RBBB is characterized by a QRS duration ≥0.12s with an RSR' pattern in V1 and a wide S wave in V6. Causes include myocardial infarction, cardiomyopathy, and pulmonary embolism. LBBB has a QS or rS pattern in V1 and a late intrinsicoid deflection in V6. It is associated with ischemic heart disease and cardiomyopathy. New onset LBBB alone is no longer considered a STEMI equivalent. The Sgarbossa criteria help identify MI in the presence of LBBB. Left anterior and posterior fascicular blocks involve specific QRS and axis changes and help localize conduction system disease. Trifascicular block represents complete heart block with bifascicular

1. BUNDLE BRANCH BLOCKS
DR.SONU KURIAN
MODERATOR:DR.MAHIM MITTAL MD

2. REFERENCES
• MARRIOT’S PRACTICAL ECG 12TH ED
• LEO SCHAMROTH’S INTRODUCTION TO ECG
7TH ED

3. Normal Electrical Conduction

4. Right bundle branch
• 40 mm long
• Conduction Velocity 2m/s
• 1cm increase conduction time increase 5ms

5. BLOOD SUPPLY
• SEPTAL BRANCHES OF LAD (90%)
• RBB,LAF
• RCA VIA AV NODAL ARTERY(90%)
• LPF
• DUAL SUPPLY TO LPF IN 40-50%

6. NORMAL QRS
NORMAL DURATION OF
QRS: 0.08-0.12SEC

7. • BLOCK IN AV JUNCTION AFFECT PR INTERVAL
• BLOCK IN BUNDLES AFFECT THE QRS
DURATION
• NORMAL DURATION OF QRS: 0.08-0.12SEC

9. RBBB
R’
s
s
r

10. RBBB
• QRS duration ≥ 0.12 s
• Lead V1 –
Late intrinsicoid(R’ peak or late R peak)
M –shaped QRS(RSR’)
Sometimes wide R or qR
• Lead V6 –
Early intrinsicoid (R peak)
Wide S wave
• Lead I-
Wide S wave

11. RIGHT BUNDLE BRANCH BLOCK
COMPLETE
• DURATION > 120MS
• rsR PATTERN IN V1 WITH
R’>r
• SLURRED S WAVE IN I & V6
INCOMPLETE
• DURATION 100-120MS
• WITH EITHER OF
• DIMINUTION OF S WAVE V2
• SLURRING UPSTROKE OF S
V2
• r’ /R’ IN V2

12. RBBB

13. Causes of RBBB
• Can be seen as a normal finding in absence of
heart disease
• In acute anterior MI –Proximal coronary artery
lesion-poor prognosis
• Cardiomyopathy
• ASD Primum ASD –LAD+ rSR’ pattern
• Secundum ASD –RAD+ rSR’ pattern
• Acute Pulmonary embolism

14. LBBB

15. LBBB
CONVENTIONAL CRITERIA
• Lead V1: QS or Rs
• Lead V6: Late intrinsicoid (R or R’ peak),
No Q waves, monophasic R
• Lead I : Monophasic R wave ,No Q

16. STRICT CRITERIA
• QRS duration ≥ 0.13 s IN WOMEN OR
≥ 0.14 s IN MEN
• Lead V1 – QS or rS
• Mid QRS notching in two of the leads
I,aVL,V1,V2,V5 or V6
LBBB

17. ST T CHANGES IN LBBB
IMPORTANT NOTE
• ST SEGMENT AND T WAVE ARE IN OPPOSITE
DIRECTIONS TO TERMINAL QRS DEFLECTION

18. LBBB

19. INCOMPLETE LBBB
• EARLIEST CHANGE:
DISAPPEARANCE OF INITIAL
q WAVE OF QR COMPLEX IN LEFT LEADS
TALL R
• SMALL INITIAL R WAVE IN RIGHT LEADS
DISAPPEAR QS COMPLEX

20. INCOMPLETE LBBB

21. CAUSES OF LBBB
• IHD
• CARDIOMYOPATHY
• HYPERTENSIVE HEART DISEASE
• ACUTE MI-can be the presenting ecg change
• Aortic stenosis
• INTRINSIC DISEASES OF CONDUCTION SYSTEM-
Primary degenerative disease (fibrosis) of the
conducting system (Lenegre disease)
• Digoxin toxicity

22. LVH IN LBBB
• BY KLEIN AND COLLEAGUES
• S WAVE IN V2+ R WAVE IN V6>45mm
• ie , V2 S+ V6 R>45mm
• Evidence of left atrial enlargement with QRS
complex>0.16s

23. NEW ONSET LBBB=> ???MI
• In 2013, the American College of Cardiology Foundation and
the American Heart Association (ACCF/AHA) revised the
electrocardiographic definition of ST elevation myocardial infarction
(STEMI) to: “new ST elevation at the J point in at least 2 contiguous leads
of ≥ 2 mm (0.2 mV) in men (≥ 2.5 mm in men under 40 years old) or ≥ 1.5
mm (0.15 mV) in women in leads V2–V3 and/or of ≥ 1 mm (0.1 mV) in
other contiguous chest leads or the limb leads.”2 In the updated
guidelines, a presumably new left bundle
branch block (LBBB) in isolation is no
longer considered STEMI equivalent.
Moreover, the American College of Cardiology (ACC) emphasized that AMI
is a syndrome, a constellation of clinical findings, including but not limited
to findings on the 12-lead ECG that are concerning for an acute infarct, but
also including the subsequent release of biomarkers indicative of
myocardial necrosis.

