Abstract 17902: Cost effectiveness of Coronary CTA or Vasodilator Stress Cardiac MRI for Determination of Invasive Angiography Following Equivocal Nuclear SPECT

Abstract

Objective: To assess the cost effectiveness of coronary CTA or vasodilator stress cardiac MRI (CMR) for determining the need of invasive angiography in patients with suspected coronary artery disease (CAD) and an equivocal SPECT.

Background: More than 10 million cardiac nuclear SPECT studies are performed in the United States per year and up to 10% are considered equivocal. The rate of obstructive CAD through invasive angiography with prior equivocal non-invasive testing is only 27%. The real-world cost effectiveness of CTA or CMR functioning as a gatekeeper to invasive angiography is not known in patients with a prior equivocal SPECT.

Methods: We prospectively enrolled 107 subjects with suspected CAD and an equivocal SPECT exam within 90 days. Vasodilator stress CMR was performed on a 1.5 Tesla scanner and was classified as ischemic or normal. CTA was performed on a 320 row system and was classified as obstructive CAD (≥50% or unevaluable) or non-obstructive. Studies were read blinded. Subjects were followed for one year to assess for downstream cardiovascular testing or major adverse cardiovascular events. Costs for CTA and CMR were estimated based on 2012 Medicare reimbursement rates plus downstream testing including catheterization. The reference comparator cost was determined assuming invasive angiography in all subjects with an equivocal SPECT and avoiding “layered” non-invasive imaging.

Results: Subjects averaged 56.1±11.9 years and 53% were men. Follow-up duration averaged 397±113 days and was obtained in all subjects. Of the 107 subjects, there were 18 obstructive and one unevaluable CTA. There were 15 ischemic and 3 non-diagnostic CMRs. There were 4 false negative CMRs and each had obstructive CTA confirmed by invasive angiography. No cardiovascular events occurred during the follow-up period in subjects with non-obstructive CTA. By utilizing a non-invasive test as a gatekeeper to invasive angiography, CTA had an overall cost savings of 51% and CMR had a 21% savings compared with an invasive strategy.

Conclusion: Layered non-invasive testing with CTA or CMR is more cost effective than an invasive strategy in patients with equivocal SPECT scans. Cardiac CTA has additional cost savings primarily due to lower expenses and higher sensitivity than CMR.