Link between SCN5A mutation and the Brugada syndrome ECG phenotype: simulation study

Area of Science:

• Computational biology
• Cardiac electrophysiology
• Mathematical modeling

Background:

• The precise alterations in sodium current (I(Na)) gating kinetics underlying specific cardiac phenotypes remain unclear.
• Investigating the impact of I(Na) kinetic changes on early repolarization (ER) and phase 2 reentry (P2R) is crucial for understanding cardiac arrhythmias.

Purpose of the Study:

• To evaluate the effects of modified I(Na) gating kinetics on ER and P2R using a theoretical epicardial ventricular fiber model.
• To explore the role of I(Na) density and conduction disturbances in precipitating these electrophysiological events.

Main Methods:

• Incorporated Miyoshi-I(CaL) into the modified Luo-Rudy dynamic (LRd) model.
• Simulated a theoretical fiber with dispersed Ito-density and gap junctions between epicardial cells.
• Modified I(Na) kinetics, including shifts in inactivation/activation curves and altered inactivation time constant (DEC).

Main Results:

• Observed P2R and ER under specific I(Na) kinetic changes, particularly with a decreased inactivation time constant (DEC).
• A decrease in I(Na)-density significantly increased the likelihood of ER and P2R, especially with DEC.
• Conduction disturbances markedly elevated the probability of ER or P2R.

Conclusions:

• DEC-I(Na) can precipitate I(Na)-blocker inducible ER in a 1D model with Ito-density dispersion.
• These findings offer a potential explanation for the ST-segment elevation observed in Brugada syndrome associated with SCN5A mutations.
• Concomitant conduction disturbances might be necessary for P2R at physiological Ito densities.