Morbidity and mortality in patients with bundle branch block

Background: Syncope is a predictor of subsequent high-degree atrioventricular (AV) block in patients with bifascicular block (BFB) but the time relationship between syncope and development of AV block has not been well-studied. Patients with BFB have a significantly higher mortality rate compared with an age and sex matched population. High-risk individuals have not been well-identified. Previous studies on bundle branch block as a risk factor in the clinical setting of acute myocardial infarction (MI) and congestive heart failure (CHF) have given conflicting results. Methods and results: In study I, 27 patients with BFB and syncope received a bradycardia-detecting pacemaker. During a median follow-up of 60 months, a bradycardia event was detected in 14 patients (52%), of whom 13 developed high-degree AV block. In 77% of patients, high-degree AV block was documented within 24 months of the syncopal episode. In study II, 100 BFB patients of whom 41 had a history of syncope, were studied. All patients were investigated with Holter-monitoring, an exercise test, an echocardiography, and an invasive electrophysiological study. During a median follow-up of 84 months, 33 patients died of whom 14, in sudden cardiac death. In a Cox multiple regression analysis, CHF was the only independent predictor of all-cause mortality and sudden cardiac death (p< 0.01). In study III, the effect of left bundle branch block (LBBB) on 1-year mortality in a population with acute MI was assessed. A prospective cohort of 87052 cases of MI from the Register of Information and Knowledge about Swedish Heart Intensive care Admissions (RIKS-HIA) in 1995-2001 was studied. LBBB was present in 9%. The unadjusted relative risk of death within 1 year was 2.16 (95% Cl, 2.08-2.24; p<0.00 1) for LBBB (42%) compared with no LBBB (22%). In a Cox regression analysis adjusting for baseline characteristics and ejection fraction, the contributing relative risk of LBBB for death was not significant, 1.08 (95% Cl, 0.93-1.25; p= 0.33). In study IV, a prospective cohort of 21685 cases of symptomatic CHF requiring hospitalization from RIKS-HIA in 1995 to 2003 was studied. LBBB was present in 20%. One-year mortality for LBBB and no LBBB was, 31.5% and 28.4% respectively. The unadjusted relative risk of death within 1 year for the LBBB patients was 1. 12 (95% Cl, 1.061. 19; p< 0.00 1). After adjustment for clinical characteristics and concomitant diseases the relative risk of I -year mortality for LBBB was 1.00 (95% CI, 0.94-1.07; p= 0.88). Conclusions: BFB patients with syncope within 24 months are recommended pacemaker treatment without prior documentation of high-degree AV block on ECG. BFB patients have a poor prognosis. Symptomatic CHF according to New York Heart Association (NYHA) classification has a very strong predictive value for mortality and sudden cardiac death. LBBB does not appear to be an important independent predictor of 1 -year mortality in a population with acute MI and highly symptomatic CHF but mainly reflects higher age, comorbid conditions, and left ventricle dysfunction