Antiarrythmias Medicines

What can cause arrhythmias?

1. Electrolyte

2. Overstimulation

What are the different types of arrhythmias?

1. Tachycardias

2. Premature contractions

3. Flutters and fibrillations

Supraventricular arrhythmias

• Originate in the atria and atrioventricular (AV) nodal areas.

• Include paroxysmal atrial tachycardia, atrial flutter, atrial fibrillation, and premature atrial contractions (PACs)

Ventricular Arrhythmias 

• Originate below the AV node.

• Include premature ventricular contractions (PVC), ventricular tachycardia, and ventricular fibrillation

Phases of the cardiac action potential

Phases of cardiac action potential.

• Phase 0 - Generation of action potential.

• Phase 1–3 - Repolarization of membrane.

• Phase 4 - Resting level

Electrophysiological properties of the heart

Conduction, refractoriness, and automaticity

Which three ions are antiarrhythmic drugs messing with?

Calcium, Potassium, and sodium

What do anti-arrhythmias do?

• Influence the movement of ions.

• Act on a specific phase of the action potential.

• Can cause proarrhythmia

Antiarrhythmic drugs are classified into the

Vaughn-Williams Classification

VW Class 1

Blocks sodium channels

Class II

Blocks beta 1 receptors

Class III

blocks potassium

IV

blocks calcium

Class I Antiarrhythmics Drugs: Sodium Channel Blcokers

Block Na ion influx during depolarization of nerves and excitable membranes.

• Prolong depolarization and conduction during phase 0.

• Subdivided into three groups based on the degree to which they block Na ions during depolarization

• 1C: intense

1A: moderate - Quinidine (No brand name)

Cardiac depressant, produces anticholinergic and alpha-blocking effects. (Old Medicatons and has a lot of side effects)

1A: mild - Procainamide (Procanbid)

Produces less anticholinergic and alpha-blocking actions than quinidine. Has a lot fewer side effects. It is administered orally and IV. Primarily used for ventricular arrythmia. Side effects include nausea, diarrhea, skin rash. Can produce changes in ECG.

1A Disopyramide (Norpace)

Produces decreased conduction and prolonged refractory period. Only approved for ventricular arrythmias. Side effects include constipation, urinary retention, and high doses can lead to toxcitiy.

Class 1B: Lidocaine (Xylocaine)

Prevents ventricular arrhythmias, depresses automaticity. Can impair liver function and can cause CNS depression and cardiac or respiratory arrest.

1B: Mexiletine (Mexitil) - Derivative of lidocaine

Used for treatment of outpatient ventricular arrythmia.

Class 1C: Flecanide (Tambocor) and propafenone (Rythmol)

Used to treat arrhythmias that are unresponsive to other antiarrhythmic drugs. Can cause heart failure. Can have GI disturbances, bradycardia, heartblock.

Class 2: Beta Blockers

Decrease heart rate, AV conduction, and automaticity of the SA and AV nodes of atrial and ventricular muscle. Mainly indicated for supraventricular arrythmias and prevents recurrent MI. 

Propranolol (Inderal)

Possesses beta- blocking and depressant effects. Side effects: hypotension, bradycardia. Overdoses can cause cardiac arrest

Esmolol (Brevibloc)

Affects beta-1 receptors in the heart. Administered in emergency situations.

CLASS 3 ANTIARRHYTHMIC DUGS: POTASSIUM CHANNEL BLOCKERS

Blocks potassium channels

Interferes with efflux of potassium during repolarization 

Amiodarone (Cordarone)

used for most supraventricular and ventricular arrhythmia. Blocks sodium and calcium channels as well. Dizziness, tremors, cardiac toxicities, heart block, heart failure. Can cause blue/gray discoloration. It is very effective at controlling arrythmias.

Sotalol (Betapace)

treats ventricular arrhythmias and atrial fibrillations. It is not class II because it blocks some potassium channels. Adverse: similar to beta blockers and can lead to fainting and ventricular tachy.

Dofetilide (Tikosyn

helps in the treatment of atrial fibrillation to normal sinus rhythm 

• Ibutilide (Corvert)

indicated for the conversion atrial flutter and atrial fibrillation to normal sinus rhythm

Class IV: Calcium Channel Blcokers

• Effect the SA node - Slow depolarization and a decrease in heart rate.

• Effect on the AV node - Slow conduction.

• Affect contraction of cardiac and smooth muscle.

• Reduce myocardial contractility

Calcium Channel Blockers

• Effect the SA node - Slow depolarization and a decrease in heart

rate.

• Effect on the AV node - Slow conduction.

• Affect contraction of cardiac and smooth muscle.

• Reduce myocardial contractility

Adenosine (Adenocard)

Used in emergency and acute situations. Can cause asystole.