ECG axis and hypertrophy

Question 1

What is the normal Heart axis?

Answer 1

90 to -30 degrees

Question 2

How do you quickly determine if heart axis is normal?

Answer 2

Check for positive QRS in Lead I and AvF

If AvF is negative, a positive II lead means the axis is still normal, but between 0 and -30 degrees

Question 3

How can you define the axis precisely?

Answer 3

Look for the limb lead with the most biphasic QRS. The axis is aproximately perpendicular to this.

I.e if it is most biphasic in lead I (0). Then the the axis must be +/- 90 degrees.

Question 4

What is the normal P wave axis?

Answer 4

0 - 70

0-90 in children

Question 5

What is the normal T-wave axis?

Answer 5

Within 50-60 degrees of the QRS axis

Question 6

What can be the cause of left axis deviation?

Answer 6

Left ventricular hypertrophy

Question 7

What can be the cause of right axis deviation?

Answer 7

Huge right ventricular hypetrophy

• (COPD -> pulm. hypertension)
• Congenital with big pressure overload of RV

Question 8

What are three signs of enlargement/hypertrophy?

Answer 8

1. Increased wave duration
2. Increased wave amplitude
3. Axis deviation

Question 9

What are ECG signs of right atrial enlargement?

Answer 9

Right axis deviation of the P wave
Tallest P no longer in II, but aVF or III

Diagnostic: P wave > 2,5mm in at least one inf. leads

P pulmonale (severe lung disease common cause)

Question 10

How do you diagnose LA enlargement?

Answer 10

Terminal part of P wave drop more than 1mm below isoelectric line in V1 + at least 0.04 s duration

(No axis deviation - LA is normally dominant)

P mitrale (mitral valve disease is common cause)

Question 11

What is two simple criteria for diagnosing RV hypertrophy, looking at V1 and V6?

Answer 11

V1: R > S wave
V6 S > R wave

also QRS axis should be > 100

Question 12

What are the two most common causes of RV hypertrophy?

Answer 12

Pulmonary disease

Congenital heart disease

Question 13

What are four criterias in the precordial leads for diagnosing LV hypertrophy?

Answer 13

1. R amplitude in V5 or V6 + S amplitude in V1 or V2 > 35mm
2. R amplitude in V5 > 26 mm
3. R amplitude in V6 >20 mm
4. R amplitude in V6 > V5

Question 14

What are four criterias in the limb leads for diagnosing LV hypertrophy?

Answer 14

1. R amplitude in aVL > 11 mm
2. aVF > 20 mm
3. lead I > 13 mm
4. R amp in I + S amp in III > 25 mm

Question 15

What is the most aacurate criteria for diagnosing LV hypetrophy, combining limb and precordial leads?

Answer 15

Cornell criteria:

R amplitude in aVL + S amplitude in V3
> 20 in women
> 28 in men

Question 16

What the top 2 causes of LV hypertrophy?

Answer 16

systemic hypertension

valvular disease

Question 17

What happens to the duration of the QRS complex in ventricular hypertrophy?

Answer 17

May be slightly prolonged, but rarely beyond 0.1 s

Question 18

What secondary repolarization changes can be seen in ventricular hypertrophy?

Answer 18

1. downsloping ST segment depression
2. T - wave inversion ( T axis different from QRS)

RV - seen in V1/V2
LV -I, AvL, V5, V6 - more common

Repolarization abnormalities usually accompany severe hypertrophy