What is the objective of programmed electrical stimulation with extrastimuli during EPS?

• A. To test inducibility of clinical arrhythmias and characterize substrate and conduction properties
• B. To measure blood pressure response to pacing
• C. To assess valve anatomy
• D. To map coronary anatomy

Answer: (C)

The objective of programmed electrical stimulation with extrastimuli during an EPS is to test whether the heart’s electrical substrate can inducibly generate arrhythmias and to characterize how easily tissue can be excited and how it conducts. By delivering a train of paced beats to bring tissue to a baseline refractory state, then introducing an extrastimulus at progressively shorter intervals, you probe the boundaries of refractoriness and conduction. If a sustained arrhythmia is induced, it reveals the presence of susceptible substrate and the conduction properties that support reentry or triggered activity, which is essential for risk assessment and planning ablation if appropriate. This approach focuses on electrical behavior, not on structural measurements like valve or coronary anatomy or on hemodynamic responses.