MedifocusHealth

Although guidelines for the management of atrial fibrillation (AF) stress the combined important role of anticoagulation and antiarrhythmic drug therapy, unfortunately, this approach is not always effective. Studies have shown that when antiarrhythmic medications are used as the sole treatment modality, up-to 50% of patients experience a recurrence of atrial fibrillation after 1-year of treatment and up-to 85% of patients experience a recurrence after 2-years. In the event that antiarrhythmic drug therapy fails to achieve either rhythm or rate control, a variety of non-pharmacological treatment options may be considered.

In a landmark study published in the New England Journal of Medicine in 1998 (Vol. 339; pp. 659-666), Haissaguerre and his colleagues reported that paroxysmal atrial fibrillation originates from ectopic ("out of place") beats in the pulmonary veins in about 90% of cases. These researchers also demonstrated that localization and ablation (destruction) of these ectopic beats in the pulmonary veins that serve as the triggers of atrial fibrillation could cure the atrial fibrillation in most patients.

Other researchers have found that in patients with persistent atrial fibrillation, the left atrium serves as the trigger and electrical driving force of the ectopic beats in most patients and that a simple left atrial ablation procedure could cure the atrial fibrillation in up-to 80% of patients.

Identification of the pulmonary veins and the left atrium as the drivers of the irregular electrical impulses in many patients with atrial fibrillation has led to the development of non-pharmacological treatment options for those patients who fail to respond to medical therapy with antiarrhythmic medications. These options include radiofrequency catheter ablation and the surgical Maze procedure.

Radiofrequency Catheter Ablation

Radiofrequency catheter ablation is a novel non-surgical procedure during which thin, flexible wires are inserted through a vein in the groin and then advanced through the vein into the heart. The tip of the wires is equipped with a special electrode through which radifrequency (heat) energy can be transmitted to ablate (destroy) areas of heart tissue that serve as the trigger points of the irregular electrical impulses that cause atrial fibrillation. The resulting scar tissue that is formed after ablation blocks the conduction of the irregular electrical impulses.

Specific areas of the heart that may be targeted by radiofrequency catheter ablation include:

• Pulmonary veins - Pulmonary vein isolation and ablation is usually performed for patients with paroxysmal atrial fibrillation because in most of these cases the abnormal electrical impulses are triggered by the pulmonary veins.

• Left atrium - In many patients with persistent or permanent atrial fibrillation, the left atrium is the source of the irregular electrical impulses and is, therefore, targeted for radiofrequency catheter ablation.

• Atrioventricular (AV) node - In those cases where the origin of the irregular electrical impulses is localized to the atrioventricular (AV) node, this area of the heart can be targeted to ablate the AV node and, thereby, prevent these abnormal electrical impulses from being transmitted between the atria and the ventricles.

Catheter ablation of the AV node usually requires the placement of a rate-modulating pacemaker that is usually implanted in conjunction with the ablation procedure. A pacemaker is a device that sends electrical impulses to the heart chamber to maintain an appropriate heart rate. The pacemaker is programmed to 80 or 90 beats per minute for the first month after ablation and, afterwards, can be adjusted to meet the individual needs of the patient. Patients with paroxysmal atrial fibrillation receive a dual-chamber rate-modulating pacemaker (DDDR) while those with permanent atrial fibrillation receive a single-chamber rate-modulating ventricular pacemaker (VVIR). Anticoagulation therapy to prevent stroke is still required following catheter ablation for atrial fibrillation.