II. Background
- Normal bundle branch transmission
- Following AV Node and His Bundle, signal divides into the left and right bundles
- Results normally in a simultaneous depolarization of each ventricle
- Bundle Branch Block
- Electrical impulse blocked in the left bundle branch or right bundle branch
- Results in a depolarization delay of the affected ventricle
- Results in overall widening of the QRS Complex (0.12 or greater meets criteria for BBB)
- QRS Axis and ventricular hypertrophy are not accurately determined in Bundle Branch Block
- Normally each ventricle's depolarization signal is simultaneous and opposes the other
- In Bundle Branch Block, these signals are offset resulting in large deflections (positive or negative)
- Right Bundle Branch Block
- Left ventricle (R) depolarizes before the right ventricle (R')
- Best seen in the right sided precordial leads (V1, V2) with characteristic 'M' appearance
- Left Bundle Branch Block
- Right ventricle (R) depolarizes before the left ventricle (R')
- Best seen in the left sided precordial leads (V5, V6) with a concave upward plateau to the top of the QRS Complex
- Q Waves absent
- Delay in left ventricular depolarization with right ventricle firing first
- Q Waves are not seen as the negative depolarization falls in the middle of wide QRS Complex
- Incomplete Bundle Branch Block
- Pattern of R and R' seen in a patient with a QRS Complex duration less than 0.12 seconds
- Critical Rate
- Rate at which Bundle Branch Block is seen (may not be evident at slower rates)
- Intrinsicoid Deflection (R-Wave Peak Time)
- Time from QRS wave onset to peak R Wave (early ventricular depolarization)
- Aberrant Conduction
- May mimic Bundle Branch Block
- Results from a discrepancy between the refractory periods between each ventricle
- Refractory period is time in ventricle following depolarization where it will not respond to a new depolarization signal
- Refractory periods may be slightly different between the ventricles
- At rapid rates, one ventricles depolarization may be delayed (offset) from the other giving the appearance of Bundle Branch Block
III. Findings: Left Bundle Branch Block
- EKG findings
- Causes
- Chronic Ischemic Heart Disease
- Chronic Hypertension (with Left Ventricular Hypertrophy)
- Chronic Congestive Heart Failure (abnormal ventricular remodeling)
- Valvular heart disease
- Old age with a fibrotic conduction system
- Massive acute Myocardial Infarction
- References
- Mattu and Herbert in Majoewksy (2012) EM:Rap 12(11): 4
IV. Findings: Right Bundle Branch Block EKG (RBBB)
- EKG Findings
- Lead V1
- Late Intrinsicoid Deflection (long duration from QRS start to R-wave peak time)
- M-shaped QRS Complex ("Rabbit Ears")
- Wide R Wave or qR (occasionally)
- Tall R Wave in Lead V1
- Lead V6
- Early Intrinsicoid Deflection (short duration from QRS start to R-wave peak time)
- Wide S wave
- Lead I
- Wide S wave
- Lead V1
- Precautions: Repolarization Abnormalities (ST Depression and T Wave Inversion)
- Unlike Left Bundle Branch Block, RBBB does not significantly interfere with Myocardial Ischemia or infarction detection
- Normal findings in RBBB (non-ischemic)
- Mild ST segment Depression or T Wave Inversion in right precordial leads (V1 with or without V2 and V3) AND
- Affected leads also have an rsR' pattern (initial R Wave may be subtle)
- Findings concerning for ischemia or infarction (or non-reassuring)
- ST depression or T Wave Inversion in other leads (aside from V1-V3 with rsR')
- ST Segment Elevation
- Upright T Waves in right precordial leads affected by RBBB (V1-V3 with rsR')
- References
- Berberian, Brady and Mattu (2023) Crit Dec Emerg Med 37(3): 14-5
- Mechanism of RBBB
- Most of right bundle branch is subendocardial and susceptible to stretch and other Trauma
- Causes: Important
- Increased right ventricular pressure
- Pulmonary Embolism
- Cor Pulmonale (May be accompanied by Right Ventricular Hypertrophy if long standing)
- Acute myocardial injury
- Myocardial Ischemia or infarction
- Inflammation (e.g. Myocarditis)
- Chest Trauma
- Electrolyte disturbance
- Increased right ventricular pressure
- Causes: Miscellaneous
- Hypertension
- Cardiomyopathy
- Congenital Heart Disease
- Right heart catheterization related injury
- Right heart fibrosis (Lev's Disease, Lenegre's Disease)
V. Findings: Left Hemiblocks (left Fascicular Block)
- Left Anterior Hemiblock EKG (Left Anterior Fascicular Block or LAFB)
- Left Axis Deviation (-45 to -90 degrees)
- Small Q Wave in Lead I and aVL may be present (qR pattern)
- Small R Wave in Lead II, III and avF (rS pattern)
- Normal QRS Duration <120 ms (unless concurrent Right Bundle Branch Block, bifascicular block)
- Prolonged R Wave peak time >= 45 ms in lead aVL
- No Right Ventricular Hypertrophy
- Left Posterior Hemiblock EKG (Left Posterior Fascicular Block or LPFB)
- Right Axis Deviation (beyond +120 degrees)
- Small R Wave in Lead I
- Small Q Wave in Lead III
- Normal QRS Duration (unless concurrent Right Bundle Branch Block, bifascicular block)
- No Right Ventricular Hypertrophy
VI. References
- Dubin (1974) Rapid Interpretation of EKGs, COVER publishing, Tampa, p. 137-47
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Related Studies
Definition (NCI) | An electrocardiographic finding of a prolongation of the QRS complex. It is caused by damage to one of the bundle branches, resulting in impaired transmission of cardiac electrical impulses. |
Definition (MSH) | A form of heart block in which the electrical stimulation of HEART VENTRICLES is interrupted at either one of the branches of BUNDLE OF HIS thus preventing the simultaneous depolarization of the two ventricles. |
Concepts | Disease or Syndrome (T047) |
MSH | D002037 |
ICD9 | 426.50 |
ICD10 | I45.4 |
SnomedCT | 251122006, 195048003, 6374002 |
English | Block, Bundle-Branch, Blocks, Bundle-Branch, Bundle-Branch Blocks, BUNDLE BRANCH BLOCK, Bundle branch block unspecif., Bundle branch block unspecified, Bundle branch block, unspecified, Bundle-Branch Block, bundle branch block (diagnosis), bundle branch block, BBB (bundle branch block), Block bundle branch, Bundle branch block NOS, Heart block bundle branch, Bundle-branch block NOS, Bundle-Branch Block [Disease/Finding], Block;bundle branch, bundle block branch, bundle branch heart block, bundle-branch block, block branch bundle heart, block bundle branch, branch bundle block, block branch bundle, blocks branch bundle, blocked branch bundle, Block, Bundle Branch, Branch Blocks, Bundle, Bundle Branch Blocks, Bundle Branch Block, Blocks, Bundle Branch, Branch Block, Bundle, Bundle branch block unspecified (disorder), Bundle-branch block, Bundle Branch Block by ECG Finding, Bundle Branch Block by EKG Finding, Bundle branch block, BBB - Bundle branch block, Bundle branch block (disorder), block; bundle-branch, bundle-branch; block, Bundle branch block, NOS |
French | BLOC DE BRANCHE, Bloc de branche non précisé, Bloc de branche SAI, Bloc de branches, Bloc de branche |
Portuguese | BLOQUEIO DE RAMO, Bloqueio de ramo NE, Bloqueio de ramo cardíaco, Bloqueio de ramo, Bloqueio do tronco, Bloqueio de Ramo |
Spanish | BLOQUEO DE RAMA, Bloqueo de rama NEOM, Bloqueo de rama no especificada, Bloqueo cardiaco de rama, bloqueo de rama no especificado, bloqueo de rama no especificado (trastorno), bloqueo de rama (trastorno), bloqueo de rama del haz de His, bloqueo de rama, Bloqueo de rama, Bloqueo de Rama |
Dutch | bundeltakhartblok, bundeltakblok NAO, bundeltakblok, niet-gespecificeerd, block; bundeltak, bundeltak; block, bundeltakblok, Blok, bundeltak-, Bundeltakblok |
German | Herzschenkelblock, Schenkelblock, unspezifisch, Schenkelblock NNB, HERZSCHENKELBLOCK, Schenkelblock |
Italian | Blocco di branca NAS, Blocco cardiaco di branca, Altro e non specificato blocco di branca, Blocco di branca |
Japanese | 脚ブロック、詳細不明, 脚ブロックNOS, キャクブロックNOS, キャクブロックショウサイフメイ, キャクブロック, 束ブロック, 脚ブロック |
Swedish | Grenblock |
Czech | blokáda Tawarova raménka, Raménková blokáda, Blokáda raménka, Blokáda raménka, blíže neurčená, Srdeční raménková blokáda, Blokáda raménka NOS |
Finnish | Haarakatkos |
