Abstract 14541: Clinical Assessment of Elastic Restoring Forces of The Left Ventricle by Multivariate Multiparametric Fitting of Conventional Pressure-Volume Curves
The analysis of LV pressure-volume-time (PVt) data obtained during acute load manipulation is the gold-standard method for assessing active and passive diastolic properties. Because elastic restoring forces are coupled to relaxation during the isovolumic phase, volume clamp experiments have been necessary to measure global chamber elastic restoring forces. Therefore, they have never been characterized in the beating human heart. We hypothesized that elastic restoring forces can be assessed by multidimensional multivariate fitting of conventional PV loops.
Methods: 28 subjects undergoing LV catheterization were studied using a conductance catheter and balloon inferior cava occlusion, and classified as patients (n= 19; coronary artery disease, dilated cardiomyopathy or cirrhosis) or controls (n= 9; normal coronary arteries and no structural LV disease). Volume signal was calibrated using simultaneous echocardiography. PV datasets were analyzed using a custom-built multivariate, iterative, trust-reflective algorithm that fits constitutive equations of diastole integrally, including all available PVt data for each run. This method provides the passive PV curve bellow and beyond the equilibrium volume (V0).
Results: The algorithm converged in 65 (100%) of the PVt datasets analyzed. Sensitivity analysis demonstrated the relative contribution of each property on instantaneous LVP. Tau was longer in patients than in controls (p= 0.01), and relaxation was not completed in two patients at end diastole. Agreement with the EDPVR method to estimate V0 was Ric = 0.93. Despite V0 and dP-/dVV0 were similar between groups, the position of the ESV relative to V0 was different (V0 - ESV= + 2 ± 22 vs. -17 ± 16 ml in controls vs. patients respectively; p= 0.02). This resulted in lower elastic recoil mediated pressure at mitral valve opening in controls (-0.1 ± 3.3 vs. 1.7 ± 3.9 mmHg; p<0.05).
Conclusions: The application of a new algorithm for multidimensional minimization allows to identify the full passive PV relationship bellow and beyond V0. For the first time, restoring forces are measured in patients. Facilitation of filling by elastic restoring forces is blunted in abnormal ventricles.
- © 2012 by American Heart Association, Inc.