Bundle Branch Block

Question 1

What is Bundle Branch Block?

Answer 1

-electrical signal from the AV node gets blocked/delayed along one of the bundle branches in the ventricles.

Question 2

Aetiology

Answer 2

• Electrical impulses = heart contract
• Impulse begins at SAN and spread to bundle branches.
• So, if has an injury – could be after MI, heart signalling mechanism could be damaged.
• Causes for right bundle branch block (RBBB)-Left ventricle contracts then right ventricle:
   Myocarditis
   MI
   Congenital heart defects
   Pulmonary hypertension
   Pulmonary embolism (PE)
• Causes for left bundle branch block (LBBB)- right ventricle contracts then left ventricle.
   Cardiomyopathy
   Hypertension
   Myocarditis
   MI

Question 3

Pathophysiology

Answer 3

• Bundle branch blocks could occur due to damage (underlying heart disease, MI/heart surgery)
• Mechanism for ventricular depolarization changes due to this
• Electrical movement could be slowed down.
• Direction of impulses can be altered since electrical impulse is not travelling through the original route of bundle branches.

Question 4

Risk factors

Answer 4

• Age
• Underlying heart conditions (hypertension/heart disease)

Question 5

Signs/Symptoms

Answer 5

• Breathlessness
• Bradycardia
• Abnormal heartbeat

Question 6

Investigations

Answer 6

• ECG
• Echocardiogram
• Blood test

Question 7

Diagnosis

Answer 7

RBBB
- QRS longer than 120ms
- Lengthens final portion of QRS complex.
- Could slightly tilt electrical axis of heart to right.
- use other leads: difference between left and right.
- chest leads: v1-v6, v1 and v6 useful,
- v1, large terminal r wave
- v6= slurred, s wave = w shape

LBBB
- v1, w shape, QS (no r wave)/RS(small r wave) wave
- v6: m shape, notched because left ventricle depolarises late.

Question 8

Management

Answer 8

• pacemaker can be used to improve heart function