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.

List of scientific papers

I. Tabrizi F, Rosenqvist M, Bergfeldt L, Englund A (2006). Time relation between a syncopal event and documentation of AV block in patients with bifascicular block - clinical implications. [Manuscript]

II. Tabrizi F, Rosenqvist M, Bergfeldt L, Englund A (2006). Long-term prognosis in patients with bifascicular block - the predective value of non-invasive and invasive assessment. Journal of Internal Medicine. [Accepted]
https://doi.org/10.1111/j.1365-2796.2006.01651.x

III. Stenestrand U, Tabrizi F, Lindback J, Englund A, Rosenqvist M, Wallentin L (2004). Comorbidity and myocardial dysfunction are the main explanations for the higher 1-year mortality in acute myocardial infarction with left bundle-branch block. Circulation. 110(14): 1896-902.
https://doi.org/10.1161/01.CIR.0000143136.51424.38

IV. Tabrizi F, Englund A, Rosenqvist M, Wallentin L, Stenestrand U (2006). Left bundle branch block has no independent predective value in 1-year mortality in population with congestive heart failure. [Manuscript]