Russian | PUCHKA GISA NOZHEK BLOKADA, FASTSIKULIARNAIA BLOKADA, ПУЧКА ГИСА НОЖЕК БЛОКАДА, ФАСЦИКУЛЯРНАЯ БЛОКАДА |
Croatian | BLOK BRANE HISOVOG SKLOPA |
Polish | Blok pęczka Hisa, Blok odnogi pęczka Hisa |
Hungarian | Tawara-szár block k.m.n., Tawara-szár block, nem meghatározott, Tawara-szár block, Tawara - szár block, Szívblock, Tawara-szár |
Norwegian | Grenblokk |
Ontology: Left Bundle-Branch Block (C0023211)
Concepts | Disease or Syndrome (T047) |
MSH | D002037 |
ICD10 | I44.7 |
SnomedCT | 155357007, 195044001, 63467002 |
LNC | LA17091-2 |
English | LBBB, LBBB - L bundle branch block, Left bundle-branch block, unspecified, BUNDLE BRANCH BLOCK LEFT, Bundle-Branch Blocks, Left, Block, Left Bundle-Branch, Blocks, Left Bundle-Branch, Left Bundle Branch Block, Left Bundle-Branch Blocks, Bundle-Branch Block, Left, left bundle branch block, left bundle branch block (diagnosis), LBBB (left bundle branch block), Left Bundle-Branch Block, Bundle branch block left, blocks branch bundle left, Block;bundle branch;left, bundle branch block left, lbbb, blocked branch bundle left, left bundle-branch block, block branch bundle left, left branch bundle block, Left bundle branch block, LBBB - Left bundle branch block, Left bundle branch block (disorder), block; bundle-branch, left, Left bundle branch block, NOS, Left bundle branch block NOS |
Italian | Blocco di branca sinistra, Blocco di branca sinistro, Blocco di branca sinistro del fascio |
Dutch | linkerbundeltakblok, LBBB, block; bundeltak, linker, Linker-bundeltakblock, niet gespecificeerd, bundeltakblok links |
French | Bloc de la branche gauche, BBG, Bloc de branche gauche, BLOC DE BRANCHE GAUCHE |
German | LBBB, Linksschenkelblock, Linksschenkelblock, nicht naeher bezeichnet |
Spanish | BRI, bloqueo de la rama izquierda del haz de His (trastorno), bloqueo de la rama izquierda del haz de His, Bloqueo de rama izquierda |
Japanese | 左脚ブロック, サキャクブロック |
Portuguese | BLOQUEIO DE RAMO ESQUERDO, Bloqueio de ramo esquerdo |
Czech | Blokáda levého Tawarova raménka, blokáda levého raménka Tawarova, blokáda levého Tawarova raménka, LBBB, BLRT |
Korean | 상세불명의 좌각 차단 |
Hungarian | LBBB, Bal Tawara-szár block |
Norwegian | Venstre gren-blokk |
Ontology: Right bundle branch block (C0085615)
Concepts | Disease or Syndrome (T047) |
MSH | D002037 |
ICD9 | 426.4 |
ICD10 | I45.0 , I45.10 |
SnomedCT | 195064006, 195055001, 155358002, 59118001 |
English | RBBB, RBBB - Rt bundle branch block, BUNDLE BRANCH BLOCK RIGHT, Right Bundle-Branch Block, Right Bundle Branch Block, Block, Right Bundle-Branch, Bundle-Branch Blocks, Right, Blocks, Right Bundle-Branch, Bundle-Branch Block, Right, Right Bundle-Branch Blocks, right bundle branch block, right bundle branch block (diagnosis), RBBB (right bundle branch block), Right bundle branch block, Bundle branch block right, Rt bundle branch block, Right bundle-branch block NOS, blocked branch bundle right, Block;bundle branch;right, blocks branch bundle right, right branch bundle block, rbbb, bundle branch block right fascicular, right fascicular block, right fascicular block (diagnosis), RBBB - Right bundle branch block, Right fascicular block, Right bundle branch block (disorder), block; bundle-branch, right, block; fascicular, right, bundle-branch; block, right, fascicular, bundle-branch; block, right, fascicular; block, right |
Italian | Blocco di branca destra, Blocco completo di branca destra, Blocco di branca destro, Blocco di branca destro del fascio |
Dutch | rechterbundeltakblok, RBTB, block; bundeltak, rechter, block; fasciculair, rechter, bundeltak; block, rechter, fasciculair, bundeltak; block, rechter, fasciculair; block, rechter, Rechter fasciculair block, bundeltakblok rechts |
French | Bloc de la branche droite, BBD, Bloc de branche droit, BLOC DE BRANCHE DROIT |
German | RBBB, Rechtsschenkelblock, Rechtsfaszikulaerer Block |
Spanish | BRD, bloqueo de la rama derecha del haz de His (trastorno), bloqueo de la rama derecha del haz de His, hemibloqueo ventricular derecho, Bloqueo de rama derecha |
Japanese | 右脚ブロック, ウキャクブロック |
