axis

Question 1

I + II + III or avF +

Answer 1

0-90+, normal axis

Question 2

I + II equiphasic III or avF -

Answer 2

Physiological LAD 0-(-30 deg)

Question 3

I + II - III or avF -

Answer 3

Pathological LAD (-30)-(-90) deg

Question 4

I - II + III or avF +

Answer 4

RAD +90 to +180 deg

Question 5

I - II - III or avF -

Answer 5

extreme R. axis deviation -90 to -180

Question 6

Causes of a RAD

Answer 6

1. If the QRS is predominantly negative in lead I and positive in lead aVF, then the axis is rightward (right axis deviation). The causes of RAD are listed below.
   
   1. Normal variant
   2. Right bundle branch block
   3. Right ventricular hypertrophy
   4. Left posterior fascicular block
   5. Dextrocardia
   6. Ventricular rhythms (accelerated idioventricular or ventricular tachycardia)
   7. Lateral wall myocardial infarction
   8. Wolff-Parkinson-White syndrome
   9. Acute right heart strain/pressure overload — also known as McGinn-White Sign or S1Q3T3 that occurs in pulmonary embolus

Question 7

Causes of a LAD

Answer 7

1. The causes of LAD are listed below. Note that the first three account for almost 90% of ECG tracings with LAD.
   
   1. Normal variant
   2. Left anterior fascicular block
   3. Left ventricular hypertrophy (rarely with LVH; usually axis is normal)
   4. Left bundle branch block (rarely with LBBB)
   5. Mechanical shift of heart in the chest (lung disease, prior chest surgery, etc.)
   6. Inferior myocardial infarction
   7. Wolff-Parkinson-White syndrome with “pseudoinfarct” pattern
   8. Ventricular rhythms (accelerated idioventricular or ventricular tachycardia)
   9. Ostium primum atrial septal defect