Right Ventricular Myocardial Metabolism and Cardiorespiratory Testing and in Patients with Idiopathic Pulmonary Arterial Hypertension

Introduction: Non-invasive diagnostic tools for the assessment of pulmonary arterial hypertension (PAH) have been under intensive investigation. Positron emission tomography (PET)/computed tomography (CT) with [13N]-ammonia and [18F]-fluorodeoxyglucose ([18F]-FDG) are the golden standard of myocardial metabolism and perfusion assessment. The relationships between RV myocardial metabolism and perfusion and cardiopulmonary exercise testing (CPET) have not been studied. The study aimed to evaluate the correlations between the CPET parameters and RV perfusion and metabolism using positron emission tomography PET/CT with [13N]-ammonia and 18F]-FDG in IPAH patients. Methods: 34 IPAH patients (34.2±8.9 years, 4 males, 6 prevalent) comprised into the study. The relationships between CPET parameters and SUVmax RV/LV metabolism and perfusion were assessed. Cardiac MRI and hemodynamics were evaluated as well. Results: Significant negative correlations were registered between SUVmax RV/LV metabolism, SUVmax RV/LV perfusion and oxygen consumption, oxygen pulse and positive correlation with the ratio of minute ventilation to carbon dioxide production. The majority of CPET indices and SUVmax RV/LV metabolism and SUVmax RV/LV perfusion differed significantly between the low-risk IPAH patients and intermediate- high-risk groups. No reliable differences in CPET indices and SUVmax RV/LV metabolism and SUVmax RV/LV perfusion registered between intermediate and high-risk patients. Tight interconnections between CPET and invasive hemodynamics, RV remodeling were confirmed. Conclusion: Significant correlations between CPET parameters and RV myocardial metabolism and perfusion parameters, MRI, and hemodynamics indicate that CPET is a reliable noninvasive diagnostic tool for distinguishing low-risk IPAH patients from intermediate-high risk population.