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Cardiovascular > Arrhythmias - Therapies > Flashcards

Arrhythmias - Therapies Flashcards

1
Q

What is an arrhythmia?

A

A deviation from the normal rhythm of the heart

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2
Q

What are some types of arrhythmias?

A

Sinus arrhythmia, bradycardias, tachycardias, supraventricular arrhythmia (AF and SVT) and ventricular arrhythmia (tachycardia and fibrillation)

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3
Q

What are the most important drugs used for treatment of arrhythmais?

A

Flecainide
Atenolol, bisoprolol
Amiodarone
Diltiazem, verapamil
Digoxin

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4
Q

How are the drugs for arrhythmias classified?

A

Class I-V
Vaughan-William’s classification - classified as which receptor they act upon

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5
Q

Explain Class I - Sodium Channel Blockers

A

Membrane-stabilizing agents which decrease size of action potential and reduce velocity of conduction/excitation
Act on fast sodium channels which are responsible for phase 0

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6
Q

Describe Class I drugs

A

Divided into IA, IB and IC agents - according to their effect on AP duration and the effective refractory period
They are more effective at higher HR

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7
Q

What is the most common Class I drug?

A

Class IC - flecainide
Strong Na+ channel blockage and keeps the same effective refractory period but slow depolarisation

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8
Q

Describe class II beta blockers

A

Act on B1 receptors to block sympathetic stimulation of the heart
This prolongs phase 4 depolarisation - slows SA discharge and AV conduction
This reduced excitability in non-nodal tissue
Also shortens phase 2 - negative effect on contractibility

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9
Q

What is Class II beta blockers used for treatment?

A

First line in atrial fibrillation - bisoprolol
Supresses VEs and some VT

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10
Q

What are some common beta blockers used?

A

Atenolol - BP control
Bisoprolol - more cardio specific
Propranolol

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11
Q

Describe Class III potassium channel blockers

A

Increase AP duration, prolong repolarisation in phase 3 and prolong the ERP
Ex. amiodarone, bretylium and sotalol

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12
Q

What is class III potassium channel blocker drugs used in treatment for?

A

Dysthymias that are difficult to treat
Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter - resistant to other drugs
Sustained ventricular tachycardia

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13
Q

What is amiodarone used for?

A

Is a class III potassium channel blocker
Used for VT and occasionally in supraventricular tachycardia

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14
Q

What is the side effects of amiodarone?

A

Thyroid - hypo or hyperthyroidism
Pulmonary fibrosis, Slate (grey pigmentation), corneal deposits and LFT abnormalities

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15
Q

Describe Class IV calcium channel blockers

A

Bind to Lcard type voltage gated channels and depress phase 4 in SA and AV nodes
This slows heart rate
Also shortens phase 2 plateau phase - reduce contractibility
More effective at higher HR

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16
Q

What are class IV calcium channel blockers used in treatment for?

A

Verapamil and diltiazem
Used for paroxysmal supraventricular tachycardia and rate control for AF and flutter

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17
Q

What is an example of a class V drug and what are they?

A

Digoxin and Adenosine
Have properties of several classes and are not placed into one particular class

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18
Q

What is the mechanism of action for digoxin?

A

Cardiac glycoside and it inhibits the sodium-potassium ATPase pump
Increases vagal tone so slows conduction, reduced refractory period in myocardium and increases intracellular Ca so positive inotropic effect

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19
Q

What are the indications for digoxin?

A

Atrial dysrhythmias - AF, atrial flutter and possibly SVT
Heart failure
These drugs are usually second line and used with BB or CCB

20
Q

How would you treat atrial fibrillation?

A

BB or CCB
If not effective rate control, therapy limited or acute HF/ hypotension then consider putting on digoxin

21
Q

Describe digoxin and renal impairment

A

Digoxin has long half life which can be increased in renal impairment. Excretion is proportional to GFR
Commonly used in elderly - cautious with does as common for elderly to have renal impairment
Monitor potassium levels for toxicity

22
Q

What are symptoms of toxicity with digoxin?

