ECG changes

Question 1

What are causes of LAD?

Answer 1

1. left anterior hemiblock
2. left bundle branch block
3. inferior myocardial infarction
4. Wolff-Parkinson-White syndrome* - right-sided accessory pathway
5. hyperkalaemia
6. congenital: ostium primum ASD, tricuspid atresia
7. minor LAD in obese people

Question 2

What are causes of RAD?

Answer 2

1. right ventricular hypertrophy
2. left posterior hemiblock
3. lateral myocardial infarction
4. chronic lung disease → cor pulmonale
5. pulmonary embolism
6. ostium secundum ASD
7. Wolff-Parkinson-White syndrome* - left-sided accessory pathway
8. normal in infant < 1 years old
9. minor RAD in tall people

*in the majority of cases, or in a question without qualification, Wolff-Parkinson-White syndrome

Question 3

What is a bifascicular block?

Answer 3

• combination of RBBB with left anterior or posterior hemiblock
• e.g. RBBB with left axis deviation

Question 4

What is trascicular block?

Answer 4

• features of bifascicular block + 1st-degree heart block

ECG showing trifascicular block: RBBB + left anterior hemiblock + 1st-degree heart block

Question 5

Correlation between ECG changes and coronary territories?

Answer 5

Question 6

What does a new LBBB indicate?point towards a diagnosis of acute coronary syndrome.

Answer 6

Point towards a diagnosis of acute coronary syndrome.

Question 7

What does digoxin show on ECG?

Answer 7

1. down-sloping ST depression (‘reverse tick’)
2. flattened/inverted T waves
3. short QT interval
4. arrhythmias e.g. AV block, bradycardia

Question 8

What does hypokalaemia show on ECG?

Answer 8

1. U waves
2. small or absent T waves (occasionally inversion)
3. prolong PR interval
4. ST depression
5. long QT

In Hypokalaemia, U have no Pot and no T, but a long PR and a long QT

ECG shows typical U waves. Note also the borderline PR interval.

Question 9

What does hypothermia show on an ECG?

Answer 9

1. bradycardia
2. ‘J’ wave - small hump at the end of the QRS complex
3. first degree heart block
4. long QT interval
5. atrial and ventricular arrhythmias

Question 10

How do you differentiate between LBBB and RBBB?

Answer 10

One of the most common ways to remember the difference between LBBB and RBBB is WiLLiaM MaRRoW

• in LBBB there is a ‘W’ in V1 and a ‘M’ in V6
• in RBBB there is a ‘M’ in V1 and a ‘W’ in V6

Question 11

What are causes of LBBB?

Answer 11

Causes of LBBB

1. Ischaemic heart disease
2. Hypertension
3. Aortic stenosis
4. Cardiomyopathy
5. Rare: idiopathic fibrosis, digoxin toxicity, hyperkalaemia

New LBBB is always pathological and may be a sign of a myocardial infarction. Diagnosing a myocardial infarction for patients with existing LBBB is difficult.

Question 12

What are the ECG changes seen in acute MI?

Answer 12

1. Hyperacute T waves are often the first sign of MI but often only persists for a few minutes
2. ST elevation may then develop
3. T waves typically become inverted within the first 24 hours. The inversion of the T waves can last for days to months
4. Pathological Q waves develop after several hours to days. This change usually persists indefinitely

Question 13

What is the definition of ST elevation?

Answer 13

• new ST elevation at the J-point in two contiguous leads with the cut-off points:
  
  • >=0.2 mV in men or >= 0.15 mV in women in leads V2-V3 and/or >= 0.1 mV in other leads

Question 14

What are normal ECG variants?

Answer 14

1. Sinus bradycardia
2. Junctional rhythm
3. First degree heart block
4. Wenckebach phenomenon

Question 15

What does increased P wave amplitude indicate?

Answer 15

cor pulmonale

Question 16

What does a prolonged PR interval indicate?

Answer 16

1. Idiopathic
2. Ischaemic heart disease
3. Digoxin toxicity
4. Hypokalaemia*
5. Rheumatic fever
6. Aortic root pathology e.g. abscess secondary to endocarditis
7. Lyme disease
8. Sarcoidosis
9. Myotonic dystrophy
10. In athletes

Question 17

What does a short PR interval indicate?

Answer 17

Wolff-Parkinson-White syndrome

Question 18

What are the casues of RBBB?

Answer 18

1. Normal variant - more common with increasing age
2. Right ventricular hypertrophy
3. Chronically increased right ventricular pressure - e.g. cor pulmonale
4. Pulmonary embolism
5. Myocardial infarction
6. Atrial septal defect (ostium secundum)
7. Cardiomyopathy or myocarditis

Question 19

What are the causes of ST depression?

Answer 19

1. Secondary to abnormal QRS (LVH, LBBB, RBBB)
2. Ischaemia
3. Digoxin
4. Hypokalaemia
5. Syndrome X

Question 20

What are the causes of ST elevation?

Answer 20

1. Myocardial infarction
2. Pericarditis/myocarditis
3. Normal variant - ‘high take-off’
4. Left ventricular aneurysm
5. Prinzmetal’s angina (coronary artery spasm)
6. Takotsubo cardiomyopathy
7. Rare: subarachnoid haemorrhage

Question 21

What are causes of peaked T waves?

Answer 21

1. Hyperkalaemia
2. Myocardial ischaemia

Question 22

What are the causes of inverted T waves?

Answer 22

1. Myocardial ischaemia
2. Digoxin toxicity
3. Subarachnoid haemorrhage
4. Arrhythmogenic right ventricular cardiomyopathy
5. Pulmonary embolism (‘S1Q3T3’)
6. Brugada syndrome