Magnetic resonance to assess disease severity and response to therapy in pulmonary arterial hypertension

Backgraund. Pulmonary arterial hypertension (PAH) is defined by a mean pulmonary arterial pressure (mPAP) > 25 mmHg at rest and normal wedge pressure. Absolute levels of mPAP and pulmonary vascular resistance (PVR) are used to measure hemodynamic impairment and define short term prognosis. Aim of the study was to assess whether the extent of the hemodynamic impairment and disease severity in PAH can be predicted by right ventricular mass index (RVMI) as non-invasive indicator of RV overload fram magnetic resonance imaging (MRI). Methods. Twenty-four patients with moderate-severe PAH, mPAP 42±1 OmmHg, wedge pressure 6±3 mmHg) were also evaluated by MRI. PAH was idiopathic (N=8), postembolic (N=9) or associated with scleroderma (N=7). RVMI, ejection fraclion (RVEF) and myocardial fibrosis (DE) were obtained from MRI study. Reslllts. In PAH patients, RVMI was direclly related with mPAP (r .53, P<.001) and PVR (r .61, P<.002). RV hypertrophy was associated with reduced RV systolic function as demonstrated by inverse relationship between RVMI and RVEF (r-.68, P=.0006). DE was detected in 20 patients (83%) and it was localized in the inferior and anterior RV-septum junctions. The extent of DE was related to mPAP (r 0.45, p<.001). In six patients a second catheterization and MRI were repeated after one year of therapy, confirming the association between RVMI and mPAP, and showing relationship between mPAP and DE reduction (r .98, p<.001) . Conclusions. In PAH pulmonary hemodynamic impairment can be predicted by MRI indexes of RV overload. The present results suggest to use MRI as a non-invasive approach for definition of disease severity in PAH and for monitoring response to therapy.