Rhythm Control

Lecture Objectives

  • Describe the cardiac conduction system of the heart

  • Identify antiarrhythmic medications used to achieve and maintain normal sinus rhythm in atrial fibrillation

  • Provide treatment options for rhythm control given concomitant disease states and medications

Conduction System of Heart

Purkinje Fiber Action Potential

Rhythm Control

  • Not a goal for every patient

  • Indications:

    • Symptomatic from AF despite attempt at rate control

    • Adequate rate control cannot be achieved

    • HF with reduced ejection fraction

    • Young or newly diagnoses

    • Low chance of recurrence

      • First episode, precipitated by acute illness

    • Tachycardia-mediated cardiomyopathy

    • Patient preference

Antiarrhythmic Drugs

Class I Antiarrhythmic Agents

  • Sodium channel blockade → Impacts phase 0

  • Activity is heart rate dependent

    • More effective at terminating acute arrhythmia

  • Class IB not used for AF → Used for ventricular arrhythmia

  • All class I need concomitant use of AV nodal blocker (beta-blocker or calcium channel blocker)

    • Risk of converting to flutter

CAST Trial

  • Recent myocardial infarction patients with asymptomatic non-threatening ventricular arrhythmias did not benefit and may have been harmed by attempts to suppress arrhythmia with flecainide or encainide

Class IA Antiarrhythmics

  • Significantly lower prescribing for AF

  • Quinidine, Procainamide, Disopyramide


Class IC Antiarrhythmics

  • Flecainide


  • Propafenone


Class III Antiarrhythmics

  • Amiodarone


    • Exclude/use with in caution in…

      • Sinus or AV node dysfunction

      • Intranodal conduciton disease

      • Lung disease

      • Prolonged QT interval

    • Dose reduction by 50% if used with…

      • Digoxin

      • Warfarin

    • Adverse Effects

      • Toxic to every organ system except kidneys → NO renal dosing

  • Dronedarone

    • Displays amiodarone MOA

    • Lacks iodine → Less toxicity

    • Metabolism: CYP3A4, 2D6, Pgp

  • Sotalol

    • Doses > 160 mg

    • Monitor QT interval and renal function

    • Contraindicaiton

      • CrCl < 40 mL/min

      • QTc > 450 msec

      • K < 4 mEq/L

      • Sick sinus syndrome

    • Must be in hospital > 3 days on maintenance dose

  • Dofetilide

    • Must be in hospital for minimum of 3 days with continuous ECG monitoring for initiation

    • Monitor

      • Initially: ECG, renal function, K+, Mg2+, HR, BP

      • 3 months: QTc, CrCl

        • D/C if QTc > 500 msec

    • Contraindications

      • Use with HCTZ

      • CrCl < 20 mL/min

      • Baseline QTc > 440 msec

    • Dosing

      • Oral 125-500 mcg BID


    • Adverse Effects

      • QT prolongation

      • Torsades de Pointes

      • Flu-syndrome



QT Prolongation

  • All antiarrhythic medications can cause QT prolongation and/or trigger ventricular arrhythmias

  • Risk factors for torsades:

    • Hyperkalemia

    • Hypomagnesemia

    • Older age

    • Bradycardia

    • QT prolongation or use of QT prolonging drugs

    • Female sex

    • Heart failure

    • Left ventricular hypertrophy

Pharmacologic Cardioversion

  • < 7 days

    • Class III agents

    • Class IC agents

  • > 7 days

    • Dofetilide (Oral)

    • Amiodarone

    • Ibutilide (IV)

Choosing Rhythm Control Agents

  • Maintenance therapy

    • Any class IC or III

  • Safe to use with HF

    • Amiodarone, dofetilide

  • Safe to use in CAD

    • Amiodarone, dronedarone, sotalol, dofetilide

Direct Current Cardioverison (DCC)

  • Indications:

    • Hemodynamically unstable

    • Severely symptomatic

    • New onset in AF in patients with ACS with:

      • Hemodynamic instability

      • Ischemia

      • Poor rate control

    • Rapid ventricular response (RVR) that does not respond to pharmacological treatment, exacerbating:

      • Cardiac ischemia

      • Hypotension

      • CHF

Anticoagulation and Cardioversion

Catheter Ablation

  • Reserved for patients with recurrent symptomatic AF

    • Refractory or cannot tolerate Class I/III agents

  • Atrioventricular nodal ablation

    • Ablate AV node and chronically pace ventricles

    • Pacemaker inserted

  • Pulmonary vein ablation

    • Ablate origin of abnormal atrial foci

      • Often near pulmonary vein/atrial tissue intersection

Surgical Based Treatments

  • Open heart surgery/MAZE procedure

    • Create surgical incisions across atria that disrupts re-entrant circuits

  • Mini-MAZE/pulmonary vein isolation

  • Left atrial appendage removal or clipping

Watchman Procedure

  • Alternative to lifelong anticoagulant use

  • Permanent implant

  • Implanted into left atrial appendage

  • Continue anticoagulant for 45 days until closed off

  • ASA + clopidogrel for 6 months then ASA indefinitely

AF Treatment Summary