24. MI IN PRESENCE OF LBBB
SGARBOSSA’S
CRITERIA

25. MI IN LBBB-Sgarbossa criteria
• ST segment elevation≥1mm and concordant
with a predominantly positive QRS complex(5)
• ST segment depression ≥1mm in leads V1,V2
or V3(3)
• ST segment elevation≥5mm and discordant
with a predominantly negative QRS
complex(2)
• >3 predicts >90% specificity of predicting MI

26. Modified Sgarbossa Criteria
• A. ≥ 1 lead with ≥1 mm of concordant ST
elevation
• B. ≥ 1 lead of V1-V3 with ≥ 1 mm of
concordant ST depression
• C. ≥ 1 lead anywhere with ≥ 1 mm STE and
proportionally excessive discordant STE, as
defined by ≥ 25% of the depth of the
preceding S-wave.
• Any of above three  STEMI equivalent

27. SGARBOSSA A

28. SGARBOSSA A

29. SGARBOSSA B

30. LBBB+AF

31. Why finding LBBB is significant in
cardiomyopathy???
In CM with LBBBCRT-biventricular pacing is
. indicated

32. LEFT BUNDLE AND FASCICLE

33. LEFT BUNDLE DIVIDES AS:
ANTEROSUPERIOR
• LONG ,THIN
• SINGLE BLOOD SUPPLY
• SEPTAL BRANCH OF LAD
WHICH ALSO SUPPLY RBB
• BLOCK:LAFB
POSTEROINFERIOR
• THICKER
• DUAL SUPPLY
• LAD+ AV NODAL ARTERY
• BLOCK:LPFB

34. LAFB
• Left axis deviation (usually ≥ -30°) !MCC!
• Small Q (qR complexes)in leads I and
aVL;small r(rS complexes)in II,III,aVF
• Minimal QRS prolongation (0.020s) from
baseline
• Late intrinsicoid (R wave peak) deflection in
aVL (>0.045s)
• Increased QRS voltage in limb leads

35. T wave changes -LAFB
• In any intraventricular conduction defect T
wave vector goes in opposite direction of main
QRS vector
• LAFB: T low or inverted in I ,aVL
T upright in II,III,aVF

36. LAFB
rS
qR
LAD

37. LAFB+LVH
• ECG S/O LAFB WITH
• S WAVE IN LEAD III > 1.5mm(0.15mV)
• Can also due to advanced LAFB

38. LPFB
• Right axis deviation(usually ≥ +120°)
• Small R in leads I and aVL(rS complexes);small
Q in II,III,aVF(qR complexes)
• Usually normal QRS duration
• Late intrinsicoid (R wave peak) deflection in
aVF (>0.045s)
• Increased QRS voltage in limb leads
• No evidence of RVH

39. T wave changes LPFB
• T inverted in II,III,aVF
• Upright T waves in lead I

40. LPFB

41. LAFB+RBBB
• Commoner than unifascicular LAFB
• S/O RBBB
• rS in II,III,aVF
• QRS Duration >0.12s
• QRS Axis: -45° to -120°(RAD)
• RAD+RBBB R/O LAFB+RBBB

42. RBBB+LAFB

43. LPFB+RBBB
Very rarely occurs
Consider only if no clinical e/o RVH
• V1 shows changes typical of RBBB
• I,aVL shows rS s/o LPFB
• Duration > 0.12s
• QRS Axis: should be > +90°

45. SEPTAL FASCICLE??
• BELIEVED TO BE RESPONSIBLE FOR INITIAL
LEFT TO RIGHT SEPTAL ACTIVATION
• INITIAL 35-40ms OF QRS COMPLEX

46. LSFB-LEFT SEPTAL FASCICULAR BLOCK
• QRS duration normal or minimally increased
• Normal QRS axis
• Prominent R waves in leads V1-V3
• Loss of septal q waves
• Initial q waves in lead V1 & V2

47. TRIFASCICULAR BLOCK
• RBB+ LAFB+ LPFB
OR
• AV NODAL BLOCK+ BIFASCICULAR
BLOCK

48. INCOMPLETE TRIFASCICULAR
• BIFASCICULAR BLOCK WITH EVIDENCE OF
DELAYED CONDUCTION IN AV NODE
• FIXED BLOCK OF ONE FASCICLE WITH
INTERMITTENT FAILURE OF OTHER TWO

49. Incomplete trifascicular block
• Bifascicular block + 1st degree AV block (most
common)
• Bifascicular block + 2nd degree AV block
• RBBB + alternating LAFB / LPFB

50. Incomplete Trifascicular Block:
• Right bundle branch block
• Left axis deviation (= left anterior fascicular
block)
• First degree AV block

51. Incomplete Trifascicular Block
• Right bundle branch block
• Left axis deviation (= left anterior fascicular block)
• First degree AV block
•

52. COMPLETE TRIFASCICULAR
• 3RD DEGREE AV BLOCK WITH FEATURES OF
BIFASCICLULAR BLOCK
• ESCAPE RHYTHM ARISES FROM LEFT
ANTERIOR OR POSTERIOR FASCICLE
PRODUCING QRS COMPLEXES WITH
APPEARANCES OF RBBB PLUS LAFB OR LPFB
RESPECTIVELY

53. COMPLETE TRIFASCICULAR BLOCK

54. ANY BROAD QRSCONDUCTION
DEFECT
• RBBB V1 RSR’
• LBBB 1, V6 M PATTERN ,NOTCHED
• LBBB IN MI-SGARBOSSA,
• LBBB +LVH V2S+V6R>45
• LAFB
• LPFB
• BIFASCICULAR RBBB+LADR/O RBBB+LAFB
• RBBB+RADR/O RBBB+LPFB
• TRIFASCICULAR