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Development and validation of an ECG algorithm based on lead V3 morphology to determine the origin of outflow tract
Ludovico Lazzari1, Stefano Donzelli1, Carmine Marallo2
1Clinical and Interventional Arrhythmology, "S. Maria" Hospital, Terni, Italy.
Introduction:
Preoperatively distinguishing the origin of outflow tract ventricular arrhythmias (OTVAs) exhibiting a precordial transition around V3 is essential for effectively planning the ablation procedure; nonetheless, this proves challenging since neighboring anatomical structures exhibit similar VA morphologies. Several diagnostic criteria analyzing leads V1 and V2 have been proposed to overcome this limitation, whose accuracy has been reviewed; recently, interest has shifted to V3. We conducted a thorough analysis of leads V1 to V3 to evaluate the diagnostic accuracy of existing criteria and to develop a novel diagnostic algorithm.
Methods:
We analyzed the ECGs of 51 patients with OTVAs originating from either ventricle who underwent successful catheter ablation. The indices yielding greater accuracy (derivation cohort) were used to guide ablation in a subsequent validation cohort (n = 31).
Results:
Among all ECG parameters, V3 R-wave percentage (V3R%) and duration index (V3Rd), calculated from amplitude and duration, respectively, demonstrated the highest AUC. A V3R% ≥50 % identified LVOT origin (sensitivity = 80.8 %, specificity = 96 %, PPV = 95.5 %, NPV = 82.8 %), while RVOT origin was associated with a V3Rd <50 % (sensitivity = 80 %, specificity = 96.2 %, PPV = 95.2 %, NPV = 83.3 %). Combining both indices into a two-step algorithm resulted in an overall accuracy of 88.23 % in the derivation cohort and 90.32 % in the validation cohort, showing higher specificity and sensitivity than criteria based on leads V1 and V2, as well as the transition zone index, and slightly higher accuracy than the V2S/V3R ratio.
Conclusions:
The proposed algorithm accurately identifies the site of origin of OTVAs in most cases, potentially simplifying the ablation strategy more effectively than existing criteria.
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