Which are examples of ventricular ectopic foci?

• A. PVC and ventricular tachyarrhythmia
• B. Atrial fibrillation
• C. Sinus tachycardia
• D. First-degree AV block

Answer: (A)

Ventricular ectopic foci are abnormal pacemaker sites within the ventricles that fire impulses independent of the normal SA nodal drive. When such a ventricular focus initiates beats, the result is premature ventricular contractions, which present as early, wide QRS complexes without a preceding P wave and with a ventricular origin. If these ectopic beats occur in rapid succession, they can trigger a ventricular tachyarrhythmia, a fast rhythm arising from the ventricles. The other options come from the atrial region or the normal conduction system rather than an ectopic ventricular site: atrial fibrillation starts in the atria, sinus tachycardia is driven by the SA node, and first-degree AV block reflects delayed conduction through the AV node, not ventricular ectopy. So PVCs and ventricular tachyarrhythmias are classic examples of ventricular ectopic foci.