Correlation of echocardiography, cardiac magnetic resonance imaging and right heart catheterization to evaluate pulmonary artery stiffness, right ventricular structure and functions in patients with pulmonary arterial hypertension

Background: Pulmonary Arterial Hypertension (PAH) is a rare, progressive and mortal disease that causes right ventricular (RV) failure. Early diagnosis and initiation of specific treatment is important to slow down the unfavorable course of the illness. Assessment of the RV structure and functions is also important in determining the prognosis and treatment response during follow-up. Echocardiography, cardiac magnetic resonance imaging (cMRI) and right heart catheterization (RHC) are the diagnostic methods by which we assess the changes in pulmonary hypertension (PHT). Definitive diagnosis of PHT is made by measuring pressures invasively with RHC. Because of the possible risk of complications, research about non-invasive diagnostic methods have gained attention recently. Pulmonary arterial stiffness (PAS) which is assessed with invasive and nonivasive methods was also studied as a prognostic marker in previous PHT studies. There is also research about if the management of clinical response to therapy can be followed with PAS. In our study we assessed RV structure, functions and PAS with these diagnostics methods. We aimed to assess PAS with cMRI and RHC. If these two methods were found to be correlating with each other it would be supporting for extensive usage of noninvasive methods in determining PHT prognosis and treatment. Methods and Results: Thirtyfive patients (27 females, 8 males) with PHT preliminary diagnosis underwent RHC and cMRI within 24 hours. Subsequently, reviewing data, 3 patients were excluded. Sixteen patients with PAH, sixteen patients who had normal mPAP in RHC were included in our study population. RV FAC was 37,95±8,39% in patients with PAH, and 46,91±6,66% in patients with no PAH (p=0,001). In patients with PAH; SPAB and MPA were higher and TAPSE and RVSm were statistically significantly lower which was not a surprising finding. There was very strong correlation between RVFAC and RVEF with cMRI. In our study, PA/Aortic diameter ratio with a 1.0377 cutoff value, estimated the mPAP≥25mmHg with 92.3% sensitivity and 81.8% specificity. RV/PA coupling with a 0.7885 cutoff value estimated the mPAP≥25mmHg with 92.3% sensitivity and 75% specificity. Pulsatility with a cutoff value of 34.70 estimated mPAP≥25mmHg with 92.3% sensitivity and 81.2% specificity. Pulsatility, PA/Aortic diameter ratio and RV-PA coupling were strongly correlated with mPAP, PVR, PVRi. PAC and PACi were moderately correlated with pulsatility, PA/Aortic diameter ratio and RV-PA coupling. RVEF, which was assessed with cMRI and RVFAC had strong negative correlation with PVRi and moderate positive correlation with PACi. Patients with PAH pulsatility, PA/Aortic diameter ratio, compliance, capacitance, RV-PA coupling were strongly correlated and elasticity modules were very strongly correlated mPAP. There were no difference in volumes, cardiac output and index between the groups. Conclusion: In our study, we found moderate, strong and very strong correlations between cMRI and RHC parameters with regard to PAH assessment. PA/Aortic diameter ratio, pulsatility, RV-PA coupling estimates mPAP≥25mmHg with high sensitivity and specificity. We need more research to use this information in our daily practice and to validate PAS parameters. With more supportive research and developing MRI technology non-invasive methods are going to be used more commonly in PAH algorithms. Keywords: Pulmonary hyepertension, vascular stiffness, pulmonary artery catheterization, magnetic resonance imaging, transthoracic echocardiography.