Background The separation of earliest activation (EA) site from the exit of the premature beat initiating tachycardia demonstrates preferential conduction (PC). We hypothesized that detailed analysis of unipolar electrogram at the PC facilitates to identify the origins of PVC and leads effective elimination of them by minimal radiofrequency (RF) lesions in patients with idiopathic right ventricular outflow tract (RVOT) ventricular tachycardia (VT).
Method and Results Twenty two patients with RVOT VT (male 10, 42.5±15.7 years old) underwent RF catheter ablation (RFCA) guided by non-contact mapping (NCM) were studied. The virtual unipolar electrograms of spontaneous premature ventricular contractions (PVC, n=45) initiated VT were analyzed. Polarities of unipolar electrotrams, QRS width, activation time, and RS or QS width of unipolar electrogram were analyzed. PC was found in 80% and the polarities of unipolar electrogram from EA to exit through the PC area were three different patterns; negative-negative (NN, n=23, 51%), negative-positive (NP, n=10, 22%), and positive-negative (PN, n=12, 27%). Successful RFCA site was RVOT septal side in 63.6%, lateral side in 18.2%, anterior side 18.2%, and posterior side 54.5%, respectively. The mean number of RFCA foci were 1.89±0.81. Initial positive polarity pattern (PN) of PVC showed longer QRS width (170.6±14.1 ms vs. 152.3±12.0 ms, p=0.001), RS duration of unipolar electrogram (51.3±12.3 ms vs. 20.5±7.8 ms, p<0.0001), and activation time (64.4±24.1 ms vs. 25.9±7.7 ms, p<0.0001) than NN or NP patterns. Higher number of RF application (19.2±11.1 vs. 7.3±3.4, p<0.0001) and line of block (75.0% vs. 24.2%, p<0.01) were required to eliminate PVC and VT compared with NN or NP patterns. At 14.3±10.1 months of follow up, PVC was recurred in one patient with PN (4.5%), but none in other patterns.
Conclusion PVC with initial positive polarity pattern at EA in patients with RVOT VT shows longer QRS width, and activation time, requires more RFCA lesions, and higher recurrence, suggesting the possibility of epicardial origin.
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