Background: Rapid leftward septal motion (RLSM) during early left ventricular diastole is observed in patients with pulmonary arterial hypertension (PAH). RLSM exacerbates right ventricular (RV) systolic dysfunction and impairs left ventricular (LV) filling. Increased RV wall tension caused by increased RV afterload has been suggested to cause interventricular relaxation dyssynchrony and RLSM in PAH. Methods: Simulations using the CircAdapt computational model were used to unravel the mechanism underlying RLSM by mechanistically linking myocardial tissue and pump function. Simulations of healthy circulation and mild, moderate and severe PAH were performed. We also assessed the effects on RLSM when PAH coexists with RV or LV contractile dysfunction. Results: Our results showed prolonged RV shortening in PAH causing interventricular relaxation dyssynchrony and RLSM. RLSM was observed in both moderate and severe PAH. A negative transseptal pressure gradient only occurred in severe PAH demonstrating that negative pressure gradient does not entirely explain septal motion abnormalities. PAH coexisting with RV contractile dysfunction exacerbated both interventricular relaxation dyssynchrony and RLSM. LV contractile dysfunction reduced both interventricular relaxation dyssynchrony and RLSM. Conclusions: Dyssynchrony in ventricular relaxation causes RLSM in PAH. Onset of RLSM in patients with PAH appears to indicate a worsening in RV function and, hence, can be used as sign of RV failure. However, altered RLSM does not necessarily imply an altered RV afterload, but it can also indicate altered interplay of RV and LV contractile function. Reduction of RLSM can result from either improved RV function or a deterioration of LV function.
- leftward ventricular septal bulging
- paradoxical interventricular septal motion
- transseptal pressure gradient
- left ventricular failure
- Copyright © 2016, American Journal of Physiology-Heart and Circulatory Physiology