The Presence of Left Atrial Diverticula During Atrial Fibrillation Ablations

Editor's note: View diagnostic video of left atrial diverticula accompanying this article.

Introduction

A regularly occurring cardiac arrhythmia seen in clinical labs is atrial fibrillation (AF). AF is typically treated either by ablations or pharmacological therapies. The frequency of catheter ablation is increasing with respect to other treatment options such as antiarrhythmic drug therapy. Complications associated with catheter ablation include catheter entrapment, perforation, and thrombus formation. The presence of left atrial diverticula (LAD) could increase the frequency of these complications.^1-7

LADs are a deformity with very thin walls that project off the left atrial wall.⁷ This projection leaves the atrial wall thinner and more susceptible to perforation as compared to an atrial wall without an LAD.

LADs in our lab are only checked for inpatients who present for AF ablation. Approximately one-third of the patients who present for AF ablation in our lab are found to have an LAD, which is consistent with published data stating that 36% of AF patients have an LAD.^6-8 The purpose of this paper is to decrease the likelihood of complications when presented with an LAD by educating physicians about all possible complications.

Case Description

A 70-year-old male with a history of AF presented to our institution. He was very symptomatic from the AF, very weak and fatigued, and experiencing shortness of breath from ongoing AF episodes. He previously was diagnosed with coronary artery disease in June 1998, and a stent was used for treatment. The AF was diagnosed in 2008 and failed to respond to amiodarone therapy. In May 2013 cardiac monitoring demonstrated an AF burden greater than 15%, so it was decided to bring the patient into the EP lab for further treatment.

The patient was brought into the EP lab in the fasting state. The right and left groins as well as left shoulder area were prepped and draped in the usual sterile fashion. Access was obtained in the left subclavian vein via the Seldinger technique over which a 7 French (Fr) sheath was placed. Through this 7 Fr sheath, a coronary sinus mapping catheter was placed in the coronary sinus with pacing recording from the left atrium. This catheter was then secured down. Access was obtained in the right femoral vein via the Seldinger technique over which an 8 and 5 Fr sheath were placed. Access was obtained in the left femoral vein via the Seldinger technique over which an 8 Fr sheath was placed. The 8 Fr sheaths were then exchanged out for Agilis sheaths (St. Jude Medical). The sheaths were then flushed and irrigated every 10 minutes. An intracardiac echo was placed in the left-sided Agilis sheath and used to visualize the right atrium, interatrial septum, and left atrium. Through the right-sided Agilis sheath, a BRK transseptal needle (St. Jude Medical) and dilator were placed. A transseptal heart catheter was then performed. The needle and dilator were advanced to the left atrium, followed by the sheath as the needle and dilator were retracted back. A heparin bolus was then given, followed by a drip. The activated clotting time remained at or about 350 throughout the extent of the case.

An AFocus mapping catheter (St. Jude Medical) was then placed into the left atrium and used to reconstruct the left atrium with the help of 3D mapping via EnSite NavX (St. Jude Medical). A pre-ablation cardiac 3D CT scan was previously performed, and showed the patient had 4 distinct veins. The EnSite Verismo segmentation tool software, developed by St. Jude Medical, was used to analyze the scans. The patient was also found to have a LAD coming off the anterior superior portion of the left atrium. This LAD is labeled in all three figures. After reconstruction of the left atrium, the AFocus catheter was removed. A standard curve 8 mm Blazer II ablation catheter (Boston Scientific) was then placed into the left atrium. The LAD was further defined and marked on EnSite NavX to prevent accidental entrapment of the ablation catheter. After full reconstruction of the left atrium, a pulmonary vein ablation technique was performed. Great care was taken to avoid ablating in close proximity to the LAD.

Discussion

With AF being such a recurrent diagnosis, complications arising from ablation could prove to be very harmful to the patient if the physician is not aware of the risks of LAD. It is crucial to be conscious of the presence of an LAD to reduce the risk of complications.

LADs were originally seen in patients referred for computed tomography coronary angiography. It is known to be as common as 36% in patients with AF.^6-8 LADs are cyst-, cone-, irregular-, or tubiform-shaped at a frequency of 53.2%, 36.3%, 4.8%, and 4.8%, respectively.⁸

LADs are composed of only a single muscle layer and are typically seen occurring alone (74%), but multiple LADs in a left atrial wall are seen at a rate of 26%.⁸ They are found protruding outward from the heart cavity, with 56.7% of patients diagnosed with AF having the LAD in the anterior superior wall.^7,8 The typical width and body length of an LAD in the right region of the anterosuperior wall is 5.4 ± 3.6 mm and 6.1 ± 2.8 mm, respectively; in the left region, the width is 4.9 ± 2.5 mm and the body length is 4.8 ± 2.1 mm.⁸

The irregular nature of an LAD creates possible sites for catheter entrapment, giving way to complications such as perforation and thrombus formation. The potential for perforation occurs due to the LAD causing a thinner left atrial wall as compared to a left atrial wall without an LAD present. An LAD is typically 0.89 ± 0.46 mm thick, while the neighboring wall of the left atrium is 2.39 ± 0.83 mm.⁸ 

With the increased use of irrigated tip catheters, entrapment can be difficult to recognize leading to cardiac perforation. The frequency of LADs is causing a need for physicians to become more cognizant of the potential for catheter entrapment and perforation.

Disclosures: The authors report no conflicts of interest regarding the content herein.

References

1. Wazni OM, Marrouche NF, Martin DO, et al. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: a randomized trial. JAMA. 2005;293:2634-2640.
2. Oral H, Pappone C, Chugh A, et al. Circumferential pulmonary-vein ablation for chronic atrial fibrillation. N Engl J Med. 2006;354:934-941.
3. Oral H, Scharf C, Chugh A, et al. Catheter ablation for paroxysmal atrial fibrillation: segmental pulmonary vein ostial ablation versus left atrial ablation. Circulation. 2003;108:2355-2360.
4. Marrouche NF, Dresing T, Cole C, et al. Circular mapping and ablation of the pulmonary vein for treatment of atrial fibrillation: impact of different catheter techniques. J Am Coll Cardiol. 2002;40:464-474.
5. Cappato R, Calkins H, Chen SA, et al. Worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation. 2005;111:1100-1105.
6. Abbara S, Mundo-Sagardia JA, Hoffmann U, Cury RC. Cardiac CT assessment of left atrial accessory appendages and diverticula. Am J Roentgenol. 2009;193:807-812.
7. Wan YD, He Z, Zhang L, et al. The anatomical study of left atrium diverticulum by multidetector row CT. Surg Radiol Anat. 2009;31:191-198.
8. Peng LQ, Yu JQ, Yang ZG, et al. Left atrial diverticula in patients referred for radiofrequency ablation of atrial fibrillation: assessment of prevalence and morphologic characteristics by dual-source computed tomography. Circ Arrhythm Electrophysiol. 2012;5:345-350.