Ectopic foci generate action potentials that do not follow normal conduction pathways. What is a consequence for ventricular depolarization?

Ectopic foci generate action potentials that do not follow normal conduction pathways. What is a consequence for ventricular depolarization?

• A. Faster ventricular depolarization
• B. Longer ventricular depolarization
• C. No change in depolarization
• D. Immediate ventricular depolarization

Answer: (B)

Ectopic foci fire impulses outside the fast His-Purkinje system, so the impulse reaches the ventricles through slower, cell-to-cell conduction in the myocardium rather than through the rapid Purkinje network. This slower spread causes a longer, less synchronized ventricular activation, which on ECG shows as a wider, longer-lasting QRS complex. In short, ventricular depolarization takes more time when activation does not follow the normal fast conduction pathways.

Ectopic foci fire impulses outside the fast His-Purkinje system, so the impulse reaches the ventricles through slower, cell-to-cell conduction in the myocardium rather than through the rapid Purkinje network. This slower spread causes a longer, less synchronized ventricular activation, which on ECG shows as a wider, longer-lasting QRS complex. In short, ventricular depolarization takes more time when activation does not follow the normal fast conduction pathways.