Therapy for arrhythmias

Question 1

What is the most common arrhythmia?

Answer 1

Atrial fibrillation

Question 2

What arrhythmia has f waves?

Answer 2

Atrial fibrillation - fine oscillations from baseline

F on atrial flutter

Question 3

What classification system is used for anti-arrhythmic agents?

Answer 3

Vaughan-Williams classification

I - Na channels (Ia, Ib, Ic)
II - symp NS inhibitors 
III - K channels
IV - Ca and AV node
V - other/unknown mechanism

Question 4

Name some Ia type anti-arrhytmics

Answer 4

Moderate Na blockade, delay repolarisation

Quinidine
Procainamide
Disopyramide

Question 5

Name some Ib type anti-arrhythmics

Answer 5

Weak Na blockade, accelerate repol.

Tocainide
Mexiletine
Phenytoin
Lidocaine

Ventricular dsyrhythmias

Question 6

Name some Ic type anti-arrhythmics

Answer 6

Strong Na blockade, no effect on repol.

Encainide
Flecainide
Propafenone
Moricizine

Severe ventricular dsyrhythmias, AF, atrial flutter

Question 7

Name some II type anti-arrhythmics

Answer 7

Affect sympathetic NS signalling

Beta blockers: atenolol, bisoprolol, propranolol

Question 8

Name some type III type anti-arrhythmics

Answer 8

Affect K+ channel to prolong repolarisation

Amiodarone
Bretylium
Sotalol

Question 9

Name some type IV anti-arrhythmics

Answer 9

Affect Ca channel and AV node

Verapamil
Diltiazem

Paroxysmal SVT, atrial flutter and AF

Question 10

Name some type V anti-arrhythmics

Answer 10

Others, don’t fit into any 1 class only

Digoxin - cardiac glycoside, inhibits Na/K pump, increased Ca for contraction

Adenosine - slows AV conduction

Question 11

Describe the mechanism of action of digoxin

Answer 11

Cardiac glycoside, inhibits Na/K ATPase to increase levels of Ca for contraction

Used for heart failure and AF

Question 12

Describe signs of digoxin toxicity

Answer 12

ECG - reverse tick of ST segments
Nausea and vomiting
Xanthopsia - yellow vision
Bradycardia/tachycardia
Arrhythmias

Question 13

How do you treat digoxin toxicity?

Answer 13

Stop immediately (long half life)
Give digibind (digoxin antibody)

Question 14

Why must care be taken with class III drug amiodarone?

Answer 14

Many DDIs, especially with digoxin

Side effects include:

• thyroid issues
• pulmonary fibrosis
• grey appearance of skin
• corneal deposits
• LFT abnormalities

Question 15

Describe amiodarone toxicity

Answer 15

Interstitial disease of lungs
Respiratory distress
Solitary pulmonary fibrotic masses
Blue-gray colouring of the skin

Question 16

Describe the mechanism of action and indication of adenosine

Answer 16

Slows AV conduction, can cause systole for a few seconds before restoring normal HR

For paroxysmal SVT

IV, short half life

Question 17

List some anti-coagulants used for arrhythmias

Answer 17

Warfarin - vit K1 oxide reductase inhibitor
Dabigatran - thrombin inhibitor
Rivaroxaban - Xa inhibitor
Apixaban - Xa inhibitor
Edoxaban - Xa inhibitor

Question 18

What are the general indications for anticoagulation?

Answer 18

Atrial fibrillation - stroke
DVT/PE
After surgery
Immobilisation - prophylactic

Question 19

What clotting factors are inhibited by warfarin?

Answer 19

Decreases clotting activity of II, VII, IX and X

Question 20

What enzyme metabolises warfarin?

Answer 20

CYP450

Question 21

What drugs increase warfarin activity?

Answer 21

Aspirin
Sulphonamides
Cimetidine
Antibiotics - macrolides
Heparin
Disulfiram

Question 22

What drugs decrease warfarin activity?

Answer 22

Barbiturates
Phenytoin (Ib) - don’t use together
Vitamin K - watch diet when on warfarin
Cholesyramine

Question 23

How do you monitor warfarin therapy?

Answer 23

International normalised ratio - calculation of standardised prothrombin time

INR in normal people = 1
Therapeutic INR = 2.5-4 (want it increased so clotting is reduced)

reduce vitamin K in diet and alcohol

Question 24

What are some adverse effects of warfarin?

Answer 24

Bleeding
Teratogenic - chondrodysplasia (1st and 3rd)
Retroplacental bleeding
Intracerebral foetal bleeding
Many DDIs

Question 25

How do you assess bleeding risk in those on warfarin?

Answer 25

CHADS2 score

C= CHF                      1
H = hypertension      1
A = age >75               1
D = DM                       1
S2 = stroke                2

Each score relates to % risk of bleeding

Question 26

What are the characteristics of an ideal anticoagulant?

Answer 26

Oral
No need for monitoring
No interaction with drugs/food
Given once/twice a day at fixed dose
As effective as warfarin
Safer than warfarin

GONNAS