Purpose: We hypothesized that Purkinje potential and their preferential conduction to the left ventricle (LV) posteroseptum during sinus rhythm (SR) are part of reentrant circuits of idiopathic left ventricular tachycardia (ILVT) and reentry anchors to papillary muscle. Materials and Methods: In 14 patients with ILVT (11 men, mean age 31.5±11.1 years), we compared Purkinje potential and preferential conduction during SR with VT by non-contact mapping (NCM). If clear Purkinje potential (SR) was observed in the LV posteroseptum and the earliest activation site (EA) of preferential conduction at SR (EA SR) was well matched with that of VT (EA VT), EA SR was targeted for radiofrequency catheter ablation (RFCA). Also, the anatomical locations of successful ablation sites were evaluated by echocardiogra-phy in five additional patients. Results: 1) All induced VTs exhibited clear Purkinje potential (VT) and preferential conduction in the LV posteroseptum. The Purkinje potential (VT) and EA VT was within 5.8±8.2 mm of EA SR. However, the breakout sites of VT were separated by 30.2±12.6 mm from EA VT to the apical side. 2) Purkinje potential(SR) demonstrated a reversed polarity to Purkinje potential(VT), and the interval of Purkinje potential (SR)-QRS was longer than the interval of Purkinje potential (VT)-QRS (p<0.02) 3) RFCA targeting EA SR eliminated VT in all patients without recurrence within 23.3±7.5 months, and the successful ablation site was discovered at the base of papillary muscle in the five additional (100%) patients. Conclusion: NCM-guided localization of EA SR with Purkinje potential (SR) matches well with EA VT with Purkinje potential (VT) and provides an effective target for RFCA, potentially at the base of papillary muscle in patients with ILVT.
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