Arrhythmia 2

Question 1

Describe what Vaughn Williams classification is?

Answer 1

Based on the electrophysiological properties:

1. Class 1: Sodium channel blockers
2. Class 2: Beta 2 blockers
3. Class 3: Amiodarone Drugs
4. Class 4: Calcium Channel Blockers

Question 2

Describe how the cardiac action potential works in phase 1 drugs?

Answer 2

1. Sodium channel blockers: Blocks the voltage gated sodium channels located in phase 0
2. Slows down the heart beat
3. Class 1b: lidocaine
   - Fast kinetics: block open channel during phase 0 reducing max depolarisation: dissociate before next beat

Question 3

Describe how the cardiac action potential works in phase 2 drugs?

Answer 3

1. Beta blockers: Block the effect of noradrenaline and adrenaline on the heart: prevent tachyarrhythmias
2. Affects phase 2 opening of L type calcium channels which reduces the force of contraction and slows heart rate
3. Affects phase 4 by reducing depolarisation

Question 4

Describe how the cardiac action potential works in phase 3 drugs?

Answer 4

1. Amiordarone like: Sotalol
2. Prolongs the refractory period that occurs in phase 3
3. Blocks the potassium channels in phase 3
4. Can lead to adverse effects such as prolonging the QT which may lead to pro arrhythmic effects
5. Also has class 2 effects of beta blockers

Question 5

Describe how the cardiac action potential works in phase 4 drugs?

Answer 5

1. Calcium channel blockers: Blocks the voltage gated calcium channels
2. Affects phase 2 by reducing the duration of its action potential
3. Slows the conduction in the sino-atrial node where activation depends on calcium entry (Verapamil is used for this)
4. Therefore leads to reduction in heart beat rate

Question 6

What are the two main anti-arrythmia drugs that aren’t classed by the Vaugh Williams classification?

Answer 6

1. Adenosine: used in SupraVentricularTachycardia
2. Digoxin: used in
   Atrial Fibrillation as it slows down the Atrial Ventricular Conduction

Question 7

What is the indication of digoxin and its mechanism of action?

Answer 7

1. Indication:
   Heart failure, Supraventricular arrhythmias, Especially (atrial fibrillation and atrial flutter)
2. Mechanism of action:
   Inhibits Na+/K+/ATPase to increase force of contraction and slow AV conduction

Question 8

Describe the non-pharmacological treatments of arrhythmias?

Answer 8

1. DC cardioversion
   - electronic paddles deliver waves of shock whilst under anaesthetic
2. Electronic pacemaker
   - Temporarily re-paces the heart (inserted permenantly) Bradyarrhythmias
3. Implantable fibrillator
   - Prevents ventricular tachycardia and ventricular fibrilation
4. Radiocatheter ablation
   - highly powered radio waves to smaller lesions that could cause tachyarrhythmias

Question 9

What are the four things that must be considered when managing arrhythmias narrow therapeutic drugs with therapy?

Answer 9

1. Eliminate cause
2. Make diagnosis
3. Determine baseline condition
4. Therapy necessary?

Question 10

Describe what supra ventricular atrial fibrillation is and what it can cause?

Answer 10

1. When the atrium beats faster than usual so the atrioventricular node cannot take all the impulses
2. Lead to pools of blood forming in the systemic circulation which leads to oedema and thrombotic events
3. Leading cause of stroke in the elderly

Question 11

What is the CHA2DS2-VASc score?

Answer 11

1. A test that’s done to assess a score

2. If you score 2 or more, anti-coagulant therapy is necessary

Question 12

How do you treat atrial ventricular fibrillation?

Answer 12

1. Rhythm control
   - Use Class 2: Beta blockers
   OR use class 4: Calcium channel blockers
   - Sedentary patients: (AVN) use digoxin
2. Rate control
   - Use Electrical cardioversion
   - Class III: amiloridone/ sotalol
3. Control of thromboembolism/ stroke
   - Eliminate the cause
   - Hyperthyroidism or previous MI

Question 13

How do you treat supra ventricular atrial flutter?

Answer 13

1. Intermediate events needed to control ventricular rate
2. Class 2 or 4 (verapamil)
3. Intravenous for rapid control
4. Conversion to sinus rhythm can be done via cardioversion or catheter
5. Class 1a to be avoided and class 2 is better but pharmacological treatments often fail
6. Stroke risk assessed and anti-thrombotic treatment is often recommended

Question 14

What does AVNRT and AVRT stand for?

Answer 14

1. AVNRT: Atrioventricular Nodal re-entrant

2. AVRT: Atrioventricular re-entrant tachycardia

Question 15

How do you terminate AVNRT and AVRT?

Answer 15

1. Carotid massage
2. Reflex vagal stimulation (immersion of face in cold water)
3. Adenosine terminates this as well (effect on K- ATP channels)
4. Class 2 drugs

Question 16

What is ventricular tachycardia and how is it caused?

Answer 16

1. Increased in heart beat in the ventricle region: major cause of cardiac arrest
2. Congenital heart disease
3. Drugs that prolong the QT interval such as Amiordarone like (sotalol)
4. Changes in blood pH and ion balance

Question 17

Describe what ventricular fibrillation does?

Answer 17

1. Seriously reduces blood pumped in emergency situation (cardiac arrest)

Question 18

How do you treat ventricular tachycardia and fibrillation?

Answer 18

1. To have sustained ventricular tachycardia, you must use class 3 (amiodarone) or class 1b (lidocaine)
2. Non sustained: betablockers or sotalol
3. Implantable cardioversion
   - often in combination with drugs