Computational Studies on the Effects of Applied Apical Torsion for Cardiac Assist on Regional Wall Mechanics

Objective: Here we report the results of parametric computational simulations evaluating the biomechanical effects of applied apical torsion (AAT) on a patient-specific bi-ventricular failing heart model. Methods: We examined the resulting effects on cardiac biomechanics with varying device coverage areas and applied rotation angles to determine the practical working limits of AAT on a dilated cardiomyopathy heart model. Results: The largest maximum principal stresses and strains observed in the heart failure model were 80.21 kPa (at the basal node of the left ventricular epicardium) and 0.56 (at the node of the device base of the left ventricular free wall). Results show that increasing levels of AAT beyond 45 degrees produce supra-physiologic levels of stress and strain in the myocardium. Conclusion: Maximum principal stresses greater than 100 kPa were observed at multiple nodes along the epicardium and endocardium of the ventricular base and in the endocardium at the device base. Maximum principal strains greater than 0.60 were observed at multiple nodes along the epicardium and endocardium of the ventricular base. Significance: This suggests that while AAT has the potential to provide meaningful returns to hemodynamic function in failing hearts, the large deformations produced by this approach with the upper bounds of applied rotation angle realistically excludes supra-physiological rotations as a means for cardiac support. However, lower AAT angles - closer to that of the native left-ventricular torsion - coupled with another means of external cardiac compression may prove to be a viable method of cardiac assist.