Background: passive LV stiffness in chronic LL compares to EL, in early systolic with diastolic LV pump dysfunction, as result from impaired LV filling has not been defined wheatear is associated with early development reduced LV stiffness with SD. Earlier increased passive LV stiffness, in development systolic with diastolic LV dysfunction is not defined in the P-V loop’s assessment of LV DD.

Objective: was to assess passive LV stiffness constant β, using bi-exponential regression analysis of EDPVR and the LVH remodeling. How it relates to early DD in HF development between 4th vs. 8th week in comparative assessment of LL and EL was measured from LV P-V loops` in a pig model.

Methods: Single mono and bi-exponential regression were used to assess the passive LV stiffness constants (α and β), so to assess relation between early development diastolic with systolic LV pump dysfunction in LL vs. EL at 4th vs. 8th week. Also how this relates to early SD having DD was assessed in the porcine model from P-V loops. Fourteen male pigs (28±3 kg) having ascending aorta stenosis with early LV afterload (EL=6), vs. descending thoracic aorta stenosis, with late LV afterload (LL=8) underwent invasive LV P-V loops’ measurements, during LV load reduction at 4th vs. 8th week. Single nonlinear mono and bi-exponential regression of EDPVR were performed for calculating passive LV stiffness and constants (β1 and β₂), using special software from maximal end-diastolic LV pressure and volume. Two-way repeated measures ANOVA, post-hoc Tukey test and were used for statistical data analysis. Results are means±SEM or median (quartiles) for significant level at p<0.05.

Results: Bi-exponential regression model, showed difference in β, with reduction in EL vs. LL at 8th weeks. α stiffness constants was also not different in LL vs. EL, though bi-exponential β₂ constant was early reduced at 4th week significantly in LL vs. EL (0.07±0.015 mmHg/ml in EL vs. 0.04±0.007 mmHg/ml in LL) that was different from shift to the right in EL vs. leftwards in LL at 8th week. Increased β2 was found in EL that did not shifted rightwards at 8th week. It showed DD at 8th week. Increased LV stiffness shows early SD present in EL at 4th and in LL at 8th week. Increased β is earlier pathologic in EL at 4th vs. 8th week, being reduced as in LL at 8th week, due to change in compliance from rightwards EDPVR shift, indicating adverse LVH remodeling.

Conclusion: β₁ as well as α are not different as found in mono-exponential regression assessment of DD in SD. Due to rightward shift of EDPVR in bi-exponential regression, as found in DD there is early systolic LV dysfunction in EL vs. LL. This shows how early SD having increased EDPVR, as LV systolic dysfunctional parameter in LL and EL in porcine mode, in absolute LV volumes.