SM 140a - Pharmacology of Anti-Arrhythmic Drugs Flashcards
Procainamide, Quinidine, and Disopyramide are Class ___ anti-arrhythmic agents that block _____
Procainamide, Quinidine, and Disopyramide are Class IA** agents that block **Na+ and K+ channels
Slow AP upstroke, prolong AP duration
Problems with ________ usually cause Ventricular Fibrillation
A. Automaticity
B. Reentry
C. Triggered Activity
B. Reentry
Most drugs that block _______ channels are proarrythmic for Torsades de Pointes.
Why?
Most drugs that block potassium channels are proarrythmic for Torsades de Pointes
Blocking potassium channels increases the length of the action potential (phases 2 and 3). Anything that prolongs phases 2 and 3 has the potential to cause Early After Depolarizations (EADs), which is the triggered activity that leads to Torsades de Pointes
Which agents can be used to suppress symptomatic PVCs and VT in the setting of MI?
- Class II
- Class III: Amiodarone only
- Class IB
- Class IA: Procainamide occasionally
Lidocaine, Mexelitine, and Phenytoin are Class ___ anti-arrhythmic agents that block _____
Lidocaine, Mexelitine, and Phenytoin are Class IB** agents that block **Na+ channels moderately (No K+ blocking action)
Slow AP upstroke
What are the general treatment principles for treating an arrhythmia that is caused by triggered activity?
(Ex: Monomorphic VT, Polymorphic VT)
- Cause: Early After Depolarizations (Phase 2-3)
- Common if action potential is prolonged
- Ex: Torsades de Pointes
-
Treat by shortening the action potential
(without messing with Na+ or Ca2+ channels)
- Cause: Delayed After Depolarizations (Phase 4)
- Common if intracellular Ca2+ is too high
- Ex: Digitalis Toxicity
- Treat by reversing the underlying cause of high Ca2+
Procainamide is a class ____ anti-arrhythmic that blocks _________ channels.
It can be used to ___________, and ____________.
Procainamide is a class IA anti-arrhythmic that blocks Na+ and K+ channels.
It is used to treat Sustained VT , and Prevent VT after MI.
(But it is rarely used because amiodarone and lidocaine are more effective)
Which tachycardias can arise from triggered activity?
- Monomorphic Ventricular Tachycardia**
- Polymorphic ventricular tachycardia
** = Can also arise from reentry (major cause) or automaticity
Veramapil is a class ____ anti-arrhythmic that blocks ______ channels. It _\_creases conduction time and _\_creases the refractory period in the AV node
It can be used to _____________ and _____________..
Veramapil is a class IV** anti-arrhythmic that blocks **Ca2+ channels. It increases conduction time and increases the refractory period in the AV node
It can be used to control heart rate in A-fib and A-flutter** and **terminate supraventricular tachycardia.
What are the major side effects of disopyrimide?
Typical anti-muscarinic side effects
- Urinary retention
- Constipation
- Blurred vision
- Dry mouth
- Closed angle glaucoma
Proarrythmic -> Torsades de Pointes, heart block
(Disopyrimide = class IA)
Which subclass (A, B, or C) of Class I anti-arrythmic drugs has the greatest potassium channel blocking action?
Class IA (Moderate Na+ and K+ channel blocking)
(Procainamide, Quinidine, Disopyramide)
A heart patient on medications is experienceing yellow vision and nausea.
Which drug might be causing this?
Digoxin
What are the major side effects of procainamide?
Drug induced lupus
Proarrythmic -> Torsades de Pointes, heart block
(Procainamide = IA)
Problems with ________ usually cause monomorphic VT
A. Automaticity
B. Reentry
C. Triggered Activity
B. Reentry
(Although monomorphic VT can also be caused by automaticity or triggered activity)
Describe the mechanism of action of lidocaine
Lidocaine binds to the activated and inactivated Na+ channel, but not the resting channel
This means it has little effect on normal, healthy tissue, whose channels are normally in the resting state.
Sick myocardium, however, is partially depolarized, so the Na+ channels are more likely to be in the activated or inactivated state.
Therefore, Lidocaine binds preferentially to sick myocardium to decrease the strength of the phase 0 upstroke
Dofetilide is a class ____ anti-arrhythmic that blocks ______ channels. It _\_creases action potential duration in heart tissues.
It can be used to _____________.
Dofetilide is a class III** anti-arrhythmic that blocks **K+ (and some Na+) channels. It increases action potential duration in heart tissues.
It can be used to maintain sinus rhythm in A-fib and A-flutter.
Which treatment strategy for atrial fibrillation involves modifying the atrial electrical properties in the SA node?
