Right Atrial Fibrosis in Pulmonary Hypertension

Right atrial (RA) function consists of a reservoir, conduit, and active contractile function and can serve as a tool for the evaluation of the severity of RV dysfunction and prognosis in pulmonary hypertension according to recent data. In-depth evaluation of phasic RA function was previously undertaken either by echocardiographic speckle tracking or by cardiac magnetic resonance (CMR) imaging-derived feature tracking. However, it is currently unknown if right atrial remodeling is present. As described for left atrial fibrosis, the presence and extent of atrial fibrosis can be quantified using CMR late gadolinium enhancement. The protocol for the assessment of left atrial fibrosis will be used and adapted to the RA. Patients will undergo 3-dimensional late gadolinium enhancement CMRI along with a contrast-enhanced magnetic resonance angiography and cine imaging in order to define the anatomy of the RA and the superior and inferior vein. High-resolution late gadolinium enhancement images of the RA will be acquired 15 to 30 min after gadolinium-based contrast agents administration using a 3-dimensional inversion-recovery prepared, respiration navigated, and electrocardiogram triggered gradient-echo pulse sequence with fat saturation. Following acquisition of the scans, the endocardial borders of the RA will be defined in each slice by manual tracing. After manual adjustment of the epicardial RA surface, the quantification of fibrosis based on the relative intensity (signal intensity) of late gadolinium enhancement will be performed. Finally, a 3-dimensional model of the RA will be rendered with the maximum enhancement intensities being projected on the model surface.