EKG Axis Deviation

Question 1

Term: average [mean] direction of depolarization [or vector] as QRS complex travels through the ventricles

Answer 1

Axis

Question 2

We care about abnormal axes because they can be suggestive of _____1_____. They do not absolutely ___2___ _3_ ____4____.

Answer 2

1. Disease
2. Rule
3. In
4. Conditions

Question 3

List the limb leads to examine to determine axis deviation (6)

Answer 3

I**

II

III

aVR

aVF**

aVL

** Focus for determination

** Need to determine if the lead is mostly upward or downward deflected

Question 4

Describe values for

1. Normal axis deviation
2. Left axis deviation
3. Right axis deviation

Answer 4

1. -30 to +90
2. More negative than - 30
3. More positive than +90

Question 5

List causes of right axis deviation (8)

Answer 5

1. Normal in children and tall thin adults
2. R ventricular hypertrophy
3. Chronic lung disease (w/ w/o pulmonary HTN)
4. Anterolateral myocardial infarction
5. L posterior hemiblock
6. Pulmonary embolus
7. Atrial septal defect
8. Ventricular septal defect

Question 6

List the causes of left axis deviation (7)

Answer 6

1. L anterior hemiblock
2. Q waves of inferior MI
3. Artificial cardiac pacing
4. Emphysema
5. Hyperkalaemia
6. Athletes [increased mm mass]
7. High BP [adapated to increased load > increased mm mass]

Question 7

Causes of extreme axis deviation (5)

Answer 7

1. Emphysema
2. Hyperkalemia
3. Lead transposition
4. Artifical cardiac pacing
5. Ventricular tachycardia

Question 8

List the 2 general methods to determine axis deviation

Answer 8

1. Mean QRS axis is midway b/t 2 leads that register tall R waves of equal amplitude
2. Mean QRS axis is directed at right angles to any extremity lead that has a biphasic isoelectric complex