Treatment Options for Atrial Fibrillation

Catheter and Surgical Ablation for Atrial Fibrillation

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.

The success of radifrequency catheter ablation for the termination of atrial fibrillation has been documented by many studies. In patients with paroxysmal atrial fibrillation, success rates of 60% to 85% have been reported following pulmonary vein isolation and ablation. In patients with persistent atrial fibrillation, radifrequency catheter ablation of the left atrium has been reported to cure atrial fibrillation is 85% to 95% of patients.

Although radifrequency catheter ablation is generally considered to be an effective and safe procedure for the treatment of atrial fibrillation, it is not completely without risk. The most frequent complication of pulmonary vein isolation and ablation is a condition known as pulmonary vein stenosis - the narrowing of the orifice of the pulmonary veins at the entrance into the left atrium. The incidence of pulmonary vein stenosis has been reported to range from 1% to 10%.

The most serious potential complication associated with radiofrequency catheter ablation of the left atrium is the formation of an atrioesophageal fistula. This is a potentially life-threatening condition whereby, as a consequence of the ablation procedure, a hole forms between the esophagus ("foodpipe") and the heart's atrial chamber. Although this complication is rare, occurring in less than 1% of patients, it is associated with a high mortality rate exceeding 50%.

Other potential complications of radifrequency catheter abalation for atrial fibrillation may include:

  • Cardiac tamponade - The pooling a large amount of blood in the pericardial sac - the thin membrane that surrounds and protects the heart. The resulting compression and constriction of the heart can lead to a drop in blood pressure and may result in shock and death. Cardiac tamponade has been reported to occur in about 2% of cases.

  • Injury to the phrenic nerve which can cause a serious condition known as diaphragmatic paralysis that may result in temporary or permanent impairment of breathing. Injury to the phrenic nerve has been reported to occur in about 0.5% of cases.

  • Stroke - The risk of stroke following radifrequency catheter ablation is about 1% with most strokes occuring within the first 30 days after the procedure. To reduce the risk of stroke, most experts recommend that anticoagulation therapy be continued for at least 30 days after the procedure. Extending anticoagulation therapy beyond 30 days after radiofrequency catheter ablation for atrial fibrillation is still controversial and is an issue that still remains to be resolved.

  • Pericarditis - Inflammation of the pericardial sac - the thin membrane that surrounds and protects the heart.

Surgical Maze Procedure

The Maze procedure is a novel and highly successful surgical technique for the treatment of atrial fibrillation that was originally developed in 1987 by Dr. James L. Cox. Since that time, the surgical technique has been revised and improved several times and has culminated in the development of the Maze III procedure which is still considered as the "gold standard" for the surgical treatment of atrial fibrillation.

The goal of the Maze procedure is to interrupt or block the conduction of the multiple re-entrant electrical circuits that are necessary for the propogation of atrial fibrillation. In the earlier versions of the Maze procedure (Maze I and II), this goal was accomplished by creating a series of linear "cut and sew" incisions throughout both the right and left atria to produce linear scars that separate the atria into small strips. The scars between the strips act as barriers that block the conduction of the multiple re-entrant electrical circuits and also enable the electrical impulses generated by the sinoatrial (SA) node to be transmitted directly to the atrioventricular (AV) node.

In the latest version of the procedure (Maze III), the "cut and sew" incisions created throughout the right and left atria are replaced with linear ablation lesions created with either radifrequency energy or cryothermy using a nitrous oxide cooled probe that is applied to the atrial tissue. Excellent results have been reported with the Maze III procedure with reported cure rates of over 90%. Despite these excellent clinical results, however, the Maze procedure has several major limitations which include:

  • Major open-heart surgery which requires the patient to be placed on cardiopulmonary bypass (heart-lung machine).

  • Technically difficult surgery which limits its widespread clinical application.

  • Limited to patients with atrial fibrillation who required cardiac surgery for another serious heart condition (e.g., coronary artery disease; mitral valve replacement). For these patients, the Maze procedure was performed concomitantly with the other cardiac surgerical procedure.

  • Not an option for younger patients with "lone" atrial fibrillation (atrial fibrillation that occurs in the absence of structural heart disease).

