Computational modeling revealed that the CACNA1C R858H mutation increases L-type calcium current, leading to afterdepolarizations, QT prolongation, and increased tissue vulnerability to reentry.
Computational modeling demonstrates that the CACNA1C R858H mutation increases arrhythmia risk in Long QT Syndrome Type 8 through altered calcium handling, APD prolongation, and increased vulnerability to unidirectional conduction block.
Functional analysis of the L-type calcium channel has shown that the CACNA1C R858H mutation associated with severe QT interval prolongation may lead to ventricular fibrillation (VF). This study investigated multiple potential mechanisms by which the CACNA1C R858H mutation facilitates and perpetuates VF. The Ten Tusscher-Panfilov (TP06) human ventricular cell models incorporating the experimental data on the kinetic properties of L-type calcium channels were integrated into one-dimensional (1D) fiber, 2D sheet and 3D ventricular models to investigate the pro-arrhythmic effects of CACNA1C mutations by quantifying changes in intracellular calcium handling, action potential profiles, action potential duration restitution (APDR) curves, dispersion of repolarization (DOR), QT interval and spiral wave dynamics. R858H ‘mutant’ L-type calcium current (ICaL) augmented sarcoplasmic reticulum calcium content, leading to the development of afterdepolarizations at the single cell level and focal activities at the tissue level. It also produced inhomogeneous APD prolongation, causing QT prolongation and repolarization dispersion amplification, rendering R858H ‘mutant’ tissue more vulnerable to the induction of reentry compared with other conditions. In conclusion, altered ICaL due to the CACNA1C R858H mutation increases arrhythmia risk due to afterdepolarizations and increased tissue vulnerability to unidirectional conduction block. However, the observed reentry is not due to afterdepolarizations (not present in our model), but rather to a novel blocking mechanism.
Bai et al. (2017) studied Long QT Syndrome Type 8 (LQT8). CACNA1C R858H Mutation (Computational Model) vs. Wild-type and other CACNA1C mutations was evaluated on Ventricular arrhythmogenesis mechanisms (APD, QT interval, afterdepolarizations). Computational modeling revealed that the CACNA1C R858H mutation increases L-type calcium current, leading to afterdepolarizations, QT prolongation, and increased tissue vulnerability to reentry.