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Ann Thorac Surg 2006;82:1322-1326
© 2006 The Society of Thoracic Surgeons

Original Articles: Cardiovascular

Three-Dimensional Echo and Videocardioscopy-Guided Atrial Septal Defect Closure

Nikolay V. Vasilyev, MDa, Joseph F. Martinez, DVMa, Franz P. Freudenthal, MDb, Yoshihiro Suematsu, MD, PhDa, Gerald R. Marx, MDa, Pedro J. del Nido, MDa,*

a Departments of Cardiac Surgery and Cardiology, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts
b Department of Pediatric Cardiology, Kardiozentrum, La Paz, Bolivia

Accepted for publication May 4, 2006.

* Address correspondence to Dr del Nido, Department of Cardiac Surgery, Children's Hospital Boston, Harvard Medical School, 300 Longwood Ave, Boston, MA 02115 (Email: pedro.delnido{at}cardio.chboston.org).

Presented at the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 
BACKGROUND: Current real-time three-dimensional echocardiography systems (RT3DE) can provide sufficient visualization to permit atrial septal defect (ASD) closure. However, detailed visualization of small objects inside the heart is still suboptimal because of limited resolution, which is a limitation for clinical application. We evaluate the complementary use of videocardioscopy in image-guided ASD closure.

METHODS: In a pig model (n = 5), a 4-mm to 8-mm ASD was created with RT3DE guidance. Defect closure was accomplished with a catheter-based patch-delivery system fixed around the defect with mini-anchors under combined RT3DE and videocardioscopy guidance. The endoscope was inserted into the heart through a custom built port designed to allow visualization in the presence of blood.

RESULTS: All ASDs were successfully closed. The combination of RT3DE and videocardioscopy allowed detailed visualization of intracardiac structures, instruments, patch, and mini-anchors.

CONCLUSIONS: Beating-heart ASD closure can be achieved with combined RT3DE and videocardioscopy imaging. Use of videocardioscopy provides high-resolution imaging and likely improves safety of the image-guided procedure.


   Introduction
Top
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 
Recent advances in imaging technology, such as real-time three-dimensional echocardiography (RT3DE), have enabled development of a broad array of image-guided techniques for cardiac interventions. Such technology gives the surgeon an accurate view of intracardiac structures, similar to that obtained with open procedures, but with the heart functioning under normal physiologic conditions. With current RT3DE systems, temporal resolution and frame rate are sufficient to permit instrument navigation and tissue manipulation with relative confidence.

We have previously demonstrated that RT3DE provides sufficient definition of the intracardiac anatomy and visualization of surgical instruments to permit atrial septal defect (ASD) closure in vivo [1]. Spatial resolution remains a limitation of ultrasound imaging with current systems, however. Detailed visualization of small objects inside the heart is still suboptimal and therefore limits the application of RT3DE in a clinical setting for image-guided surgery because there may be times when high-resolution imaging is required. The improvement of ultrasound resolution, particularly in 3D, will likely require a number of technologic developments that are currently not available.

Video-assisted optical endoscopy provides excellent spatial resolution, affords the option of using magnification to improve visualization, and is readily available as an image-guidance tool in minimally invasive cardiac surgery [2]. Nevertheless, use of this technique as a sole navigation tool in beating-heart interventions is limited owing to difficulties of visualization inside the heart in the presence of blood. To partly overcome this limitation, an endoscopic port was developed (Y Suematsu and Nipro Corp, Osaka, Japan). The port has an optical window at the tip that can house a conventional endoscope that provides a near-field high-resolution view when approximated to the intracardiac structures, even inside a beating heart. The objective of our study was to evaluate use of combined RT3DE and video-assisted cardioscopy (VAC) imaging during beating heart surgery for patch ASD closure.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 Discussion
 Acknowledgments
 References
 
Animals
The experimental protocol for this study was approved by the Children's Hospital Boston Institutional Animal Care and Use Committee. All animals received humane care in accordance with the 1996 Guide for the Care and Use of Laboratory Animals recommended by the US National Institutes of Health.

