arrhythmia therapy

Question 1

what is an arrhythmia

Answer 1

a deviation from the normal rhythm of the heart

Question 2

class I

Answer 2

Sodium channel blocker
1. decrease size of action potential
2. reduces velocity of conduction/excitability
3. act on fast sodium channels responsible for phase 0

Question 3

most common class I drug

Answer 3

flecainide

Question 4

class II

Answer 4

beta blocker
1. acts via beta receptors to block sympathetic stimulation of the heart
2. prolongs stage 4 depolarisation which slows SA discharge and AV conduction
3. shortens phase 2

Question 5

class II drugs

Answer 5

bisoprolol is used for atrial fibrillation
propranolol, atenolol

Question 6

class III

Answer 6

potassium channel blockers
1. increase action potential duration
2. prolong depolarisation in phase 3 increasing refractory period

used for dysrhythmias that are hard to treat

Question 7

amiodarone

Answer 7

class III, used for VT and STV
interacts with many drugs (digoxin)
can be very toxic- thyroid problems, pulmonary fibrosis, corneal deposits,

Question 8

class IV

Answer 8

calcium channel blockers
1. bind to Lcard type voltage gated calcium channels
2. depress phase 4 depolarisation in SA and AV nodes which slows heart rate
3. shortens phase 2 which reduces contractility

Question 9

class 4 drugs

Answer 9

verapamil, diltazem

Question 10

class V

Answer 10

any other antiarrhythmics which have properties of several classes

Question 11

digoxin

Answer 11

cardiac glycoside which inhibits the sodium potassium ATpase pump
1. increases vagal tone
2. effects cardiac action potential
3. increases intracellular calcium causing a positive inotropic effect

Question 12

when would you use digoxin

Answer 12

atrial dysrhythmias
AF
Atrial Flutter
(SVT)
heart failure

Question 13

digoxin toxicity

Answer 13

Nausea and vomiting
Xanthopsia- yellow halos around eyes
Bradycardia
Tachycardia
Arrhythmias: VT and VF
reverse tick appearance of ST segment in lateral leads

Question 14

what is adenosine

Answer 14

Bind to adenosine receptors in the AV node
Slows/ Blocks conduction through the AV node
Used to convert paroxysmal supraventricular tachycardia to sinus rhythm

Question 15

what is adenosine

Answer 15

Bind to adenosine receptors in the AV node
Slows/ Blocks conduction through the AV node
Used to convert paroxysmal supraventricular tachycardia to sinus rhythm

Question 16

effects of adenosine

Answer 16

Very short half-life
Only administered as fast IV push
May cause asystole for a few seconds (cessation of electrical and mechanical activity of heart)
Other side effects minimal

Question 17

effects of adenosine

Answer 17

Very short half-life
Only administered as fast IV push
May cause asystole for a few seconds (cessation of electrical and mechanical activity of heart)
Other side effects minimal

Question 18

when would you use coagulants

Answer 18

when someone has atrial fibrillation, risk of stroke or peripheral emboli

Question 19

characteristics of an ideal coagulant

Answer 19

oral
no monitoring
no interaction with food or drugs
as effective as warfarin but safer than warfarin

Question 20

name 3 oral coagulants

Answer 20

Vitamin K antagonist- warfarin
Direct thrombin inhibitor- dabigatran
Direct 10a inhibitor- rivaroxaban, apixaban

Question 21

how to inhibit clotting factors

Answer 21

warfarin reduces levels of vitamin K so no clotting factors produced

Question 22

adverse effects of warfarin

Answer 22

Bleeding, interactions with multiple drugs, can’t use pregnant

Question 23

drugs that increase warfarin activity will cause

Answer 23

decreased binding to albumin (aspirin), inhibit degradation (erythromycin) and decrease synthesis of clotting factors (antibiotics)

Question 24

drugs that promote bleeding….

Answer 24

inhibit platelets and clotting factors (aspirin and heparin antimetabolites)

Question 25

drugs that decrease warfarin activity….

Answer 25

induction of cytochrome p450 (barbiturates)
promote clotting factor synthesis and reduce absorption

Question 26

cytochrome p450 inhibitors

Answer 26

omeprazole, erythromycin, ethanol, isoniazid

Question 27

cytochrome p450 inducers

Answer 27

alcohol, barbiturates, phenytoin, rifampicin, carbamazepine