Am Fam Physician. 2000;61(2):539-540
The prevalence of atrial fibrillation increases with age and is associated with a higher risk of cardiovascular death, congestive heart failure and stroke in older patients. Aronow reviews current approaches to management of atrial fibrillation in patients more than 60 years of age.
Atrial fibrillation may be discovered incidentally after a stroke or an episode of congestive heart failure or pulmonary edema. When present, symptoms may include palpitations, chest pain, dizziness, cough, fatigue or syncope. Diagnostic testing should include 12-lead electrocardiography (ECG) with a one-minute rhythm strip, echocardiography and, possibly, 24-hour ambulatory ECG. Noncardiac causes of atrial fibrillation should be investigated as well, so thyroid function tests should also be ordered. Underlying causes of atrial fibrillation should be treated, including infection, congestive heart failure, hypoxia, hypokalemia and pneumonia. Patients with atrial fibrillation should be advised to avoid caffeine and alcohol, as these precipitate and exacerbate the problem.
Immediate direct-current cardioversion is indicated to control a rapid ventricular rate in patients who have atrial fibrillation and acute myocardial infarction or ischemia, severe congestive heart failure, syncope or hypotension. If the patient has no concurrent medical problems, intravenous verapamil, diltiazem or beta blockers can be used. The initial dose of verapamil is 0.075 mg per kg, up to 5 mg, with a second dose 10 minutes later if the rate is still not slowed. The initial dose of diltiazem is 0.25 mg per kg given over 2 minutes, with a second dose of 0.35 mg per kg 15 minutes later if the rate is not slowed. Propranolol in a dose of 1 mg should be given over five minutes, followed by 0.5 mg per minute, up to 0.1 mg per kg. After the ventricular rate is slowed, the oral forms of these medications should be started (verapamil in a dosage of 80 to 120 mg every six to eight hours; diltiazem in a dosage of 60 to 90 mg every six hours; propranolol in a dosage of 10 to 80 mg every six hours).
Digoxin is used to control a rapid ventricular rate that is not associated with increased sympathetic tone (e.g., hyperthyroidism, fever or acute blood loss), Wolff-Parkinson-White syndrome or hypertrophic obstructive cardiomyopathy. The initial dose should be 0.5 mg orally, followed by 0.25 mg six to eight hours later if the rate is not slowed. A third dose of 0.25 mg may be needed after another six to eight hours. The usual maintenance dosage in older patients is 0.125 to 0.25 mg daily, as these patients are more susceptible to digitalis toxicity. If a rapid ventricular rate persists despite digoxin therapy, oral verapamil, diltiazem or a beta blocker should be added to the regimen. If drug therapy does not successfully control the rate, radiofrequency catheter modification of atrioventricular conduction may be necessary, followed by ablation if the rate remains uncontrolled.
Elective direct-current cardioversion is indicated in some patients. For a list of favorable and unfavorable conditions, see the accompanying table about elective cardioversion. Use of class I antiarrhythmic drugs after cardioversion does not seem to maintain sinus rhythm. Therefore, anticoagulant therapy and an agent to control ventricular rate, if needed, are advisable in older patients with atrial fibrillation. Beta blockers are useful in these cases as they act to control ventricular arrhythmias; thus, if atrial fibrillation recurs after conversion to sinus rhythm, the beta blocker will help slow the ventricular rate.
The risk of stroke is higher in patients with atrial fibrillation who have one or more risk factors (see the accompanying table about risk factors). The risk of stroke is 18.6 percent per year in patients with three or more risk factors and 6 percent per year with one or two. In patients with no risk factors, the risk of stroke is only 1 percent per year. Warfarin reduces the risk of thromboembolic stroke in patients with atrial fibrillation by 68 percent. In older patients (mean age 84 years in one study), this risk was reduced by 76 percent when the International Normalized Ratio (INR) was maintained between 2 and 3. Warfarin is more effective than aspirin in reducing the risk of stroke but is associated with an increased risk of bleeding events (1.1 and 0.7 percent per year, respectively).
The author concludes that older patients with atrial fibrillation who are at high risk for stroke should take warfarin if there are no long-term contraindications. Patients at low risk or who have warfarin contraindications should take 325 mg of aspirin daily.