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| Image = Right bundle branch block ECG characteristics.png| | | Image = Right bundle branch block ECG characteristics.png| |
| Caption = ECG characteristics of a typical RBBB showing wide QRS complexes with a terminal R wave in lead V1 and slurred S wave in lead V6.| | | Caption = ECG characteristics of a typical RBBB showing wide QRS complexes with a terminal R wave in lead V1 and slurred S wave in lead V6.| |
| DiseasesDB = 11620 |
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| ICD10 = {{ICD10|I|45|1|i|30}} |
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| OMIM = |
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| }} | | }} |
| {{SI}} | | {{Right bundle branch block}} |
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| {{CMG}} '''Associate Editor-In-Chief:''' {{CZ}}
| | '''For patient information click [[Heart block (patient information)|here]]''' |
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| {{SK}} RBBB | | {{CMG}}; {{AE}} {{CZ}}; {{AN}}; {{RT}} |
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| ==Overview==
| | {{SK}} RBBB; bundle branch block right; rt bundle branch block |
| '''Right bundle branch block (RBBB)''' results from a defect in the heart's electrical conduction system. There is a delay in failure of transmission of electrical impulses down the right bundle of the heart. As a result, the right ventricle depolarizes by an alternate mechanism. This is by means of cell-to-cell conduction. These cell to cell conduction impulses spread more slowly than usual from the interventricular septum to the [[left ventricle]] and to the [[right ventricle]]. This delay in conduction results in the characteristic [[ECG]] pattern which is a wide and notched [[QRS]]. Although conduction down the right bundle is delayed, conduction down the left bundle is normal. As result, the interventricular septum and [[left ventricle]] depolarize in the normal fashion.
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| ==Pathophysiology== | | ==[[Right bundle branch block overview|Overview]]== |
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| Three types of [[RBBB]] have been identified based upon electrophysiologic studies.
| | ==[[Right bundle branch block historical perspective|Historical Perspective]]== |
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| In each of the three types of RBBB, the surface ECG pattern remains the same.
| | ==[[Right bundle branch block classification|Classification]]== |
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| '''1. Proximal, or central, RBBB:'''
| | ==[[Right bundle branch block pathophysiology|Pathophysiology]]== |
| This type of conduction defect occurs when the conduction block is located just distal to the bundle of His in the superior aspect of the right bundle branch. This type of block occurs when the proximal bundle is injured during surgery for an inlet or membranous [[ventricular septal defect]] ([[VSD]]).
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| '''2. Interruption between the proximal and distal aspects of the right bundle branch:'''
| | ==[[Right bundle branch block causes|Causes]]== |
| This type of right bundle branch block occurs when the impulse is interrupted between the proximal and distal aspects of the right bundle branch. This type of bright bundle branch block is most commonly observed after surgical division of the moderator band.
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| '''3. Distal RBBB:'''
| | ==[[Right bundle branch block differential diagnosis|Differentiating Right bundle branch block from other Diseases]]== |
| This form is observed when distal ramifications of the right bundle are disrupted during right ventriculotomy or resection of muscle bundles in the right ventricular outflow tract.
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| ===Genetics === | | ==[[Right bundle branch block epidemiology and demographics|Epidemiology and Demographics]]== |
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| There can be familial cases of [[right bundle branch block]] such as that observed in 4 Lebanese families and the abnormality was mapped to chromosome 19.
| | ==[[Right bundle branch block risk factors|Risk Factors]]== |
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| There is a subset of patients with [[Brugada syndrome]] who have mutations in SCN5A, the gene encoding for the voltage-gated cardiac sodium channel.
| | ==[[Right bundle branch block natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| ===Associated syndromes===
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| *[[Duchenne muscular dystrophy]]
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| *[[Myotonic dystrophy]] Other ECG findings include [[first-degree AV block]], [[left anterior fascicular block]], and intraventricular conduction delay. Patients may have arrhythmias and/or [[Stokes-Adams attacks]].