Five Yorkshire pigs (70 to 80 kg) were anesthetized by intramuscular injection of tiletamine/zolazepam (7 mg/kg) and xylazine (4 mg/kg). The animals were intubated with a cuffed endotracheal tube and ventilated with a Healthdyne 105 pressure control ventilator (Healthdyne Technologies, Marietta, GA). Anesthesia was maintained with 2% isoflurane. The electrocardiogram was continuously monitored.

Surgical Procedure
A median sternotomy was performed, and a few stay sutures were placed on the pericardium to optimize access to the right atrium. Two purse-string sutures of 3-0 polypropylene were placed on the right atrial appendage for instrument insertion. The ultrasound probe was applied directly on the surface of the right atrium. After intravenous heparin administration (100 U/kg), an ASD was created solely under RT3DE guidance as previously described [1]. First, a transseptal puncture was performed, and a balloon catheter was inserted across the septum. After balloon atrial septostomy, the defect was enlarged with a Kerrison bone punch. Then, the ASD was closed using the patch delivery device fixed around the defect with mini-anchors under combined RT3DE and VAC guidance.

After ASD closure, the residual atrial shunt was assessed by 2D and 3D epicardial echocardiography and VAC. Finally, the heart was excised and the efficacy of closure and patch fixation was confirmed.

Real-Time Three-Dimensional Echocardiography
RT3DE was performed using the X4 matrix transducer on a SONOS 7500 system (Philips Medical Systems, Andover, MA) as previously described [1].

Video-Assisted Cardioscopy
Standard video-endoscopic equipment (Smith and Nephew, Dyonics, Inc, Andover, MA) with a 5-mm rigid 0° endoscope (Olympus Corp, Tokyo, Japan) was used for VAC. The endoscope was inserted into the right atrium through the originally designed port (Nipro Corp, Osaka, Japan), which allows visualization in the presence of blood (Fig 1). The inner compartment of the port has a transparent plastic bulb at the end for endoscope access. The outer working channel of the port is used for instrument access. The port was held with a custom-build snake-type mechanical arm.


Figure 1
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  		Fig 1. The endoscopic port. The endoscope (arrow) is inserted into the inner compartment of the port, and the instrument (arrow) is inserted into the working channel. (A) Front view; (B) side view.

 
Surgical Devices
Custom-designed surgical devices were used for ASD patch closure. The patch delivery device consists of a self-expanding frame made of 0.25 mm x 0.75 mm Nitinol wire (wire 1) covered by a polyethylene tube (1.5 mm in diameter) and a grip. A 0.1-mm Dacron (Dupont, Wilmington, DE) patch is appropriately trimmed, and then attached to the frame by 0.1 mm Nitinol wire (wire 2). The device is delivered through a long sheath (5 mm in diameter), and the frame with the patch is deployed through the end of the sheath and allowed to expand (Fig 2A, B). The patch is attached to the atrial septum by Nitinol mini-anchors (Fig 2A, inset) and deployed using a pistol-type anchor delivery device. After the patch is fixed to the septum (Fig 2C, D), the wire 2 is removed, releasing the patch from the frame, and the frame is withdrawn into the sheath (Fig 2E, F).


Figure 2
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  		Fig 2. Atrial septal defect patch closure system ex vivo. (A) The atrial septal defect patch. (Inset) Nitinol anchor with 2-mm loop and 10-mm arms. (B) The device is delivered through an introducer, and the frame expands. (C, D) The Dacron patch is attached to the atrial septum by Nitinol mini-anchors. (E) The wire is removed, and the frame is withdrawn into the introducer. (F) Final view shows repair of the defect.

 

   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 Discussion
 Acknowledgments
 References
 
Atrial Septal Defect Creation
In all animals, the atrial septal defects were successfully created by balloon atrial septectomy and subsequently enlarged by biting off the rim of the ASD with a Kerrison bone punch. These maneuvers were performed by RT3DE-guided assessment of the spatial relationship between the ASD and the intracardiac structures. The mean size of the ASD created was 6.8 ± 1.8 mm (4 to 8 mm) as determined by 2D color Doppler echocardiography (Fig 3A). Successful creation of the defects was also confirmed by 3D color Doppler echocardiography and VAC (Fig 3B, C). Use of VAC allowed a detailed visualization of the rim of the defect and surrounding anatomic structures in high resolution and magnification, which gave the surgeon confidence for subsequent maneuvers.


