Electrophysiological changes in the conducting properties of fast pathway following modification of the slow pathway of the atrio ventricular node for atrio ventricular nodal re-entrant tachycardia

Objectives: To determine the possible changes in the conducting properties of the fast pathway after modification of the atrioventricular slow pathway for AVNRT which leads to the failure of the induction of tachycardia. Methods: This study was conducted in the Cardiac electrophysiology Laboratory of Hayatabad Medical Complex, Peshawar, Pakistan from March 2017 to March 2018. All the patients underwent radiofrequency modification of the slow pathway for AVNRT. Patients in whom typical AVNRT was inducible with demonstration of dual AV nodal physiology were included in the study. Results: A total of 171 cases were included in the study, 42 (25%) were males, mean age recorded was 47 +/- 15 years. There were no significant changes pre and post ablation in the base line parameters like VV interval, atrioventricular nodal (AV nodal) Wenckebach cycle length, slow pathway effective refractory period (SPERP) or fast and slow pathways maximal Atrio His interval. However significant change was observed in the effective refractory period of the fast pathway 350 +/- 49 Vs 290 +/- 32 (p value 0.0001). The difference between slow and Fast pathway ERP was also decreased significantly 82 +/- 36 Vs 56 +/- 24 (p value 0.004). Conclusion: Our study showed that ablation of AV nodal slow pathway for atrioventricular nodal reentrant tachycardia leads to changes in the effective refractory period of the fast pathway.