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Isolated bundle branch block and left ventricular dysfunction
Seung-Joon Lee1, Charles McCulloch, Iqwal Mangat
1University of California, San Francisco, USA.
Insights
Left bundle branch block (BBB) can independently cause ventricular dysfunction, even without other heart disease. This finding highlights BBB as a potential risk factor for worsening cardiac health over time.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Imaging
Background:
- Bundle branch block (BBB) is a known mortality risk factor in cardiac patients.
- The impact of chronic ventricular dyssynchrony from conduction delay alone on ventricular function remains unclear.
Purpose of the Study:
- To investigate the effect of isolated bundle branch block on left ventricular function over time.
- To determine if left bundle branch block itself can lead to ventricular dysfunction.
Main Methods:
- Retrospective analysis of electrocardiogram database for subjects with QRS prolongation.
- Inclusion of subjects with no evidence of heart disease and serial cardiac evaluations.
- Longitudinal follow-up assessing left ventricular ejection fraction over a mean of 52 months.
Main Results:
- Isolated left bundle branch block (LBBB) cohort showed a significant annual decline in left ventricular ejection fraction (-7.3%).
- Isolated right bundle branch block (RBBB) and non-specific intraventricular conduction delay cohorts demonstrated smaller reductions in ejection fraction (-1.9% and -1.1% respectively).
- The difference in ejection fraction decline between LBBB and other cohorts was statistically significant (P = .019).
Conclusions:
- Left bundle branch block may be an independent cause of ventricular dysfunction.
- Chronic dyssynchrony from LBBB can negatively impact left ventricular function.
- Findings suggest LBBB warrants closer monitoring for cardiac health progression.
Background:
Population studies have identified the presence of bundle branch block (BBB) as a risk factor for increased mortality in patients with known cardiac disease. It is unknown how chronic ventricular dyssynchrony resulting solely from conduction delay affects ventricular function.
Methods And Results:
Subjects were retrospectively identified from the University of California, San Francisco, electrocardiogram database with QRS prolongation. Subjects who had no evidence of heart disease and had baseline and serial studies evaluating ongoing risk of coronary artery disease status and left ventricular function were followed over time. Documentation of a minimum of 2 serial evaluations of cardiac status were present in a total of 51/176 (20%) subjects with isolated BBB who constitute the study population. After a mean follow-up of 52 +/- 45 months-adjusting for differences due to age, sex, the presence of hypertension, hyperlipidemia, and diabetes mellitus-left ventricular ejection fraction diminished by -7.3 +/- 12% per year in the isolated left BBB cohort versus -1.9 +/- 4% in isolated right BBB cohort and -1.1 +/- 3% reduction in the isolated nonspecific intraventricular conduction delay cohort (P =.019).
Conclusions:
Left bundle branch block itself may be a cause of ventricular dysfunction.