ATP works best on what type of arrhythmia?

• A. Atrial fibrillation
• B. Re-entrant
• C. Ventricular fibrillation
• D. Sinus tachycardia

Answer: (B)

Anti-tachycardia pacing works by interrupting a re-entrant conduction loop. In a re-entrant tachycardia, the heart’s impulse circuits around a pathway, sustaining a fast rhythm. Delivering a train of paced beats at a rate faster than the tachycardia can invade the circuit and reset or overdrive the tissue enough that the circuit can no longer sustain itself, effectively terminating the rhythm.

This is why the approach is best suited for re-entrant tachycardias: the mechanism relies on disrupting a stable conduction loop. Atrial fibrillation is a chaotic, non-structured atrial activity without a single re-entrant circuit to reset. Ventricular fibrillation is chaotic ventricular activity that requires defibrillation, not pacing. Sinus tachycardia is a normal, physiologic speeding up of a single pacemaker and does not involve a propagating re-entrant circuit to disrupt with ATP.