Right bundle branch block explained

Right bundle branch block
Field:Cardiology
Types:complete right bundle branch block (CRBBB)
incomplete right bundle branch block (IRBBB)

A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system.[1]

During a right bundle branch block, the right ventricle is not directly activated by impulses traveling through the right bundle branch. However, the left bundle branch still normally activates the left ventricle. These impulses can then travel through the myocardium of the left ventricle to the right ventricle and depolarize the right ventricle this way. As conduction through the myocardium is slower than conduction through the bundle of His-Purkinje fibres, the QRS complex is seen to be widened. The QRS complex often shows an extra deflection that reflects the rapid depolarisation of the left ventricle, followed by the slower depolarisation of the right ventricle.

Incomplete right bundle branch block

An incomplete right bundle branch block (IRBBB) is a conduction abnormality in the right bundle branch block. While a complete RBBB has a QRS duration of 120 ms or more, an incomplete RBBB has a wave duration between 100 and 120 ms. It has a relatively high prevalence, a study conducted on young Swiss military conscripts with a mean age of 19 years found a prevalence of 13.5%.[2] It affects patients of all ages, more commonly males and athletes, however it is not always a benign finding. Therefore, if abnormalities are detected on the physical exam, further testing should be done to exclude heart disease.[3]

There is no consensus in the literature regarding criteria for diagnosis. However, according to the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society (AHA/ACCF/HRS) it is defined by the following finding in adults:

  1. QRS wave duration between 100 and 120 ms.
  2. rsr, rsR, or rSR in leads V1 or V2.
  3. S wave of longer duration than R wave or greater than 40 ms in leads I and V6.
  4. Normal R wave peak time in both V5 and V6, but greater than 50 ms in V1.

The first three criteria are needed for diagnosis. The fourth is needed when a pure dominant R waver is present on V1.[3]

Causes

Common causes include normal variation, changes in bundle branch structure - such as mechanical stretching, chest trauma, right ventricular hypertrophy or strain, congenital heart disease such as atrial septal defect, and ischemic heart disease. [4] In addition, a right bundle branch block may also result from Brugada syndrome, Chagas disease,[5] [6] pulmonary embolism, rheumatic heart disease, myocarditis, cardiomyopathy, or hypertension.[7]

Causes for incomplete right bundle branch block (IRBBB) often involve exercise-induced right ventricular remodeling, increased right ventricular (RV) free wall thickness, especially in athletes due to prolonged endurance exercise.[8]

Diagnosis

The criteria to diagnose a right bundle branch block on the electrocardiogram:

The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction.

Treatment

The underlying condition may be treated by medications to control hypertension or diabetes, if they are the primary underlying cause. If coronary arteries are blocked, an invasive coronary angioplasty may relieve the impending RBBB.[10]

Epidemiology

Prevalence of RBBB increases with age due to changes in the heart's conduction system. It's estimated up to 11.3% of the population by the age of 80 have RBBB.[11]

See also

Notes and References

  1. Web site: Conduction Blocks . https://web.archive.org/web/20090509204757/http://courses.kcumb.edu/physio/blocks/index.htm . 9 May 2009 . 2006 . Kansas City University of Medicine & Biosciences . Department of Physiology . 20 January 2009 .
  2. Kobza R, Cuculi F, Abächerli R, Toggweiler S, Suter Y, Frey F, Schmid JJ, Erne P . Twelve-lead electrocardiography in the young: physiologic and pathologic abnormalities . Heart Rhythm . 9 . 12 . 2018–2022 . December 2012 . 23102624 . 10.1016/j.hrthm.2012.08.034 .
  3. Floria M, Parteni N, Neagu AI, Sascau RA, Statescu C, Tanase DM . Incomplete right bundle branch block: Challenges in electrocardiogram diagnosis . Anatolian Journal of Cardiology . 25 . 6 . 380–384 . June 2021 . 34100724 . 8210929 . 10.5152/AnatolJCardiol.2021.84375 . 235368614 .
  4. Book: Goldman L . Goldman's Cecil Medicine. limited. Elsevier Saunders. Philadelphia. 2011. 978-1-4377-2788-3. 400–401. 24th.
  5. Web site: Chagas Disease: What U.S. Clinicians Need to Know . Centers for Disease Control and Prevention . CDC . 3 October 2023.
  6. Rojas LZ, Glisic M, Pletsch-Borba L, Echeverría LE, Bramer WM, Bano A, Stringa N, Zaciragic A, Kraja B, Asllanaj E, Chowdhury R, Morillo CA, Rueda-Ochoa OL, Franco OH, Muka T . Electrocardiographic abnormalities in Chagas disease in the general population: A systematic review and meta-analysis . PLoS Neglected Tropical Diseases . 12 . 6 . e0006567 . June 2018 . 29897909 . 5999094 . 10.1371/journal.pntd.0006567 . free .
  7. Ikeda T . Right Bundle Branch Block: Current Considerations . Current Cardiology Reviews . 17 . 1 . 24–30 . January 2021 . 32640959 . 8142372 . 10.2174/1573403X16666200708111553 .
  8. Floria M, Parteni N, Neagu AI, Sascau RA, Statescu C, Tanase DM . Incomplete right bundle branch block: Challenges in electrocardiogram diagnosis . Anatolian Journal of Cardiology . 25 . 6 . 380–384 . June 2021 . 34100724 . 8210929 . 10.5152/AnatolJCardiol.2021.84375 . 235368614 .
  9. Web site: Yanowitz FG . University of Utah School of Medicine . Lesson VI - ECG Conduction Abnormalities . https://web.archive.org/web/20080126080609/http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson6/index.html . 26 January 2008 . 2009-01-07.
  10. Web site: Right Bundle Branch Block. Symptoma . 2015-08-13.
  11. Book: Harkness WT, Hicks M . Right Bundle Branch Block . 2022 . http://www.ncbi.nlm.nih.gov/books/NBK507872/. StatPearls. Treasure Island (FL). StatPearls Publishing. 29939649. 2022-02-24.