Abstract 15283: QRS Voltage in Precordial Leads Predicts Survival After Cardiac Resynchronization Therapy in Non-Left Bundle Branch Block Patients

Introduction: The QRS complex reflects the summation of all instantaneous electrical forces during ventricular depolarization. In patients with intraventricular conduction abnormalities, whether left bundle branch block (LBBB) or non-LBBB, the propagation of the electrical wavefront is dyssynchronous and unopposed and is thereby associated with an increase in the QRS voltage in the precordial leads. Hypothesis: The aim of this study was to assess the impact of cardiac resynchronization therapy (CRT) on QRS voltage and its ability to predict survival in non-LBBB patients who are known to have lower response rates to conventional CRT. Methods: Twelve-lead EKGs were analyzed in 101 consecutive non-LBBB patients (age 65±12 years, 79 men, LVEF 22±4%, QRS width 154±21ms) who received CRT for a median duration of 43 months. Results: During the follow-up period 39 patients died. Total QRS amplitude in leads V2-V4 decreased significantly with CRT (values preimplant/immediately postimplant, P<0.001 for all changes): lead V2 2.1±0.9mV/0.9±0.7mV, lead V3 2.3±0.8mV/1.4±0.7mV, and lead V4 1.4±0.7mV/0.8±0.6mV. Patients in whom the total QRS amplitude in lead V4 decreased with CRT had significantly better survival than patients in whom it increased or did not change (Figure). Changes in QRS amplitude in lead V4 correlated with changes in LVEF over a period of 6 months post implant (r=-0.439, p=0.017). Total QRS amplitude in lead V4 and its change with CRT independently predicted event free survival in multivariate Cox models that included age, gender, baseline LVEF and the change in QRS duration. Conclusion: A reduction in the QRS voltage in the precordial lead V4 is predictive of response to CRT in non-LBBB patients.