Atrial fibrillation: Beyond "irregularly irregular"

Nursing, 2003 by Josephson, Linda, McMullen, Maureen

Sotalol, a Class III nonselective beta-blocker, and procainamide, a Class IA antiarrhythmic, can also be considered for chemical cardioversion, but the ACC/AHA/ESC guidelines state that they're less effective and not as well researched for pharmacologic conversion of AE

Electrical cardioversion may be combined with drug therapy Class I drugs can delay recurrence of AF but don't seem to contribute to successful cardioversion. In contrast, according to various studies, the Class III drug amiodarone appears to increase the success of cardioversion and to be 60% effective in maintaining sinus rhythm, even in patients whose AF has lasted more than 6 years.

Any patient whose AF has lasted more than 48 hours (or the duration of AF is unknown) requires anticoagulation before cardioversion. Typically, warfarin is administered for 3 to 4 weeks to achieve an international normalized ratio (INR) range between 2 and 3. Following successful cardioversion, the patient should continue taking warfarin until normal sinus rhythm has been maintained for at least 4 weeks.

Because AF recurs in about half of all patients treated with antiarrhythmic drugs, attempting to eliminate recurrence altogether may be unrealistic. Taking a more moderate approach-simply striving to decrease the frequency and severity of AF recurrence-the drug of choice

becomes the one best tolerated by the patient, with the mildest adverse effects and the easiest administration.

For a look at drugs used to maintain sinus rhythm once its achieved see Using Drugs to Maintain Sinus Rhythm.

Preventing thromboembolism. Stroke is one of the most serious complications of AF, even in patients with no valvular problems. The risk of stroke in elderly patients with AF is about 5% (six times that of the general population). Patients at highest risk for thromboembolic problems have at least one of these risk factors: age greater than 75 years, hypertension, left ventricular dysfunction, or diabetes, CAD, or thyrotoxicosis.

Anticoagulation with warfarin can reduce the risk of stroke by as much as 70%. Maintaining an INR between 2 and 3 reduces the risk of serious bleeding to about 1%, depending on the patients age and other risk factors. Aspirin, although offering some protection, is significantly less effective at preventing stroke in AF than warfarin.

By understanding the pathophysiology and treatment of AF, you can help your patient prevent complications associated with thromboembolism.

SELECTED REFERENCES

Benjamin, E., et al.: "Impact of Atrial Fibrillation on the Risk of Death: The Framingham Heart Study," Circulation. 98(10):946-952, September 8, 1998.

Cummins, R. (ed): Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Dallas, Tex., American Heart Association, 2000.

Reiffel, J.: "Impact of Structural Heart Disease on the Selection of Class III Antiarrhythics for Prevention of Atrial Fibrillation and Atrial Flutter," American Heart Journal. 135(4):551-556, April 1998.

Roy, D., et al.: "Amiodarone to Prevent Recurrence of Atrial Fibrillation," The New England Journal of Medicine. 342(13):913-920, March 30, 2000.