Anti-arrythmic drugs

Question 1

Definition of an arrhythmia

Answer 1

Heart condition resulting in rate and/or timing of contraction which is insufficient to maintain a normal CO

Question 2

Causes of abnormal impulse generation

Answer 2

Automatic rhythms - enhanced automaticity (more AP from SAN) or ectopic (AP not from SAN)
Triggered rhythms - conduction block (impulses not conducted from atria to ventricles) or reentry e.g WPW or post MI

Question 3

Aim of drugs treating abnormal impulse generation

Answer 3

Decrease phase 4 slope in SAN

Raise VGNa channels threshold

Question 4

Aim of drugs treating abnormal impulse conduction

Answer 4

Decrease conduction velocity

Increase effective refractory period

Question 5

Prescribe phases of ventricular AP

Answer 5

0: Na influx
1: K efflux
2: Ca influx
3: K efflux
4: Na-K-ATPase mediated repolarisation

Question 6

Which phases of ventricular AP make up the effective refractory period

Answer 6

0,1,2 and initial part of 3

Question 7

Phases of pacemaker AP

Answer 7

0: Ca influx
2: peak of Ca influx
3: K efflux
4: HCN channel, funny current

Question 8

What does gradient of phase 0 indicate

Answer 8

Conduction velocity

Question 9

Treatment for sinus bradycardia

Answer 9

IV atropine

Question 10

Treatment for stress induced arrhythmia

Answer 10

Beta blockers e.g bisoprolol or propranolol

Question 11

MoA of atropine

Answer 11

Muscurinic antagonist which increases conduction through the AVN

Question 12

Treatment for SVT

Answer 12

If systolic >90 vagal stimulation first, then IV adenosine

If systolic <90 do cardioversion

Question 13

MoA of adenosine

Answer 13

Binds to A1 receptors in AVN and SAN which activates K channels.
This leads to hyper polarisation, inhibition of Ca channels and slows AVN conduction
‘Feeling of impending doom’

Question 14

Treatment for pulseless VT

Answer 14

Defibrillator

Question 15

Treatment for VT with pulse

Answer 15

If systolic <90 do cardioversion

If systolic >90 give amiodarone

Question 16

Treatment for AF and atrial flutter

Answer 16

Systolic <90 do cardioversion

Systolic >90 give beta blockers, flecainide, amiodarone, digoxin

Question 17

MoA of digoxin

Answer 17

Inhibits Na-K-ATPase so has a positive ionotropic effect

Stimulates vagal activity so slows AVN conduction and increases effective refractive period

Question 18

Describe class 1A anti arrhythmia drugs and give examples

Answer 18

Procainamide, quinidine, disopyramide
Block Na channels and dissociate slowly during diastole (frequency dependent block) so they slow phase 0 and increases effective refractory period

Question 19

Describe class 1B anti arrhythmia drugs and give examples

Answer 19

Lidocaine
Block inactivated Na channels and dissociate rapidly in diastole
Ischaemic tissue more susceptible as more Na channels inactivated

Question 20

Describe class 1C anti arrhythmia drugs and give examples

Answer 20

Flecainide
Block Na channels and dissociate VERY slowly during diastole so significantly slow phase 0 and increase effective refractory period

Question 21

Describe class 2 anti arrhythmia drugs and give examples

Answer 21

Propranolol, bisoprolol, metoprolol

Have negative chronotropic effect as they increase refractory period in AVN

Question 22

Contraindications of class 2 anti arrhythmia drugs

Answer 22

Heart block

Question 23

Examples of class 3 anti arrhythmia drugs

Answer 23

Amiodarone

Sotalol

Question 24

MoA of amiodarone

Answer 24

Decreases AVN conduction

Slows phase 0 (Increases ERP)

Question 25

Side effects of amiodarone

Answer 25

Lung fibrosis
Hepatotoxic
Increased LDLs
Thyroid disease
Optic neuritis

Question 26

MoA of sotalol

Answer 26

Increase ERP
Slows phase 4
Slows AVN conduction

Question 27

Which anti arrhythmia drugs are most pro-arrhythmic

Answer 27

1A
1C
Sotalol

Question 28

Describe class 4 anti arrhythmia drugs and give examples

Answer 28

Verapamil

Diltiazem

Question 29

MoA of class 4 anti arrhythmia drugs

Answer 29

L type Ca channel blockers

Slow AVN conduction, negative ionotropic effect

Question 30

Contraindications of class 4 anti arrhythmia drugs

Answer 30

If patients on beta blockers as risk of asystole

Question 31

Treatment for secondary and tertiary heart blocks

Answer 31

Systolic >90 give atropine

Systolic <90 urgent pacemaker