ECG interpretations

Question 1

Right bundle branch block - characteristic ECG findings

Answer 1

WIDE QRS COMPLEX (>120ms)

M wave in V1
W wave in V6

remember - William Marrow

Question 2

Left bundle branch block - characteristic ECG findings

Answer 2

WIDE QRS COMPLEX (>120ms)

W wave in V1
M wave in V6

remember - William Marrow

Question 3

True or false - a new left bundle branch block is always pathological

Answer 3

TRUE

Question 4

What are the possible causes of left bundle branch block?

Answer 4

• aortic stenosis
• ischaemic heart disease
• hyperkalaemia
• digoxin toxicity
• myocardial infarction
• hypertension
• cardiomyopathy

Question 5

What are the possible causes of right bundle branch block?

Answer 5

	normal (especially with increasing age)
	right ventricular hypertrophy 
	cor pulmonale 
	pulmonary embolism
	ischaemic heart disease
	myocardial infarction 
	atrial septal defect 
	cardiomyopathy or myocarditis

Question 6

Atrioventricular block - characteristic ECG findings in first degree AV block AND what needs to be done to manage it

Answer 6

Consistent prolonged PR interval (>200ms/5sqs)

No management

Question 7

Atrioventricular block - characteristic clinical/ECG findings in second degree mobitz I AND what needs to be done to manage it

Answer 7

Progress prolonged PR interval, until QRS is missed (dropped beat) – PR interval longest before dropped beat

(Long, long, drop)

Regularly irregular rhythm

No management (unless bradycardic then atropine)

Question 8

Atrioventricular block - characteristic clinical/ECG findings in second degree mobitz II AND what needs to be done to manage it

Answer 8

QRS regularly missed, consistent PR interval duration, regularly irregular rhythm

(Normal, normal, drop)

Regularly irregular rhythm

Consider interim atropine
Permanent pacemaker

Question 9

Atrioventricular block - characteristic clinical/ECG findings in complete heart block

Answer 9

Severely bradycardic
May also have cannon A waves

Complete AV dissociation
(most commonly due to RCA occlusion)

Permanent pacemaker

Question 10

Atrial fibrillation - characteristic ECG findings

Answer 10

Irregularly irregular pulse
Absent A wave in JVP

Absent P waves
Irregular QRS complex
Chaotic baseline

Question 11

Paroxysmal SVT - characteristic ECG findings

Answer 11

HR 140-280bpm

P waves often unidentifiable/not visible

Regular narrow QRS complex (QRS<120ms)
UNLESS SVT w/BBB then wide QRS complex (QRS>120ms)

Question 12

Ventricular tachycardia - characteristic ECG findings

Answer 12

wide complex tachycardia (>120ms) at a rate of ≥100bpm

monomorphic - commonly caused by MI

polymorphic + subtype torsades de pointes

cannon A waves in JVP

Question 13

Ventricular fibrillation - characteristic ECG findings

Answer 13

Chaotic irregular deflections of varying amplitude – polymorphic and irregular

No identifiable/clear P waves, QRS complexes or T waves

Rate 150 – 500 bpm

Amplitude decreases with duration

Question 14

Paroxysmal SVT - how do patients classically present

Answer 14

Palpitations is the MAIN symptom - usually they are otherwise well (haemodynamically stable)

Subsequently usually find a high HR (140-280bpm)

Question 15

Hypokalaemia - causes

Answer 15

• Excess alcohol
• Excessive laxative use +/- Diarrhoea
• Diuretics use (especially potent diuretics like furosemide)

Question 16

Hypokalaemia - ECG findings

Answer 16

• U waves
• small or absent T waves (occasionally inversion)
• prolong PR interval
• ST depression
• long QT

Question 17

Pulmonary embolism - ECG findings

Answer 17

inverted T waves
right bundle branch block
right axis deviation

Question 18

Cor pulmonale - ECG findings

Answer 18

right axis deviation
right bundle branch block
increased P wave amplitude