Antiarrhythmics Flashcards
Atrial Fibrillation (common mechanism)
- disorganized “functional” reentry
- continual AV node stimulation –> irregular, often rapid ventricular rate
Atrial Fibrillation (acute therapy)
- control ventricular response: AV nodal block (adenosine, Ca++ channel block, beta-blockers)
- restore sinus rhythm: DC cardioversion
Atrial Fibrillation (chronic therapy)
- control ventricular response: AV nodal block
2. maintain normal rhythm (amiodarone, dronedarone, dofetilide, flecainide, propafenone, sotalol)
Atrial Flutter (common mechanism)
- stable reentrant circuit in the right atrium
- continual AV node stimulation and irregular, often rapid, ventricular rate
- ventricular rate often rapid and irregular
Atrial Flutter (acute therapy)
-same as atrial fibrillation
Atrial Flutter (chronic therapy)
-ablation
Atrial Tachycardia (common mechanism)
-enhanced automaticity, DAD-related automaticity, or reentry within the atrium
Atrial Tachycardia (acute therapy)
-AV node block until ablation can be performed
Atrial Tachycardia (chronic therapy)
-ablation
AV nodal reentrant tachycardia (PSVT) (common mechanism)
-reentrant circuit within or near AV node
AV nodal reentrant tachycardia (acute therapy)
- adenosine
- AV nodal block
AV nodal reentrant tachycardia (chronic therapy)
- AV nodal block
- ablation
VT in patients with remote myocardial infarction (common mechanism)
-reentry near the healed myocardial infarction
VT in patients with remote MI (acute therapy)
- lidocaine
- procainamide
- DC cardioversion
VT in patients with remote MI (chronic therapy)
- ICD
- Amiodarone
- K+ channel block
VT in patients without structural heart disease (mechanism)
-DADs triggered by increased sympathetic tone
VT in patients without structural heart disease (acute therapy)
- adenosine
- verapamil
- beta-blockers
- DC cardioversion
VT in patients without structural heart disease (chronic therapy)
- verapamil
- beta blockers
- ablation
VF (common mechanism)
-disorganized reentry
VF (acute therapy)
-DC cardioversion
VF (chronic therapy)
- ICD
- amiodarone to block reoccurance
Torsades de Pointes congenital or acquired (common mechanism)
-early afterdepolarization-related triggered activity
Torsades de Pointes congenital or acquired (acute therapy)
- magnesium
- pacing
Torsades de Pointes congenital or acquired (chronic therapy)
- beta-blockade
- pacing
Procainamide
- Class 1A
- use- and state-dependent block of sodium channels - some block of potassium channels
- slowed conduction velocity and pacemaker activity
- prolonged action potential duration and refractory period
- treatment in atrial and ventricular arrhythmias, especially after MI
- oral and parenteral - oral slow release forms available
- duration: 2-3 hrs
- Toxicity: increased arrhythmias, hypotension, lupus-like syndrome
Disopyramide
- similar to procainamide, but longer duration of action
- toxicity includes antimuscarinic effects and heart failure
Quinidine
-similar to procainamide, but toxicity includes cinchonism (tinnitus, headache, GI disturbance) and thrombocytopenia
Lidocaine
- Class 1B
- highly selective use- and state-dependent sodium block
- minimal effect in normal tissue
- no effect on potassium channel
- used to treat ventricular arrhythmias, post-MI and digital induced arrhythmias
- IV and IM
- duration: 1-2 hrs
- Toxicity: CNS sedation or excitation
Mexiletine
similar to lidocaine, but oral activity and longer duration of action
Flecainide
- Class IC
- selective use- and state-dependent block of sodium channel
- slowed conduction velocity and pacemaker activity
- treats refractory arrhythmias
- oral duration: 20 hours
- Toxicity: increased arrhythmias, CNS excitation
Metoprolol
- Class 2
- similar to propranolol, but beta-1 selective
Esmolol
- Class 2
- selective beta-1 receptor blockade
- IV only, 10 min duration
- used in perioperative and thyrotoxicosis arrhythmias
Propranolol
- Class 2
- block of beta receptors
- slowed pacemaker activity
- post MI as prophylaxis against sudden death, ventricular fibrillation; thyrotoxicosis
- oral, parenteral duration: 4-6 hrs
- Toxicities: bronchospasm; cardiac depression; AV block; hypotension
Sotalol
- Class 2
- beta adrenoceptor block and potassium block (class III activity)
- treats ventricular arrhythmias and atrial fibrillation
- oral duration: 7 hrs
- Toxicity: dose-related Torsades de Pointes; cardiac depression
Amiodarone
- Class III
- strong potassium block produces marked prolongation of action potential and refractory period
- Group I activity slows conduction velocity
- Group 2 and 4 activity confer additional antiarrhythmic activity
- treats refractory arrhythmias - used off-label in many arrhythmias (broad spectrum of therapeutic action)
- oral and parenteral
- half-life and duration of action: 1-10 weeks
- Toxicities: thyroid abnormalities, deposits in skin and cornea, pulmonary fibrosis, optic neuritis
- torsades de pointes is rare with amiodarone
Dronedarone
- Class III
- structural analog of amiodarone lacking iodine
- half-life: 24 hrs
- lacks major side effects of amiodarone
- diarrhea, nausea, vomiting, abd pain, photosensitivity, QT prolongation
Ibutilide
- Class III
- selective potassium block
- prolonged action potential and QT interval
- treatment of acute atrial fibrillation
- IV only
- duration: 6 hrs
- Toxicity: Torsades de Pointes
Dofetilide
- Class III
- like ibutilide
- treatment and prophylaxis of atrial fibrillation
- oral
- duration: 7 hrs
- Toxicity: Torsades de Pointes
Verapamil
- Class IV
- state and use-dependent calcium channel block
- slows conduction in AV node and pacemaker activity
- PR interval prolongation
- treats AV nodal arrhythmias, especially in prophylaxis
- oral and parenteral
- Duration: 7 hours
- Toxicity: cardiac depression; constipation; hypotension
Diltiazem
- Class IV
- like verapamil
- rate control in atrial fibrillation
- oral and parenteral
- duration: 6 hrs
- Toxicity: cardiac depression; constipation; hypotension
Dihydropyridines
- Class IV
- calcium channel blockers but not useful in arrhythmias; sometimes precipitate them
Adenosine
- miscellaneous
- increase in diastolic potassium channel of AV node that causes marked hyperpolarization and conduction block
- reduced calcium channel
- treats acute nodal tachycardias
- IV only
- Toxicity: flushing, bronchospasm, chest pain, headache
Potassium ion
- miscellaneous
- increase in all potassium currents
- decreased automaticity
- decreased digitalis toxicity
- treats digitalis toxicity and other arrhythmias if serum potassium is low
- oral and IV
- Toxicity: both hypokalemia and hyperkalemia are associated with arrhythmogenesis; severe hyperkalemia causes cardiac arrest
Magnesium ion
- miscellaneous
- poorly understood
- possible increase in Na/K ATPase activity
- treats digitalis arrhythmias or other arrhythmias if serum Mg is low
- IV only
- Toxicity: muscle weakness, respiratory paralysis
