Effects of wall stress on the dynamics of ventricular fibrillation: a simulation study using a dynamic mechanoelectric model of ventricular tissue.
BACKGROUND
To investigate the mechanisms underlying the increased prevalence of ventricular fibrillation (VF) in the mechanically compromised heart, we developed a fully coupled electromechanical model of the human ventricular myocardium.


RESULTS
The model formulated the biophysics of specific ionic currents, excitation-contraction coupling, anisotropic nonlinear deformation of the myocardium, and mechanoelectric feedback (MEF) through stretch-activated channels. Our model suggests that sustained stretches shorten the action potential duration (APD) and flatten the electrical restitution curve, whereas stretches applied at the wavefront prolong the APD. Using this model, we examined the effects of mechanical stresses on the dynamics of spiral reentry. The strain distribution during spiral reentry was complex, and a high strain-gradient region was located in the core of the spiral wave. The wavefront around the core was highly stretched, even at lower pressures, resulting in prolongation of the APD and extension of the refractory area in the wavetail. As the left ventricular pressure increased, the stretched area became wider and the refractory area was further extended. The extended refractory area in the wavetail facilitated the wave breakup and meandering of tips through interactions between the wavefront and wavetail.


CONCLUSIONS
This simulation study indicates that mechanical loading promotes meandering and wave breaks of spiral reentry through MEF. Mechanical loading under pathological conditions may contribute to the maintenance of VF through these mechanisms.
Hirabayashi
Satoko
S
Computational Biomechanics Laboratory, Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan. hirabayashi@sml.k.u-tokyo.ac.jp
Inagaki
Masashi
M
Hisada
Toshiaki
T
D000818:Animals; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D055119:Elastic Modulus; D004581:Electronics; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008955:Models, Cardiovascular; D033081:Shear Strength; D013314:Stress, Mechanical; D014693:Ventricular Fibrillation / Q000503:physiopathology*