A 77-yr-old woman was scheduled to undergo left atrial appendage (LAA) excision and bilateral pulmonary vein isolation through successive right and left mini-thoracotomy incisions for chronic atrial fibrillation. We used a conventional two-dimensional (2D) imaging probe/system (IE-33 Philips Medical Systems, Andover, MA) for a comprehensive transesophageal echocardiographic (TEE) examination and LAA interrogation. Starting from the midesophageal four-chamber plane, the LAA was visualized at 5° increments from 0° to 180° and the presence of spontaneous echo contrast or thrombus was excluded. LAA ejection velocity using pulse wave Doppler in the midesophagus at 0° and 90° rotation was >20 cm/s.1 Initially, the right-sided pulmonary veins were isolated through a right mini-thoracotomy incision. A left mini-thoracotomy was then performed and LAA excision was performed with a stapling device after left pulmonary venous isolation. Post-LAA excision 2D examination demonstrated a possible “incomplete” excision of the base of the LAA, which appeared as a residual “stump/pouch” of the LAA (Fig 1) (Video 1; please see video clips available at www.anesthesia-analgesia.org). Because of limited TEE windows secondary to right lateral decubitus position and the small size of the pouch, definite flow could not be demonstrated using color flow Doppler (CFD) despite decreasing the Nyquist limit to 25 cm/s. To confirm our diagnosis of incomplete excision, we decided to use the real-time three-dimensional (RT3D) TEE imaging probe on the same system for LAA visualization. Specifically, we used the “3D zoom” mode, which enables live 3D imaging of the intracardiac structures. An en-face view of the staple suture line from within the left atrium (LA) was obtained (Video 1). We were able to appreciate a small residual pouch. This residual LAA was then reexcised with simultaneous visualization with the “live” RT3D system. Positioning and placement of the stapling device was adjusted with simultaneous observation of disappearance of the pouch on the RT3D image. We then observed in “real-time” the application of the staples on the residual defect and its disappearance. Complete excision of the residual stump was also confirmed as absence of the previously visualized defect at the base of the LAA on 2D image as well (Video 1).
Ligation of the LAA can be performed during mitral valve surgery or as a separate procedure thoracoscopically in patients with chronic atrial fibrillation.2,3 The LAA can be ligated and isolated from the main body of the LA either from within the body of the LA or from the exterior. In either situation, the LAA is ligated and isolated from the LA and not actually excised. Inadequate ligation of the LAA has been found in 36%–40% of the cases regardless of type of surgery (mitral valve replacement/repair) or the operative approach (sternotomy/port access approach).4,5 In the Katz et al. study of the 50 patients with LAA ligation, 20 patients were diagnosed as having CFD signal between the LA and the ligated LAA, and four of these patients, i.e., 22% had thromboembolic events. Hence, a residual LAA after ligation is associated with a definitive risk of thromboembolism. Performance of this procedure on a flaccid and decompressed LA on cardiopulmonary bypass (CPB) could explain the high rate of inadequate ligation of the LAA on CPB.4,5 Suture dehiscence is another possible explanation for the long-term failure of ligation and isolation. In our case, the LAA ligation and excision was performed without using CPB via bilateral successive thoracotomy incisions using a stapling device. A residual pouch of the LAA was still seen with 2D imaging after the first attempt at excision. In addition to ligation failure and thromboembolism, ligation of the LAA can be complicated by injury to the circumflex branch of the left main coronary artery, which is located in close proximity to the base of the LAA.2,6 The benefits of a complete ligation have to be weighed against the risk of inadvertent inclusion of the LA wall in the suture line and subsequent vascular injury.
The advent of the RT3D matrix TEE transducer (Philips Medical Systems, Andover) has made it possible to visualize the intracardiac anatomy “live” providing unique en-face views of intracardiac structures. In our case, the RT3D imaging ensured the completeness of LAA ligation and excision. During the second attempt, the visualization of the appropriate placement of the stapling device ensured that only the visible defect was included in the suture line. This may have the potential of preventing inadvertent inclusion of the LA wall in the suture line thus preventing vascular injury.
Performance of LAA ligation through minimally invasive thoracotomy incisions makes it critical to have optimal echocardiographic imaging because of limited surgical visualization. RT3D TEE uses a second-generation matrix phased-array transducer to provide a “surgical view” of the LAA from within the LA. The image can be rotated and manipulated in multiple planes in three dimensions for optimal visualization.7 It is possible to incorporate CFD information during 3D TEE imaging. However, this imaging is not live and has to be gated to the electrocardiogram “R” wave over multiple beats. The 3D image is then reconstructed with the CFD information by the computer for further analysis. The incorporation of CFD information during R wave gated image acquisition leads to a reduced frame rate and hence significant deterioration in resolution. However, the RT3D also allows the echocardiographer to manipulate the image in real-time and view the same cardiac structure from multiple perspectives. As demonstrated in our case, the RT3D TEE image provided us with additional views and perspective of the LAA which may have prevented inadequate ligation and excision. Despite its limitations, the use of RT3D technology during LAA ligation may be helpful in confirming a complete ligation and may therefore improve postoperative outcome after this procedure (Fig. 2).
1. Goldman ME, Pearce LA, Hart RG, Zabalgoitia M, Asinger RW, Safford R, Halperin JL. Pathophysiologic correlates of thromboembolism in nonvalvular atrial fibrillation. I. Reduced flow velocity in the left atrial appendage (The Stroke Prevention in Atrial Fibrillation [SPAF-III] study). J Am Soc Echocardiogr 1999;12:1080–7
2. Onalan O, Crystal E. Left atrial appendage exclusion for stroke prevention in patients with nonrheumatic atrial fibrillation. Stroke 2007;38(suppl 2):624–30. Review
3. Odell JA, Blackshear JL, Davies E, Byrne WJ, Kollmorgen CF, Edwards WD, Orszulak TA. Thoracoscopic obliteration of the left atrial appendage: potential for stroke reduction? Ann Thorac Surg 1996;61:565–9
4. Healey JS, Crystal E, Lamy A, Teoh K, Semelhago L, Hohnloser SH, Cybulsky I, Abouzahr L, Sawchuck C, Carroll S, Morillo C, Kleine P, Chu V, Lonn E, Connolly SJ. Left Atrial Appendage Occlusion Study (LAAOS): results of a randomized controlled pilot study of left atrial appendage occlusion during coronary bypass surgery in patients at risk for stroke. Am Heart J 2005;150:288–93
5. Katz ES, Tsiamtsiouris T, Applebaum RM, Schwartzbard A, Tunick PA, Kronzon I. Surgical left atrial appendage ligation is frequently incomplete: a transesophageal echocardiograhic study. J Am Coll Cardiol 2000;36:468–71
6. Sukernik MR, Davidson WR. Incidental finding of incompletely ligated left atrial appendage in a patient with systemic hypotension. Anesth Analg 2008;106:771–2
7. Agoston I, Xie T, Tiller FL, Rahman AM, Ahmad M. Assessment of left atrial appendage by live three-dimensional echocardiography: early experience and comparison with transesophageal echocardiography. Echocardiography 2006;23:127–32