Anti-Arrhythmia Drugs Flashcards
(43 cards)
What are the Vaughn-William class 1 drugs we have to know?
1A- Quinidine (Na channel blocker)
1B- Lidocaine (Na channel blocker)
1C- Flecainide (Na channel blocker)
What are the Vaughn-William class 2 drugs?
They are the B-blockers.
- Metoprolol
- Propanolol
What are the Vaughn-William class 3 drugs?
These are the K-channel blockers.
- Amiodarone
- Dofetilide
What are the Vaughn William class 4 drugs?
Ca-channel blockers.
- Verapamil
- Diltiazem
Nifedipine does not have a strong affect on arrhythmias.
What are the 6 main types of antiarrhythmic drugs?
- Na channel blockers
- B blockers
- K channel blockers
- Calcium channel blockers
- Digoxin (cardiac glycoside)
- Adenosine
What are the 4 main goals of antiarrhythmia drugs?
- prevent SCD
- diminish symptoms
- diminish complications secondary to arrhythmias (emboli, syncope, hypotension)
- suppress arrhythmic events in patients with ICD to prevent excessive firing of the device
Treatment of arrhythmias uses a combination of invasive, non-invasive and pharmacological measures. _____________ and _______ therapy currently plats a more important role than __________ therapy.
Procudures and device-based play a more important role than drug-based.
How are class I antiarrhythmic drugs subdivided? Which is the most effective at terminating and preventing arrhythmias?
A- intermediate dissociation rate (Quinidine)
B- fast dissociation rates (lidocaine)
C- slow dissociation rates (flecainide)- MOST EFFECTIVE AT TREATING ARRHYTHMIA
What is the method of action of quinidine? What class of drug is it? What are the electrophysiological effects?
It is a class 1A antiarrhythmic that blocks Na channels (predominantly) and K channels. It has intermediate dissociation.
- lengthen the QT interval
- widen QRS
- raise threshold
- increase effective refractory period
What is the main therapeutic use of Quinidine?
What are the adverse effects?
It maintains sinus rhythm in a patient with atrial flutter or fibrillation to prevent V tach and V fib.
It is RARELY used.
Adversely- since it prolongs QT it can lead to Torsades des Pointes.
What is class of Lidocaine? What is the mechanism of action? What are the electrophysiological effects?
It is a class 1B antiarrythmic. It blocks Na channels exclusively. (has a fast dissociation)
- raise threshold
- decrease automaticity
- increase effective refractory period
Why doesn’t lidocaine work for atrial arrhythmias?
It has a fast dissociation rates, so it only is able to inhibit Na channels for a brief period.
What are the therapeutic uses of lidocaine? What are the adverse effects?
Therapy-
1. acute IV therapy for ventricular arrhythmia
Adverse Effect-
Survival was found to be WORSE with lidocaine
What class of drug is flecainide? What is the mechanism of action? What are the electrophysiological effects?
It is a class IC antiarrhythmia drug. It binds Na channels to block AND K channels. It may also weakly block Ca channels
- increased threshold
- increased effective refractory period
- slowed conduction (Na block)
- slowed repolarization (K block)
What changes would you see on an EKG of someone taking flecainide?
- Prolonged PR
- Wide QRS
- Long QT interval
What is the therapeutic use for flecainide?
What are the adverse effects?
- PSVT
- Atrial flutter and A. fib in patients WITHOUT structural heart disease
Adverse effects:
- new or worse arrhythmia (VT, VF, torsade de pointes)
- Increase ventricular rate in a patient with Atrial flutter
- worsen CHF, MI
What class of drug is amiodarone? What is the mechanism of action?
It is a class III drug and blocks K channels (mainly) but has slight effect on Na and Ca channels. It also non-competitively blocks adrenergic receptors.
What are the electrophysiological effects of amiodarone? What is seen on the EKG?
- slows conduction (Na block) which increases QRS
2 Slows AV-nodal conduction (Ca Block and adrenergic) which increases PR
3.Increases AP duration and increases QT (K block)
What are the therapeutic uses for amiodarone?
- Recurrent VT or VF resistant to other drugs
2. Maintain sinus rhythm with AF
What are the 3 most important adverse effects of IV amiodarone?
- Cause sinus bradycardia and inhibit automaticity (AV block)
- Hypotension due to vasodilation
- worsen arrhythmias and create new (long QT can lead to VT and Torsades des pointes)
3.
What are the 4 most important negative effects of oral amiodarone?
- Pulmonary toxicity/fibrosis (unusual at low dose)
- Worsens arrhythmias
- Liver injury (raised enzymes)- usually asymptomatic
- Hypo/Hyperthyroidism due to it blocking peripheral thyroxine (T4) to triiodothyronine (T3)
What is important about the pharmacokinetics of amiodarone?
It is metabolized in the liver and it interacts with drugs that are also metabolized by P450
What class of drug is Dofetilide? What is the mechanism of action?
It is a class III anti-arrhythmic that exclusively blocks K channels. Its action is specific to cardiac muscles
What are the electrophysiological effects of dofetilide? What do you see on the EKG?
- prolonged action potential (increased QT)