Complications of the Maze procedure are similar to those reported for other types of open-heart surgery and may include:

  • Bleeding
  • Infection
  • Stroke
  • Heart attack

The Maze procedure continues to undergo refinements in an effort to simplify and improve the surgical technique originally developed by Dr. James L. Cox and his colleagues back in the late 1980s. Recently, surgeons have developed a modification of the Maze procedure known as a "Mini-Maze". Advantages of the "Mini-Maze" technique include:

  • May be performed using a minimally-invasive approach through a small thoracotomy incision instead of splitting the breastbone (sternum) as was necessary for previous versions of the Maze procedure.

  • Requires a shorter duration of cardiopulmonary bypass (heart-lung machine) compared to the standard Maze procedure.

  • Less need for insertion of a pacemaker as compared to the standard Maze procedure.

  • Reduced blood loss, faster recovery, and less time spent in the hospital as compared to the standard Maze procedure.

More recent advances in the field of surgical ablation for atrial fibrillation using minimally-invasive "keyhole" techniques and thoracoscopic approaches have extended the utility of surgical ablation for atrial fibrillation beyond only those patients who required concomitant surgery for other heart problems such as coronary artery disease or valvular heart disease. Surgical ablation for atrial fibrillation is now being used even for younger patients with "lone" atrial fibrillation who do not have any underlying structural cardiac problems using these newer minimally-invasive or thoracoscopic surgical approaches that do not require any cardiopumonary bypass. The basic objective of these newer surgical ablation techniques still remains the elimination of the irregular electrical impulses that serve as the triggers for atrial fibrillation. In patients with paroxysmal atrial fibrillation these triggers originate in the pulmonary veins while in those with persistent or permanent atrial fibrillation the trigger for the abnormal impulses is the left atrium. These newer surgical ablation techniques, therefore, usually target these structures by pulmonary vein isolation and excision or exclusion of the left atrial appendage. Most commonly, radiofrequency energy or cryothermy (a nitrous oxide cooled probe) is used for surgical ablation of atrial fibrillation, however, alternative energy sources such as microwave, ultrasound, or laser may also be used. Early experience with the newer approaches for the surgical ablation of atrial fibrillation are encouraging and demonstrate a success rate of about 85% for the cure of paroxysmal atrial fibrillation after a 6-month follow-up period.

Pacemaker Therapy

Patients with atrial fibrillation who develop symptomatic bradycardia (slow heart rate) as a consequence of antiarrhythmic drug therapy or who have a high-degree of atrioventricular (AV) block may require implantation of a permanent pacemaker. A pacemaker is a device that sends electrical impulses to the heart muscle to maintain an appropriate heart rate. Various pacemaker strategies are available including atrial pacing without ventricular pacing, single-chamber ventricular pacing, or dual-chamber pacing. If you require a pacemaker, your doctor will determine an optimal pacing strategy for you based on the dual objectives of better managing the arrhythmia and optimizing heart-rate function to the greatest extent possible.

Implantable Cardioverter-Defibrillator

Implantable cardioverter-defibrillators (ICDs) have been used for several years for patients who are prone to develop ventricular fibrillation and are at risk for sudden death. Ventricular fibrillation is a serious condition in which the ventricles of the heart contract in rapid and unsynchronized rhythms so that the heart cannot efficiently pump blood to the body. Implantable cardioverter-defibrillators are programmed to automatically respond to an episode of atrial fibrillation with a small shock delivered inside the heart to convert the atrial fibrillation back to normal sinus rhythm. These devices can be used for patients with recurrent, highly symptomatic atrial fibrillation who do not respond to therapy with antiarrhythmic medications.

Percutanous Left Atrial Appendage Transcatheter Occlusion (PLAATO)

A new technique is being investigated to prevent blood clots from forming in the left atrial appendage and causing stroke, especially in patients who cannot take anticoagulant medications. PLAATO is a percutaneous left atrial appendage transcatheter occlusion system which is introduced through the venous system during a cardiac catheterization procedure. This device has a self-expanding nitinol cage which is covered with a polymeric membrane. The device is inserted via the catheter into the left atrial appendage and held in place by small anchors which protrude through the membrane and hold the device in the mouth of the left atrial appendage. The catheter is then removed leaving this occluding device in place. Studies have shown that once this occluding device occupies the left atrial appendage, there is a marked decrease in the chance of clot formation and stroke.

For additional information about PLAATO, the reader is referred to the following articles: