Arrythmias ☺️

Question 1

What are the types of AV block

How would you differentiate between them on an ECG

Answer 1

1st degree AV block
-elongated PR interval due to DELAY through AV node

2nd degree AV block

• failure to conduct an impulse => skipped QRS
• Wenckebach - PR gets progressively longer until QRS lost
• Mobitz II - repeated pattern between normal beats and loss of QRS

3rd degree AV block

• no coordination between atria and ventricles, distal slower pacemakers take over
• P and QRS are not coordinated

Question 2

How would you manage AV heart block

Answer 2

Asymptomatic 1st degree or Wenckebach => monitoring for progressions

Symptomatic 1st degree or Wenckeback, Mobitz II, 3rd degree

• risk and benefit of discontinuing causative medications
• may consider PPM with or without an ICD

Question 3

What is atrial fibrillation

• causes and pathophysiology
• signs
• investigations

Answer 3

Damage to the atria is the most common cause => multiple rotating electrical impulses bombard the AV with many signals

• not all signals result in QRS => irregularly irregular
• paroxysmal <=> persistent

Palpitations, SOB, chest pain, fatigue, dizziness
-Irregularly irregular HR

FBC => non cardiac causes (anemia, infection)
Electrolytes U&E => assess for CKD and K abnormalities
TFTs => thyrotoxicosis can cause AF
ECG => f waves, no p waves with irregular QRS
TnT => assess for MI
Assess for causative elements that need urgent treatment
CXR => assess for other cardiac, pulmonary causes of presentation
Echo => visualise abnormal movement

Question 4

How would you manage AF

• drugs
• lifestyle

Answer 4

Rate control - AVN blocker

• Bb (bisoprolol) or
• nonDHP CCB (diltiazem, verapamil)

Use CHA2DS2VASc score to consider stroke risk
Use HAS-BLED to assess bleed risk

Lifestyle changes to reduce CV risk

• physical activity
• weight loss
• alcohol reduction

Anticoagulation Bb CCB, Digoxin, Electrocardioversion

Question 5

How do these antiarrythmic drugs work
-Class I
-Class II
-Class III
-Class IV
-Class V
What are some examples

Answer 5

Class I => Na block (rhythm)

• Decrease excitability of membrane
• Quinidine, lidocaine

Class II => Bb (rate)

• Decrease conduction via AVN => decrease HR and contractility
• bisoprolol, propranolol

Class III => K block (rhythm)

• Prolong repolarisation to prevent reentrant arrythmias
• Amiodarone, soltalol

Class IV => Ca block (rate)
-Decrease conduction via AVN and shorten action potential => retains HR and
contractility
-Diltiazem - peripheral and coronary VD
-Verapamil - K blocker to prolong repolarisation

Class V => other

• Digoxin - decrease AVN conduction, increase vagus
• Adenosine - decrease AVN conduction, K efflux Ca inh => prolong repolarisation

Question 6

What is the

• cause and pathophysiology
• signs
• investigations for ventricular tachycardia

Answer 6

Any heart conditions (CHD, cardiomyopathy, MI) that result in ventricular scarring 
-ectopic PM
-reentry
Or electrolyte abnormalities
FAST REGULAR RHYTHM

Chest pain, palpitations, SOB, dizziness, heart failure

• may or may not have CO
• fast regular rhythm

ECG => wide QRS, tachycardia (monomorphic or polymorphic)
Electrolytes => assess for K imbalances
TnT => assess for MI
Echo => image abnormal heart movement

Question 7

How would you manage ventricular tachycardia

• electrical
• medication
• surgical

Answer 7

Cardioversion => synchronised on R wave for unstable tachyarrythmias
-if patient has a pulse

Defibrillation => not synchronised shock
-if pulseless

Medication => may consider antiarrythmics (Bb, Ca)

Surgical

• ICD implantation
• catheter ablation

Question 8

What is the

• cause and pathophysiology
• signs
• investigations for ventricular fibrillation

Answer 8

Chaotic multiple impulses spreading through ventricles due to scarring
FAST IRREGULAR RHYTHM

Chest pain, rapid heartbeat, SOB, dizziness
Hypotensive => cardiac arrest

ECG => no QRS, chaotic activity

Question 9

How would you manage ventricular fibrillation

• medical stabilisation
• maintenance

Answer 9

Medical stabilisation
-CPR, defibrillation

Maintenance
-ICD insertion

Question 10

What is 3rd degree heart block

• pathophysiology
• causes
• signs
• investigations

Answer 10

Dissociation of atrial and ventricular depolarisation due to faulty AV conduction
-distal pacemakers take over

Inferior MI
AV blocking drugs

Bradycardia
Dizzy, faint, SOB, fatigue
Chest pain

Diagnostic => ECG
-p waves and QRS complexes are dissociated from each other
TnT for evidence of current MI

Question 11

Most common cause of sudden cardiac death

Answer 11

Coronary artery disease