| Right bundle branch block | |
|---|---|
_of_the_human_heart.svg) | |
| An illustration of a right bundle branch block located inintraventricular septum | |
 | |
| ECG characteristics of a typical RBBB showing wide QRS complexes with a terminal R wave in lead V1 and a prolonged S wave in lead V6. | |
| Specialty | Cardiology |
| Types | complete right bundle branch block (CRBBB) incomplete right bundle branch block (IRBBB) |
Aright bundle branch block (RBBB) is aheart block in theright bundle branch of theelectrical conduction system.[1]
During a right bundle branch block, the rightventricle 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 themyocardium 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 thebundle of His-Purkinje fibres, theQRS 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.
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 theAmerican Heart Association/American College of Cardiology Foundation/Heart Rhythm Society (AHA/ACCF/HRS) it is defined by the following finding in adults:
The first three criteria are needed for diagnosis. The fourth is needed when a pure dominant R waver is present on V1.[3]
Common causes include normal variation, changes in bundle branch structure - such as mechanical stretching, chest trauma,right ventricular hypertrophy orstrain,congenital heart disease such asatrial septal defect, andischemic heart disease.[4] In addition, a right bundle branch block may also result fromBrugada syndrome,Chagas disease,[5][6]pulmonary embolism,rheumatic heart disease,myocarditis,cardiomyopathy, orhypertension.[7]
Causes for incomplete right bundle branch block (IRBBB) often involve exercise-induced rightventricular remodeling, increased right ventricular (RV) free wall thickness, especially in athletes due to prolonged endurance exercise.[8]
The criteria to diagnose a right bundle branch block on theelectrocardiogram:
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.[citation needed]
The underlying condition may be treated by medications to control hypertension or diabetes, if they are the primary underlying cause. Ifcoronary arteries are blocked, an invasive coronaryangioplasty may relieve the impending RBBB.[10]
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]
