Atrial fibrillation (AF) is the most common tachyarrhythmia in humans, increasing in incidence with age and the presence of heart disease. Re-entry is the most likely primary mechanism. Anatomic and electrophysiologic changes in the atrial tissue are linked to a sustained abnormal rhythm. Patients with AF have a loss of atrial muscle and increased fibrous tissue. Recent work has renewed interest in the ectopic-focus theory, which suggests that rapidly firing atrial foci cause premature atrial complexes, short runs of atrial tachycardia or AF. Prystowsky describes the three basic therapeutic strategies for treatment of AF.
The three principal strategies are to restore and maintain sinus rhythm, to control ventricular rate and to prevent stroke. Combination therapy often is most appropriate. Anticoagulation and stroke prevention are supported by data from randomized controlled trials. Patients at high risk for stroke should be given warfarin and maintained at an International Normalized Ratio (INR) of 2.0 to 3.0. High risk factors for stroke include the following: (1) age greater than 65 years; (2) recent congestive heart failure; (3) diabetes mellitus; (4) a previous stroke or transient ischemic attack; or (5) hypertension.
Maintaining sinus rhythm has a number of advantages, including relieving symptoms, improving hemodynamics and, possibly, decreasing the incidence of thromboembolic events and electrical atrial remodeling. The principal disadvantage is the risk of life-threatening side effects associated with drug therapy; however, typically only a small number of patients is affected. Control of ventricular rate also reduces symptoms and is easier to achieve than maintaining sinus rhythm. The disadvantage of this approach, however, is that an irregular ventricular response may preclude symptom relief for many patients. Regularization of sinus rhythm also yields better hemodynamic function than does rate control. In some patients, the drugs needed to reduce ventricular response may cause very slow heart rates, requiring that a permanent pacemaker be implanted.
Multiple approaches are available to achieve the three primary goals of AF management. Therapies for rate control or maintenance of sinus rhythm can be pharmacologic, nonpharmacologic or surgical. For a more complete delineation of these therapeutic modalities, see the accompanying figure. Catheter ablation of a focal initiating source of rhythm disturbance to prevent AF is the most promising of all nonpharmacologic techniques.
The author concludes that the primary goal of management is to preserve the brain by providing long-term anticoagulation in patients with AF who are at high risk for stroke. This is best done by anticoagulation but also can be achieved by left atrial appendectomy because most left atrial thrombi begin in this appendage and then move into the systemic circulation. Additional research is needed to evaluate the safety and efficacy of this procedure.