The pressure recovery ratio: The invasive index of LV relaxation during filling. model-based prediction with in-vivo validation

Using a simple harmonic oscillator model (PDF formalism), every early filling E-wave can be uniquely described by a set of parameters, (x_o, c, and k). Parameter c in the PDF formalism is a damping or relaxation parameter that measures the energy loss during the filling process. Based on Bernoulli´s equation and kinematic modeling, we derived a causal correlation between the relaxation parameter c in the PDF formalism and a feature of the pressure contour during filling - the pressure recovery ratio defined by the left ventricular pressure difference between diastasis and minimum pressure, normalized to the pressure difference between a fiducial pressure and minimum pressure [PRR = 3D(P_Diastasis-P_Min)/(P_Fiducial-P_Min)]. We analyzed multiple heart beats from one human subject to validate the correlation. Further validation among more patients is warranted. PRR is the invasive causal analogue of the noninvasive E-wave relaxation parameter c. PRR has the potential to be calculated using automated methodology in the catheterization lab in real time.