Risk stratification of CAD with SPECT-MPI in women with known estrogen status

Abstract

ObjectiveTo compare exercise tolerance testing (ETT) with gated single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) risk stratification in women with an intermediate to high CAD pretest risk and known estrogen status (ES). BackgroundSPECT-MPI is an effective test for risk stratifying patients with stable angina. However in women, the current guidelines recommend the exercise tolerance testing (ETT) as first line test. Further, the relationship of stress imaging to ES, an independent risk indicator for CAD, is unknown. Methods2,194 women with an intermediate to high CAD pre-test risk were referred for a clinically indicated ETT with gated SPECT-MPI. Duke treadmill scores (DTS) and summed stress score (SSS) were calculated. SSS were classified as normal (SSS < 3), mildly abnormal (SSS 4-8), or moderate-severely abnormal (SSS > 8). The ES was assessed as premenopausal, postmenopausal on hormone replacement therapy (HRT) as ES+ while postmenopausal not on HRT were ES−. An annualized cardiac event rate of a composite of cardiac death, unstable angina (UA) leading to hospitalization, non-fatal myocardial infarction, or late coronary revascularization was calculated for all the groups. ResultsThe annualized cardiac event rate was 1.3% PPY, 2.1% PPY, and 3.2% PPY for low, intermediate, and high risk DTS (P = .2). Patients with intermediate DTS and mildly abnormal or moderate-severely abnormal gated SPECT-MPI had a significantly higher cardiac event rates (5.3% PPY and 10.8% PPY, respectively) than those with a normal gated SPECT-MPI (1.2%, PPY, P = .01). This was also demonstrated on further Cox-regression analysis. Risk stratification of SPECT-MPI over DTS was independent of ES. ConclusionGated SPECT-MPI provides risk stratification beyond standard exercise stress testing for women with suspected coronary artery disease, especially in patients with intermediate DTS and is independent of ES.