Which medications in the drug class Antidysrhythmics, Class III are used in the treatment of Atrial Flutter?

Updated: Nov 18, 2019
  • Author: Lawrence Rosenthal, MD, PhD, FACC, FHRS; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

Antidysrhythmics, Class III

Class III antidysrhythmics are used to slow ventricular response by inhibiting AV nodal conduction during atrial fibrillation or flutter. They are also indicated for use in conjunction with class IA and IC antiarrhythmics, which slow atrial fibrillation or flutter rate and may cause more rapid ventricular response.

Beta blockers currently play more of a secondary role in rate control in atrial flutter or fibrillation. Patients receiving these agents require careful monitoring of blood pressure.

Amiodarone (Cordarone, Parcerone, Nexterone)

Amiodarone may inhibit AV conduction and sinus node function. It prolongs the action potential and refractory period in myocardium and inhibits adrenergic stimulation. It blocks sodium channels with high affinity for inactive channels, blocks potassium channels, and weakly blocks calcium channels. In addition, amiodarone noncompetitively blocks alpha- and beta-adrenergic receptors. Before administration, control ventricular rate and heart failure (if present) with digoxin or calcium channel blockers.

Dronedarone (Multaq)

Dronedarone blocks sodium channels, blocks beta1-adrenergic receptors, and alters adenyl cyclase generation (ie, it has negative inotropic effects). It blocks potassium channels (eg, hERG) and therefore prolongs cardiac repolarization.

Dronedarone is indicated for reducing the risk of cardiovascular hospitalization in patients with paroxysmal atrial fibrillation or atrial flutter who have had a recent episode of either arrhythmia, are in sinus rhythm or will be cardioverted, and have associated cardiovascular risk factors.

Sotalol (Betapace, Betapace AF, Sorine)

This class III antiarrhythmic agent blocks potassium channels, prolongs action potential duration, and lengthens the QT interval. It is a non–cardiac-selective beta-adrenergic blocker. Sotalol is be effective in the maintenance of sinus rhythm, even in patients with underlying structural heart disease. Class III effects are seen only at oral dosages of 160 mg/day or higher.

Ibutilide (Corvert)

Ibutilide is a newer class III antiarrhythmic agent that may work by increasing action potential duration and thereby changing atrial cycle length variability. It is indicated for acute termination of atrial fibrillation or flutter of recent onset. Potentially fatal arrhythmias can occur with ibutilide, usually in association with QT prolongation, during or within a number of hours after its administration.

Dofetilide (Tikosyn)

Dofetilide is the prototype of a "pure" class III agent. It has been approved by the US Food and Drug Administration (FDA) for maintenance of sinus rhythm after conversion from atrial fibrillation or atrial flutter lasting longer than 1 week. It is also indicated for conversion of atrial fibrillation and atrial flutter to normal sinus rhythm. If patients do not convert within 24 hours of initiation of therapy, electrical cardioversion should be considered.

Torsades de pointes is the only complicating arrhythmia showing a dose-response relation. The prevalence with supraventricular arrhythmia is 0.8%. The majority of torsades de pointes episodes occur within the first 3 days of therapy.

Dofetilide has no effect on cardiac output, cardiac index, stroke volume index, or systemic vascular resistance in patients with ventricular tachycardia, mild to moderate heart failure, angina, and either normal or reduced left ventricular ejection fraction (LVEF). It does not affect blood pressure.

Dofetilide blocks delayed rectifier current (IKr) and prolongs action potential duration; indeed, even at higher dosages, it has no effect on other depolarizing potassium currents (IKs and Ik1). It terminates induced reentrant tachyarrhythmias (atrial fibrillation or flutter and ventricular tachycardia) and prevents their reinduction. At clinically prescribed concentrations, it has no effect on sodium channels, which are associated with class I effects. Furthermore, no effect is noted on alpha- or beta-adrenergic receptors.

Dofetilide must be initiated with continuous ECG monitoring, and monitoring must be continued for at least 12 hours after conversion. The dosage must be individualized according to creatinine clearance (CrCl) and QTc (use the QT interval if the heart rate is below 60 beats/min). There is no information on use of this drug for heart rates lower than 50 beats/min.


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