A

Nausea and vomiting, dehydration, xanthopsia, bradycardia, tachycardia and arrhythmias - VT and VF

23
Q

What are signs of toxicity of digoxin on an ECG?

A

Reversed rick appearance of ST segment in lateral leads

24
Q

What is the treatment for digoxin toxicity?

A

Stop digoxin but long half life
Give Digibind if level and risks are high of significant arrhythmia
Digoxin toxicity is more serious if potassium levels are low

25
Q

Explain the drug Digibind

A

Has digoxin immune antibody, binds with digoxin which forms complex molecules and excreted in the urine

26
Q

What is the mechanism of action for adenosine?

A

Bind to adenosine receptors in the AV node - slows/blocks conduction through the AV node

27
Q

What is adenosine used in treatment for?

A

Used to convert paroxysmal SVT to sinus rhythm

28
Q

What is the effect of adenosine on SVT?

A

Very short half life, only administered as fast IV push
May cause asystole for a few seconds and other minimal side effects
Avoided in patients with asthma as can cause marked bronchospasm

29
Q

What is a side effect of antiarrhythmics?

A

Can cause arrhythmias

30
Q

How does AF lead to thrombus formation?

A

AF causes flutters where blood is not properly squeezed into ventricles and can lead to stasis in left atrial appendage - thrombosis as Virchow’s triad

31
Q

What is the chadsvasc score classification?

A

Calculates score for risk of stroke and if patient should be put on anticoagulants
If stage 2 and above then anticoagulants are given

32
Q

Explain the chadsvasc score risk factors

A

Congestive heart failure
Hypertension
Age > 75
Age 65-74
Diabetes melilitus
Stroke/TIA/thromboembolism
Vascular disease
Sex female

33
Q

What are the characteristics of an ideal anticoagulant?

A

Oral, no need for monitoring, no interactions with food or drugs, given once or twice a day, as effective as warfarin and safer then warfarin

34
Q

What are the different types of oral anticoagulants used in AF?

A

Vitamin K antagonists - warfarin
Direct thrombin inhibitor - dabigatran
Direct Xa inhibitors

35
Q

Describe the mechanism of action of warfarin

A

Inhibits production of active clotting factors - II, VII, IX and X
Structurally related to vitamin K

36
Q

How is warfarin therapy monitored?

A

International normalised ratio (INR)
Actual prothrombin time/ standard prothrombin time
Normal is 1

37
Q

What are some adverse effects of warfarin?

A

Bleeding, interactions with other drugs - P450 mechanism, pregnancy (teratogenic and avoid where possible)

38
Q

What is the Hasbled classification used for?

A

Assess risk of bleeding

39
Q

What are the Hasbled clinical characteristics?

A

Hypertension, abnormal liver function, abnormal renal function, stroke, bleeding, labile INRs, elderly, drugs and alcohol

40
Q

What are some drugs which increase warfarin activity?

A

Aspirin - decrease binding to albumin
Cimetidine, erythromycin - inhibits degradation
Antibiotics - decrease synthesis of clotting factors

41
Q

What are some drugs which promote bleeding with warfarin?

A

Aspirin - inhibition of platelets
Heparin - inhibition of clotting factors

42
Q

What are some of the drugs which decrease warfarin activity?

A

Brabiturates and phenytoin - induce metabolising enzymes
Vitamin K - promotes clotting factor synthesis
Cholestyramine - reduced absorption

43
Q

What are some inhibitors of cytochrome p450?

A

Omeprazole, disulfiram, erythromycin, valproate, isoniazid, ciprofloxacin an cimetidine, ethanol acutely and sulphonamides

44
Q

What are some inducers of cytochrome p450?

A

Alcohol chronic use, barbiturates, carbamazepine, phenytoin, rifampicin and sulphonylureas

45
Q

What are some new anticoagulants which can help reduce risk of stroke with AF?

A

Dabigatran, Rivaroxaban and Apixaban - less bleeding risk

46
Q

What are some other cardiovascular indications for anticoagulation?

A

Metallic Heart Valves
DVT/PE - treatment and prophylaxis

Cardiovascular (33 decks)

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