RV form and function: a piston pump, vortex impeller, or hydraulic ram?

d n d T he iPIX by Saremi et al. (1) in this issue of iJACC highlights the precision of current imaging techniques in displaying the complex 3-dimensional structure of the right entricle (RV). The investigators illustrate the inricacy of normal RV geometry, highlighting the istributions of anatomical folds, irregular trabeulations and, more importantly, the RV inundibulum. These remarkable pictures only make ne question more on the physiological relevance f the complex RV geometry. The separation of a hin-walled, highly compliant RV and a thickalled, highly contractile left ventricle (LV) has een justified to the evolutionary needs of air reathing and high metabolism (2). The separaion of the right and the left circulations ensure resence of lower blood pressures in the pulmoary circulation; in its absence the thin blood-gas arrier required for high oxygen demands would e breached with the least amount of exertion. iven that the 2 chambers require being separate, here has been little information, however, to jusify why the geometry of the 2 chambers need to e so different. RV as a piston pump. Longitudinal shortening and base-to-apex piston-like motion of the atrioventricular plane have been suggested to be a greater contributor to RV stroke volume than short-axis or circumferential shortening. A number of measurements have therefore been explored, including the tricuspid annular plane systolic excursion (TAPSE), RV free wall annular velocities, and longitudinal strain of the RV free wall. However, RV function is sustainable even in the absence of RV free wall activity, which can be completely excised and replaced by an inert prosthetic patch as long as LV function is preserved. These observations question