The Electrocardiogram: Basic Concepts and Lead Monitoring

Question 1

Normal QRS Axis

Answer 1

• Left Lower Quadrant: between -30 and 90 degrees
• aVF positive
• Lead I positive

Question 2

Left Axis Deviation (LAD)

Answer 2

• Any axis deviation in the left upper quadrant. Between 0 and -90 degrees.
• aVF negative
• Lead I positive

Question 3

Right Axis Deviation (RAD)

Answer 3

• Any axis deviation in the right lower quadrant. Between 90 and 180 degrees.
• aVF positive
• Lead I negative

Question 4

Indeterminate Axis

Answer 4

• Also known as Extreme RAD or “no mans land”
• aVF negative
• Lead I negative

Question 5

List the cardiac and pulmonary causes of left axis deviation (LAD)

Answer 5

• left anterior hemiblock
• Q waves of inferior myocardial infarction
• artificial cardiac pacing
• emphysema
• hyperkalaemia
• Wolff-Parkinson-White syndrome - right sided accessory pathway
• tricuspid atresia
• ostium primum ASD
• injection of contrast into left coronary artery

note: left ventricular hypertrophy is NOT a cause left axis deviation

Question 6

List the cardiac and pulmonary causes of right axis deviation (RAD)

Answer 6

• (RAD is a normal finding in children and tall thin adults)
• right ventricular hypertrophy
• chronic lung disease even without pulmonary hypertension
• anterolateral myocardial infarction
• left posterior hemiblock
• pulmonary embolus
• Wolff-Parkinson-White syndrome - left sided accessory pathway
• atrial septal defect
• ventricular septal defect