ECG

Question 1

Myocardial ischaemia ECG features

Answer 1

• A prolonged PR interval
• A long QT interval
• Right bundle branch block
• Right axis deviation
• Peaked T waves
• Inverted T waves
• Left bundle branch block
• ST depression
• ST elevation

Question 2

Causes of ST-segment elevation

Answer 2

• STEMI
• LV aneurysm
• Takotsubo (stress) cardiomyopathy
• Coronary vasospasm (Prinzmetal angina)
• Acute stroke
• Early repolarisation
• Pericarditis (saddle shaped)
• During angioplasty
• Non-standard ECG acquisition settings (eg on monitor)
• Normal variant - ‘high take-off’
• Subarachnoid haemorrhage

Link

Question 3

Lengthens QT interval

Answer 3

Congenital:

• Jervell-Lange-Nielsen syndrome (includes deafness and is due to an abnormal potassium channel),
• Romano-Ward syndrome (no deafness)

Drugs:

• amiodarone,
• sotalol,
• class 1a antiarrhythmic drugs,
• tricyclic antidepressants,
• selective serotonin reuptake inhibitors (especially citalopram),
• methadone,
• chloroquine,
• erythromycin,
• haloperidol,
• ondansetron

Others:

• electrolyte disturbances (hypocalcaemia, hypokalaemia, hypomagnesaemia),
• acute myocardial infarction,
• myocarditis,
• hypothermia,
• subarachnoid haemorrhage

MCQs

Question 4

Short QT interval

Answer 4

• Hypercalcaemia
• Digoxin toxicity
• Hyperkalemia
• Hyperthermia
• Acidosis
• Effect of catecholamine
• Activation of ATP-sensitive potassium current
• Activation of acetylcholine-sensitive potassium current
• Effects of drugs like digitalis
• Myocardial ischemia
• Increased vagal tone

Question 5

Prolonged PR interval

Answer 5

• Idiopathic
• Ischaemic heart disease
• Digoxin toxicity
• Hypokalaemia
• Rheumatic fever
• Aortic root pathology e.g. abscess secondary to endocarditis
• Lyme disease
• Sarcoidosis
• Myotonic dystrophy

Note: no hypocalcemia

Question 6

Short PR interval

Answer 6

• Wolff-Parkinson-White (WPW) syndrome

Question 7

Inverted T waves

Answer 7

• Myocardial ischaemia
• Digoxin toxicity
• Subarachnoid haemorrhage
• Arrhythmogenic right ventricular cardiomyopathy
• Pulmonary embolism (‘S1Q3T3’)
• Brugada syndrome

Question 8

Peaked T waves

Answer 8

• Hyperkalaemia
• Myocardial ischaemia

Question 9

Causes of ST depression

Answer 9

• Secondary to abnormal QRS (LVH, LBBB, RBBB)
• Ischaemia
• Digoxin
• Hypokalaemia
• Syndrome X

Question 10

Causes of LBBB

Answer 10

• Ischaemic heart disease
• Hypertension
• Aortic stenosis
• Cardiomyopathy
• Rare: idiopathic fibrosis, digoxin toxicity, hyperkalaemia

Question 11

Causes of RBBB

Answer 11

• Normal variant - more common with increasing age
• Right ventricular hypertrophy
• Chronically increased right ventricular pressure - e.g. cor pulmonale
• Pulmonary embolism
• Myocardial infarction
• Atrial septal defect (ostium secundum)
• Cardiomyopathy or myocarditis
• According to OE both primum & secundum cause RBBB

Question 12

Causes of left axis deviation (LAD)

Answer 12

• Left anterior hemiblock
• Left bundle branch block
• Wolff-Parkinson-White syndrome (right-sided accessory pathway)
• Hyperkalaemia
• Congenital: ostium primum ASD, tricuspid atresia
• Minor LAD in obese people

Question 13

Causes of right axis deviation (RAD)

Answer 13

• Right ventricular hypertrophy
• Left posterior hemiblock
• Chronic lung disease → cor pulmonale
• Pulmonary embolism
• Ostium secundum ASD
• Wolff-Parkinson-White syndrome (left-sided accessory pathway)
• Normal in infant < 1 years old
• Minor RAD in tall people

Question 14

Causes of RBBB + RAD

Answer 14

• Right ventricular hypertrophy
• Pulmonary embolism
• Cor pulmonale
• Ostium secundum ASD

Question 15

Causes of RBBB + LAD

Answer 15

• Ostium primum ASD

Question 16

Causes of tall R waves in V1

Answer 16

• Right ventricular hypertrophy (myriad causes)
• RBBB
• Posterior infarction
• Dextrocardia
• WPW syndrome with left ventricular pathway insertion (often referred to as type A)
• HCM (septal mass greater than posterior wall).

Question 17

Specific features of pericarditis on ECG

Answer 17

• Diffuse St elevation
• PR segment depression
• No reciprocal changes

Question 18

Right ventricular hypertrophy ECG features

Answer 18

• Right axis deviation
• Right bundle branch block

Question 19

Cor pulmonale (ECG)

Answer 19

• Increased P wave amplitude
• Right bundle branch block
• Right axis deviation

Question 20

Digoxin toxicity (ECG)

Answer 20

• a short QT interval
• ST depression
• a prolonged PR interval
• inverted T waves