Stress myocardial perfusion single-photon emission computed tomography is clinically effective and cost effective in risk stratification of patients with a high likelihood of coronary artery disease (CAD) but no known CAD

Abstract

Objectives: We sought to evaluate the prognostic and cost implications of stress myocardial perfusion single-photon emission computed tomography (SPECT), or MPS, in patients with a high pretest likelihood (>0.85) of coronary artery disease (CAD) with no previous CAD.

Background: Sparse data are available regarding the prognostic performance characteristics of MPS in this patient group.

Method: We followed up 1,270 consecutive patients with no previous revascularization or myocardial infarction (MI), with a pre-exercise tolerance test (ETT) likelihood of CAD > or =0.85, who underwent exercise or adenosine stress MPS (follow-up 94.4% complete; 2.2 +/- 1.2 years; 60 hard events [5.9%, 2.6%/year]). Risk adjustment of survival data was done using Cox proportional hazards analysis. Costs per reclassification of risk were calculated using assumed costs and threshold analyses.

Results: In patients treated medically after MPS, normal MPS had a low risk of cardiac death and hard events (0.6% and 1.3% per year, respectively). With increasing extent and severity of MPS defects, the risk of both cardiac death and hard events increased significantly (p < 0.05). Cox models indicated that the addition of MPS data resulted in incremental prognostic value over pre-MPS data (chi-square increase 48 to 87, p < 0.0001). Compared with strategies of initial referral to ETT in patients able to exercise, initial referral to MPS appeared to be a more cost-effective strategy. Similarly, compared with a strategy of direct referral to catheterization in patients with a high likelihood of CAD, initial referral to MPS is a cost-saving approach.

Conclusions: In patients with a high likelihood of CAD but without known CAD, stress MPS yields incremental value and achieves risk stratification in a cost-effective manner. The current results support a strategy of initial stress imaging in this patient cohort, as a reasonable alternative to direct referral to catheterization or initial ETT.