SPECT-guided myocardial perfusion and metabolic fatty acid planar imaging to assess the severity of the pulmonary hypertension in patients with chronic thromboembolic pulmonary hypertension

Abstract

Abstract Background Patients with chronic thromboembolic pulmonary hypertension (CTEPH) represent right ventricular (RV) enlargement and hypertrophy, which consequently increase the RV myocardial perfusion. Although the main energy source of myocardium is fatty acid, it remains unknown whether myocardial fatty acid metabolism is altered in loaded RV. Herein, we report a novel approach to assess the RV perfusion and fatty acid metabolism, which is called SPECT-guided planar imaging. Purpose To evaluate if SPECT-guided myocardial perfusion and metabolic fatty acid planar imaging reflects the severity of the pulmonary hypertension in patients with chronic thromboembolic pulmonary hypertension. Methods The study groups included 30 patients with CTEPH and 20 healthy controls. In these patients with CTEPH, 15 patients underwent pulmonary thromboendarterectomy (PEA). Mean pulmonary artery pressure (mPAP) by right heart catheterization was obtained in all CTEPH patients. 201Thallium (201Tl) and iodine-123-beta-methyl iodophenyl pentadecanoic acid (123I-BMIPP) planar myocardial imaging was performed in all participants. For the patients undergoing PEA, repetitive SPECT-guided 201Tl and 123I-BMIPP planar imaging was performed one year after the procedure. To assess the RV overload, the planar images were performed in left anterior oblique position, optimized to separate the RV from the left ventricular (LV) using SPECT-guided transverse imaging. We measured the total counts of 201Tl and 123I-BMIPP in both the RV and LV. Moreover, we calculated their relative counts of the RV to LV (abbreviated as HR/HL (Tl) and HR/HL (BMIPP), respectively) to determine the indices of myocardial perfusion and fatty acid metabolism, respectively. Results Both HR/HL (Tl) and HR/HL (BMIPP) were elevated in the CTEPH patients compared with control (0.62±0.14 vs. 0.36±0.07, p<0.01 and 0.57±0.14 vs. 0.34±0.06, p<0.01, respectively). In the CTEPH patients, average mPAP was 44.0±9.52 mmHg, which was correlated with HR/HL (Tl) (r=0.675, p<0.001) and HR/HL (BMIPP) (r=0.685, p<0.01). Furthermore, the decrease of average mPAP 1 year after PEA was positively associated with the decrease of HR/HL (Tl) (r=0.646, p<0.01) and HR/HL (BMIPP) (r=0.504, p<0.05) 1 year after PEA. Conclusions In patients with CTEPH, RV myocardial perfusion and fatty acid metabolism was upregulated and moderately correlated with mPAP. SPECT-guided 201Tl and 123I-BMIPP planar imaging is a novel and noninvasive imaging modality to assess the severity of PH. Funding Acknowledgement Type of funding sources: None.