New Therapies in the Treatment of Atrial Fibrillation:
Left Atrial Appendage Exclusion
LAA exclusion in patients with atrial fibrillation at high risk for embolic stroke and limited options.
The most severe consequence of atrial fibrillation is an embolic stroke. In patients with AF, there is a five-fold increased incidence of embolic stroke 1. The risk of embolic stroke in the general population increases with age. Therefore, AF is one of the most important causes of embolic stroke in people over the age of 75 years2. The left atrial appendage (LAA) is recognized as a source of thromboemboli. Currently, oral anticoagulation (OAC) therapy is the most effective available prophylactic approach in patients with AF at high risk of thromboembolic events3,4. However, certain patients develop bleeding problems while on OAC therapy; and the risk of severe bleeding increases with age 5. Other patients have embolic events while taking OAC therapy. Patients with either contraindications to OAC therapy, embolic events while on OAC therapy or intolerance to OAC therapy have few options. Surgical exclusion of the LAA has been performed for over 70 years. The AHA/ACC/ESC guidelines for treatment of atrial fibrillation (AF) and the AHA/ACC/ESC guidelines for treatment of mitral disease recommend exclusion of the LAA during concomitant procedures as a prophylactic measure to eliminate a primary source of thrombus6,7.
Investigators, led by Dr. Randall Lee, from UCSF pioneered the development of a percutaneous approach using an epicardial suture for exclusion of the LAA as an option to surgery for those patients with atrial fibrillation at high risk for embolic events with contraindications to OAC therapy, OAC therapy failures or OAC intolerances. The percutaneous catheter-based LAA ligation procedure using the LARIAT suture delivery device (SentreHeart, Inc, Redwood City, CA) is feasible and effective in humans and produces complete closure of the LAA 8.
LAA exclusion in the treatment of AF
Pulmonary vein isolation (PVI) for persistent/chronic AF has a 70% single procedure success rate at 1 year with a high rate of recurrence. Catheter ablation of electrical activity in the LAA for recurrent AF has been successful, leading to increased success rates 9. However, electrical isolation of the LAA with catheter ablation is limited by the risk of tamponade and electromechanical dissociation with the potential for LAA thrombus formation. LAA occlusion with a percutaneous suture ligation method has been shown to be feasible for acute closure of the LAA and has been shown to result in LAA necrosis and atrophy 10. In addition, LAA isolation with a LAA exclusion device has been reported as a successful therapy for LAA tachycardias 11. Furthermore, LAA isolation & exclusion may contribute to the success of the Cox Maze IV surgical ablation for AF by eliminating focal LAA triggers for atrial tachycardias/atrial fibrillation 12. We have shown that LAA ligation leads to electrical isolation of the LAA and have started a clinical study to determine the effectiveness of LAA ligation and PVI in patients who have had a recurrence of AF after a PVI or in patients with chronic AF.
What is the LAA?
The left atrial appendage is a pouch that extends off the top left chamber of the heart (the left atrium). The left atrial appendage is known to start atrial fibrillation and serves as a source of blood clots in patients with atrial fibrillation. The risk of these blood clots is that they can break off and travel to other areas of the body to cause a stroke and/or block blood flow to a part of your body. The left atrial appendage ligation is a procedure that places a suture (type of string) around the bottom of the pouch (appendage). The suture cuts off blood flow to the appendage and prevents a blood clot from forming inside the appendage. Only the left atrial appendage will be tied off, so this procedure will not affect blood flow to any other part of the heart. By getting rid of the electrical triggers from the appendage, this procedure may also make an atrial fibrillation ablation more successful.
How is LAA ligation performed?
The LAA ligation is performed after entering the epicardial space through a subxiphoid puncture and the left atrium through a transseptal puncture. A transseptal puncture is a standard procedure used to cross the septum (barrier) between the top 2 chambers of the heart. This procedure uses a special needle and sheath (A sheath is a tube inserted through a vein in the leg and taken up to the heart. For the purposes of the LAA ligation, a wire is placed through the sheath into the tip of the LAA in order to see the location of the appendage by X-ray. A subxiphoid puncture is a procedure used to enter the epicardial space (space between the heart and the sac surrounding the heart). With a subxiphoid puncture a needle is inserted into the skin below the breastbone and directed towards the heart using X-ray. This gives your doctor access to the space around the heart so that a suture may be placed around the bottom of the left atrial appendage. A magnet tipped guide wire is placed at the tip of the LAA via the transseptal catheter and an epicardial magnet tipped guide wire is connected to the endocardial magnet tipped guide wire to stabilize the LAA. The LARIAT suture delivery device is then guided over the epicardial guide wire and the snare is placed over the LAA. A balloon catheter inside the LAA allows for the proper positioning of the suture. The suture is placed using ultrasound and X-ray pictures and is left in place permanently on the outside surface of the heart.
- Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation: a major contributor to stroke in the elderly. The Framingham Study. Arch Intern Med 1987;147:1561-4.
- Hart RG, Halperin JL. Atrial fibrillation and stroke : concepts and controversies. Stroke 2001;32:803-8.
- Hart RG, Benavente O, McBride R, Pearce LA. Antithrombotic therapy to prevent stroke in patients with atrial fibrillation: a meta-analysis. Ann Intern Med 1999;131:492-501.
- Hart RG, Pearce LA, Aguilar MI. Meta-analysis: antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Ann Intern Med 2007;146:857-67.
- Tulner LR, Van Campen JP, Kuper IM, et al. Reasons for undertreatment with oral anticoagulants in frail geriatric outpatients with atrial fibrillation: a prospective, descriptive study. Drugs Aging;27:39-50.
- Calkins H, Brugada J, Packer DL, et al. HRS/EHRA/ECAS expert Consensus Statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm 2007;4:816-61.
- Fuster V, Ryden LE, Cannom DS, et al. 2011 ACCF/AHA/HRS focused updates incorporated into the ACC/AHA/ESC 2006 Guidelines for the management of patients with atrial fibrillation: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines developed in partnership with the European Society of Cardiology and in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. J Am Coll Cardiol;57:e101-98.
- Bartus K, Han FT, Bednarek J, Myc, Kapelak B, Sadowski J, Lelakowski J, Bartus S, Yacobov SJ, Lee RJ. Percutaneous Left Atrial Appendage Suture Ligation Using the LARIAT in Patients with Atrial Fibrillation: Initial Clinical Experience. JACC 2012 (In press).
- Di Biase L, Burkhardt JD, Mohanty P, et al. Left atrial appendage: an underrecognized trigger site of atrial fibrillation. Circulation;122:109-18.
- Lee RJ, Bartus K, Yakubov SJ. Catheter-based left atrial appendage (LAA) ligation for the prevention of embolic events arising from the LAA: initial experience in a canine model. Circ Cardiovasc Interv;3:224-9.
- Benussi S, Mazzone P, Maccabelli G, et al. Thoracoscopic appendage exclusion with an atriclip device as a solo treatment for focal atrial tachycardia. Circulation;123:1575-8.
- Weimar T, Schena S, Bailey MS, et al. The cox-maze procedure for lone atrial fibrillation: a single-center experience over 2 decades. Circ Arrhythm Electrophysiol;5:8-14.