In choosing among therapeutic options, it is important to establish clear goals. For example, three options are available in patients with atrial fibrillation: (1) Reduce the ventricular response using AV nodal blocking agents such as digitalis, verapamil, diltiazem, or b adrenergic antagonists (Table 34—2); (2) restore and maintain normal rhythm using drugs such as quinidine, flecainide, or amiodarone; or (3) decide not to implement antiarrhythmic therapy, especially if the patient truly is asymptomatic. Most patients with atrial fibrillation also benefit from anticoagulation to reduce stroke incidence regardless of symptoms.
Factors contributing to choice of therapy include not only symptoms but also the type and extent of structural heart disease, the QT interval prior to drug therapy, the coexistence of conduction system disease, and the presence of noncardiac diseases. In the rare patient with the WPW syndrome and atrial fibrillation, the ventricular response can be extremely rapid and can be accelerated paradoxically by AV nodal blocking drugs such as digitalis or Ca2+ channel blockers; deaths owing to drug therapy have been reported.
The frequency and reproducibility of arrhythmia should be established prior to initiating therapy because inherent variability in the occurrence of arrhythmias can be confused with a beneficial or adverse drug effect. Techniques for this assessment include recording cardiac rhythm for prolonged periods or evaluating the response of the heart to artificially induced premature beats. It is important to recognize that drug therapy may be only partially effective: A marked decrease in the duration of paroxysms of atrial fibrillation may be sufficient to render a patient asymptomatic even if an occasional episode still can be detected.
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