Rhythm control
Problems with ________ usually cause AVRT
A. Automaticity
B. Reentry
C. Triggered Activity
B. Reentry
Which class of anti-arrhytmic drugs are considered Ca2+ channel blocker?
Class IV
(Verapamil, Diltiazem)
What are the major side effect of digoxin?
- Anorexia
- Nausea, vomiting
- Disorientation
- Hallucination
- Yellow vision
Proarrhythmic ->
- AV nodal block (due to vagal tone)
- Ventricular Premature Beats (due to increased Ca2+)
- VT (due to reeentry or premature beats)
What are the major side effects of Quinidine?
Nausea, vomit, diarrhea
Cinchoism: CNS toxicity (Tinnitus, hearing loss, delerium, psychosis)
Proarrythmic -> Torsades de Pointes, Heart block
(Quinidine = Class IA)
Problems with ________ usually cause Ventricular Premature Beats
A. Automaticity
B. Reentry
C. Triggered Activity
A. Automaticity, and B. Reentry
Quinidine is a class ____ anti-arrhythmic that blocks _________ channels.
It can be used to ___________, and ____________, but it is most useful as an anti-malarial agent.
Quinidine is a class IA** anti-arrhythmic that blocks **Na+ and K+ channels.
It can be used to convert atrial fibrillation or atrial fluttur to sinus rhythm** , and **maintain sinus rhythm in atrial fibrillation patients, but it is most useful as an anti-malarial agent
(Other agents are more effective for these arrhthmias)
What are the major side effects of amiodarone?
- Hypo- or hyper-thyroidism
- Pulmonary fibrosis
- Hepatotoxicity
- Gray/blue skin discoloration
Proarrythmic -> Sinus bradycardia, AV block
Note: the only K+ channel blocker that does not cause Torsades de Pointes
(Amiodarone = class III anti-arrythmic)
Problems with ________ usually cause Atrial Flutter
A. Automaticity
B. Reentry
C. Triggered Activity
B. Reentry
Verapamil and diltiazem are Class ___ agents that block _____
Verapamil and diltiazem are Class IV** anti-arrhythmic agents that block **L-type Ca2+ channels
Prolong conduction time, refractory period in the AV node
What are the major side effects of dofetilide?
Headache GI effects
Proarrythmic -> Increase risk of hypokalemia, new or worse VT (ex: Torsades de Pointes)
(Dofetilide = Class III anti-arrythmic)
Ibutilide is a class ____ anti-arrhythmic that blocks ______ channels. It _\_creases action potential duration in heart tissues.
It can be used for _____________.
Ibutilide is a class III** anti-arrhythmic that blocks **K+** channels. It **increases action potential duration in heart tissues.
It can be used for acute termination of A-fib and A-flutter.
Which antiarrythmic might be useful in a patient with a loud systolic murmur that gets louder when standing from a squatting position?
This murmer is present in hypertrophic cardiomyopathy.
Treat with disopyramide
[Thank you Nathin Shlobin!]
Sotalol is a class ____ anti-arrhythmic that blocks ______ channels. It _\_creases action potential duration in heart tissues.
It can be used to _____________, ____________ and _____________.
Sotalol is a class III** anti-arrhythmic that blocks **K+ channels (also has some beta-blocking activity). It increases action potential duration in heart tissues.
It can be used to maintain sinus rhythm in A-fib and A-flutter**, **prevent AVNRT, AVRT** and **treat ventricular tachyarrythmias.
A heart patient on medications has shortness of breath and increased patellar reflexes on physical exam.
What medication might be casuing this?
Procainamide
Side effect = drug induced lupus, which induces arthralgia, leading to increased patellar reflexes and pleuritis (-> shortness of breath)
[We (thank you Nathan Shlobin) are pretty sure about this, but if you know of another drug suggest an edit!]
Amiodarone, Dronedarone, Soltalol, Ibutilide, and Dofetilide are Class ___ anti-arrhythmic agents that block _____
Amiodarone, Dronedarone, Soltalol, Ibutilide, and Dofetilide are Class III** agents that block **K+ channels (primarily)
Increase AP duration, Increase effective refractory period
Which drug is considered the most effective anti-arrythmic agent?
Why isn’t it always used?
Amiodarone (class III anti-arrythmic)
It is not alwyas used because thee side effects can be severe
- Hypo- or hyper-thyroidism
- Pulmonary fibrosis
- Hepatotoxicity
- Gray/blue skin discoloration
What are the major side effects of lidocaine?
CNS toxicity
(Confusion, delerium, parasthesias, grand mal siezures)
(Lidocaine = Class IB)