Atrial fibrillation is the most common supraventricular arrhythmia and a major cause of morbidity. Arrhyth-mogenic foci originating within the pulmonary veins are an important cause of both paroxysmal and persistent atrial fibrillation. A variety of surgical and endovascular techniques have been used to electrically disconnect the pulmonary veins from the left atrium. Pulmonary venogra-phy for localization of the pulmonary vein os-tium can be difficult to perform during the ablation procedure. Pulmonary vein anatomy is variable; therefore, noninvasive imaging of the individual pulmonary vein anatomy before ablation is useful. MRI, echocardiography, and transesophageal sonography have been used. However, more recently MDCT has been used as an excellent tool to define the pulmonary venous anatomy and to observe patients for complications after the procedure, particularly pulmonary vein stenosis.
Atrial fibrillation, the most common sustained cardiac arrhythmia, is a major cause of stroke [1] and the most common cardiac arrhythmia requiring hospitalization [2]. It may occur in patients with normal hearts in times of stress, such as after surgery, after strenuous exercise, or with stimulants such as coffee or alcohol [2]. Atrial fibrillation is more frequent in patients with structural heart disease such as hypertension, valvular heart disease (especially rheumatic), and coronary artery disease [2]. A strong association exists with other arrhythmias, such as Wolff-Parkinson-White syndrome, atrioventricular nodal reentrant tachycardias, and sick sinus syndrome. In addition, it may also occur in patients with cardiopulmonary disease resulting in hypoxia or hypercapnia, such as chronic obstructive pulmonary disease or hypertension, or in patients with metabolic or electrolyte disturbances, such as diabetes mellitus and hyperthyroidism [2].
Atrial fibrillation usually begins as paroxysmal atrial fibrillation, with approximately 60% of patients converting spontaneously to normal sinus rhythm. Approximately 40% of patients develop persistent atrial fibrillation requiring medical or procedural intervention to restore normal sinus rhythm. Up to 50% of patients develop recurrent atrial fibrillation within the first year of initial onset [2]. Patients with atrial fibrillation have a mortality rate twice that of control subjects and are exposed to considerable morbidity, such as stroke [2].
The main symptoms associated with atrial fibrillation are related to the rapid ventricular
rate. This may cause hypotension or induce angina because patients often have coincidental ischemic heart disease. A rapid ventricular rate may also lead to the loss of atrioventricular synchrony, as well as to an impaired cardiac response to exercise. The major complication of atrial fibrillation is the formation of atrial thrombi with the risk of systemic embolization, placing these patients at considerable risk for stroke.
The electrocardiographic characteristics of atrial fibrillation are an undulating or sawtooth baseline with absent P waves, an atrial rate of 300-600 beats per minute, and an irregularly irregular ventricular response. Paroxysmal atrial fibrillation is usually found in the absence of structural heart disease. Over years it may progress to persistent atrial fibrillation if substantial atrial remodeling has occurred. Atrial fibrillation is considered persistent if it lasts for more than 30 days and requires cardioversion for termination.