Corresponding author:
Debabrata Bera. Rabindranath Tagore International Institute of Cardiac Sciences (RTIICS), 124 Mukundapur, Kolkata. West Bengal, India. PIN- 700099.
Ph: +91-8013894181, Fax: +91-33 2426 4204.Email- debu2000pgi@gmail.com
Key words: atypical AVNRT; fast slow AVNRT; long VA tachycardia after slow pathway modification; polarity reversal.
Funding: None
Conflict of interest: None
Acknowledgements: None.
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Case
A 45-year-old lady presented with recurrent narrow QRS tachycardia. Echocardiography was normal. During EP study dual AV nodal physiology was demonstrated: with PR interval exceeding RR interval during decremental pacing, AH jump and AV nodal echo (slow-fast). It was followed by easily inducible typical slow-fast atrioventricular nodal reentrant tachycardia (AVNRT, tachy1, septal VA= 0 ms) [Post ventricular entrainment- VAHV response, Stim A - VA= 125 ms, corrected post-pacing interval-tachycardia cycle length =116 ms ] (Fig 1A,1B). After slow pathway (SP) modification in lower triangle of Koch, (although only very few junctional beats were generated in 4 radiofrequency (RF) lesions, total 150 sec of RF energy), during decremental pacing PR interval didn’t exceed RR interval, no AH jump, no typical echo; but consistently had one and half long VA echo(Fig2A). After isoprenaline, sustained tachycardia with similar long VA (septal VA= 144 ms) was induced (Fig 2A). Attempted ventricular overdrive pacing (VOP) to entrain the tachycardia repeatedly terminated tachycardia (Fig 2C) without entraining tachycardia even after 7-8 beats.