a fit and healthy 25-year - old male presented with palpitations from a regular broad complex tachycardia ( bct ) of left bundle branch block ( lbbb)-like morphology , 330-ms cycle length , and no discernible  p waves . intravenous adenosine terminated the bct , resting electrocardiogram ( ecg ) was not pre - excited , and echocardiogram was normal . during the electrophysiologic study , retrograde conduction was central and decremental . 1a shows that conduction switched from nodal ( narrow qrs complexes with distinct his potential  solid blue arrow ) to the atriofascicular pathway ( lbbb - like complexes and interpolation of the his potential  dotted blue arrow ) during wenckebach - pacing maneuver . 1b shows that the intellatip mifi ablation catheter was used to map the atriofascicular pathway potential in sinus rhythm . the 8-mm tip ablation catheter has three radially positioned , equally spaced mini - electrodes , 2  mm from the tip . bipolar recordings were made between these mini - electrodes : m12 , m23 , and m31 . this enabled precise signal localization and clearer identification of the pathway potential than the conventional ablation distal bipolar recording ( blue dotted box , fig . the gains on the catheter mini - electrodes were 5000-fold greater , and those in the conventional distal pole of the ablation catheter were 10,000-fold greater . radiofrequency ablation ( rfa ) at this site ( 60  c , 70  w , and 120  s ) resulted in no pathway conduction and non - inducible bct . atriofascicular pathways consist of fibers arising from the right atrial free wall and insert at or adjacent to the distal right bundle . they usually only conduct in an anterograde manner , participating in the anterograde limb of an antidromic atrioventricular reciprocating tachycardia ( avrt ) with lbbb - like morphology and decremental properties . standard therapy involves targeted rfa around the tricuspid annulus as guided by pathway potentials also known as mahaim ( m ) potentials , . these m potentials can be as large as the his deflection or can be small and narrow with a low amplitude . furthermore , unintentional mechanical trauma by catheter manipulation can result in transient abolition of these potentials from a few minutes to a few hours , . these m potentials are also recorded only in close proximity to the atrial insertion site , and thus , accurate localization and ablation at this site result in successful abolition of this pathway , , . the intellatip mifi catheter has been shown to delineate local electograms better in the isthmus than the conventional bipolar electrode during atrial flutter ablation . the signal amplitude in the mini - electrodes has been noted to be higher than that of the conventional bipolar catheter . we used the same principle in this case to make use of the special characteristics of the novel ablation catheter to localize the atrial insertion point accurately . furthermore , the m potentials , as recorded from the distal mini - electrodes , were clearer and of higher amplitude compared with those recorded using the conventional distal pole of the ablation catheter . we did not compare this with a standard ablation catheter in the same patient to keep the costs of the procedure within reasonable limits and to avoid causing unintentional mechanical trauma to the atrial insertion site .
atriofascicular pathways are a rare cause of antidromic atrioventricular reciprocating tachycardia . the intellatip mifi ablation catheter ( boston scientific , 
 ma , usa ) is a novel ablation catheter that allows enhanced signal clarity with highly localized electrograms . 
 this is the first report of this catheter being successfully used to map and ablate the atriofascicular pathway potentials .