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

BackgroundOver 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 ResultsA 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.ConclusionsIn systolic HF, dLBBB is associated with a worse clinical, neurohormonal, and prognostic profile. LBBB classification could represent a useful tool in routine clinical evaluation.