Myocardial Perfusion Imaging With PET; A Head-to-Head Comparison of 82 Rubidium Versus 15 O-water Tracers Using Invasive Coronary Measurements as Reference

BACKGROUND: Myocardial perfusion imaging by positron emission tomography (PET) is recommended as a first-line test in stable patients with chest pain symptoms and as a selective second-line test after an abnormal coronary computed tomography angiography (CTA). It is, however, unknown whether the use of Rubidium-82 ( 82 Rb) versus [ 15 O]H 2 O ( 15 O-water) affects the diagnostic performance in coronary artery disease (CAD). The aim of this study was to compare 82 Rb-PET versus 15 O-water-PET head-to-head for diagnosing obstructive CAD. METHODS: The study included consecutive patients (n=1000) referred for CTA with symptoms suggestive of obstructive CAD. Patients with suspected stenosis based on CTA were referred for both 82 Rb-PET, 15 O-water-PET, and subsequently invasive coronary angiography (ICA), including 3-vessel fractional flow reserve and coronary flow reserve measurements. RESULTS: In total, 196/270 (73%) patients with suspected stenosis on CTA completed 82 Rb-PET, 15 O-water-PET, and ICA. Myocardial blood flow measurements from 82 Rb-PET and 15 O-water-PET correlated strongly at rest (ρ, 0.62–0.69) but only moderately during hyperemia (ρ, 0.41–0.59). Only weak correlations were demonstrated between myocardial blood flow reserve by both PET tracers compared with ICA coronary flow reserve (ρ, 0.11–0.38). Hemodynamically obstructive CAD defined as ICA fractional flow reserve ≤0.80, was identified in 86/196 (44%) patients. Using predefined cutoffs, the diagnostic accuracies of 82 Rb-PET versus 15 O-water-PET were similar (sensitivity 69% [58–78%] versus 71% [60–80%], P =0.59; specificity 85% [76–91%] versus 77% [68–85%], P =0.12). Using ICA diameter stenoses >70% as a reference, only 48/196 (24%) patients had anatomically severe CAD, and 82 Rb-PET and 15 O-water-PET sensitivities increased to >85%. CONCLUSIONS: For detection of obstructive CAD by PET myocardial perfusion imaging, 82 Rb versus 15 O-water have similar diagnostic performance. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04707859.