arrhythmia therapy Flashcards
what is an arrhythmia
a deviation from the normal rhythm of the heart
class I
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
most common class I drug
flecainide
class II
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
class II drugs
bisoprolol is used for atrial fibrillation
propranolol, atenolol
class III
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
amiodarone
class III, used for VT and STV
interacts with many drugs (digoxin)
can be very toxic- thyroid problems, pulmonary fibrosis, corneal deposits,
class IV
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
class 4 drugs
verapamil, diltazem
class V
any other antiarrhythmics which have properties of several classes
digoxin
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
when would you use digoxin
atrial dysrhythmias
AF
Atrial Flutter
(SVT)
heart failure
digoxin toxicity
Nausea and vomiting
Xanthopsia- yellow halos around eyes
Bradycardia
Tachycardia
Arrhythmias: VT and VF
reverse tick appearance of ST segment in lateral leads
what is adenosine
Bind to adenosine receptors in the AV node
Slows/ Blocks conduction through the AV node
Used to convert paroxysmal supraventricular tachycardia to sinus rhythm
what is adenosine
Bind to adenosine receptors in the AV node
Slows/ Blocks conduction through the AV node
Used to convert paroxysmal supraventricular tachycardia to sinus rhythm
effects of adenosine
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
effects of adenosine
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
when would you use coagulants
when someone has atrial fibrillation, risk of stroke or peripheral emboli
characteristics of an ideal coagulant
oral
no monitoring
no interaction with food or drugs
as effective as warfarin but safer than warfarin
name 3 oral coagulants
Vitamin K antagonist- warfarin
Direct thrombin inhibitor- dabigatran
Direct 10a inhibitor- rivaroxaban, apixaban
how to inhibit clotting factors
warfarin reduces levels of vitamin K so no clotting factors produced
adverse effects of warfarin
Bleeding, interactions with multiple drugs, can’t use pregnant
drugs that increase warfarin activity will cause
decreased binding to albumin (aspirin), inhibit degradation (erythromycin) and decrease synthesis of clotting factors (antibiotics)
drugs that promote bleeding….
inhibit platelets and clotting factors (aspirin and heparin antimetabolites)
