Arrhythmias treatment Flashcards
What is Vaughan-Williams classification of drugs used to treat arrhythmias
Class 1 -Class Ia -Class Ib -Class Ic Class II Class III Class IV Other
What is the electrophysiologic property of class IA
Fast* sodium-channel blockade
What is the electrophysiologic property of class IB
Intermediate* sodium-channel blockade
What is the electrophysiologic property of class IC
Slow* sodium-channel blockade
What is the electrophysiologic property of class II
Β-Adrenergic receptor antagonism
What is the electrophysiologic property of class III
Prolong refractoriness
What is the electrophysiologic property of class IV
Calcium channel blockade
What are class I drugs, and what do they all do
Membrane-stabilizing agents
- sodium channel blockers
What is examples of class Ia
quinidine, procainamide, disopyramide
How do class Ia drugs block sodium channels
Delay repolarization
Increase the action potential duration
What are class Ia drugs used for
Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome
What is examples of class Ib drugs
tocainide, mexiletine, phenytoin, lidocaine
How does class Ib drugs block sodium channels
Accelerate repolarization
Decrease the action potential duration
What are class Ib drugs used for
ventricular dysrhythmias only (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation)
Digoxin toxicity
What is examples Ic drugs
encainide, flecainide, propafenone
What is Ic drugs affect onaction potential duration or repolarization
Little effect
What class 1 drug is the stronger sodium channel blocker
class Ic
What is class Ic drug used for
Used for severe ventricular dysrhythmias
May be used in atrial fibrillation/flutter
What are class II drugs, and how do they work
Beta blockers
Reduce or block sympathetic nervous system stimulation, thus reducing transmission of phase 4 depolarisation of impulses in the heart’s conduction system
What is examples of class II drugs
atenolol, bisoprolol, propranolol
What is the use of class 11 drugs
General myocardial depressants for both supraventricular and ventricular dysrhythmias
What is first line use for atrial fibrillation
Class II - bisoprolol
How does class III prolong refractoriness
Increase action potential duration by prolonging repolarization in phase 3
Slowing the rate pottasium coming out the cell
What is examples of class III drugs
amiodarone, bretylium, sotalol,
When is class III drugs used
Used for dysrhythmias that are difficult to treat
Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs
Sustained ventricular tachycardia
How does class IV drugs acts as calcium channel blockers
By depressing phase 4 depolarization
What is examples of class IV drugs
verapamil, diltiazem
What are class IV drugs used for
paroxysmal supraventricular tachycardia; rate control for atrial fibrillation and flutter
What is examples of antidysrhythmics
Digoxin
adenosine
What kind of drug is digoxin and whats it affect on the heart
Cardiac glycoside
Positive ionotrope
Improves strength of cardiac contraction
How does digoxin affect the hearts contractility
Inhibits the sodium-potassium ATPase pump
Allows more calcium to be available for contraction
What is digoxin used for
Used for heart failure and atrial dysrhythmias
What is the disadvantages of digoxin used
Low therapeutic jinxed therefore drug levels must be monitored for toxicity
What patient in digoxin commonly used in and why
Commonly used in elderly, as digoxin has a reduced globular filtration rate, therefore as elderly more likely to have renal impairment its more beneficial
What is the side affect of digoxin toxicity
Nausea and vomiting Xanthopsia Bradycardia Tachycardia Arrhythmias: VT and VF
What is the problem in treating digoxin toxicity
Long half life
not effectively removed by dialysis
Half life increased in renal impairment
What is the treatment plan in digoxin toxicity, and what is the further treatment plan if levels are high with a risk of arrhythmia
Stop digoxin
Give digibind
-Digoxin immune antibody
Binds with digoxin, forming complex molecules
Excreted in urine
When are digoxin toxicity more serious
if potassium levels are low
risk of developing arrhythmia
What is the side effect of the drug interaction between digoxin and amiodarone (class II drug)
Thyroid (hypo or hyperthyroidism) Pulmonary fibrosis Slate – grey pigmentation Corneal deposits LFT abnormalities
How does the antidysrhythmics adenosine affect the heart rate
Slows conduction through the AV node
What is adenosine used for
to convert paroxysmal supraventricular tachycardia to sinus rhythm
How is adenosine administrated
administered as fast IV push
What is the side effect of adenosine
May cause asystole for a few seconds, other side effects minimum
(very short half life)
Whats is one of the main side effects of antiarrhythmics
arrhythmias
What is the treatment for sinus tachycarida
Class II - beta blockers
Class IV - calcium channel blockers
what is the treatment for atrial fibrillation/flutter
Class IA, IC, -sodium channel blockers
Class II - Beta blocker
Class III - prolong refractoriness
Class IV - calcium channel blockers
Anticoagulation
What is the treatment for Paroxysmal supraventricular tachycardia
Class IA/ IC, - sodium channel blockers II,
Class III, prolong refractoriness
Class IV, - calcium channel blockers
adenosine - decreases HR
What is the treatment for AV block
atropine
What is the treatment for ventricular tachycardia
Class I - sodium channel blockers
Class II - Beta blcokers
Class III - prolong refractoriness
Why it is wise to give anticoagulation with atrial fibrillation
As increase risk of stroke and peripheral emboli
What is examples of anticoagulation drugs
Warfarin
- Structurally related to vitamin K therefore Inhibits production of active clotting factors
Dabigatran/Apixaban
- direct thrombin inhibitor
Rivaroxaban
- Factor Xa inhibitor
Preventing the formation of thrombin
What is the indications of anticoagulation therapy
Atrial fibrillation - reduce stroke risk by 80%
DVT/PE
After surgery
Immobilisation: those at high risk of DVT
What are the drugs that interact with warfarin and increase activity and how
Aspirin, Sulfonamides - decrease binding to albumin
Cimetidine, Disulfiram - inhibit degradation
Antibiotics (oral) - decrease synthesis of clotting factors
What are the drugs that interact with warfarin and promote bleeding
Aspirin - Inhibition of platelets
antimetabolites + heparin - Inhibition of clotting factors
What are drugs that interact with warfarin and decrease activity
Barbiturates + pheytoin
= Induction of metabolizing
Enzymes (cytochrome P450)
Vitamin K - promote clotting factor synthesis
Cholestyramine - reduced absorption
Where is warfarin metabolised and how is the therapy monitored
In the liver by the cytochrome P450 system
International normalised ratio (INR)
=Standard thromboplastin time
Normal INR = 1
educate patients
watch alcohol intake
What do you give first in the indication of DVT
Heparin
What is the disadvantages to warfarin therapy
Can promote Bleeding
Is a tetraogenic
- chondrodysplasia - malformation of cartilage
Wha conditions increases you risk of bleeding on warfarin
C - congestive heart failure H - hypertension A - age > 75 years D - diabetes mellitus S - stroke (or TIA)
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