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Cardio > Arrhythmia therapy > Flashcards

Arrhythmia therapy Flashcards

1
Q

What protein is mainly responsible for creating the resting membrane potential

A

Sodium-potassium ATPase

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2
Q

Give an example of a Class 1A antiarrhythmic and describe how it works

A

QUINIDINE
Procainamide
Dyspyrimide

(Moderate) sodium-channel blockade, thus reducing amplitude of AP and conduction velocity

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3
Q

Give an example of a Class 1B drug and describe how it works

A

LIDOCAINE
Mexiletine
Tocainide

(Weak) sodium-channel blockade, thus reducing amplitude of AP and conduction velocity

Reduce the effective refractory period

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4
Q

Give an example of a Class 1C drug and describe its mechanism of action

A

FLECAINIDE
propafenone

(Strong) sodium-channel blockade, thus reducing amplitude of AP and conduction velocity

Increase the effective refractory period

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5
Q

What is the alternative name for Class 2 antiarrhythmics?

A

Beta blockers

Eg Bisoprolol, atenolol

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6
Q

Describe the mechanism of Class 2 antiarrhythmic drugs

A

Block Beta 1 adrenergic receptors at the SA node

Slows SA discharge & AV conduction

Also reduces contractility

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7
Q

Give an example of a Class III antiarrhythmic and describe its mechanism of action

A

Amiadarone
Bretylium
Sotalol

Prolong refractory period by slowing K+ outflow from cells
This increases the duration of the action potential

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8
Q

Give an example of a class IV antiarrhythmic and explain its mechanism of action

A

Class IV = Rate limiting Calcium channel blockers

Eg Diltiazem, Verapamil

Decrease automaticity & slows AV conduction ∴ reduces heart rate

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9
Q

Give an example of a class V antiarrhythmic and explain how it works

A

Digoxin

Blocks Na-K ATPase

Slows SA & AV conduction

(another is adenosine)

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10
Q

A patient has Atrial fibrillation

What drug would you first prescribe to treat AF and why?

A

Bisoprolol

Inhibits B1 receptors at the SA node to block sympathetic stimulation of the heart.
This slows SA discharge and AV conduction.

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11
Q

Your first choice treatment for Atrial fibrillation is not working. What is used now?

A

Amiadarone

Prolongs the refractory period by slowing K+ outflow from cells

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12
Q

What would you use to treat Ventricular tachycardia?

A

Amiadarone

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13
Q

What precautions would you take before prescribing amiadarone?

A

Avoid giving it alongside Digoxin

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14
Q

What are the possible side effects of amiadarone?

A

Hyper or hypothyroidism

Pulmonary fibrosis

Slate-grey pigmentation of skin

Corneal deposits of keratin

Liver function impairment

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15
Q

What is digoxin used to treat?

A

Atrial fibrillation (if bisoprolol isn’t working)

Atrial flutter

Supraventricular tachycardia

Heart failure

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16
Q

What precautions must be taken when prescribing Digoxin?

A

Check renal function

Monitor potassium and digoxin levels in the blood to avoid toxicity

Monitor heart rate

Monitor heart rhythm

Check patients vision

17
Q

What are the effects of Digoxin toxicity?

A

Nausea / vomiting

Xanthopsia (patient sees yellow)

Bradycardia

Tachycardia

Arrhythmias (VT & VF)

18
Q

Why is it important to check a patient’s heart rate and rhythm when giving them digoxin?

A

Digoxin toxicity can cause Bradycardia, tachycardia, VT or VFib

‘Reverse tick’ appearance of ST segment in lateral leads of ECG

19
Q

When could you use Class IV antiarrhythmics?

A

Paroxysmal SVT

Rate control for AFib and Atrial flutter

20
Q

What is used to treat Digoxin toxicity?

A

Digibind

This Digoxin immune antibody will bind to digoxin and be excreted in urine

21
Q

What is the use and mechanism of adenosine?

A

IV adenosine

Slows/blocks conduction through the AV node

Used to convert paroxysmal SVT to sinus rhythm (may cause asystole for a short time)

22
Q

What factors increase the risk of a stroke for a patient with AFib?

A 
Smoking 
Diabetes 
Previous CVD
Previous AF
Hypertension
23
Q

Give examples of oral anticoagulants

A

Warfarin

Dabigatran

Rivaroxaban, Apixaban

24
Q

Describe the mechanism of warfarin

A

Vitamin K epoxide reductase antagonist

Vitamin K used to convert precursor molecules to clotting factors

∴ reduced clotting factors ∴ less thrombin ∴ less fibrin

25
Q

How does dabigatran work?

A

Directly inhibits thrombin from converting fibrinogen to fibrin ∴ stops clot formation

26
Q

How do anticoagulants like rivaroxaban or apixaban work?

A

Directly inhibit Xa ∴ stops conversion of prothrombin to thrombin

Stops fibrin production ∴ stops clot formation

27
Q

What is the INR?

A

International normalised ratio (for monitoring warfarin)

Normal is 1

Therapeutic INR is 2.5 - 4.0

28
Q

What are the contraindications for Warfarin usage?

A

Previous haemorrhagic stroke

Brain trauma / surgery within the past 6 months

Known bleeding disorder / active bleeding

If they are on one of the million drugs that interacts with warfarin badly

Pregnancy

29
Q

Why is pregnancy a contraindication for warfarin?

A

Teratogenic (chondrodysplasia)

Increased risk of retroplacental bleeding and foetal intracerebral bleeding

Avoid in 1st and 3rd trimesters

30
Q

How would Aspirin or sulfonamides affect the activity of warfarin?

A

Decrease the binding of Warfarin to albumin

∴ increase Warfarins activity

31
Q

What is the effect of Cimetidine, Erythromycin or Clarithromycin on warfarin?

A

These inhibit the degradation of warfarin through the Cytochrome P450 pathway

This means that giving them together increases the activity of warfarin

32
Q

How would Oral antibiotics affect warfarin?

A

Increase it’s activity through decreasing the synthesis of clotting factors

33
Q

What is the effect of giving both warfarin and aspirin together?

A

Inhibition of platelets promotes bleeding

34
Q

What is the effect of giving warfarin alongside Heparin or antimetabolites?

A

Inhibits clotting factors

∴ promotes bleeding

35
Q

What is the effect of barbiturates or Phenytoin on warfarin’s activity?

A

Decrease Warfarins activity

They do this through the induction of cytochrome P450 enzymes

Warfarin is metabolised by the Cytochrome P450 pathway

36
Q

What is the effect of Vitamin K on warfarin’s activity?

A

Decrease warfarin’s activity

Vitamin K promotes clotting factor synthesis

37
Q

What is the effect of cholestyramine on the activity of Warfarin?

A

Decrease the activity of Warfarin by reducing it’s absorption

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