Management

2. Rhythm Control:

    a. Pharmacologic Options

Rhythm control is described as conversion and maintenance of atrial fibrillation to normal sinus rhythm.  This can be achieved through pharmacologic or direct-current cardioversion.  Rhythm control with drug appears simpler, but is usually less effective, and imposes the risk of toxicity and drug-induced torsades de pointes.  Pharmacologic cardioversion has a success rate of 30 to 60% while direct current cardioversion one of 75 to 95%.  Any attempt at rhythm control is more likely to succeed if used within 7 days of onset.  Other things to keep in mind are that a large majority of patients will have a spontaneous cardioversion within the first 24-48h, and that some drugs have a on onset of action of several days. 

Each cardioversion must be carefully planned, using anticoagulation for at least three weeks in those with atrial fibrillation for more than 48 hours.  This waiting period can be avoided, if a transesophageal echocardiogram ruled out the possibility of an atrial thrombus.

The thromboembolic risk remains elevated up to 10 days post cardioversion because of the early atrial mechanical dysfunction promoting thrombus formation in the left atrium (atrial stunning).  It is recommended that patient should also be anticoagulated for up to 4 weeks post sinus rhythm restoration. 

Unfortunately, only 20 to 30% of successfully cardioverted patients will remain in sinus rhythm after one year without chronic antiarrhythmic therapy.  The use of long term rhythm control agents increase the likelihood of success and prevent recurrence of arrhythmias.  They should be used in patients with severe symptoms on rate control regimens.  Under those circumstances, flecainide and propafenone are recommended long term agents in presence of minimal heart disease, and amiodarone and dofetilide in those with heart failure.  In asymptomatic patient it is not recommended to apply this approach as the risks of long term antiarrhythmics use outweigh their benefits.  Most patients requiring cardioversion needs to be hospitalized watching for proarrhythmia, and bradycardia.

 

Table 3. Rhythm Control Pharmacological Options
Drug Loading dose by
route of administration
Onset of action Maintenance dose Major side effect
Amiodarone 5 - 7 mg/Kg IV over
30 to 60 min
Days 0.5 - 1 mg/min IV for a total of
1.2 - 1.8 g/day until 10 g total then 200 to 400 mg/day
Hypotension*, heart block,
pulm toxicity, thyroid dysfct,
warfarin interaction,
1.2 to 1.8 g/day PO in divided doses until 10 g total then 200 to 400 mg/day 1 to 3 wks

1.2 to 1.8 g/day PO in divided doses until 10 g total then 200 to 400 mg/day Hypotension*, heart block,
pulm toxicity, thyroid dysfct,
warfarin interaction,
Dofetilide None 2 to 3 hrs Creatinine clearance / dose
      (ml/min)     /   (ug bid) PO
        > 60                500
       40 - 60             250
       20 - 40             125
        < 20        Contraindicated
QT prolongation,
torsades de pointes
Flecainide None 1.5 to 3 hrs 1.5 to 3.0 mg/kg IV over
10 to 20 min

Hypotension,
rapid atrial flutter

200 to 300 mg PO
divided bid
Hypotension,
rapid atrial flutter
Propafenone None 2 to 3 hrs 1.5 to 2.0 mg/kg IV over
10 to 20 min
Hypotension,
rapid atrial flutter
400 to 600 mg PO Hypotension,
rapid atrial flutter
Quinidine None 0.75 to 1.5 g PO divided
qid or bid
QT prolongation, torsades de pointes, GI upset, Hypotension
Sotalol None 1 to 2 hrs 160 to 320 mg PO divided bid QT prolongation, torsades de pointes, HF
Procainamide None 10 to 30 mins 1 to 4 g PO divided GI complaint, Hypotension

*     Do not use if systolic blood pressure less than 90 mmHg
**   Severe contraindication
*** Do not use or need careful monitoring in renal failure patient

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Table 4. Vaughan Williams Classification of Antiarrhythmic Drugs
Type IA Disopyramide
Procainamide
Quinidine
Type IB Lidocaine
Mexiletine
Type IC Flecainide
Propafenone
Type II Beta Blockerss (Proponolol)
Type III Amiodarone
Dofetilide
Sotalol
Ibutilide
Type IV Nondihydropyridine calcium channel
Antagonists (Verapamil and Diltiazem)

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