ECG

Question 1

LBBB & RBBB

Answer 1

One of the most common ways to remember the difference between LBBB and RBBB is WiLLiaM MaRRoW
in LBBB there is a ‘W’ in V1 and a ‘M’ in V6
in RBBB there is a ‘M’ in V1 and a ‘W’ in V6

New LBBB is always pathological.

Causes of LBBB include:
myocardial infarction
diagnosing a myocardial infarction for patients with existing LBBB is difficult
rhe Sgarbossa criteria can help with this - please see the link for more details
hypertension
aortic stenosis
cardiomyopathy
rare: idiopathic fibrosis, digoxin toxicity, hyperkalaemia

Causes of RBBB
normal variant - more common with increasing age
right ventricular hypertrophy
chronically increased right ventricular pressure - e.g. cor pulmonale
pulmonary embolism
myocardial infarction
atrial septal defect (ostium secundum)
cardiomyopathy or myocarditis

Question 2

ECG: axis deviation

Answer 2

Causes of left axis deviation (LAD)
left anterior hemiblock
left bundle branch block
inferior myocardial infarction
Wolff-Parkinson-White syndrome* - right-sided accessory pathway
hyperkalaemia
congenital: ostium primum ASD, tricuspid atresia
minor LAD in obese people

Causes of right axis deviation (RAD)
right ventricular hypertrophy
left posterior hemiblock
lateral myocardial infarction
chronic lung disease → cor pulmonale
pulmonary embolism
ostium secundum ASD
Wolff-Parkinson-White syndrome* - left-sided accessory pathway
normal in infant < 1 years old
minor RAD in tall people