Radiofrequency Catheter Ablation ofIdiopathic LeftVentricular Tachycardia Guided bya Purkinje Potential

idiopathic left ventricular tachycardia (ILVT)withright bundle branch block configuration andleft-axis deviation hasbeensuggested tooriginate fromtheleft posterior fascicle. Thepurposeofthisstudy was todetermine howfequently potentials generated bythePurkinje fiber network(Ppotential) can berecorded preceding ventricular activation, andtheroleoftheP potential inguiding radiofrequency catheter ablation. Methods andResults. Eightpatients (meanage,26±10years) withILVT(cycle length, 346±59 milliseconds) werestudied. Right andleft ventricular endocardial mapping during tachycardia identified earliest ventricular activation attheposteroapical left ventricular septum. Inallpatients, earliest ventricular activation during tachycardia was preceded bya distinct potential. Thispotential also preceded ventricular activation during sinusrhythm, consistent withactivation ofa segment oftheleft posterior fascicle (Ppotential). Theearliest recorded Ppotential preceded theQRSduring tachycardia by 15to42milliseconds (mean, 27±9milliseconds). Theapplication ofradiofrequency current at1to4sites (median, 1)eliminated ILVTinalleight patients. Inthesevenpatients withP potentials recorded at multiple sites within theposteroapical septum, ablation was successful atthesiteoftheearliest P potential andunrelated tothetiming ofventricular activation. Intheremaining patient, ablation was successful atasite recording alate Ppotential fusing withearliest ventricular activation. During follow-up (1to67months; median, 10.5) ILVTrecurred only inthelatter patient. Pacemapping during tachycardia atthesuccessful ablation site infourpatients produced a similar QRSwithstimulus-QRS interval equal toP-QRSinterval during tachycardia. However, asimilar QRSwasobtained bypacing atnearby sites that recorded a later P potential. Conclusions. Thesefindings support thehypothesis thatILVToriginates fromthePurkinje network of theleft posterior fascicle. AP potential canberecorded attheposteroapical left ventricular septumduring ILVT,andablation issuccessful atthesite recording theearliest P potential. Pacemapping withsimilar QRSisnotspecific duetocapture ofthePurkinje fiber network ata site remotefromtheorigin ofthe tachycardia. (Circulation. 1993;88:2607-2617.)