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, |
| 200 to 300 mg PO divided bid |
Hypotension, rapid atrial flutter |
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| 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 |
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| 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 |
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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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