Essentials of Diagnosis
Palpitations, shortness of breath, chest pain, dizziness.
Rapid, irregular pulse (may be regular in atrial flutter).
ECG demonstrates atrial fibrillation or atrial flutter.
General Principles in Older Adults
The prevalence of AF increases with age. Currently, there are approximately 3 million people in the United States with AF, and this number is projected to double by the year 2050, with 50% of affected individuals being older than the age of 80 years. AF is more common in men than in women at all ages. Atrial flutter (AFL) is closely related to AF, and patients frequently will have both arrhythmias at different times.
In older adults, AF most commonly occurs in the setting of hypertension, coronary artery disease (CAD), valvular abnormalities, or HF. AF also occurs frequently in older patients with systemic illnesses, such as pneumonia, and following cardiac or noncardiac surgery. Hyperthyroidism (including subclinical hyperthyroidism), acute or chronic lung disease, sleep-disordered breathing, pulmonary embolism, and pericardial disease are additional precipitants of AF. Prevention and appropriate treatment of these conditions can reduce incident AF.
Symptoms associated with AF are highly variable. Palpitations caused by rapid ventricular rates are common, as are shortness of breath, fatigue, and dizziness. Many patients are asymptomatic or mildly symptomatic. Acute HF caused by tachycardia and loss of atrial contraction is a common presentation of AF in older patients, especially those with impaired diastolic function. Some patients have no cardiac symptoms but present with thromboembolic events, such as a transient ischemic attack or stroke. Rarely, asymptomatic patients with AF and rapid ventricular rates present with HF symptoms as a result of tachycardia-mediated cardiomyopathy.
The cardinal physical finding of AF is an irregularly irregular rhythm. AF can be very rapid, with ventricular rates of 130–180 beats/min In older patients with conduction disease, ventricular rates can be normal or even slow. AFL is often regular as a result of more organized atrial activity that conducts to the ventricle with 2:1, 3:1, or 4:1 AV block. An irregular rhythm caused by variable block is also common, and may be indistinguishable from AF based on physical examination alone. Signs of volume retention and HF may be seen in patients with diastolic or systolic ventricular dysfunction in whom the loss of atrial contraction diminishes cardiac output.
The ECG is diagnostic in patients with ongoing AF or AFL. AF is characterized by lack of organized atrial activity and irregular QRS intervals. AFL is more organized, and the most common finding is a “sawtooth” pattern best seen in the inferior leads (II, III, and aVF).
Echocardiography is useful to assess underlying cardiac disease and chamber dimensions, and to rule out tachycardia-mediated cardiomyopathy. Increasing left atrial size is associated with greater risk for recurrent arrhythmias. Severe valvular disease, systolic dysfunction, and pulmonary hypertension are associated with reduced likelihood of restoring and maintaining sinus rhythm.
Cardiac catheterization is not routinely indicated in evaluation of AF, but may be considered for assessment of CAD, cardiomyopathy, or valvular abnormalities.
Serum electrolytes and thyroid function tests should be measured in all patients with newly diagnosed AF or AFL. In patients with a permanent pacemaker or ICD, device interrogation can provide information about rate control and overall AF burden.
AF and AFL must be distinguished from other types of supraventricular arrhythmias. Frequent premature atrial complexes, paroxysmal atrial tachycardia, and multifocal atrial tachycardia (MAT) may present with similar symptoms and physical findings to those seen with AF or AFL, but in most cases the 12-lead ECG is sufficient to establish the correct diagnosis. Occasionally, vagal maneuvers or administration of adenosine may be necessary to distinguish AFL from other supraventricular arrhythmias. AF or AFL may also present as a wide complex tachycardia that may be difficult to distinguish from ventricular tachycardia.
AF and AFL are not immediately life-threatening but can result in significant complications if not properly treated. The most devastating complication is stroke. Stroke can occur in the presence or absence of AF; indeed, in 1 major study more than 60% of patients were in sinus rhythm at the time of stroke. Risk factors for stroke, as indicated by the CHADS2 score, include congestive HF, hypertension, age 75 years or older, diabetes, and prior stroke or transient ischemic attack (TIA). CHADS2 assigns 2 points for stroke and 1 point for each of the other risk factors. Patients with no risk factors have an annual stroke risk of less than 3%, whereas those with all 5 risk factors have an annual stroke risk of greater than 18%. A recent update of the CHADS2 scoring system (CHA2DS2-VASc) assigns 2 points for age 75 years or older, 1 point for age 65–74 years, 1 point for vascular disease (coronary, aortic, or peripheral arterial disease), and 1 point for female sex. A CHADS2 or CHA2DS2-VASc score of ≥2 is associated with an annual stroke risk of at least 4%. In addition to stroke and TIA, thromboembolic events attributable to AF can affect circulation to the bowel, kidney, other organs, or limbs.
