Sensitivity analysis of left ventricle with dilated cardiomyopathy in fluid structure simulation

Abstract

Dilated cardiomyopathy (DCM) is the most common myocardial disease. It not only leads to systolic dysfunction but also diastolic deficiency. We sought to investigate the effect of idiopathic and ischemic DCM on the intraventricular fluid dynamics and myocardial wall mechanics using a 2D axisymmetrical fluid structure interaction model. In addition, we also studied the individual effect of parameters related to DCM, i.e. peak E-wave velocity, end systolic volume, wall compliance and sphericity index on several important fluid dynamics and myocardial wall mechanics variables during ventricular filling. Intraventricular fluid dynamics and myocardial wall deformation are significantly impaired under DCM conditions, being demonstrated by low vortex intensity, low flow propagation velocity, low intraventricular pressure difference (IVPD) and strain rates, and high-end diastolic pressure and wall stress. Our sensitivity analysis results showed that flow propagation velocity substantially decreases with an increase in wall stiffness, and is relatively independent of preload at low-peak E-wave velocity. Early IVPD is mainly affected by the rate of change of the early filling velocity and end systolic volume which changes the ventriculo:annular ratio. Regional strain rate, on the other hand, is significantly correlated with regional stiffness, and therefore forms a useful indicator for myocardial regional ischemia. The sensitivity analysis results enhance our understanding of the mechanisms leading to clinically observable changes in patients with DCM.

Figure 1. Basic geometry of the LV in the computational model.

Figure 2. Temporal waveforms of the inlet velocity for normal, impaired relaxation, pseudonormal, and restrictive filling patterns.

For each of the filling pattern, E-wave refers to the first wave while A-wave refers to the second wave.

Figure 3. Relationship between nominal stress and strain for the normal, idiopathic DCM and ischemic DCM (basal and apical region) models.

Semi-log plot (y-axis) on the right.

Figure 4. Instantaneous vorticity (contour plot) in normal LV, idiopathic DCM (impaired relaxation) and ischemic DCM (impaired relaxation) during peak E-wave, end of E-wave and end of filling phases.

Vorticity levels: from 5 to 100, step 10.

Figure 5. Temporal waveforms of the intraventricular pressure difference (IVPD) for normal, idiopathic and ischemic DCM with impaired relaxation, pseudonormal and restrictive filling patterns.

Figure 6. von Mises stress (top) and total strain (bottom) distribution for (a) normal, (b) idiopathic DCM (impaired relaxation) and (c) ischemic DCM (impaired relaxation) during end of the filling phase.

Figure 7. Pressure volume relationship for normal, idiopathic and ischemic DCM cases throughout the filling phase.

Figure 8. Effects of DCM parameters on fluid dynamic measurements.

The percentage change in the vortex intensity (Γ_I), flow propagation velocity (V_p), early peak intraventricular pressure difference (IVPD) and end diastolic pressure (EDP) with a 2X increase in the peak E-wave velocity (E peak, baseline value = 0.7 m/s), end systolic volume (ESV, baseline value = 50 mL), wall stiffness (Stiffness, baseline value obtained from the normal condition) and sphericity index (SI, baseline value = 0.52).

Figure 9. Effect of DCM parameters on wall mechanics measurement.

The percentage change in the average von Mises stress (vMS), longitudinal strain rate (SR_L), circumferential strain rate (SR_C) and radial strain rate (SR_R) with a two-fold increase in the peak E-wave velocity (E peak, baseline value = 0.7 m/s), end systolic volume (ESV, baseline value = 50 mL), wall stiffness (Stiffness, baseline value obtained from the normal condition) and sphericity index (SI, baseline value = 0.52).

Figure 10. von Mises stress (left) and total strain (right) distribution for ischemic DCM (lateral infarct) during end of the filling phase.

Figure 11. Pressure-volume relationship for the ischemic DCM cases (apical infarction and lateral infarction) throughout the filling phase.