This presentation tackles the topic of left bundle branch block.
Presentation provides critical information but should be combined with knowledge of the presenter since it's meant for proper presentating and not read-only.
Use freely to study or present.
2. Definition
Left Bundle Branch Block is a
common electrocardiographic
abnormality seen in patients whose
normal cardiac conduction down both
anterior and posterior left fascicles of
the His-Purkinje system is
compromised.
Although LBBB is often seen in
patients with significant heart disease
and is often a result of myocardial
injury, strain or hypertrophy it may be
seen in patients without particular
clinical disease.
3. Etiology
Stretching of cardiac tissue can lead to conduction issues therefore any diseases like
cardiac myositis, cardiomegaly, hypertrophy, dilation etc. may put patient at risk of
developing LBBB.
Specifically enlargement of left ventricle causing stretching and separation of the
Purkinje fibers.
4. Epidemiology
LBBB is prevalent in approximately 0,06 to 0,1 % of the general population.
Around 33 % of patients with heart failure have LBBB.
Incidence increases with severity of left ventricular failure in heart failure patients.
5. Causes
Out of many factors and disorders that can cause LBBB we can name:
- Aortic stenosis
- Dilated cardiomyopathy
- Acute myocardial infarction
- Primary disease of conduction system
- Lyme disease
- Side effects of trauma/surgeries etc.
6. Pathophysiology
LBBB which is caused by conduction disorders appears due to stretching and/or
discontinuation of nerve fibers.
What can lead to those disruptions:
- Cardiac stretching
- Cardiac scarring
- Infiltration
- Myocardial infarction
- Myocardial fibrosis
7. Clinical manifestations
Left Bundle Branch Block itself has no clinical symptoms therefore diagnosis may
be difficult.
The only diagnostics can be made due to ECG changes.
Where to run diagnostics:
- Chest pain
- Patients after myocardial infarction
8. ECG Changes
There are several ECG changes that all together can confirm diagnosis of LBBB.
1. QRS > 120 ms
2. Wide, “teething” R or R with plateau on peak in (I, aVL, V5, V6) - (V5, V6 may appear as RS)
3. QS Complexes in (V1-V3)
4. Time to R peak in (V5-V6) > 50 ms
5. Changes to ST segment, T wave opposite to main direction of QRS
6. Correct variant for LBBB may be positive T wave in leads with dominant R wave
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13. Treatment
There is no specific treatment to LBBB. Condition is usually permanent and requires of underlying
causes/disorders.
The exception to this is HFrEF with Sinus Rhythm and LBBB with QRS complex duration greater than
150 ms (with NYHA class II-IV) HF.
Secondary recommendation is people with no sinus rhythm (Atrial Fibrillation) and QRS duration of
120-149 ms (but this is a weaker recommendation).
Main treatment is installation of the bi-ventricular pacemaker (CRT) that allows heart to synchronise
its work by forcing simultaneous contraction of both ventricles. Use as recommended by ACC and
AHA.
CRT cannot be performed on people that do not fulfill recommendation. (it not only doesn’t benefit
them but also gives them risks of CRT therapy).
CRT reduces death rate by 37%
15. Prognosis
In general, prognosis in patients with otherwise decent health condition is good and mortality hazard
ratio is only 1.3 of normal. On the other hand with patients with new LBBB onset is greater than 10.0.
It’s hard to precisely describe mortality of LBBB since LBBB is more of a symptom (of dilated
cardiomyopathy) rather than a causative agent in the progression of a disease.
16. References
1. National Library of Medicine, 22.12.2020,
<https://www.ncbi.nlm.nih.gov/books/NBK482167/>
2. American Heart Association, 22.12.2020, <https://www.heart.org/en/health-
topics/heart-failure/treatment-options-for-heart-failure/cardiac-
resynchronization-therapy-crt>
3. The Johns Hopkins University, 22.12.2020,
<https://www.hopkinsmedicine.org/health/treatment-tests-and-
therapies/cardiac-resynchronization-therapy>
