The Holy Grail in the quest for treating atrial fibrillation has been to develop a way to cure the arrhythmia with ablation. Ablation is a procedure performed either during an electrophysiology study or in the surgical suite, in which the source of a patient's heart arrhythmia is mapped, localized, and then destroyed (i.e., ablated.) Generally, ablation is accomplished by applying radiofrequency (RF) energy, applying electrical energy, or freezing the offending area (usually through a catheter,) thus creating a small scar that is electrically inactive and thus incapable of generating heart arrhythmias. Many forms of cardiac arrhythmias have been rendered curable by ablation techniques over the past 15 years, but atrial fibrillation has remained a challenge.
Why Has Ablating A-Fib Been So Difficult?
Most cardiac arrhythmias are caused by a small area of electrical abnormality somewhere within the heart. For most arrhythmias, then, ablation simply requires locating that small abnormal area. In contrast, the electrical abnormalities associated with atrial fibrillation have been thought to be much more generalized - essentially encompassing most of the left and right atrium (upper heart chambers). Consequently, ablating this arrhythmia has been regarded as being extremely difficult.Indeed, initially the most common approach to ablating atrial fibrillation was to create a series of complex linear "scars" throughout the atria. This approach works reasonably well when performed by surgeons in the operating room, but applying this technique via catheter (a tube inserted into the heart) has proved extremely difficult.
A Newer Option?
More recently, in some centers, electrophysiologists now report that they can achieved successful ablations of atrial fibrillation with another form of ablation procedure. This newer procedure involves ablating in 3 or 4 specific areas within the left atrium, namely, near the openings of the 4 pulmonary veins. (The pulmonary veins are the blood vessels that deliver oxygenated blood from the lungs to the heart.) It appears that atrial fibrillation may originate in the pulmonary veins in many patients, and that electrically isolating these veins using catheter-based ablation techniques can keep atrial fibrillation from occurring. Ablating the openings of the pulmonary veins is technically much easier than making a series of linear ablations, and takes much less time (though it still takes up to 4 - 5 hours.)
Problems remain, however. This new approach works best in patients who have "paroxysmal" atrial fibrillation - that is, relatively brief episodes. It works less well in patients with persistent atrial fibrillation. Also, while it is much quicker than the "linear" approach, it is still a lengthy procedure. And since most of that time is spent working in the left atrium, there may be a substantial risk of stroke or other neurological complications during the procedure. (The left heart is in direct communication with the body's circulation, and blood clots forming there can travel to the brain.)
Further, ablating in or near the pulmonary veins can cause partial obstruction of the veins, leading to pulmonary vein stenosis - a very serious and potentially life-threatening condition.
Before this procedure becomes routine, both the instrumentation and the techniques will have to improve in order to reduce the time it takes to perform the procedure, and to reduce or eliminate the risk of neurological complications and of pulmonary vein stenosis. While some electrophysiologists maintain that we have already reached this point, most disagree, and want to see hard evidence a) that the procedure is effective enough, b) the procedure is safe enough, and c) that clinical outcomes of patients subjected to this procedure are substantially improved.
Patients considering this kind of ablation procedure need to question their electrophysiologists closely about their own personal safety and efficacy statistics with atrial fibrillation ablation - and not allow their doctor to quote their overall ablation statistics, or statistics from the medical literature (which are generally only reported by the very best centers).
Sources:
Fogoros, RN. "Transcatheter Ablation: Therapeutic Electrophysiology." In: Fogoros, RN. Electrophysiologic Testing. Blackwell Publishing: Malden, MA, 2006.
