Ventricular repolarization components on the electrocardiogram: cellular basis and clinical significance

Area of Science:

• Cardiology
• Electrophysiology
• Molecular Biology

Background:

• Ventricular repolarization on ECG, including J-waves, ST-segments, and T-waves, changes with disease and influences arrhythmias.
• Understanding the ionic and cellular basis of these ECG components is crucial for clinical interpretation.

Purpose of the Study:

• To identify the ionic and cellular basis of ventricular repolarization components on the surface ECG.
• To discuss the clinical significance of these ECG findings in normal and pathological states.
• To link clinical ECG tracings with transmembrane electrical recordings.

Main Methods:

• Review of existing literature on ventricular repolarization.
• Correlation of surface ECG findings with transmembrane action potential recordings.
• Analysis of ionic currents (e.g., I(to)) and their role in action potential morphology.

Main Results:

• J-waves result from transmural voltage gradients due to epicardial I(to)-mediated AP notch, linked to early repolarization and Brugada syndromes.
• ST-segment elevation in Brugada syndrome and ischemia may stem from loss of the epicardial AP dome, not just injury currents.
• T-waves reflect transmural dispersion of repolarization; R-on-T phenomenon may cause re-entry or early afterdepolarization, leading to ventricular arrhythmias.

Conclusions:

• The ionic and cellular mechanisms underlying ECG repolarization components provide critical insights into their clinical significance.
• Abnormalities in ion channel function and action potential propagation directly manifest as specific ECG patterns.
• This understanding aids in diagnosing and managing potentially life-threatening ventricular arrhythmias.