Advanced Echocardiographic Evaluation of Right Ventricular Function in Patients with Pulmonary Hypertension

Background: the right ventricle (RV) is a complex shaped cardiac chamber, whose pump function is mainly driven by a longitudinal deformation, as showed by anatomical studies. Conventional echocardiography showed several limitations in the analysis of RV size and function. RV systolic dysfunction is an important prognostic factor in several pathological condition, among which pulmonary hypertension (PH). However, the progression of RV mechanical changes that lead to the RV pump function impairment remains to be clarified. The new echocardiographic techniques, two dimensional-speckle tracking (2D-STE) and three-dimensional echocardiography (3DE), allow to investigate volumes, ejection fraction and myocardial mechanics of the RV. Moreover, we developed a custom-made software package that applied to the 3DE beutel of the RV allows to discriminate between the relative contribution of the longitudinal and radial displacement to the global RV pump function. Purpose: to value the mechanics of RV in healthy condition, in presence of systemic sclerosis (SSc), a condition predisposing to PH, and in presence of PH. Methods: we enrollled 270 healthy subjects, 75 patients affected by SSc (a pathological condition at high risk of PH), without PH, and 59 patients affected by PH (excluded PH type 2). Some of PH patients underwent to more than one echocardiograms, for a total of 81 exams. 57 age- and gender-matched healthy volunteers have been selected. All subjects underwent a complete echocardiogram, including dedicated 3DE acquisition of the RV. A dedicated software has been applied on apical 2D image of the RV in order to measure the longitudinal strain (LS) and the transversal displacement (TD) of both the free-wall (RVFW) and the interventricular septum (IVS). 3DE data sets of the RV have been analyzed by RV function 2.0 (TomTec) in order to obtain volumes and ejection fraction (RVEF). Then PH have been divided according to RV-EF: preserved (≥45%) or impaired (<45%). Finally, the 3DE RV beutels were analyzed by our custom made software package obtaining the longitudinal EF (LongEF) and radial EF (RadEF) and their relative contribution to RVEF by calculating the ratios LongEF/RVEF and RadEF/RVEF. Results: the analysis of the healthy volunteers provided reference values of RV volumes, ejection fraction, LS and TD. The 3DE RV beutel analysis showed that in healthy subjects the relative contribution of longitudinal and radial motion is equal. In SSc patients no significant differences about RV size and function have been demonstrated. PH patients showed significantly larger 3DE RV end-diastolic and end-systolic volumes (106±39 ml vs 67 ±14 ml and 65±33 vs 28±7 ml, respectively; p<0.0001), lower 3D RVEF (41±11% vs 58±4%; p<0.0001), lower LS values and impaired TD values than controls. Similarly, both LongEF and RadEF were lower (18±7% vs 27±4% and 15±7% vs 27±5%, respectively; p<0.0001) in PH patients. However, only the RadEF/RVEF appeared impaired (36±11 vs 47±6, p<0.0001), whereas LongEF/RVEF (47±9 vs 47±6, p=NS) was similar between pts and controls. Looking at the subgroup of patients with reduced RVEF, RV pump dysfunction was mainly driven by progressive reduction of the radial component of RV wall displacement. Conclusions: in healthy condition, the radial component of RV wall displacement is as important as the longitudinal one to determine global RV pump function. In patients with PH, the impairment of RV pump function seems to be mainly driven by the progressive reduction of RV radial displacement.