A single atrial stimulation resetting his bundle during tachycardia: a new diagnostic methods of atrial tachycardia distinguishing from other tachycardias

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUNDS: Catheter ablation for paroxysmal supraventricular tachycardia (PSVT) is curative treatment. However, diagnosis of atrial tachycardia (AT) distinguishing from other PSVTs are often challenging, especially when the tachycardia terminates after pacing or does not sustain long enough for diagnostic maneuvers. We sought a new method for diagnosis of AT. METHODS: One-hundred and thirty-four PSVTs including 20 ATs, 84 atrioventricular nodal reentrant tachycardias (AVNRTs) and 30 orthodromic reciprocating tachycardias (ORTs) were studied. Single atrial stimulation was started at intervals of 20ms shorter than the tachycardia cycle length during the tachycardia and coupling interval was shortened by 10ms. The pacing was performed from the proximal coronary sinus, which was not the earliest excitatory site, and pacing continued until the His potential was reset or the tachycardia terminated. The incidence of tachycardia resetting and the patterns of tachycardia termination were examined. RESULTS: Resetting of His was obtained in all AT patients without tachycardia termination. All ATs were not reset despite of His resetting.(Figure 1A) In AVNRTs or ORTs patients, 31 tachycardias (27%) were terminated with AH block before His resetting. In the 83 AVNRTs or ORTs, tachycardia was also reset when His was reset simultaneously.(Figure 1B) When tachycardia resetting was not observed despite His resetting, the diagnostic power of AT was 100% in sensitivity, specificity, positive predictive value, and negative predictive value. All cases which PSVTs were terminated before His resetting were AVNRTs or ORTs.(Figure 2) CONCLUSIONS: A single atrial programmed stimulation resetting His during tachycardia was effective for differentiating PSVT even in cases that tachycardia terminates by the pacing. [Figure: see text] [Figure: see text]