The role of Purkinje and pre-Purkinje potentials in the reentrant circuit of verapamil-sensitive idiopathic LV tachycardia

Although the mechanism of verapamil-sensitive idiopathic left ventricular t achycardia (ILVT) is usually reentry, the actual reentrant circuit is not c learly understood. This study examined the relationship between the Purkinj e potential (PP) and a dull potential preceding PP (pre-PP) during ILVT to elucidate the roles of these potentials in the reentrant circuit of ILVT. E lectrophysiological studies and radiofrequency catheter ablation were perfo rmed in ten patients (7 men, 3 women, mean age 29 years) who had an ILVT wi th a right bundle branch block configuration and left-axis deviation. Left ventricular endocardial mapping using an octapolar catheter and entrainment and resetting studies during VT was performed by pacing from the right ven tricular outflow tract (RVOT) and each sire of the left ventricular mapping catheter. PP and pre-PP M ere recorded simultaneously during VT in all pat ients. The earliest PP during VT was recorded at the inferoposterior septum , and PP was activated bidirectionally toward the proximal (basal) and dist al (apical) sites along the left posterior fascicle. in contrast, pre-PP wa s recorded at sites slightly proximal to the earliest PP recording site, an d was activated toward the earliest PP sire. Pacing from RVOT confirmed man ifest entrainment, and the stimulus to pre-PP interval was prolonged with a shorter pacing cycle length. Concealed entrainment was demonstrated by cap ture of the PPs of the left ventricular mapping catheter in six patients, a nd the postpacing interval at each PP site was equal to the tachycardia cyc le length. The pre-PP was orthodromically activated from the proximal to th e distal site during pacing. More rapid pacing also produced delay in activ ation from PP to indicating slow conduction in ILVT. Catherer ablation was performed at the pre-PP recording sire during VT, and sas successful in all patients. The reentrant circuit of ILVT could be constructed based on the pre-PP, PP, and slow conduction between the PP and pre-PP. Catheter ablatio n of ILVT was successful at the pre-PP recording site.