A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system. During a right bundle branch block, the right ventricle is not directly activated by impulses travelling through the right bundle branch. The left ventricle, however, is still normally activated by the left bundle branch. These impulses are then able to travel through the

myocardium Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

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 Purkinje fibers (; often incorrectly ; Purkinje tissue or subendocardial branches) are located in the inner ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purkinje fibers are specia ...

, the

QRS complex The QRS complex is the combination of three of the graphical deflections seen on a typical electrocardiogram (ECG or EKG). It is usually the central and most visually obvious part of the tracing. It corresponds to the depolarization of the ri ...

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

Incomplete right bundle branch block (IRBBB) is an conduction abnormality in the right bundle branch block. While a complete RBBB has a QRS duration of 120 ms or more, an incomplete block has a wave duration between 110 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%. It affects patients of all ages, more commonly males and athletes, however is not always a benign finding. Therefore, if abnormalities are detected on the physical exam, further testing should be done to exclude heart disease. 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 Foundation (AHA/ACCF/HRS) it is defined by the following finding in adults: #QRS wave duration between 110 and 120 ms. #rsr, rsR, or rSR in leads V1 or V2. #S wave of longer duration than R wave or greater than 40 ms in leads I and V6. #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.

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 A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...

such as

atrial septal defect Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria (upper chambers) of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this d ...

, and

ischemic heart disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic pl ...

. In addition, a right bundle branch block may also result from

Brugada syndrome Brugada syndrome (BrS) is a genetic disorder in which the electrical activity of the heart is abnormal due to channelopathy. It increases the risk of abnormal heart rhythms and sudden cardiac death. Those affected may have episodes of synco ...

pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream ( embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathin ...

rheumatic heart disease Rheumatic fever (RF) is an inflammatory disease that can involve the heart, joints, skin, and brain. The disease typically develops two to four weeks after a streptococcal throat infection. Signs and symptoms include fever, multiple painf ...

myocarditis Myocarditis, also known as inflammatory cardiomyopathy, is an acquired cardiomyopathy due to inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. Th ...

cardiomyopathy Cardiomyopathy is a group of diseases that affect the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. ...

, or

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

. Causes for incomplete right bundle branch block are exercise-induced right

ventricular remodeling In cardiology, ventricular remodeling (or cardiac remodeling) refers to changes in the size, shape, structure, and function of the heart. This can happen as a result of exercise (physiological remodeling) or after injury to the heart muscle (pathol ...

, increased RV free wall thickness, especially in athletes due to prolonged endurance exercise.

Diagnosis

The criteria to diagnose a right bundle branch block on the electrocardiogram: * The heart rhythm must originate above the ventricles (i.e., sinoatrial node, atria or atrioventricular node) to activate the conduction system at the correct point. * The QRS duration must be more than 100 ms (incomplete block) or more than 120 ms (complete block). * There should be a terminal R wave in lead V₁ (often called "R prime," and denoted by R, rR', rsR', rSR', or qR). * There must be a prolonged S wave in leads I and V₆ (sometimes referred to as a "slurred" S wave). 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 Angioplasty, is also known as balloon angioplasty and percutaneous transluminal angioplasty (PTA), is a minimally invasive endovascular procedure used to widen narrowed or obstructed arteries or veins, typically to treat arterial atheroscle ...

may relieve the impending RBBB.

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.

Gallery

image:RBBB with first degree AV block.jpg, RBBB with associated first degree AV block image:Cardiogram indicating right bundle branch block with tachycardia.jpg, RBBB with associated tachycardia Image:Cardiogram indicating right bundle branch block.jpg, RBBB

References

External links

{{Circulatory system pathology Cardiac arrhythmia fr:Bloc de branche#Bloc de branche droit