ECG Changes

Question 1

LBBB vs RBBB:
What are the causes of a LBBB?

What are the causes of a RBBB?

How can you distinguish between LBBB and RBBB on ECG?

Answer 1

➊ • AS
• IHD
• MI
• Hyperkalaemia
• Digoxin toxicity

➋ • PE
• RV hypertrophy
• IHD
• Congenital heart disease (ASD)

➌ WiLLaM MaRRoW:

LBBB - W shaped QRS in V1, and M shaped QRS in V6
RBBB - M shaped QRS in V1, and W/normal shaped QRS in V6

Question 2

Right Heart Strain:
What are its causes?

What ECG changes occur with it?

Answer 2

➊ PE
Pulmonary HTN
Chronic lung disease
Pulmonary stenosis
PTX

➋ • Sinus tachycardia (most common)
• RAD
• P Pulmonale - Big, tall, peaked P waves
• ST depression and T-wave inversion (V1-4 and III)
• RBBB

N.B. Can be remembered with S1Q3T3. S waves in Lead I, Q waves and T wave inversion in Lead III.