Concordant Versus Discordant Left Bundle Branch Block in Heart Failure Patients: Novel Clinical Value of an Old Electrocardiographic Diagnosis

Abstract

Background Over the last 50 years left bundle branch block (LBBB) has been defined as homophasic (concordant: cLBBB) or heterophasic (discordant: dLBBB) when associated with a positive or negative T wave in leads I and V5-V6, respectively. LBBB is recognized as an adverse prognostic factor in heart failure (HF). The prevalence and clinical significance of cLBBB and dLBBB in HF patients are unknown. Methods and Results A total of 897 consecutive systolic HF patients (age 65 ± 13 years, left ventricular ejection fraction [LVEF], 34 ± 10%) underwent clinical characterization, electrocardiographic evaluation for LBBB diagnosis and classification, and follow-up for cardiac events (median 37 months, range 1-84). LBBB was diagnosed in 232 patients (26%), cLBBB in 71 (31%), and dLBBB in 161 (69%). The dLBBB patients were older than those with cLBBB, and presented with lower LVEF, greater left ventricular telediastolic diameter and left ventricular mass index, higher level of brain natriuretic peptide, N-terminal pro-brain natriuretic peptide, renin activity, and norepinephrine (all P < .05). At Kaplan-Meier analysis, LBBB ( P = .003) and dLBBB ( P = .036) were associated with a worse prognosis when the composite end point of sudden death and implantable cardioverter defibrillator shock was considered. Conclusions In systolic HF, dLBBB is associated with a worse clinical, neurohormonal, and prognostic profile. LBBB classification could represent a useful tool in routine clinical evaluation.