Portuguese | BLOQUEIO DE RAMO DIREITO, Bloqueio de ramo direito |
Czech | Blokáda pravého Tawarova raménka, Blok pravého raménka, blokáda pravého Tawarova raménka, BPRT, RBBB, blokáda pravého raménka Tawarova |
Korean | 우 섬유속 차단 |
Hungarian | Jobb Tawara szár block, Jobb Tawara-szár block, RBBB |
Norwegian | Høyre gren-blokk |
Ontology: Monofascicular block (C0264911)
Concepts | Disease or Syndrome (T047) |
SnomedCT | 2374000 |
English | Monofascicular block (disorder), Monofascicular block, Monofascicular block, NOS |
Spanish | bloqueo monofascicular (trastorno), bloqueo monofascicular |
Ontology: Left anterior fascicular block (C0264912)
Concepts | Disease or Syndrome (T047) |
ICD10 | I44.4 |
SnomedCT | 37760005, 285801000119101 |
English | Left anterior fascicular block, LAFB - Left ant fascicul block, left anterior block bundle branch hemiblock (diagnosis), left anterior block bundle branch hemiblock, LBBB anterior hemiblock, left anterior fascicular block, anterior block fascicular left, Left anterior hemiblock, Left anterior hemiblock (disorder), LAFB - Left anterior fascicular block, Left anterior fascicular block (disorder), block; bundle-branch, left, fascicular, anterior, bundle-branch; block, left, fascicular, anterior, fascicular; block, left, anterior, Block, left anterior fascicular |
Dutch | linker voorste fasciculair blok, linkervoorste hemiblok, block; bundeltak, linker, fasciculair, anterior, bundeltak; block, linker, fasciculair, anterior, fasciculair; block, linker, anterior, Linker anterior fasciculair block |
French | Hémibloc antérieur gauche, Bloc fasciculaire antérieur gauche |
German | linksanteriorer Hemiblock, Linksanteriorer Faszikelblock |
Italian | Emiblocco anteriore sinistro, Blocco fascicolare anteriore sinistro |
Portuguese | Bloqueio fascicular anterior esquerdo, Hemibloqueio anterior esquerdo |
Spanish | Hemibloqueo anterior izquierdo, Bloqueo fascicular izquierdo anterior, hemibloqueo anterior izquierdo, dup, hemibloqueo anterior izquierdo, dup (trastorno), bloqueo de la rama izquierda anterior del haz de His (trastorno), bloqueo de la rama izquierda anterior del haz de His, bloqueo fascicular izquierdo anterior, hemibloqueo anterior izquierdo |
Japanese | 左脚前枝ヘミブロック, 左脚前枝ブロック, サキャクゼンシブロック, サキャクゼンシヘミブロック |
Czech | Levý přední hemiblok, Levý přední fascikulární blok |
Korean | 좌전 섬유속 차단 |
Hungarian | Bal anterior hemiblock, Bal anterior fascicularis block |
Ontology: Left posterior fascicular block (C0264913)
Concepts | Disease or Syndrome (T047) |
ICD10 | I44.5 |
SnomedCT | 62026008 |
English | Left post fascicular block, Left posterior hemiblock, left posterior bundle branch hemiblock, LBBB posterior hemiblock, left posterior bundle branch hemiblock (diagnosis), Left posterior fascicular block, Left posterior fascicular block (disorder), block; bundle-branch, left, fascicular, posterior, bundle-branch; block, left, fascicular, posterior, fascicular; block, left, posterior, Block, left posterior fascicular |
Dutch | linkerachterste hemiblok, linker posterior fasciculair blok, block; bundeltak, linker, fasciculair, posterior, bundeltak; block, linker, fasciculair, posterior, fasciculair; block, linker, posterior, Linker posterior fasciculair block |
French | Hémibloc postérieur gauche, Bloc fasciculaire postérieur gauche |
German | linksposteriorer Hemiblock, Linksposteriorer Faszikelblock, Linksposteriorer faszikulaerer Block |
Italian | Emiblocco posteriore sinistro, Blocco fascicolare posteriore sinistro |
Portuguese | Hemibloqueio posterior esquerdo, Bloqueio fascicular posterior esquerdo |
Spanish | Hemibloqueo posterior izquierdo, Bloqueo fascicular izquierdo posterior, bloqueo de la rama izquierda posterior del haz de His (trastorno), bloqueo de la rama izquierda posterior del haz de His, bloqueo fascicular izquierdo posterior, hemibloqueo posterior izquierdo |
Japanese | 左脚後枝ヘミブロック, サキャクコウシヘミブロック, 左脚後枝ブロック, サキャクコウシブロック |
Czech | Levý zadní hemiblok |
Korean | 좌후 섬유속 차단 |
Hungarian | Bal posterior fascicularis block, Bal hátulsó hemiblock |