Three-dimensional echocardiographic assessment
Six-beat full-volume 3D acquisitions, with electrocardiographic gating during breath holding, were performed after the 2D examination by the same researcher using the 4V probe. LV-focused 3D data sets were obtained from the apical four-chamber view, while RV-focused 3D data sets were obtained from the apical RV-focused view, as recommended [12]. Image post-processing and reconstruction were performed offline using 4D Auto-LVQ software (EchoPAC BT 12, GE Vingmed-Ultrasound, Horten, Norway) for the LV volumes and LVEF and 4D RV-Function software (TomTec Imaging Systems, Unterschleissheim, Germany) for the RV volumes and RVEF (Figure 1). The endocardial surface of the ventricles was traced at both end-systole and end-diastole [14, 15]. Subsequently, the software generated the biventricular volumes and ejection fractions.
We estimated the RVPAC non-invasively as the ratio between the 3D RV SV and the 3D RV ESV. This ratio has been previously used as a marker of the ventriculo-vascular interaction [7, 22, 23] and it has shown good correlation with invasive RVPAC derived from RHC [13].