Paroxysmal 1:1 narrow complex tachycardia: What is the mechanism?

Figures

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  Figure 1. A 4-wire electrophysiology study demonstrating a short RP narrow complex tachycardia. Oscillations of the His bundle potential on HIS 3–4 precede changes of the atrial electrogram on CS 9–10. CS = coronary sinus; HIS = recording of His bundle potential; HRA = high right atrium; Map 1–2 = positioned at right ventricular apex.

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  Figure 2. Programmed extrastimulus from the high right atrium at the time of His refractoriness. Each panel demonstrates the response to an atrial premature depolarization from the high right atrium at time of His refractoriness. CS = coronary sinus; HIS = recording of His bundle potential; HRA = high right atrium; Map 1–2 = positioned at right ventricular apex.

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  Figure 3. Ventricular pacing maneuvers during tachycardia. A: Shows the response to a ventricular premature depolarization at time of expected His. B: Shows ventricular overdrive pacing with a long postpacing interval and a long stimulus-His (St-H) interval; arrows indicate location of and acceleration of His to paced cycle length. C: Shows response to ventricular overdrive pacing with His electrograms labeled (H) and a St-H arrow; H* indicates first entrained His. CS = coronary sinus; HIS = recording of His bundle potential; HRA = high right atrium; Map 1–2 = positioned at right ventricular apex.