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| *[[Kearns-Sayre Syndrome]]
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| *[[Brugada syndrome]]: This syndrome is due to a channelopathy mediated by the SCN5A gene. It is important to note that the RBBB pattern seen in patients with this syndrome is not actually RBBB but is instead due to a repolarization abnormality. In this syndrome, the ECG shows ST-segment elevation in leads V1-V3. [[Cocaine]] consumption and / or the use of the antiarrhythmic [[propafenone]] may unmask the ECG findings of [[Brugada syndrome]].
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| ==Causes==
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| *Surgery for correction of congenital heart disease is the most common cause of [[RBBB]] among children any United States. This includes surgery for repair of an isolated [[VSD]] or another [[congenital heart disease]] that includes a [[VSD]] (eg, double-chambered right ventricle, AV canal defect, or [[tetralogy of Fallot]]). The incidence of [[RBBB]] varies and ranges from 25-81% after repair of a VSD to 60-100% after repair of [[tetralogy of Fallot]]. The risk of [[RBBB]] after surgery varies depending upon the proximity of the [[VSD]] to the His-Purkinje system.
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| *Blunt [[trauma]]
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| *[[Polymyositis]]
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| *[[Premature atrial contraction]]s or supraventricular tachycardia may cause a transient form up right bundle branch block. This occurs when a premature impulse is conducted from the AV node to the His bundle while the right bundle branch remains in its refractory period, but the left bundle is not. As a result, conduction down the right bundle branch is delayed or blocked.
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| *Prenatal exposure to each one HIV type 1 may cause right anterior hemiblock.
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| * Familial
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| ==Differential Diagnosis==
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| * [[Pulmonary Embolism|Acute pulmonary embolism]]
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| * [[Atrial septal defect]]
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| * [[Ddx:Cardiomyopathy|Cardiomyopathy]]
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| * [[Cor Pulmonale]]
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| * [[Coronary Heart Disease]]
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| * [[Lenegre's Disease]]
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| * [[Lev's Disease]]
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| * [[STEMI|Myocardial Infarction]]
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| * [[Myocarditis]]
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| ==Epidemiology and Demographics==
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| ===Age===
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| The [[prevalence]] of RBBB increases with age.
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| ==Natural Hisstory==
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| In general, the natural history of right bundle branch block benign. There are three scenarios in which right bundle branch block can be associated with poor prognosis:
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| #[[Brugada syndrome]]: if right bundle branch block is present, then [[sudden death]] may occur.
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| #[[Kearns Sayre syndrome]]: again, if right bundle branch block is present than [[sudden death]] may occur.
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| #[[Tetralogy of Fallot]]: if right bundle branch block is present with a markedly prolonged [[QRS]] (< 180 ms), then the patient may be at risk for ventricular [[arrhythmias]] and [[sudden death]].
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| If right bundle branch block is due to surgery then there are generally no acute [[hemodynamic]] consequences. The subsequent courses also quite benign. An exception is if there is substantial injury to the His-Purkinje system in which case [[left anterior hemiblock]] or [[first-degree AV block]] may be present.
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| There are familial cases of right bundle branch block, which are benign.
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| ==Diagnosis== | | ==Diagnosis== |
| === Physical Examination ===
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| ====Heart====
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| Right bundle branch block is associated with a persistently split second heart sound with normal respiratory variation in the splitting interval.
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| ===Laboratory Findings ===
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| If there is a history of blunt trauma or any symptoms to suggest polymyositis then [[troponin]], [[creatine kinase]] ([[CK]]) and an echocardiogram should be obtained.
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| ===Electrocardiogram===
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| * The heart rhythm must be supraventricular in origin
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| * The QRS axis can be either normal, or right or left axis deviation may be present.
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| * The QRS duration must be = or > 120 ms
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| ** For complete RBBB, the patient's age must be taken into account to determine if the duration of the QRS complex is prolonged for the patient's age.
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| ***Maximum QRS durations are 0.07 s for newborns <6 days, 0.08 s for patients aged 1 week to 7 years, and 0.09 s for patients aged 7-15 years.
