Although considered benign in its own right, atrial fibrillation (AF) in combination with heart failure is a major cause of morbidity and decreased survival. In a vicious circle in which it is both an effect and aggravating factor, it exacerbates the underlying disease and increases the risk of thromboembolism. Drugs are the first-line therapy, and many trials the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM), SAFET (Sotalol vs Amiodarone For maintaining sinus rhythm after cardiovErsion for aTrial fibrillation), etc have sought to identify the optimal agent and dosage. Unfortunately, the response is often transient at best.
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The AF tends to recur in one form or another, with increasingly adverse clinical and hemodynamic effects. Nonpharmacologic therapies have therefore been developed (Table).
The maze procedure (requiring cardiopulmonary bypass) consists of the excision of the atrial appendages, isolation of the pulmonary veins, and creation of a tortuous path of atrial tissue by carefully placed incisions that direct the sinus node impulses across the atria to the atrioventricular node. The incisions are placed so that no area is wide enough to sustain multiple reentry circuits, and thus atrial fibrillation cannot occur. Several dead-end alleyways create a maze-like pathway and permit the depolarization of all the atrial tissue. However, the operative risk that accompanies this procedure precludes its application in heart failure, although recent evidence suggests that minimally invasive surgery and cryoablation can be used to accomplish the maze procedure in the beating heart without cardiopulmonary bypass.
This approach is indicated when the source of AF can be localized to an arrhythmic focus in the myocardial tissue. In a substantial proportion of patients, this is adjacent to the ostia of the four pulmonary veins. Catheter ablation consists of inserting a catheter electrode to destroy the focus by electrocauterization. A major complication is pulmonary ostial stenosis, which occurs in 10% to 30% of cases, and to a clinically significant degree in 1% to 15%. Stroke is an additional complication. A less traumatic modification of this technique has recently been introduced, circumferential radiofrequency ablation, which separates the pulmonary veins from the left atrium using circumferential radiofrequency lesions around each ostium.
Defibrillation with high-frequency burst antitachycardia pacing.
This approach is indicated in patients with poorly tolerated supraventricular tachycardia requiring an implantable atrial defibrillator (IAD). As soon as the IAD senses an episode of tachycardia, it generates a high-frequency shock that usually terminates the arrhythmia. Unfortunately, this solution is invasive, and causes pain and discomfort.
Whether different pacing strategies are an effective treatment of AF is debated. It is thought that the more physiologic the pacing modality, the greater the likelihood of preventing AF. This said, dualchamber pacing is more effective than single ventricular pacing, which on the contrary seems to possess a pro-AF effect.
Radiofrequency ablation of the atrioventricular node and permanent pacemaker implantation.
This approach may be indicated for patients with a poorly tolerated and drug-resistant ventricular rate. Atrioventricular node ablation is followed by implantation of a permanent pacemaker. The advantage is that optimization of the ventricular rate guarantees clinical improvement. However, this is another instance of an invasive and costly treatment for what is essentially a benign condition.
Thus, despite the many nonpharmacologic options in AF, the efficacy and specific indications of each remain unvalidated. Much work is still required before they can become well-established therapeutic options.
Management; atrial fibrillation; nonpharmacological treatment; defibrillation; pacing; radiofrequency ablation.