PO-02-235 MOVING BEYOND QRS DURATION: QRS VOLTAGE-TIME-INTEGRAL (AREA) IS A SUPERIOR PREDICTOR OF CLINICAL RESPONSE TO CARDIAC RESYNCHRONIZATION THERAPY

Abstract

Cardiac resynchronization therapy (CRT) can alleviate left ventricular (LV) electrical dyssynchrony mediated systolic heart failure (HF). 15% reduction in LV end systolic volume (LVESV) with CRT is a validated surrogate of improved clinical outcomes. Prolonged baseline QRS duration (QRSd) is the only conventional quantitative ECG criteria to assess left ventricular electrical dyssynchrony. In addition to QRS duration, we evaluated the baseline QRS voltage-time-integral (VTI) and its reduction after CRT as predictors of LV reverse remodeling. We included 595 patients (68.1±11.5 yr., 32.6% women, 43.9% ischemic cardiomyopathy) who underwent CRT-defibrillator implant for clinical indications 2012-2019 and analyzed their ECGs before and after CRT. Orthogonal X, Y, Z leads were reconstructed from 12-lead ECG using Kors’s matrix. VTIQRS-X, Y ,Z and VTIQRS-3D were obtained from integration over the duration of QRS in X, Y, Z, and root-mean-squared (3D) ECGs respectively. We reviewed echocardiogram reports to obtain LV measures before and 3-12 months after CRT, including ejection fraction (LVEF), internal dimensions in diastole (LVIDd) and systole (LVIDs), end-diastolic (LVEDV) and LVESV. We used linear regression models to evaluate ECG variables as predictors of change in LV measures. We further used unadjusted and multivariable-adjusted logistic regression models to predict ≥15% reduction in LVESV from ECG variables. Baseline LVEF was 25.8±8.3%, LVIDd 5.7±0.9 cm, LVIDs 4.8±0.9 cm, LVEDV 164±67 and LVESV 109±56 mL. QRSd reduced from 153±26 to 137±22 ms with CRT. VTIQRS-3D and VTIQRS-Z of 104±49 and 75±44 respectively improved to 67±34 and 33±24 μVs. Baseline and change in VTIQRS-Z and VTIQRS-3D were more significantly associated with change in echo variables as compared to baseline and change in QRSd (Table 1). ≥15% reduction in LVESV was independently predicted by baseline VTIQRS-Z ≥71 μVs (OR 2.0, 95% CI 1.3-3.0, p=0.0009) and Δ VTIQRS-Z ≥42 μVs (OR 2.1, 1.4-3.1, p=0.004). In patients undergoing CRT, baseline QRS VTI from Z (anteroposterior) axis ECG ≥71 μVs independently predicted 2 times higher odds of salutary reverse LV remodeling post CRT. Further, a reduction in VTIQRS-Z ≥42 μVs also predicted more than 2 times odds of revrse remodeling. VTIQRS-Z is a superior automatically calculable quantitative summary ECG marker for CRT patient selection and prognostication as compared to QRS duration.