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The QRS-right ventricular apex interval as a cut-off value to differentiate the origin of outflow tract premature
Emad Effat Fakhry1, John Kamel Zarif2
1Department of Cardiology, Faculty of Medicine, Ain Shams University, Cairo, Egypt. emad_effat@med.asu.edu.eg.
Background:
Many electrocardiography (ECG) criteria have been proposed for the localization of outflow tract premature ventricular contractions (PVCs); however, in some cases, it is difficult to accurately localize the origin of PVCs using the surface ECG. The authors aimed to study the QRS-right ventricular apex (RVA) interval measured during electrophysiological study and its role in the differentiation between different sites of origin of outflow tract PVCs.
Methods:
The study included 90 patients (81 females, mean age 37.20 ± 7.87) referred for outflow tract PVC ablation. The authors measured the interval from the onset of the earliest QRS complex of the PVCs to the distal RVA intracardiac signal (the QRS-RVA interval) during the electrophysiological study and correlated this interval with the origin of outflow tract PVCs as identified by successful ablation during the procedure.
Results:
The QRS-RVA interval was significantly longer in PVCs originating from the left ventricular outflow tract (LVOT) compared to the right ventricular outflow tract (RVOT) (67.33 ± 7.56 for LVOT PVCs vs. 37.11 ± 4.34 for RVOT PVCs, p < 0.001). Receiver operating characteristic (ROC) analysis showed that a QRS-RVA interval ≥ 48 ms predicted an LVOT origin of PVCs. A shorter interval was noted in PVCs originating from the RVOT free wall rather than the septal RVOT wall, and a shorter interval was also noted in LVOT PVCs originating from the right coronary cusp as compared to other LVOT PVCs, although these differences did not reach statistical significance.
Conclusion:
Measuring the QRS-RVA interval is a simple and accurate method for differentiating the origin of outflow tract PVCs during an electrophysiological study. A QRS-RVA interval ≥ 48 ms predicts an LVOT origin of PVCs rather than an RVOT origin.
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