ECG Pathology

Question 1

What are the normal rangers for the following:
- PR interval,
- QRS,
- QT interval

Answer 1

• PR interval: <1 large square/200ms
• QRS: < 3 small squares/120ms
• QT interval < 11 small squares/440ms
• P waves are less than 0/25mv in height

Question 2

What is a good systematic approach to analysing an ECG

Answer 2

1. Check date, time, patient and artefact.
2. Look at rhythm strim for QRS rate and rhythm. Identify P waves, QRS and T waves.
3. Look at limb leads: Determine cardiac axis
4. Look across all leads

Or ARIBAR - Any electrical activity, Rate, Irregular/regular, Broad QRS, Are there P waves and Relationship between P waves and QRS

Question 3

What are the possible differential diagnoses for a regular broad complex tachycardia

Answer 3

1. VT,
2. SVT with BBB
3. SVT conducted over an AP,
4. Ventricular pacing

Question 4

Describe ECG features of a Left BBB

Answer 4

• QRS > 120ms
• Dominant S wave seen in V1 (W-shape)
• Broad, notches R wave (M-shaped)

Question 5

Describe the ECG features of a Right BBB

Answer 5

• QRS > 120ms
• RSR’ pattern seen in V1-3 which gives M-shape
• Wide slurred S wave seen in leads I, aVL, V5-V6 (looks like mini W at top of S wave)

Question 6

Describe presentation of right axis deviation on an ECG

Answer 6

• QRS is positive in leads II, III and aVF.
• QRS is negative in lead** I** (S wave is dominant)
• The axis was Left Two the Right One. So if lead I is negative then its RAD but if lead II is negative then its LAD

Question 7

Describe features of a left axis deviation

Answer 7

• QRS is positive in lead I (R wave is dominant)
• QRS is negative in leads II, III and aVF

The axis was Left Two the Right One

Question 8

Describe appearence of P Mitrale on an ECG

Answer 8

Bifid P waves associated with left atrial hypertrophy

Question 9

Describe the appearence of P Pulmonale on an ECG

Answer 9

Peaked P waves associated with right atrial hypertrtophy

Question 10

What valves close at the 1st and 2nd heart sounds?

Answer 10

1st heart sound - Closure of mitral and tricuspid.
2nd heart sound - Closure of aortic and pulmonary values.

Question 11

What is the most common cause of left axis deviation?

Answer 11

Defects in the conduction system

Question 12

What can cause a low voltage QRS?

Answer 12

• Hypothyroidism,
• COAD,
• Myocarditis
• Pericarditis and pericardial effusion

Question 13

What is the appearence of a left ventricle hypertrophy on an ECG?

Answer 13

Left - R wave in V5 is >25mm

Question 14

What are some causes of a prolonged QT interval

Answer 14

• Acute myocardial ischaemia,
• Bradycardia,
• Myocarditis,
• Head injury,
• Hypothermia,
• U+E imbalance,
• Congenital
• Drugs eg, quinidine, antihistamines

Question 15

How does digoxin toxicity present?

Answer 15

T wave inversion and ST segment sloping depression

Question 16

What is the appearence of hyper/hypo-kalaemia on an ECG?

Answer 16

Hyper - Tall, tented T waves and widened QRS
Hypo - Small T waves and prominant U waves

Question 17

How does hyper/hypo-calcaemia present on an ECG?

Answer 17

Hyper - Short QT,
Hypo - Long QT

Question 18

In what rhythms are P waves absent?

Answer 18

• Atrial fibrillation,
• Junctional bradycardia