Atrial fibrillation: Beyond "irregularly irregular"

Nursing, 2003 by Josephson, Linda, McMullen, Maureen

Avoid rate-controlling drugs in patients with suspected Wolff-- Parkinson-White syndrome because they can cause ventricular tachycardia or fibrillation. (Drugs that slow AV nodal conduction facilitate antegrade conduction along the bypass tract in these patients.) The treatment of choice for these patients is electrical cardioversion, especially if the arrhythmia is associated with hemodynamic compromise. If electrical cardioversion isn't possible, I.V. procainamide or amiodarone may be given to prolong the refractory period of the bypass

tracts. Remember that I.V. procainamide has a greater negative inotropic effect than I.V. amiodarone, so if cardiac impairment is known or suspected, amiodarone may be the better choice.

If long-term drug therapy fails, the practitioner may recommend a permanent pacemaker or AV nodal ablation.

Reestablishing sinus rhythm. Restoring sinus rhythm improves hemodynamics, alleviates symptoms, restores AV synchrony and physiologic control of heart rate, and prevents atrial dilation, left ventricular dysfunction, and thromboembolism. About half of all patients with recent-- onset AF will spontaneously convert to sinus rhythm within 24 to 48 hours. Spontaneous conversion is less frequent in patients with AF of more than 7 days' duration. Otherwise, in these patients, cardioversion with electrical current or drugs (or a combination of the two) may restore sinus rhythm.

For patients who don't convert spontaneously, the cardioversion method chosen depends on hemodynamic stability, pattern of presentation of AF, severity of symptoms, duration of the arrhythmia, coexisting conditions, history of AF, likelihood of long-term success, and the patients wishes.

If the patient is unstable with serious signs and symptoms related to the rapid heart rate, immediate electrical cardioversion is recommended.

Direct current electrical cardioversion carries the risk of skin burns; postshock AV block, sinus arrest, or other arrhythmias; respiratory compromise; or an embolic event if the patient hasn't been adequately anticoagulated. Serious ventricular arrhythmias may occur if the patient has hypokalemia or digoxin toxicity.

Electrical cardioversion is less likely to restore and maintain sinus rhythm if AF has been present for more than a year. Provide procedural sedation, if the patients clinical condition permits, to alleviate pain and anxiety.

Drugs available to chemically restore sinus rhythm include amiodarone (a Class III antiarrhythmic) and ibutilide (a newer Class III drug). Ibutilide seems significantly more effective in converting AF and atrial flutter. Ibutilide prolongs repolarization of the atria and ventricles by activating a slow inward sodium current rather than blocking the outward flow of potassium, as do most Class III drugs. So far, it's available in IN form only

Patients treated with ibutilide should be observed carefully for several hours after conversion to sinus rhythm because the drug has a relatively high rate (8%) of torsades de pointes.