Repolarization indicates electrical instability in ventricular arrhythmia originating from papillary muscle

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmia

Background:

• Papillary muscle (PM) arrhythmias can trigger ventricular fibrillation (VF), leading to sudden cardiac death, even without structural heart disease.
• Distinguishing benign premature ventricular contractions from fatal arrhythmias remains challenging.
• Electrophysiological changes preceding VF degeneration are not fully understood, though altered repolarization is implicated.

Purpose of the Study:

• To investigate the mechanisms by which stable ventricular arrhythmias (VA) degenerate into VF in structurally healthy hearts.
• To identify electrophysiological parameters that can differentiate self-limiting arrhythmias from those prone to VF degeneration.

Main Methods:

• Ventricular arrhythmia (VA) was induced in healthy sheep via aconitine injection into papillary muscles (PMs).
• Endocardial high-density and epicardial mapping were performed during sinus rhythm (SR) and VA.
• Electrical restitution curves were analyzed, relating diastolic interval to activation recovery interval (a surrogate for action potential duration).

Main Results:

• Electrical restitution curves were steeper during VA compared to non-arrhythmic states, indicating electrical instability.
• The parameter repolarization time in relation to cycle length (RT/CL) effectively differentiated self-limiting from degenerating arrhythmias with high specificity and sensitivity.
• Steeper restitution curves are associated with increased propensity for VF degeneration.

Conclusions:

• Repolarization time in relation to cycle length (RT/CL) may serve as a simple index to differentiate self-limiting from electrically unstable arrhythmias.
• RT/CL can help identify electrical instability in patients, aiding in the prediction of VF risk.
• This index is independent of cycle length, facilitating its clinical application.