Cardiac positron emission tomography in prediction of the clinical course of chronic thromboembolic pulmonary hypertension: prospective cohort study

INTRODUCTION: During the development of CTEPH maladaptive mechanisms in the right ventricle are accompanied by disturbances in myocardial energy metabolism and perfusion. These changes can be assessed visually and quantitatively using the molecular imaging method — PET with [¹⁸F]-FDG and [¹³N]-NH₃.

OBJECTIVE: Using cardiac PET/CT investigate the relationship between perfusion and metabolism of the right ventricular myocardium and the results of other instrumental examination methods in patients with CTEPH of different severity, as well as to calculate the threshold PET values to determine the group of patients with an unfavorable clinical course of the disease.

MATERIALS AND METHODS: The study included 36 patients with a verified diagnosis of CTEPH, who were examined using a standard diagnostic protocol. Patients underwent cardiac PET/CT examinations with two radiopharmaceuticals: with [¹⁸F]-FDG to study the metabolism of the ventricular myocardium and with [¹³N]-NH₃ to assess cardiac perfusion. For each radiopharmaceutical semi-quantitative accumulation indices (SUV) and the ratio of the levels of radiopharmaceutical uptake in the right and left ventricles (SUV RV/SUV LV) were obtained. Statistics: Shapiro-Wilk test, Student’s t-test, and Mann-Whitney U-test, Pearson correlation analysis, linear regression analysis, ROC analysis.

RESULTS: The level of [¹⁸F]-FDG accumulation in the right ventricular myocardium is higher in patients with a high functional class of PH than in groups I, II (p<0.01). All indicators of SUV RV/SUV LV for [¹⁸F]-FDG demonstrate a direct linear relation-ship with the level of mean PAP (r=0.691, p<0.0001), PVR (r=0.715, p<0.0001), right ventricular size (r=0.658, p<0.0001), PASP (r=0.581, p<0.001) and inverse linear relationship with the functional parameters of the right ventricle CI (r=–0.555, p=0.001), CO (r=–0.488, p=0.005), TAPSE (r=–0.552, p<0.001), TAVS (r=–0.537, p<0.001), and SvO₂ (r=–0.666, p<0.0001). A correlation was found between the accumulation of [¹³N]-NH₃ and the main hemodynamic parameters used to assess the severity of the disease (СI, SvO₂). The threshold values of [¹⁸F]-FDG and [¹³N]-NH₃ accumulation indices have been obtained, which with high sensitivity (69.2–83.3%), specificity (68.4–94.7%) and diagnostic accuracy (0.73–0.83) make it possible to identify patients with a low cardiac index and an unfavorable prognosis.

DISCUSSION: The obtained results confirm the presence of glucose hypermetabolism in right ventricular cardiomyocytes in the development of pulmonary hypertension and the association of these metabolic changes with the severity of PH. A significant correlation was demonstrated between the accumulation of both radiopharmaceuticals in the heart and the results of other examination methods characterizing the severity of disease and the prognosis of patients with CTEPH. Using a non-invasive PET/CT procedure, threshold values of PET parameters were obtained, which in the future can be used to identify patients with an unfavorable clinical prognosis.

CONCLUSION: Cardiac PET/CT with [¹⁸F]-FDG and [¹³N]-NH₃ is a promising non-invasive imaging technique that can be used to study metabolic and perfusion changes in the right ventricular myocardium in CTEPH, as well as to identify patients with a high risk of adverse events.

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