In patients with chronic AF and rapid ventricular rates, tachycardia-mediated cardiomyopathy can occur. HF and SCD may result from the cardiomyopathy. In older patients with LV hypertrophy and diastolic dysfunction, myocardial ischemia and non–ST-elevation MI can occur as a result of oxygen supply–demand mismatch.
Management of patients with new-onset AF or AFL should begin with identification of possible precipitating causes (see above). The primary objectives of treatment include prevention of stroke and other thromboembolic events, controlling the ventricular rate, and alleviating symptoms.
The risks of thromboembolic events are not significantly different between AF and AFL, or between paroxysmal and persistent forms of AF. Stroke risk should be assessed using the CHADS2 or CHA2DS2-VASc score. If the score is 2 or higher, long-term anticoagulation with warfarin or one of the newer agents is recommended. Note that under the CHA2DS2-VASc system, all men age 75 years or older and all women age 65 years or older are candidates for systemic anticoagulation, even in the absence of other risk factors. Furthermore because stroke risk increases progressively with age, older patients derive the greatest absolute benefit from anticoagulation.
The annual risk of serious bleeding on warfarin is estimated at 3%, and there is no evidence that older patients have higher incidences of significant bleeding as long as the dose is carefully adjusted to maintain the international normalized ratio (INR) between 2.0 and 3.0. (Exception: Patients with mechanical prosthetic valves require an INR from 2.5–3.5.) Foods high in vitamin K (eg, green leafy vegetables), antibiotics, and amiodarone can all affect INR levels. Older patients should be cautioned against concomitant use of warfarin and nonsteroidal antiinflammatory drugs because of increased risk of gastrointestinal bleeding. Patients with CAD are often treated with warfarin, aspirin, and another antiplatelet agent (eg, clopidogrel). To minimize the risk of bleeding, unnecessary agents should be discontinued when clinically appropriate (eg, clopidogrel 3–12 months after percutaneous coronary intervention).
Recently, 3 new anticoagulants became available with therapeutic effects comparable to warfarin. Rivaroxaban, apixaban (factor Xa inhibitors) and dabigatran (a direct thrombin inhibitor) have been shown to be as effective as warfarin in preventing thromboembolic events in patients with AF, without an increase in major bleeding and with reduced risk of intracranial hemorrhage (ICH). All have the advantage of a fixed-dose regimen without the need for INR monitoring. However, there are no available measures to acutely reverse the effects of these agents in patients with significant bleeding. In older patients with decreased creatinine clearance, lower doses are recommended, and the drugs are contraindicated in patients with creatinine clearances <15 mL/min. In addition, postmarketing data have raised concern that the risk of serious or life-threatening bleeding may be increased in patients older than 80 years of age who are receiving dabigatran.
In patients with absolute contraindications to warfarin and other anticoagulants, such as history of bleeding requiring blood transfusions or ICH, daily aspirin is reasonable. Combination therapy with clopidogrel and aspirin is more effective than aspirin alone in reducing stroke risk, but the risk of bleeding is similar to that of warfarin.
Effective control of ventricular rate during AF and AFL is a primary goal in both acute and chronic phases of management. Optimal rate control is traditionally defined as a resting heart rate (in AF) of 60–80 beats/min and a heart rate of 90–115 beats/min with activity. However, “lenient” rate control, defined as a resting heart rate of <110 beats/min, is associated with similar quality-of-life scores as stricter rate control. β Blockers are the drugs of choice in patients with CAD or reduced systolic function. Calcium channel blockers are not recommended in patients with depressed LV systolic function. Digoxin slows ventricular conduction through its effect on the parasympathetic nervous system but has limited efficacy in patients with high sympathetic tone, such as during physical exertion, in the immediate postoperative period, or in the setting of infection. In relatively sedentary patients, low-dose digoxin may provide adequate rate control, alone or in combination with β blockers or calcium channel blockers. In patients refractory to pharmacologic rate control, radiofrequency ablation of the AV node with permanent pacemaker implantation is an effective method of rate control and is associated with improved quality of life.
