- In population studies, LBBBs prevalence increases steadily from below 1% at age 50 to 6% by 80 years. (Eriksson P, ..., Dellborg M. BBB in a general male population: the study of men born 1913. Circulation 1998;98:2494e2500.)
- Factors that have been associated with its development include LV hypertrophy on the electrocardiogram, an increased cardiac volume, hypertension, valvular heart disease, cardiomyopathies, myocarditis, and coronary artery disease. (Imanishi R,..., Akahoshi M. Prognostic significance of incident complete LBBB observed over a 40-year period. Am J Cardiol 2006;98:644e648.)
- Some, however, develop LBBB in the absence of any of these risk factors. Population-based studies of those with LBBB have shown an increase or a trend toward increased cardiovascular mortality, sudden cardiac death, coronary artery disease, and HF. (Schneider JF,..., Kannel WB. Newly acquired LBBB: the Framingham study. Ann Intern Med 1979;90:303e)
- Those who developed LBBB at a younger age (below 45 years of age) and who were free from cardiovascular risk factors did much better than those who developed LBBB during or after their fifth decade and had associated risk factors. (Rotman M, Triebwasser JH. A clinical and follow-up study of right and left BBB. Circulation 1975;51:477e484.)

- It seems that LBBB can result from either intrinsic conduction system degeneration or an extrinsic insult from a variety of cardiovascular diseases, and the outcome of these 2 distinct populations with LBBB is divergent. In the absence of consensus guidelines on how to evaluate these patients, a noninvasive assessment for structural heart disease and ischemia is reasonable, especially in patients with known cardiovascular risk factors. (Vineet Kumar MD.,...,Fadi G. Hage MD. Implications of Left Bundle Branch Block in Patient Treatment. Am J Cardiol 2013;111:291e300)
- We do echo for asymptomatic LBBB, but it is not rare to see asymptomatic LBBB with a good LV. We know, not only is there the effect on the myocardium, but there is a higher risk of developing spontaneous AV block.
- In the Framingham Study, coincident with or subsequent to the detection of LBBB, 48% of individuals developed symptomatic CAD or CHF. Within 10 years from LBBB detection, CV mortality was 50%; and at 18 years follow-up, only 11% of LBBB patients remained free of detectable CV abnormalities. In men, the appearance of LBBB contributed independently to an increased risk of cardiovascular disease mortality. Comparison with age- and sex-matched control subjects free from LBBB confirmed that in the general adult population, newly acquired LBBB is most often a hallmark of advanced hypertensive or ischemic heart disease, or both.
- So in clinical practice, we follow up on asymptomatic LBBB with a good LV, at least every 5 years with echo and ECG (or at least with ecg). Over 55 yrs old patients are at higher risk, so for them maybe routine follow up could be every 3-4 years.
- Some experts are going to rule out obstructive coronary disease and they do CTCA, certainly in all those with CV risk factors.