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| * There should be a terminal R wave in lead V1-V3R (e.g., R, rR', rsR', rSR' or qR')
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| ** This pattern is present because the initial R wave represents septal activation, the S wave represents left ventricular activation, and the R' represents activation of the right ventricle from the septum and left ventricle.
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| * There should be a slurred S wave in leads I and V6. This represent left ventricular activation.
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| ** Because transmission of the electrical impulse through the left bundle is normal, this results in normal depolarization of the septum and the left ventricle. As a result, there is an initial R wave in lead I and V1 and the Q wave in V6.
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| 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]].
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| Below is an electrocardiogram showing the main characteristics of right bundle branch block on lead V1.
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| [[File:Right bundle branch block 3.png|center|300px]]
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| The rhythm is sinus. The QRS is wide (>120ms.) and the axis is markedly negative. There are small R waves in the inferior leads. The recording shows a right bundle branch block and a left anterior fasicular block.
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| [[File:Right bundle branch block 2.jpg|center|500px]]
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| ===EKG Examples===
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| EKG below is from an elderly woman who had previously undergone surgery for recurrent ventricular tachycardia. She was being treated with Tambacor and metoprolol. The cardiogram shows sinus rhythm with a wide QRS of 159ms consistent with a RBBB and a rightward axis suggesting right posterior hemi-block. The PR interval is slightly prolonged at 2121ms. The poor R wave progression seen best in lead V2 suggests previous anterior wall MI.
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| [[Image:Right bundle branch block.jpg|center|500px]]
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| EKG below is a recording from an older man in the [[surgical intensive care unit]]. He was recovering from a [[motor vehicle accident]] where he sustained a [[chest injury]] from his seat belt. The rhythm is [[sinus rhythm]] with a prolonged p wave duration in lead III( >140ms) and a pronounced terminal negativity in V1 suggestive of left atrial abnormality. The [[QRS]] is wide with a duration of 137ms and a superior and right ward axis. There is an [[RSR]] in V1 and the S wave is greater than the R in V6. This is an unusual pattern for aberrance and is more in keeping with ventricular ectopy. In this case, this appears to be a [[right bundle branch block]] with a possible left posterior hemi-block.
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| Of note, in spite of this conduction disturbance the patient was able to sustain reentrant supraventricular tachycaridas requiring intravenous [[adenosine]] for termination.
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| [[Image:Right bundle branch block 1.jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 4.jpg|center|500px]]
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| ----
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 5.png|center|500px]]
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| ----
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 6 .jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 7 .jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 8 .jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block.
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| [[File:Right bundle branch block 9 .jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block with [[first degree AV block]].
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| [[File:Right bundle branch block 11 .jpg|center|500px]]
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| Below is an electrocardiogram showing right bundle branch block with right atrial hypertrophy.
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| [[File:Right bundle branch block 12 .jpg|center|500px]]
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| Electrocardiogram of the same patient. Of note here is ST elevation in lead V4R.
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| [[File:Right bundle branch block 14.jpg|center|500px]]
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| The same patient before [[acute MI]] developed. Horizontal axis shown.
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| [[File:Right bundle branch block 15.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with [[supraventricular tachycardia]] with [[RBBB]].
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| [[File:Right bundle branch block 16.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with old [[Acute MI|Anterior MI]] with [[RBBB]].
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| [[File:Right bundle branch block 17.jpg||center|500px]].
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| Below is an electrocardiogram of a patient with Old [[Acute MI|Inferior MI]] and [[Acute MI|Anterior MI]] with [[RBBB]] and [[LAFB]].
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| [[File:Right bundle branch block 18.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with Old [[Acute MI|Inferior MI]] with [[RBBB]]
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| [[File:Right bundle branch block 19.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with [[RBBB]] and [[LAFB]].
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| [[File:Right bundle branch block 20.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with [[RBBB]], [[LAFB]] and [[First Degree AV Block]].
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| [[File:Right bundle branch block 21.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with [[RBBB]] and [[LAFB]].
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| [[File:Right bundle branch block 22.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with [[RBBB]] and [[LAFB]].