Figure 3
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  		Fig 3. (A) A two-dimensional color Doppler image shows the created atrial septal defect. (B) A three-dimensional color Doppler image shows the top view from the right atrium. (C) Video-assisted cardioscopy image shows the rim of the defect (arrowheads). CS = coronary sinus; LA = left atrium; RA = right atrium.

 
Atrial Septal Defect Closure
The patch delivery device was inserted through the purse-string suture in the right atrium and advanced toward the ASD. The average size of the patch used was 12.0 ± 2.7 mm (range, 10 to 15 mm). The frame with the patch was easily deployed and covered the defect. The port with the endoscope was inserted through another purse-string suture and fixed by the mechanical arm. These maneuvers were easily guided by RT3DE. The final positioning of the tip of the endoscopic port was carefully confirmed by using VAC.

The anchor delivery device was inserted into the outer working channel of the port and advanced toward the target. The anchors were deployed one-by-one in two steps. First, the arms of the anchor were deployed, and the successful penetration of both the patch material and the septum was confirmed visually by VAC and tactilely by applying of gentle pulling-out force. Next, an anchor loop was fully deployed, and the anchor was disconnected from the device. The successful deployment of each anchor was confirmed by RT3DE and VAC (Fig 4A, B). The mean number of anchors per patch was 9.4 ± 1.9 (range, 8 to 12).


Figure 4
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  		Fig 4. (A) A real-time three-dimensional echocardiographic image of the patch fixed around the atrial septal defect by the anchors (arrowheads). (B) Video-assisted cardioscopy image shows the deployed anchor. (C) A postmortem photograph shows the repaired atrial septal defect. RA = right atrium; W = working channel of the endoscopic port.

 
All of the ASDs were successfully closed. The absence of residual shunts was confirmed by 2D and 3D color Doppler echocardiography and VAC. The examination after excision of the heart showed that the patches were deployed in the proper positions in all cases (Fig 4C). The anchors consistently penetrated the atrial septum tissue and the patch material. No surrounding anatomic structures were compromised in any of the pigs. The use of the mechanical arm allowed one surgeon to perform the procedure.


   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
Discussion
 Acknowledgments
 References
 
Since the first experimental attempt of ASD closure in 1939 by Arthur Blakemore and the first successful clinical operations in 1952 independently by Robert Edward Gross and F. John Lewis [3], this procedure has been on the front line of the new technology-driven evolution of intracardiac interventions. After the dominant era of ASD closure under cardiopulmonary bypass (CPB), a transcatheter device technique was introduced in 1974 by King and Mills [4].

Although the transcatheter device technique is now a routine procedure in most pediatric cardiology intervention labs, it has its limitations and occasional complications. Poor patient selection based on inaccurate judgment of the anatomy, the presence of associated left ventricular dysfunction, inadequate device-to-defect ratio selection, and operator-related failures resulting from insufficient experience have been reported. These may result in late complications such as erosions of the atrial wall or the aortic root, thromboembolic episodes, and bacterial infection of the devices [5].

During the last two decades, minimally invasive surgical techniques for ASD closure through a variety of small incisions and later through ports with robotic assistance have arrived as an alternative approach for transcatheter device closure. Successful results have been achieved [6, 7], but most of the procedures were performed under CPB, which has widely recognized potentially deleterious effects resulting in blood coagulation abnormalities, renal and pulmonary dysfunction, nonspecific inflammatory response, and neurologic injury [8]. Thus, a repair that accomplishes this through a smaller incision than that needed for conventional open surgery and avoids CPB might become a superior alternate approach to device closure.

Reliable visualization inside the heart in the presence of blood has been one of the main obstacles to successful beating-heart surgical interventions. Three-dimensional ultrasound and video-assisted cardioscopy have been used individually as the sole imaging tool for guidance in experimental beating-heart ASD closure. Downing and colleagues [9] demonstrated the feasibility of ASD closure under 3D echocardiographic guidance in a water tank. Previous results of animal experiments from our group [1] demonstrate that despite adequate spatial resolution for anatomic definition and gross navigation of the instruments, current RT3DE still needs to be optimized for visualization of small metal objects (staples, anchors, needles), which is especially important for safe surgical maneuvers inside the beating heart.

