LAUSR

Three main mechanisms contribute to right ventricular (RV) pump function: (1) shortening of the longitudinal axis with traction of the tricuspid annulus towards the apex; (2) inward (radial) movement of the RV free wall, which is often referred as the “bellows effect”; and (3) bulging of the interventricular septum into the RV during the left ventricular contraction and stretching of the free wall over the septum (causing shortening in the anteroposterior direction). Despite the established clinical value of the functional changes among the aforementioned components, their relative importance remains to be quantified during physiological conditions. Accordingly, the aim of our study was to evaluate the relative contribution of the different RV motion directions to global RV function on both global and segmental level in a large set of healthy individuals. We have recruited 231 healthy volunteers (44% female, with a wide and balanced age range from 8 to 81 years) from two experienced centers performing transthoracic 3D echocardiography (3DE) on a routine basis. 3DE datasets focused on the RV were obtained using multi-beat acquisition. We determined RV volumes and subsequent ejection fraction (RVEF) by dedicated software. Using the ReVISION method, we have decomposed the motion of the RV to determine longitudinal (LEF), radial (REF) and anteroposterior ejection fraction (AEF). Their ratio to RVEF quantifies the relative contribution of the given component to global RV function. Moreover, regional subvolumes were also analyzed in a 15-segment model. Mean value of RVEF was significantly higher in female subjects compared to male subjects (60±7 vs. 56±7%, p<0.001). The relative contributions of LEF and REF to RVEF were comparable, while the contribution of AEF was significantly lower (LEF/RVEF vs. REF/RVEF vs. AEF/RVEF: 0.48±0.08 vs. 0.49±0.07 vs. 0.39±0.11, p<0.001) in the pooled population as well as in the genders separately. In line with higher RVEF found in women, female gender was associated with a higher longitudinal and radial contribution compared to males, however, AEF was similar (women vs. men; LEF/RVEF: 0.49±0.08 vs. 0.47±0.07, p<0.05; REF/RVEF: 0.50±0.07 vs. 0.48±0.06, p<0.01; AEF/RVEF: 0.38±0.12 vs. 0.40±0.10, p=NS). Interestingly, AEF/RVEF showed a significant deterioration with age (r=−0.354, p<0.001), while age-dependency of the longitudinal and radial contributions were not observed concerning both genders. An age-related decrease could be demonstrated by the volume fractions of the 5 septal volumetric segments (r=−0.229, p<0.001). Motion decomposition and the 15 segments In physiological conditions, the relative importance of longitudinal and radial wall motions is similar in determining global RV function. Aging accompanied by a decrease in anteroposterior shortening, which may point to a deteriorating systolic LV-RV interaction. Our results may facilitate further research concerning the alterations of RV mechanical pattern in various disease states.