86 | Chapter 5 The parameter subset θ included for estimation was based on a previous sensitivity analysis4 and is shown in Table 1. Parameters included were regional parameters describing the constitutive behaviour of active (SfAct) and passive stress (k1), activation delay (dT), reference wall area (AmRef), and global parameters relative systole duration (RSD), and CO. Heart rate (HR) in the model was set to match clinically measured HR to ensure equal cycle lengths in measured and modelled signals. Strain was defined as the segmental displacement relative to its reference length at end diastole. Additionally, EF, EDV, and RVD were included. Modelled EDV was defined as the maximum cavity volume of the LV cavity assuming perfect valve behaviour. EF was defined as the ratio of stroke volume over maximum volume. RVD was defined as the maximum cavity diameter between the RVfw and IVS. Table 1. parameters included in this study Model parameter Unit Description Sample distribution Parameter range N parameters SfAct kPa Active stress scaling factor logituniform (0, 1000) 5 (LVfw, IVS, RVapex, RVmid, RVbase) k1 - Stiffness exponent logituniform (1, 100) 5 (LVfw, IVS, RVapex, RVmid, RVbase) dT ms Activation delay logituniform (-200, 800) 5 (LVfw, IVS, RVapex, RVmid, RVbase) AmRef cm2 Eccentric hypertrophy log-uniform (0, ∞) 3 (LVfw, IVS, RVfw) RSD - Global systolic duration scaling log-uniform (0, ∞) 1 Global Q0 L/min Cardiac Output log-uniform (0, ∞) 1 Global 20 Likelihood function As shown in Equation 4, the likelihood function was based on the summed squared error Χ2. This error consists of the error in strain of the 5 segments and on the error in EF, EDV, and RVD. Because the measured diastolic strain is less reliable due to the drift affecting most of this phase, we only included strain during the systolic phase in this study. This systolic phase was
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