How to treat arrythmias

Question 1

What do Class 1 drugs do?

Answer 1

Block Sodium channels

They are membrane stabilising agents which means they block the propagation of an action potential

Question 2

Class 1a drugs

Answer 2

• They are moderate sodium channel blockers
• They delay the time of repolarasation
• They increase the time for propagation of an A.P.
• used for all arrhythmias

Question 3

Main class 1a drug to know

Answer 3

Disopyramide, quinidine

Question 4

Class 1B drugs

Answer 4

• they are slow sodium channel blockers
• they increase the time of repolarisation
• they decrease the time of a.p. propagation
• used for ventricular arrythmias

Question 5

Main class 1B drugs (2)

Answer 5

Lidocaine

Phenytoin

Question 6

Class 1c drugs

Answer 6

• Fast sodium channel blockers
• have little effect on the time of repolarisation
• used for severe ventricular arrhythmias
• used for atrial arrhythmias

Question 7

Main 1c drug?

Answer 7

Flecainide

Question 8

Class 2 drugs

Answer 8

• decrease the effect of the sympathetic system- therefore decrease the number of impulses sent to the heart-reduce HR
• used for the treatment of supraventricular, ventricular arrhythmias
• first line of treatment for AF

Question 9

main class 2 drugs

Answer 9

beta blockers such a bisoprolol and atenolol

bisoprolol now used as first line against atrial fibrillation

Question 10

class 3 drugs

Answer 10

increases repolarisation time

blocks K+/ca 2+ channels

Question 11

main class 3 drug?

Answer 11

Amiodarone

Sotalo

Question 12

Class 4 drugs

Answer 12

Calcium channel blocker

Slow down depolarisation

Question 13

main class 4 drug

Answer 13

verapamil

Question 14

Digoxin

Answer 14

• Cardiac glucoside: inhibits the sodium- potassium pump
• This alters the normal function of the sodium- channel pump so more calcium is available inside the cell for contraction
• Improves the strength of cardiac contraction= +ve ionotrope
• used for HF and AF
• need to monitor potassium levels in the elderly as digoxin has high toxicity levels

Question 15

Digoxin toxicity levels

Answer 15

• used in the elderly : has a low GFR filtration so most of it is excreted
• however it does have a long half life of 36-48 hours which makes it prone to high toxicity levels
• side effects: nausea, vomiting, bradycardia, tachycardia, Xanthopsia (colour blindness)
• how to treat toxicity: add DIGIBAND- binds to digoxin and is excreted in urine

Question 16

Adenosine

Answer 16

• Slows down rate of conduction through AV node
• Has a short half life
• can be given IV- can lead to Asystole

Question 17

Anticoagulants

Answer 17

• AF can lead to stroke
• Warfarin is the main anticoagulant used
• Warfarin is associated with vitamin K and so tissue factor clotting
• Need to control the levels of warfarin in the blood: measure the INR
• side effects of warfarin include: bleeding, teratogenic effects

Question 18

INR

Answer 18

-actual thromboplastin time/ standard thromboplastin time
which indicates the time is takes for blood to clot based on a tissue factor.
-should be 1
-in therapeutic range is 2.5-4.0

Question 19

Contraindications for type 1 drugs

Answer 19

• HF
• Heart block
• Ischaemic heart disease

Question 20

Cautions for type 1 drugs

Answer 20

• pregnancy
• prostate enlargement
• liver failure
• glaucoma

Question 21

Drug-drug interactions for warfarin

Answer 21

• Aspririn, antibiotics, cimetidine- increase activity of warfarin
• vitamin K, barbituates inhibit the activity of warfarin

Question 22

side effects for amiodarone

Answer 22

• thyroid problems
• grey pigmentation of the skin-slate
• pf
• corneal deposits
• liver failure

Question 23

how do class 3 drugs work?
when are they used

Answer 23

potassium channel blockers

ventricular and supra ventricular arrhythmias

Question 24

When do you choose cardioversion over medication

Answer 24

Patient is mentally unstable

Question 25

Cardioversion over defibrillation

Answer 25

Cardioversion in patients who are conscious