II. Background

  1. Normal bundle branch transmission
    1. Following AV Node and His Bundle, signal divides into the left and right bundles
    2. Results normally in a simultaneous depolarization of each ventricle
  2. Bundle Branch Block
    1. Electrical impulse blocked in the left bundle branch or right bundle branch
    2. Results in a depolarization delay of the affected ventricle
    3. Results in overall widening of the QRS Complex (0.12 or greater meets criteria for BBB)
      1. Left and right bundles signals are separated in time (no longer simultaneous or overlapped)
      2. Shape of QRS is also modified to have two R Waves, with the delayed R Wave referred to as R'
    4. QRS Axis and ventricular hypertrophy are not accurately determined in Bundle Branch Block
      1. Normally each ventricle's depolarization signal is simultaneous and opposes the other
      2. In Bundle Branch Block, these signals are offset resulting in large deflections (positive or negative)
  3. Right Bundle Branch Block
    1. Left ventricle (R) depolarizes before the right ventricle (R')
    2. Best seen in the right sided precordial leads (V1, V2) with characteristic 'M' appearance
  4. Left Bundle Branch Block
    1. Right ventricle (R) depolarizes before the left ventricle (R')
    2. Best seen in the left sided precordial leads (V5, V6) with a concave upward plateau to the top of the QRS Complex
    3. Q Waves absent
      1. Delay in left ventricular depolarization with right ventricle firing first
      2. Q Waves are not seen as the negative depolarization falls in the middle of wide QRS Complex
  5. Incomplete Bundle Branch Block
    1. Pattern of R and R' seen in a patient with a QRS Complex duration less than 0.12 seconds
  6. Critical Rate
    1. Rate at which Bundle Branch Block is seen (may not be evident at slower rates)
  7. Intrinsicoid Deflection (R-Wave Peak Time)
    1. Time from QRS wave onset to peak R Wave (early ventricular depolarization)
  8. Aberrant Conduction
    1. May mimic Bundle Branch Block
    2. Results from a discrepancy between the refractory periods between each ventricle
      1. Refractory period is time in ventricle following depolarization where it will not respond to a new depolarization signal
      2. Refractory periods may be slightly different between the ventricles
      3. 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

  1. EKG findings
    1. Lead V1
      1. QS or rS
    2. Lead V6
      1. Late intrinsicoid deflection
      2. No Q Wave
      3. Monophasic R Wave
    3. Lead I
      1. Monophasic R Wave
      2. No Q Wave
  2. Causes
    1. Chronic Ischemic Heart Disease
    2. Chronic Hypertension (with Left Ventricular Hypertrophy)
    3. Chronic Congestive Heart Failure (abnormal ventricular remodeling)
    4. Valvular heart disease
    5. Old age with a fibrotic conduction system
    6. Massive acute Myocardial Infarction
      1. See New Left Bundle Branch Block
      2. See Sgarbossa Criteria
  3. References
    1. Mattu and Herbert in Majoewksy (2012) EM:Rap 12(11): 4

IV. Findings: Right Bundle Branch Block EKG (RBBB)

  1. EKG Findings
    1. Lead V1
      1. Late Intrinsicoid Deflection (long duration from QRS start to R-wave peak time)
      2. M-shaped QRS Complex ("Rabbit Ears")
      3. Wide R Wave or qR (occasionally)
      4. Tall R Wave in Lead V1
    2. Lead V6
      1. Early Intrinsicoid Deflection (short duration from QRS start to R-wave peak time)
      2. Wide S wave
    3. Lead I
      1. Wide S wave
  2. Precautions
    1. Mild ST segment Depression or T Wave Inversion in right precordial leads may be seen in normal RBBB
      1. However, ST or T Wave changes in other leads is considered abnormal
  3. Mechanism of RBBB
    1. Most of right bundle branch is subendocardial and susceptible to stretch and other Trauma
  4. Causes: Important
    1. Increased right ventricular pressure
      1. Pulmonary Embolism
      2. Cor Pulmonale (May be accompanied by Right Ventricular Hypertrophy if long standing)
    2. Acute myocardial injury
      1. Myocardial Ischemia or infarction
      2. Inflammation (e.g. Myocarditis)
      3. Chest Trauma
    3. Electrolyte disturbance
      1. Hyperkalemia
  5. Causes: Miscellaneous
    1. Hypertension
    2. Cardiomyopathy
    3. Congenital Heart Disease
    4. Right heart catheterization related injury
    5. Right heart fibrosis (Lev's Disease, Lenegre's Disease)

V. Findings: Left Hemiblocks (left Fascicular Block)

  1. Left Anterior Hemiblock EKG (Left Anterior Fascicular Block or LAFB)
    1. Left Axis Deviation (beyond -60 degrees)
    2. Small Q Wave in Lead I and aVL may be present (qR pattern)
    3. Small R Wave in Lead II and III (rS pattern)
    4. Normal QRS Duration (unless concurrent Right Bundle Branch Block, bifascicular block)
    5. No Right Ventricular Hypertrophy
  2. Left Posterior Hemiblock EKG (Left Posterior Fascicular Block or LPFB)
    1. Right Axis Deviation (beyond +120 degrees)
    2. Small R Wave in Lead I
    3. Small Q Wave in Lead III
    4. Normal QRS Duration (unless concurrent Right Bundle Branch Block, bifascicular block)
    5. No Right Ventricular Hypertrophy

VI. References

  1. Dubin (1974) Rapid Interpretation of EKGs, COVER publishing, Tampa, p. 137-47

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Bundle-Branch Block (C0006384)

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
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