Abstract:
Heart Failure with preserved ejection fraction (HFpEF) has emerged as a prevalent heart disease which has high risk of short-term and long-term mortality rate. The progression of HFpEF along with the key factors which contributes to this process is an area of active research. Since the structural and functional changes of Left Ventricle (LV) governs the progression of HFpEF, computational models have emerged as a robust tool to study the features of HFpEF as well as to develop effective treatment plan in recent years. Though the ejection fraction is preserved apparently, the proper understanding of the left ventricular function in HFpEF patients is not well understood. Moreover, the synergy between the left atrium (LA) and the left ventricle (LV) is also disrupted in HFpEF. The malfunction and remodeling of LA frequently occur in the HFpEF patients, as a result of which the proper functioning of the LV is also affected due to having the direct connection between the LV and the LA through the mitral valve. In the present study a coupled left ventricular finite element-lumped parameter systemic circulatory modeling framework has been used to assess the effect of left atrial malfunction on the performance of left ventricle in HFpEF patients. The model was calibrated using the measurements taken from the literature for a healthy person and patients with HFpEF. To account for the wide range of LV geometry reported in HFpEF patients in the literature, two distinct LV geometries have been used in this study, one with a smaller LV cavity (HFpEF I) and one with a slightly dilated LV cavity (HFpEF II) in comparison to the healthy LV geometry. Both HFpEF geometries had a thicker wall and higher mass than the healthy case. Simulations were performed using the normal, HFpEF-I, and HFpEF-II LV models to quantify the effects of the variation of LA contractility (90% and 110% of healthy contractility) and LA stiffness (90%, and 110% healthy stiffness) on LV function. Increased LA contractility produced elevated pressure and enlarged volume in LA and as a consequence, the LV function gradually improved as indicated by higher ejection fraction and higher peak longitudinal and circumferential strains in both HFpEF cases. In case of increased LA stiffness, similar results have been found for both HFpEF cases where LV ejection fraction and peak longitudinal and circumferential strains have gradually increased. Finally, combinations of both LA contractility and stiffness were used which also showed a gradual improvement of LV function as indexed by the ejection fraction and the peak longitudinal and circumferential strains with elevated LA pressure for both HFpEF cases. The results of the study suggests that the enlargement of LA and elevated LA pressure improves the overall LV function. As enlargement of LA with elevated LA pressure is a common feature found in HFpEF, the results suggest that this mechanism could be a possible way which aid LV to preserve its ejection fraction.