Restoration and maintenance of sinus rhythm is often necessary to alleviate symptoms. Rhythm control has not been shown to reduce mortality or strokes, and it does not circumvent the need for long-term anticoagulation in patients at high risk for thromboembolic events. Rhythm control is more difficult to achieve in patients with prolonged AF duration, depressed systolic function, severe diastolic dysfunction, or larger atrial size.
In patients who present with AF and rapid ventricular rate who are hemodynamically unstable, immediate electrical cardioversion is indicated. In stable patients, rate control with β blockers or calcium channel blockers should be initiated. In patients who remain symptomatic, electrical cardioversion may be performed with a low risk of thromboembolic events if the duration of AF is less than 48 hours or if the patient has been on warfarin with therapeutic INRs for at least 3 consecutive weeks. If the duration of AF is unknown, if the patient is not on long-term anticoagulation, or if recent INRs have been subtherapeutic, a transesophageal echocardiogram should be performed to rule out the presence of left atrial thrombus before cardioversion. Anticoagulation must be continued for a minimum of 1 month after cardioversion because of continuing risk of thrombus formation from atrial stunning after cardioversion. In patients with risk factors for stroke, anticoagulation should be continued indefinitely. Elective cardioversion with the new anticoagulants has not been well studied. Preliminary data suggest that continuous use of dabigatran for a minimum of 3 weeks before cardioversion is not associated with increased risk of stroke relative to warfarin.
Cardioversion may be performed either pharmacologically or electrically. Direct current cardioversion is more effective and safer than pharmacologic cardioversion. The only intravenous agent approved by the FDA for conversion of AF is ibutilide, but there is a risk of inducing prolonged QT interval and torsades de pointes ventricular tachycardia, especially in patients with HF. Although widely used, intravenous amiodarone is no more effective than placebo in the acute conversion of AF to sinus rhythm.
Long-term maintenance of sinus rhythm usually requires an oral antiarrhythmic agent. Quinidine and procainamide are rarely used because of limited efficacy and multiple side effects. Disopyramide is relatively contraindicated in older adults as a result of prominent anticholinergic side effects. Flecainide and propafenone are relatively effective for maintaining sinus rhythm but should not be used in patients with structural heart disease. Sotalol and dofetilide are renally cleared and can prolong the QT interval; consequently, these agents must be used cautiously, especially in older women (who tend to have longer QT intervals at baseline) with decreased creatinine clearance. Amiodarone is commonly used because of its effectiveness and relative lack of short-term side effects. However, thyroid, liver, neurologic, and lung toxicity may occur during long-term use, and routine monitoring of these organ systems is essential. Dronedarone is an agent similar to amiodarone without long-term organ toxicities, but rare cases of acute liver failure have been reported. Dronedarone is contraindicated in patients with active HF or persistent AF.
Radiofrequency ablation for typical “sawtooth” AFL is commonly performed with high success and low complication rates. Ablation of AF, which mainly involves electrical isolation of the pulmonary veins from the left atrium, has become a frequently performed and relatively effective procedure. The success rate, defined as freedom from recurrence of AF at 1 year, is approximately 70% for paroxysmal AF, but much lower for persistent or permanent AF. Major complications, including stroke, pulmonary hemorrhage, deep venous thrombosis, pulmonary embolism, cardiac perforation or tamponade, esophageal perforation, and death, occur in 3% to 5% of cases. AF ablation has not been shown to reduce stroke risk, so it does not obviate the need for long-term anticoagulation in high-risk patients. Few studies have specifically examined the efficacy and safety of AF ablation in older patients, but limited retrospective data suggest that in selected octogenarians outcomes are similar to those in younger patients, although postprocedure hospitalization times are longer. A surgical approach for treatment of AF, the Cox-Maze procedure, has a success rate of greater than 90% for curing AF, and has been shown to reduce strokes. In patients with a history of AF who require valvular or bypass surgery, concomitant Coz-Maze procedure should be considered.
Untreated AF is associated with increased mortality mainly as a consequence of strokes and tachycardia-induced cardiomyopathy with resultant HF and increased risk of sudden death. With appropriate treatment, the long-term prognosis of AF and AFL is excellent, and survival rates are similar in patients managed with rate control or rhythm control. Hemodynamic instability or severe symptoms attributable to AF are associated with significant morbidity and high costs from recurrent hospitalizations, procedures, and antiarrhythmic medications.