L-type Ca2+ channel mutations and T-wave alternans: a model study.

Area of Science:

• Cardiovascular physiology
• Computational biology
• Molecular cardiology

Background:

• Timothy Syndrome (TS) is a multisystem disorder associated with severe cardiac arrhythmias.
• The precise mechanisms linking TS mutations to arrhythmias remain poorly understood.
• L-type Ca(2+) channels play a critical role in cardiac excitation-contraction coupling.

Purpose of the Study:

• To investigate the multi-scale effects of a TS mutation in the L-type Ca(2+) channel on cardiac dynamics.
• To connect the L-type Ca(2+) channel mutation to arrhythmia susceptibility.
• To elucidate the underlying mechanisms of TS-related cardiac dysfunction.

Main Methods:

• Theoretical simulations of cardiac function from gene mutation to ECG.
• Analysis of L-type Ca(2+) channel dynamics in single cells and coupled tissue.
• Computation of electrocardiogram (ECG) patterns from simulated mutant cardiac tissue.

Main Results:

• The TS mutation disrupts rate-dependent dynamics and promotes alternans in single cardiac cells.
• In coupled tissue, the mutation leads to discordant alternans and conduction block at physiological heart rates.
• Simulated ECGs show prolonged QT intervals, T-wave alternans, and T-wave inversion, consistent with TS patient data.

Conclusions:

• Enhanced Ca(2+) influx due to the TS mutation causes cellular electrical instabilities.
• The interplay of faulty Ca(2+) influx and action potential duration restitution drives arrhythmogenic alternans.
• The L-type Ca(2+) channel mutation is sufficient to cause the TS clinical phenotype, revealing complex underlying current interactions.