TÌM HIỂU VAI TRÒ CỦA TỶ LỆ SV2/RV3 TRÊN ĐIỆN TÂM ĐỒ TRONG CHẨN ĐOÁN PHÂN BIỆT NGOẠI TÂM THU THẤT CÓ NGUỒN GỐC ĐƯỜNG RA THẤT PHẢI VÀ ĐƯỜNG RA THẤT TRÁI

Abstract

Introduction: Ventricular arrhythmias in humans without structural heart disease, also known as idiopathic ventricular arrhythmias, mostly originate in the ventricular outflow tract. Distinguishing ventricular extrasystoles from right ventricular outflow tract or left ventricular outflow tract remains challenging, especially in the form of ventricular arrhythmias with left bundle branch block with transition at V3. The objectives of our study were: to describe the surface electrocardiographic features of ventricular extrasystoles originating from right ventricular outflow tract and from left ventricular outflow tract; and also explore the role of SV2/RV3 ratio on surface electrocardiogram in differential diagnosis of ventricular extrasystoles originating in left ventricular outflow tract and right ventricular outflow tract. Methods: cross-sectional description of 150 patients with ventricular extrasystoles without structural heart disease having indications for electrophysiology study and RF ablation. Results: We conducted a study of 150 patients with left bundle branch block type ventricular extrasystoles who underwent electrophysiology study and successful RF ablation in the right ventricular outflow tract (RVOT; n=110) or left ventricular outflow tract (LVOT; n= 40). The wave amplitude sizes were measured with an electronic caliper. The SV2/RV3 ratio is the S wave amplitude in lead V2 divided by the R wave amplitude in lead V3 of a ventricular ectopic beat. The results of SV2/RV3 index in the left ventricular outflow tract were statistically significant smaller than in the right ventricular outflow tract (1.23 ± 0.78 versus 6.07 ± 6.32 and p < 0.001). The area under the curve (AUC) for the SV2/RV3 index was 0.934, with a critical value of ≤ 1.6 predicting left ventricular outflow tract extrasystoles with a sensitivity of 90.9 % and a specificity of 80. %. When comparing this index with a number of other indices in both the study group and the group of patients with transition at V3, we found that our index gives the highest result in terms of the value under the ROC curve and sensitivity and specificity. This index is also of great value in clinical applications for pacifiers because it is relatively easy and quick to calculate with only a 12-lead routine electrocardiogram. Conclusion: The SV2/RV3 ratio is very valuable in the differential diagnosis of left ventricular outflow tract and right ventricular outflow tract extrasystoles, and is useful in clinical practice for pacing physicians.