Stress myocardial perfusion imaging in patients presenting with syncope: Comparison of PET vs. SPECT

Abstract

Background: The role of myocardial perfusion imaging (MPI) in patients with suspected coronary artery disease (CAD) presenting with syncope is controversial. We aimed to determine diagnostic yield of MPI for evaluation of syncope in patients without known CAD, as a function of pre-test patient risk and test modality (PET vs SPECT).

Methods: Between 1/2010 and 12/2016, 1324 consecutive patients presenting with syncope without known CAD underwent MPI with PET (n = 640) or SPECT (n = 684). Rates of abnormal MPI (summed difference score (SDS) > 2 or left ventricular ejection fraction (LVEF) reserve ≤ 0 for PET and SDS > 2 or post-stress LVEF ≤ 45% for SPECT) were determined among patients stratified by pre-test risk. In patients who were referred for coronary angiography, diagnostic yield of obstructive CAD was calculated in the overall cohort as well as in a propensity-matched cohort compared to patients without syncope.

Results: Abnormal MPI was noted in 36.5% (201/551) of patients who had PET compared with 13.0% (87/671) who had SPECT (P < 0.001), which is largely related to higher comorbidity burden and greater pre-test CAD risk in the PET population. Among patients who had an abnormal MPI, 8.5% (47/551) with PET and 0.7% (5/671) with SPECT were found to have obstructive CAD if referred for coronary angiography. Patients at intermediate-high pre-test risk had a higher proportion of abnormal MPIs and obstructive CAD as compared to those at low risk in both the PET and SPECT cohorts. The rate of abnormal testing and diagnostic yield of PET MPI was similar and proportionate to pre-test likelihood among matched patients with and without syncope.

Conclusions: Among patients referred for PET MPI with syncope at an intermediate-high pre-test CAD risk, 1 in 3 had an abnormal MPI and 1 in 10 had obstructive CAD. The value of MPI was related to pre-test risk as opposed to the presence of syncope, and MPI testing with PET or SPECT in the low-risk population was low value.

Keywords: Diagnostic and prognostic application; Image guided application; MPI.

Figure 1:. Yield of positron emission tomography myocardial perfusion imaging in patients with syncope, stratified by pre-test risk probability for coronary artery disease

Diagnostic yield defined as presence of obstructive CAD (left main ≥50% or any epicardial coronary artery ≥70% stenosis) on coronary angiogram within 6 months of the stress MPI test. Pre-test CAD risk calculated using CAD Consortium Risk Calculator. Low risk = 0-14%, Intermediate= 15-85%, High= 86-100%. Cath= coronary angiogram. Abnormal MPI refers to MPI with summed difference score >2 or left ventricular ejection fraction reserve ≤0.