Arrhythmias

Question 1

Name four drugs used for RATE control in patients with AF

Answer 1

• beta-blockers
• Ca-channel blockers
• digoxin

Question 2

What class of drug is sotalol and how does it work to maintain sinus rhythm in patients with a history of AF?

Answer 2

potassium channel blocker and beta-blocker that slows ventricular rate

Question 3

what is the mechanism of action of amiodarone?

Answer 3

blocks sodium, calcium and potassium channels and is an alpha- and beta-adrenergic receptor antagonist.

• it reduces spontaneous depolarisation (automaticity)
• it slows conduction velocity and increases resistance to depolarisation (including in the AV node)
• it’s thought to increase the chance of conversion to sinus rhythm
• in SVT involving a ‘re-entry’ circuit that includes the AV node, amiodarone may break the circuit and restore sinus rhythm
• its effects in suppressing spontaneous depolarisations make it an option for both treatment and prevention of VT and for improving the chance of successful defibrillation in refractory VF

Question 4

what 3 drugs should you half the dose of if your patient is on them before starting amiodarone?

Answer 4

• digoxin
• diltiaxem
• verapamil

Question 5

is amiodarone safe to give chronically?

Answer 5

it can be but it also has many side effects, some of which are serious, so its continued use needs to be thought about carefully

Question 6

Name 4 drugs that could be used to maintain sinus RHYTHM in patients with a history of AF

Answer 6

• sotalol
• amiodarone
• flecainide
• disopyramide

Question 7

what factors might favour rate control over rhythm control?

Answer 7

• > 65yrs age

- history of IHD

Question 8

what factors might favour rhythm control over rate control in a patient?

Answer 8

• age <65yrs
• symptomatic
• first presentation
• lone AF or AF secondary to a corrected precipitant (e.g. alcohol)
• CHF

Question 9

other than rhythm or rate controlling medication, what else might you give someone with AF?

Answer 9

anticoagulants (DOAC or warfarin)

Question 10

what is the CHA2DS2 VASc score used for and name all of the components

Answer 10

calculating stroke risk in people with AF.
Congestive HF - 1 point
HTN - 1 point
Age >/=75 - 2 points
DM - 1 point
Stroke/TIA history - 2 points
Vascular disease - 1 point
Age 65-74 - 1 point
Sex (female) - 1 point

Question 11

Name the Vaughn Williams classification of antidysrhythmic drugs

Answer 11

Class I - sodium channel inhibitors
Class II - beta-blockers
Class III - potassium channel inhibitors
Class IV - calcium-channel blockers

Question 12

Give an example of a Class Ia drug,
how they work and,
what they can be used to treat

Answer 12

Disopyramide, quinidine, procainamide.
Prolong repolarisation therefore extending the duration of the AP.
Effective for treatment of both SV arrhythmias and VAs

Question 13

Give an example of a Class Ib drug,
how they work and,
what they can be used to treat

Answer 13

Lidocaine, phenytoin
they slow impulse conduction in abnormal (i.e. ischaemic) myocardium.
only effective for treatment of VAs

Question 14

Give an example of a Class Ic drug,
how they work and,
what they can be used to treat

Answer 14

flecainide, propafenone.
Slow impulse conduction by Na channel blockade.
effective for both AV arrhythmias and VAs

Question 15

Give an example of a Class II drug,
how they work and,
what they can be used to treat

Answer 15

propanolol, metoprolol.
Reduce spontaneous depolarisation of SA and AV nodal tissue and reduce conduction through AV node. they can also inhibit ectopic pacemakers that have developed dominant automaticity.
Effective for SV arrhythmias and VAs

Question 16

Give an example of a Class III drug,
how they work and,
what they can be used to treat

Answer 16

amiodarone, sotalol
prolong duration of AP.
Effective for both SV arrhythmias and VAs

Question 17

Give an example of a Class IV drug,
how they work and,
what they can be used to treat

Answer 17

verapamil, diltiazem
slow conduction of AP, particularly in the AV node.
Only effective for treatment of SV arrhythmias.

Question 18

What are the uses of digoxin in terms of arrhtymias?

Answer 18

control ventricular rate in AF and atrial flutter by reducing conduction through AV node.

Question 19

what is the MoA of adenosine and thus what can it be used for?

Answer 19

Agonist of adenosine receptors on cell surfaces meaning it reduces the frequency of spontaneous depolarisation (automaticity) and increases resistance to depolarisation.
It is therefore able to break the re-entry circuit by increasing refractoriness in the AV node (cardioversion).
In atrial flutter the circuit does not involve the AV node so adenosine will not cause cardioversion but by blocking conduction to the ventricles it allows closer inspection of the atrial rhythm on ECG

Question 20

MOA and uses of atropine

Answer 20

antimuscarinic drug that reduces the inhibitory effect of the vagus nerve on the heart. SA node firing rate increases which increases conduction through AV node.
Used for treating sinus bradycardia and AV block

Question 21

When might you use magnesium sulphate?

Answer 21

to control ventricular arrhythmia torsade de pointes and digitalis-induced VA

Question 22

during CPR, how often would you give adrenaline?

Answer 22

every 3-5 minutes

Question 23

during CPR when would you give amiodarone?

Answer 23

after 3 shocks