Anti-arrhythmic's

Question 1

What are pacemakers used for?

Answer 1

1. Symptomatic sick sinus node disease

2. High grade AV block

Question 2

What are defibrillators used for?

Answer 2

High risk or aborted SCD

Sustained VT in structural heart disease

Question 3

What is CRT used for?

Answer 3

Cardiomyopathy with LBBB

Question 4

What do anti-arrhythmics affect?

What changes occur with cell membranes?

Answer 4

1. cell membranes, ANS, vagal tone

2. cell membrane activity affects CV, ERP, SAN/AVN automaticity

Question 5

Class IA -

• What effects do they have?
• 2 examples?
• What do they enhance?

Answer 5

decrease Vmax, increase APD/ERP, increase QT interval, widen QRS
Procainamide, quinidine
enhance AVN conduction

Question 6

Class IB -

• What effects do they have?
• 3 examples?

Answer 6

No change in Vmax, reduce APD/ERP

Phenytoin, lignocaine, tocainide

Question 7

Class IC -

• What effects do they have?
• 2 examples

Answer 7

Reduce Vmas + reduce APD = result is no effect on ERP

flecainide, encainide, popafenone

Question 8

Class II -

• What do they do? what is the effect on AVN
• SEs? (3)

Answer 8

beta-blockers - antagonise beta-receptors + reduced sympathetic drive
Reduce HR/BP, reduce AVN conduction
Positive inotropes, some mortality benefits
for fast AF - rate control
SEs = bradycardia, fatigue, bizarre dreams/nightmares

Question 9

Class III -

• What do they do?
• 3 effects
• Alter DFT
• Amiodarone = SEs, toxicity, drug interactions
• Sotalol - dose-dep

Answer 9

block K channels - also affect Na + Ca channels + activity across all classes
most potent rhythm disturbers
sotalol reduces DFT + amiodarone increases DFT
AMIODARONE = all classes, blue/grey skin discolouration, myalgia, gait disturbance, insomnia. cumulative toxicities (liver/renal failure, photosensitivity/corneal deposits, hyper/hypothyroid, pulm fibrosis). potentiate warfarin/digoxin
SOTALOL - also a beta-blocker. K+ channel activity at high doses

Question 10

Class IV -

• Channels affected?
• 3 examples
• SEs? (4)

Answer 10

L-type Ca channel blockers
verapamil, diltiazem (used for fast AF - rate control), nifedipine
main effect on SAN/AVN
not pro-arrhythmic
SEs = flushing, headache, peripheral oedema, bradycardia

Question 11

Adenosine

Answer 11

Short-acting anti-arrhythmic disrupting short circuits
IV bolus/flush + fast-acting to prevent immediate paroxysmal VT
purine nucleotide analogues - hyperpolarise = transient AV block

Question 12

What are antedromic + orthodromic tachycardias (AV reentrant)?

Answer 12

antedromic = through accessory pathway
orthodromic = through AVN

Question 13

AF -

• Who?
• Symptoms?
• Complications?
• Treatment?
• Types?

Answer 13

1. Occurs in elderly, HF patients + heart valve lesions
2. Usually asymptomatic - potential limited exercise capacity, palpitations, syncope
3. Stroke, rate-related cardiomyopathy
4. Requires anti-coagulation
5. Types -
   - Paroxysmal = stops spontaneously
   - Persistant = lasts >7days without spontaneous reversion. can cardiovert
   - Permanent = unable to cardiovert - requires RATE control

Question 14

What are the 5 steps in management of VT/VF?

Answer 14

1. Emergency management - resuscitation/cardioversion
2. Treat underlying pathology - ischaemia, bradycardia, structural heart disease, metabolic/drug causes
3. Ventricular support - anti-ischaemics (b-blockers, CCBs, nitrates), ACEis
4. anti-arrhythmics = class II/III, or I w/ ICD
5. Device = pacemaker/ICD
6. Intervention = surgery (CABG, aneurysmectomy), ablation