Key result
A linear model with varying volume intercept (LinFree) provided the best fit for simulating the instantaneous left ventricular pressure-volume relation, though all six models performed similarly for PV-loop shape (Hamming distance 20-23%).
For realistic simulation of the instantaneous left ventricular pressure-volume relation, a linear model with a free volume intercept is sufficient and performs best among the tested models.
Simplest linear PV model suffices for animal simulations; leaves open human validation before clinical use.
Simulations are useful to study the heart's ability to generate flow and the interaction between contractility and loading conditions. The left ventricular pressure-volume (PV) relation has been shown to be nonlinear, but it is unknown whether a linear model is accurate enough for simulations. Six models were fitted to the PV-data measured in five sheep and the estimated parameters were used to simulate PV-loops. Simulated and measured PV-loops were compared with the Akaike information criterion (AIC) and the Hamming distance, a measure for geometric shape similarity. The compared models were: a time-varying elastance model with fixed volume intercept (LinFix); a time-varying elastance model with varying volume intercept (LinFree); a Langewouter's pressure-dependent elasticity model (Langew); a sigmoidal model (Sigm); a time-varying elastance model with a systolic flow-dependent resistance (Shroff) and a model with a linear systolic and an exponential diastolic relation (Burkh). Overall, the best model is LinFree (lowest AIC), closely followed by Langew. The remaining models rank: Sigm, Shroff, LinFix and Burkh. If only the shape of the PV-loops is important, all models perform nearly identically (Hamming distance between 20 and 23%). For realistic simulation of the instantaneous PV-relation a linear model suffices.
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Lankhaar et al. (2009) studied Left ventricular pressure-volume relation modeling (n=5). Six isochrone models (LinFix, LinFree, Langew, Sigm, Shroff, Burkh) vs. Measured PV-loops was evaluated on Akaike information criterion (AIC) and Hamming distance. A linear model with varying volume intercept (LinFree) provided the best fit for simulating the instantaneous left ventricular pressure-volume relation, though all six models performed similarly for PV-loop shape (Hamming distance 20-23%).
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