Cellular mechanisms of arrhythmogenic cardiac alternans

Area of Science:

• Cardiology
• Molecular Biology
• Electrophysiology

Background:

• Sudden cardiac death is strongly associated with heart mechanical dysfunction and arrhythmias.
• The precise causal relationship remains poorly understood.
• Intracellular calcium handling is critical for cardiac function and has been implicated in arrhythmogenesis.

Purpose of the Study:

• To elucidate the cellular mechanisms of cardiac alternans.
• To describe how calcium handling abnormalities link mechanical dysfunction to electrical instability.
• To establish cardiac alternans as a mechanistic bridge between cardiac mechanical problems and sudden cardiac death.

Main Methods:

• Review of cellular mechanisms governing cardiac alternans.
• Analysis of the interplay between intracellular calcium cycling and membrane currents.
• Examination of the coupling between calcium transient alternans and repolarization alternans.

Main Results:

• Cardiac alternans can be mediated by impaired intracellular calcium handling, specifically abnormal release or reuptake by the sarcoplasmic reticulum.
• Calcium transient alternans are coupled to repolarization alternans through various pathways.
• These alternans create a substrate conducive to reentrant excitation, a common cause of arrhythmias.

Conclusions:

• Cardiac alternans represent a key cellular mechanism linking mechanical dysfunction to electrical instability.
• Abnormal intracellular calcium cycling is a primary driver of calcium transient alternans.
• Understanding cardiac alternans is vital for comprehending the pathogenesis of sudden cardiac death.