Test-retest Assessment of Biventricular Myocardial Oxidative Metabolism and Perfusion in Pulmonary Hypertension...

¹¹C-acetate PET is used to measure biventricular oxygen myocardial consumption rate (MVO₂) and myocardial blood flow (MBF) changes associated with right ventricular (RV) remodelling. We studied PET reproducibility and repeatability for such RV assessments.

10 pulmonary hypertension (PH) patients underwent ¹¹C-acetate PET. Five of these patients also had a repeat scan after 26 ± 2 weeks. A one-tissue compartment model was used to measure the myocardial tissue-activity washout rate (k2 [1/min] for MVO₂ estimation) and the blood-to-tissue activity flux (K1 [1/min] for MBF calculation). Values were measured by 2 blinded observers and analyzed by ANOVA and Bland-Altman tests. The interquartile ranges (IQR), within-subject coefficients of variation (wCV), and intraclass correlation coefficients (ICC) were reported.

All patients had stable PH with the clinical assessments showed comparable biventricular function and size between baseline and follow-up. The k2-derived MVO₂ and K1-derived MBF values were consistently higher in the LV than RV. The high inter- and intra-observer reproducibility (for biventricular MVO₂ and MBF) was indicated by low IQR (≤ 7.6%) and wCV (≤ 8%) as well as high ICC (≥ 95%). The test-retest (baseline to follow-up) repeatability showed larger IQR (≤ 35.4%) and wCV (≤ 29%) but consistently high ICC (= 95%).

MVO₂ and MBF values measured in the RV of patients with PH were highly reproducible and repeatable. This can help inform the design of clinical research studies using serial ¹¹C-acetate PET imaging to evaluate RV metabolism.