Optical imaging has excellent live resolution; however, it is also problematic to use as a sole navigational tool in beating-heart procedures. Sogawa and associates [10] reported closure of the foramen ovale without CPB using an intracardiac endoscope in a canine experiment. They found it impossible to fire the staples for foramen ovale closure under endoscopic monitoring, necessitating blind stapling.

We believe that the key to success in safe navigation inside the beating heart is to use combined imaging modalities. RT3DE gives surgeons superior large volume spatial orientation and VAC offers detailed, high-magnification pictures of the target, which provides surgeons with greater confidence for maneuvers.

Beating-heart ASD patch closure without CPB can be successfully achieved with combined RT3DE and VAC imaging for navigation throughout the procedure. Use of VAC improves safety of the procedure without sacrificing its relative simplicity. This approach can be utilized for any ASD geometry and size.


   Discussion
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 Discussion
Acknowledgments
 References
 
DR FRANK A. PIGULA (Boston, Massachusetts): With the cardioscope, does that need to be in contact to be able to see the patch, or can you stand off from the object of interest?

DR VASILYEV: Yes, the tip of the endoscopic port has to be with contact of the target. That is why the field of view is relatively narrow.

DR CHRISTOPHER A. CALDARONE (Toronto, Ontario, Canada): If there is a large shunt, is there any difficulty in getting the patch to stay in place while you apply the anchors?

DR VASILYEV: We had this issue in the beginning when we used thin Nitinol wire as a patch frame material. The patch was flapping over the ASD. We solved that problem by using thicker Nitinol wire for the last modification of the patch delivery device. We have not had any problems since that.


   Acknowledgments
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 Discussion
 Acknowledgments
References
 
This work was supported in part by National Institutes of Health Grant No. HL-073647 and HL71128 (PJdN). The equipment and technology used in the study were purchased with academic funds. The authors had full control of the design of the study, methods used, outcome measurements, analysis of data, and production of the written report.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 

  1. Suematsu Y, Martinez JF, Wolf BK, et al. Three-dimensional echo-guided beating heart surgery without cardiopulmonary bypass: atrial septal defect closure in a swine model J Thorac Cardiovasc Surg 2005;30:1348-1357.
  2. Burke RP. Video-assisted endoscopy for congenital heart repair Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2001;4:208-215.[Medline]
  3. Alexi-Meskishvili VV, Konstantinov IE. Surgery for atrial septal defect: from the first experiments to clinical practice Ann Thorac Surg 2003;76:322-327.[Free Full Text]
  4. Mills NL, King TD. Nonoperative closure of left-to-right shunts J Thorac Cardiovasc Surg 1976;72:371-378.[Abstract]
  5. Knirsch W, Dodge-Khatami A, Valsangiacomo-Buechel E, Weiss M, Berger F. Challenges encountered during closure of atrial septal defects Pediatr Cardiol 2005;26:147-153.[Medline]
  6. Bichell DP, Geva T, Bacha EA, Mayer JE, Jonas RA, del Nido PJ. Minimal access approach for the repair of atrial septal defect: the initial 135 patients Ann Thorac Surg 2000;70:115-118.[Abstract/Free Full Text]
  7. Argenziano M, Oz MC, Kohmoto T, et al. Totally endoscopic atrial septal defect repair with robotic assistance Circulation 2003;108(Suppl 1):II191-II194.
  8. Jaggers J, Ungerleider RM. Cardiopulmonary bypass in infants and childrenIn: Mavroudis C, Backer CL, editors. Pediatric cardiac surgery. 3rd ed.. Philadelphia, PA: Mosby; 2003. pp. 178-183.
  9. Downing SW, Herzog Jr WR, McElroy MC, Gilbert TB. Feasibility of off-pump ASD closure using real-time 3-D echocardiography Heart Surg Forum 2001;5:96-99.
  10. Sogawa M, Moro H, Tsuchida M, Shinonaga M, Ohzeki H, Hayashi J. Development of an endocardioscope for repair of an atrial septal defect in the beating heart ASAIO J 1999;45:90-93.[Medline]



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