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| [[File:Right bundle branch block 23.jpg|center|500px]]
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| Below is an electrocardiogram of a patient with atrial fibrillation with a controlled ventricular rate. The QRS is wide (>120ms) and has a tall R' in V1 and an S wave in V6. There is a left axis deviation. The cardiogram suggests a right bundle branch block and a left anterior hemiblock. The patient has a cardiomyopathy with an ejection fraction of 20%.
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| [[File: Right bundle branch block 24.jpg|center|500px]]
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| | [[Right bundle branch block history and symptoms|History and Symptoms ]] | [[ Right bundle branch block physical examination|Physical Examination]] | [[Right bundle branch block laboratory findings|Laboratory Findings]] | [[Right bundle branch block electrocardiogram|Electrocardiogram]] | [[Right bundle branch block EKG examples|EKG Examples]] | [[Right bundle branch block echocardiography|Echocardiography]] | [[Right bundle branch block other imaging findings|Other Imaging Findings]] | [[Right bundle branch block other diagnostic studies|Other Diagnostic Studies]] |
| The cardiogram below shows sinus rhythm with a normal [[PR interval]] and a prolonged QRS interval (>120ms). There is a conduction abnormality best described as a right bundle branch block due to the rsR' wave in V1. Note the S wave in V6 which is due to the RBBB is smaller than the R wave in V6. The axis of the QRS is difficult to determine, but one usually looks at the first 60 ms. (1 1/2 small squares) to determine the axis with a RBBB. If the axis of the first 60 ms. of the QRS is more than 90 degrees and there is an rS in lead I and a Q in lead III then on would consider a left [[posterior fasicular block]]. This is not the case here.
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| [[File:Right bundle branch block 25.jpg|center|500px]] | |
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| ---- | | ==Treatment== |
| | [[Right bundle branch block medical therapy|Medical Therapy]] | [[Right bundle branch block surgery |Surgery]] | [[Right bundle branch block primary prevention|Primary Prevention]] | [[Right bundle branch block secondary prevention|Secondary Prevention]] | [[Right bundle branch block cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Right bundle branch block future or investigational therapies|Future or Investigational Therapies]] |
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| Below is an electrocardiogram of patient with [[RBBB]]
| | ==Case Studies== |
| | | [[Right bundle branch block case study one|Case #1]] |
| [[File:Right bundle branch block 26.jpg|center|500px]] | |
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| == Treatment ==
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| In general treatment for right bundle branch block is not necessary. These patients need not limit their activity. However, if the RBBB progresses to heart block, the patient may be at risk for adverse clinical outcomes. In these patients further electrophysiologic testing may be necessary. Those patients who develop right bundle branch block after surgery should undergo EKG testing each year to evaluate for interval changes. In particular, care should be taken to observe for the development of [[sinus bradycardia]] supraventricular or ventricular ectopy.
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| ==Related Chapters== | | ==Related Chapters== |
| | *[[Electrical conduction system of the heart]] |
| | *[[Electrocardiogram]] (ECG or EKG) |
| | *[[SA node]] |
| | *[[AV node]] |
| | *[[Second degree AV block]] |
| | *[[Third degree AV block]] |
| | *[[Bundle branch block]] |
| | *[[Left bundle branch block]] |
| | *[[Hemiblock]] |
| | *[[Infra-Hisian Block]] |
| | *[[Left anterior fascicular block]] |
| | *[[Left posterior fascicular block]] |
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| * [[Bundle branch block]]
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| * [[Left bundle branch block]]
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| ==Sources==
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| Copyleft images obtained courtesy of ECGpedia, http://en.ecgpedia.org/index.php?title=Special:NewFiles&offset=&limit=500
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| ==References==
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| {{Reflist|2}}
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| {{WH}} | | {{WH}} |
| {{WS}} | | {{WS}} |
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| {{Electrocardiography}}
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| {{Circulatory system pathology}}
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| {{Link_FA|de}}
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| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
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| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| [[Category:Emergency medicine]] | | [[Category:Emergency medicine]] |
| | [[Category:Arrhythmia]] |
