Aim: The diagnosis of ventricular tachycardia can be made using V1 lead. In structurally normal hearts, ventricular tachycardia can develop through the outflow tract. The study intended to establish the use of V3 precordial transition to diagnose the origin of outflow tract ventricular arrhythmias (OTVAs).
Methods: In a retrospective study, 45 patients with a left bundle branch block pattern OTVAs (RVOT 48.9%, LVOT 51.1%) were analyzed for their ECG characteristics. All patients had undergone successful catheter ablation. The persistent arrhythmia suppression due to delivery of radiofrequency in a particular region assisted in its identification as the site of origin. In addition, the area under the curve in the ROC curve and correlation with body surface area (BSA) and body mass index (BMI) was established for every duration or amplitude variable.
Result: The result for patients with LVOT origin was noted as:
Males: (82.6% vs 54.5%, p = 0.042)
Age: (59.91 ± 10.48 vs 50.95 ± 15.48, p = 0.027)
BSA (1.83 ± 0.12 vs 1.77 ± 0.16, p = 0.157)
BMI (24.74 ± 2.76 vs 24.09 ± 2.94, p = 0.45)
Patients with LVOT exhibited similar BSA and BMI and older patients had a higher tendency to display an LVOT origin.
ECG variables noted in the lead V3 were:
The V3 R wave percentage (amplitude of the R wave with respect to the global amplitude of the QRS); AUC 0.888, LVOT origin if ≥ 50%, OR 36 95% CI (6.19 – 209.06), p < 0.001.
The V3 R wave duration index (R wave \ QRS duration); AUC 0.905, LVOT origin if ≥ 50%, OR 74.80 95% CI (7.97 – 701.48), p < 0.001
The V3 R wave duration; AUC 0.900, LVOT origin if ≥ 80 msec, OR 47.25 95% CI (7.73 – 288.82), p < 0.001
A less specific but very sensitive V3 transition ratio (AUC 0.843, LVOT origin if ≥ 1) was calculated based on the V2 transition ratio formula.
For LVOT origin, an independent predictor was noted to be only a V3 R wave percentage ≥50%.
Conclusions: Diagnostic algorithms can be created based on the elements obtained from lead V3.