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Introduction: ECG criteria for left ventricular (LV) hypertrophy in absence of left bundle branch block (LBBB) rely on QRS amplitudes. ECG correlates of LVH in setting of LBBB are not well established. We sought to evaluate quantitative LBBB ECG predictors of echocardiographic LV measurements [LV mass, end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF)]. Hypothesis: QRS duration (QRSd) is a better predictor of LV hypertrophy than QRS amplitudes. Methods: We included adult patients with typical LBBB having ECG and echocardiogram performed within 3 months of each other in 2010-2020. Digital 12-lead ECGs were processed to reconstruct orthogonal X, Y, Z leads using Kors matrix. Amplitudes and voltage-time-integrals (VTIs) from all 12 leads, X, Y, Z leads and 3D (root-mean-square) ECG, and QRSd were evaluated. We used age, sex and BSA-adjusted linear regressions to predict LV measurements, and separately generated ROC curves for identifying LV abnormalities. Results: We included 413 patients (53% women, age 73±12 yr). Among all the ECG variables, QRSd was most strongly correlated with all 4 LV measurements (all p<0.00001, see Table 1a showing QRSd compared to VTI and amplitude from 3D QRS). Table 1b shows area under ROC curves to identify LV abnormalities. QRS duration ≥150 ms in women had sensitivity 56.3%, specificity 64.4% for LVMi >95 g/m 2 and sensitivity 62.7%, specificity 67.8% for LVEDVi >61 mL/m 2 . QRS duration ≥160 ms in men had a sensitivity 63.1%, specificity 72.1% for LVMi >115 g/m 2 and sensitivity 58.3%, specificity 74.5% for LVEDVi >74 mL/m 2 . Conclusions: In patients with LBBB, QRS duration ≥150 in women and ≥160 in men is a superior predictor of adverse LV remodeling esp. eccentric LV hypertrophy/dilation. The weak correlation of QRS amplitude with hypertrophy may be due to the dominant effect of electrical dyssynchrony on voltage, and the heterogeneous effects of fibrosis, infiltrative cardiomyopathy, epicardial fat and LV dilation.

Introduction: Right bundle branch block (RBBB) is the most common His-Purkinje conduction abnormality seen on ECG. It is currently unclear if there are any quantitative ECG differences in RBBB without and with structural right ventricular (RV) disease. Our aim was to evaluate quantitative ECG predictors of echocardiographic RV measurements [tricuspid annular plane systolic excursion (TAPSE), tissue Doppler imaging RV S’, RV basal and mid diameters, RV systolic pressure (RVSP)]. Hypothesis: QRS-T VTI in patients with RBBB is a marker for adverse RV remodeling and dysfunction. Methods: We included adults with ECG demonstrating typical RBBB and echocardiogram performed within 3 months of each other in 2010-2020. Orthogonal X, Y, Z ECG leads were reconstructed using Kors matrix. In addition to overall QRS duration, QRS voltages and QRS/QRS-T VTIs from 12 standard leads, X, Y, Z leads, and 3D (root-mean-square) ECG were evaluated. Age, sex and BSA-adjusted linear regressions were used to assess associations between ECG variables and RV measurements. We separately generated ROC curves for predicting abnormal RV measurements from ECG variables. Results: We included 782 patients (33% women, 71±14 years). Amongst the ECG variables, BSA-indexed Z-axis QRS-T VTI (VTI QRST-Z *√BSA) was the strongest independent predictor of all 5 RV measurements (Table 1a shows a comparison of QRS duration, Z-axis amplitude and VTI). VTI QRST-Z *√BSA cutoff 62 μVsm had a sensitivity 62.7% and specificity 65.7% to distinguish presence of ≥3 abnormal out of the 5 RV measurements (Table 1b). Conclusions: Adverse RV remodeling causes augmentation of the anterior-posteriorly directed QRS-T potential which is seen as a change in Z-axis VTI. VTI QRST-Z *√BSA could be used as a marker for right heart failure in patients with RBBB.

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