What type of pacing stimulus is used to determine VERP?

• A. Ventricular extrastim pacing
• B. Atrial extrastim pacing
• C. Ventricular incremental pacing
• D. Atrial pacing

Answer: (A)

Verp is determined by testing the ventricle’s ability to respond to a premature beat. You start with a train of paced ventricular beats to reset the tissue, then deliver a premature ventricular stimulus (an extrastimulus) at progressively shorter coupling intervals until you no longer get a depolarization. The shortest interval that still captures defines the ventricular effective refractory period. This is why ventricular extrastimulus pacing is the appropriate method—it directly probes ventricular excitability and refractoriness. Using an atrial extrastimulus would assess atrial tissue rather than ventricular, and ventricular incremental pacing or atrial pacing wouldn’t isolate the ventricular refractory response in the same way.