Impact of choice of imaging modality accompanying outpatient exercise stress testing on outcomes and resource use after revascularization for acute coronary syndromes

Abstract

Background: Exercise stress testing is commonly obtained after percutaneous coronary intervention (PCI) performed for acute coronary syndromes (ACS). We compared the relationships between exercise echocardiography and nuclear testing after ACS-related PCI on outcomes and resource use.

Methods: Longitudinal observational study using fee-for-service Medicare claims to identify patients undergoing outpatient exercise stress testing with imaging within 15 months after PCI performed for ACS between 2003 and 2004.

Results: Of 63,100 patients undergoing stress testing 3 to 15 months post-PCI, 31,731 (50.3%) underwent an exercise stress test with imaging. Among 29,279 patients undergoing exercise stress testing with imaging, 15.5% received echocardiography. Echocardiography recipients had higher rates of repeat stress testing (adjusted hazard ratio [HR] 2.60, CI 2.19-3.10) compared with those undergoing nuclear imaging in the 90 days after testing, but lower rates of revascularization (adjusted HR 0.87, CI 0.76-0.98) and coronary angiography (adjusted HR 0.88, CI 0.80-0.97). None of these differences persisted subsequent to 90 days after stress testing. Rates of death and readmission for myocardial infarction rates were similar. Total Medicare payments were lower initially after echocardiography (incremental difference $498, CI 488-507), an effect attributed primarily to lower reimbursement for the stress test itself, but not significantly different after 14 months after testing.

Conclusions: In this study using administrative data, echocardiography recipients initially had fewer invasive procedures but higher rates of repeat testing than nuclear testing recipients. However, these differences between echo and nuclear testing did not persist over longer time frames.

Figure 1

A and B, A cohort selection diagram illustrating a process by which study cohort was identified. Included patients were those receiving an outpatient exercise nuclear or echocardiography stress test not preceded by another cardiac event.

Figure 2

Unadjusted outcomes by stress test imaging modality. Curves illustrate unadjusted cumulative incidence of outcomes, based on time since stress testing. P values are for comparison of nuclear versus echocardiography using Gray test.

Figure 3

Unadjusted and adjusted incremental total Medicare payments. A comparison of exercise echocardiography and exercise nuclear. Dotted lines indicate incremental difference in cost accruing during the day of initial stress testing.

Figure 4

Inverse propensity weighted–adjusted cumulative incremental costs. A comparison of echocardiography and nuclear imaging with costs stratified by stress test–related versus all other.