write that it is likely that further cardiac testing was frequently ordered by physicians because abnormal CCTA results were common in this patient cohort (because the prevalence of anatomical CAD increases steadily with age and the median [midpoint] age of patients in this study was 73.6 years). "We do not have data on the results of any of the diagnostic tests used in this study, however, so clinical registry studies will be needed to further explore the reasons for increased testing after CCTA compared with stress testing."

"CCTA still comprises a relatively small proportion [about 3 percent] of noninvasive testing for coronary disease in the United States, but a substantial increase in use of CCTA is likely over the next decade. Our data suggest that increased use of CCTA may greatly increase subsequent diagnostic testing and invasive cardiac procedures. The increased use of invasive procedures and the higher spending on care after CCTA documented in this study suggest that clinicians and policy makers should critically evaluate the use of CCTA in clinical practice, based on studies of subsequent outcomes," the authors conclude.