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The differential diagnosis of a regular, narrow QRS, long-RP tachycardia includes atypical atrioventricular nodal reentry tachycardia (AVNRT), atrial tachycardia and atrioventricular reentry tachycardia (AVRT) via a slowly conducting accessory pathway usually presenting decremental conduction properties.
Ventricular overdrive pacing is the proposed initial diagnostic manoeuvre. During ventricular overdrive pacing the following criteria are assessed: (A) post-pacing response (V-A-V versus V‑A-A-V) and (B) post-pacing interval (PPI) minus tachycardia cycle length (TCL). A V-A-A-V response strongly suggests atrial tachycardia, while a V-A-V response is encountered in both AVRT and AVNRT [1]. The PPI-TCL differentiates an atypical AVNRT from an AVRT with a discriminant value of 115 msec (>115 msec suggests atypical AVNRT, while <115 msec an AVRT) [2].
In our case, ventricular overdrive pacing resulted in consistent retrograde atrial capture, V‑A-V post-pacing response, with a PPI-TCL of 64 msec which led to the diagnosis of an AVRT (Fig. 1). During mapping, the earliest retrograde atrial activation was identified in a coronary sinus branch, suggestive of a coronary sinus-ventricular accessory pathway (Fig. 2) [3]. Ablation in the area of retrograde atrial prematurity with an irrigating catheter (20 W) resulted in tachycardia termination. Successful ablation was validated by post-ablation para-Hisian pacing, which showed a nodal response and adenosine administration during ventricular pacing.
Ventricular overdrive pacing from the RV apex with retrograde atrial capture during the regular, long-RP, narrow QRS tachycardia (cycle length 370 ms). The post-pacing response demonstrated a V-A-V pattern with a PPI-TCL <115 msec which leads to the diagnosis of an atrioventricular reentry tachycardia using a slowly conducting accessory pathway. From top to bottom surface ECG leads (I, III, aVR, aVL, V1 and V6) and electrograms recorded from the distal and proximal bipole of a catheter located at the His (HBED: distal bipole, HBEP: proximal bipole) and a decapolar catheter placed in the coronary sinus (PCS: proximal coronary sinus, DCS: distal coronary sinus)
The diagnosis of an AVRT using a slowly conducting accessory pathway should be taken into consideration in the differential diagnosis of a regular, narrow QRS, long-RP tachycardia even among patients with a first presentation within middle adulthood and an episodic occurrence on Holter recording, suggestive of an atrial tachycardia.
References
Veenhuyzen GD, Quinn FR, Wilton SB, et al. Diagnostic pacing maneuvers for supraventricular tachycardia: part 1. Pacing Clin Electrophysiol. 2011;34:767–82.
Michaud GF, Tada H, Chough S, et al. Differentiation of atypical atrioventricular node re-entrant tachycardia from orthodromic reciprocating tachycardia using a septal accessory pathway by the response to ventricular pacing. J Am Coll Cardiol. 2001;38:1163–7.
Sun Y, Arruda M, Otomo K, et al. Coronary sinus-ventricular accessory connections producing posteroseptal and left posterior accessory pathways: incidence and electrophysiological identification. Circulation. 2002;106:1362–7.
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Tzeis, S., Pastromas, S., Sikiotis, A. et al. Regular, narrow QRS, long RP tachycardia – what is the mechanism?. Neth Heart J 25, 60–62 (2017). https://doi.org/10.1007/s12471-016-0897-4
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DOI: https://doi.org/10.1007/s12471-016-0897-4