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Modified Precordial Lead R-Wave Deflection Interval Predicts Left- and Right-Sided Idiopathic Outflow Tract
Robert D Anderson1, Saurabh Kumar2, Simon Binny3
1Department of Cardiology, Royal Melbourne Hospital, Faculty of Medicine, Dentistry, and Health Science, University of Melbourne, Melbourne, Victoria, Australia; Department of Cardiology, Westmead Hospital, Westmead, New South Wales, Australia; Westmead Applied Research Centre, University of Sydney, New South Wales, Australia.
Objectives:
This study evaluated if modifying electrocardiographic (ECG) precordial leads to a higher intercostal position improved the accuracy of outflow tract ventricular arrhythmia (OTVA) localization.
Background:
Precordial ECG prediction algorithms that use a standard lead configuration localize OTVA with variable accuracy.
Methods:
Patients who underwent OTVA ablation were prospectively enrolled to have a standard and modified (high) precordial ECG. R- and S-wave amplitudes and intervals were measured to develop an algorithm that differentiated the right ventricular outflow tract (RVOT) and the left ventricular outflow tract (LVOT) with high accuracy-the modified lead R-wave deflection interval (RWDI). This interval was defined from the earliest QRS onset (using all modified leads) to the lead with longest R-wave deflection. The RWDI was compared with all other ECG algorithms.
Results:
A total of 50 patients (38 women; mean age 51 ± 17 years) had successful catheter ablation for OTVA (RVOT 60%, LVOT 40%). The modified lead RWDI was significantly shorter in the RVOT group (18.5 ms, interquartile range 25th to 75th percentile [IQR25-75]: 0 to 29.5 ms) compared with the LVOT group (67.5 ms, IQR25-75: 56.5 to 77 ms; p < 0.05). Using a RWDI ≤40 ms to predict an RVOT focus, the sensitivity and specificity of the modified lead RWDI were 100% and 95%, respectively; the area under the receiver-operating characteristic curve was 0.96. This was superior to all previously developed algorithms. In a computed tomography analysis (n = 50), the modified leads were significantly closer to the outflow tracts compared with the standard precordial leads.
Conclusions:
The modified lead RWDI is a simple, easily interpretable algorithm that can potentially differentiate a right- or left-sided origin of OTVA with high accuracy.
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