Ventricular Mechanical Asynchrony in Pulmonary Arterial Hypertension: A Model Study

In pulmonary arterial hypertension (PH), increase of myofiber contraction duration in the right ventricular (RV) free wall as compared to that in the left ventricular (LV) free wall leads to mechanical asynchrony. We used the lumped TriSeg model describing ventricular mechanics to determine effects of increasing pulmonary resistance and of changing time of RV free wall activation on ventricular pump mechanics and on myofiber mechanics in the ventricular walls. Simulated circumferential strain in the ventricular walls under normal and PH conditions agreed with measurements in patients. When the RV free wall was early activated with respect to the LV free wall and septum, simulations showed decreased RV volume and decreased myofiber work in the RV free wall whereas LV free wall and septal myofiber work increased. This suggests that RV free wall pacing in PH improves RV pump function and increases homogeneity of myofiber load in the ventricular walls.