Abstract 16858: QRS/T Ratio With Progression of Left Bundle Branch Block From New to Old: Is Voltage-Time-Integral Better Than Amplitude in Discriminating of Chronicity of Block?

Abstract

Introduction: Discriminating acute versus chronic left bundle branch block (LBBB) has well known and important clinical implications. QRS/T vector magnitude ratio, and ratio of deepest S to tallest T in precordial leads, have been shown to discriminate new vs old LBBB. We sought to evaluate how QRS/T voltage-time-integral (VTI) ratio, as opposed to QRS/T amplitude ratio changes with progression of LBBB from new to old. Hypothesis: We proposed that QRS/T VTI ratio would be equivalent to QRS/T amplitude ratio in distinguishing new from old LBBB. Methods: We analyzed ECGs of patients with known chronic LBBB (n=385, 53.5% female, age 70.6±12) against ECGs of patients with acute LBBB (n=79, 53.6% female, age 77.7±9.5) one day post transcatheter aortic valve replacement (TAVR) and at 1 month post TAVR utilizing VTI of 3D QRS and 3D T-wave ratio. Orthogonal X, Y, Z leads were reconstructed from 12-lead ECG using Kors’s matrix. VTI X, Y ,Z and VTI 3D were obtained from temporal integration of voltage in X, Y, Z and root-mean-squared (3D) ECGs respectively. We compared changes in QRS/T amplitude, VTI ratios, and maximum precordial S/T magnitude ratio 1 month after versus day 1 of new LBBB using pairwise t-tests. Results: We found acute post-TAVR LBBB was best distinguished utilizing VTI of 3D QRS (3.37±1.27, p <0.0005) compared to 3D T-wave ratio (2.90±1.00, p <0.003). We also found LBBB post TAVR at one month is best distinguished by the 3D QRS/T-wave VTI ratio (1.53±0.32, p < 0.0001) and less so by the 3D amplitude ratio (3.27±1.37, p 0.003) Acute max precordial S/T magnitude was not able to differentiate chronic from acute LBBB ( p 0.1). At one month follow up, acute LBBB TAVR QRS-T amplitude ratios were found to return to their baseline values (3.37±1.27 for acute and 3.27±1.37 with p 0.5). Conclusions: Between VTI of 3D QRS and 3D T wave ratio, VTI 3D QRS proved to be more reliable for distinguishing acute versus chronic LBBB. Chronicity of LBBB was not predicted by maximum precordial S/T magnitude.