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Ann Thorac Surg 2006;82:687-693
© 2006 The Society of Thoracic Surgeons

Original article: Cardiovascular

Robotically Assisted Totally Endoscopic Atrial Septal Defect Repair: Insights From Operative Times, Learning Curves, and Clinical Outcome

Nikolaos Bonaros, MDa,*, Thomas Schachner, MDa, Armin Oehlinger, MDa, Elisabeth Ruetzler, MDa, Christian Kolbitsch, MDb, Wolfgang Dichtl, MDc, Silvana Mueller, MDc, Guenther Laufer, MDa, Johannes Bonatti, MDa

a Department of Cardiac Surgery, Innsbruck Medical University, Innsbruck, Austria
b Department of Anesthesia and Intensive Care Medicine, Innsbruck Medical University, Innsbruck, Austria
c Department of Cardiology, Innsbruck Medical University, Innsbruck, Austria

Accepted for publication March 10, 2006.

* Address correspondence to Dr Bonaros, University of Innsbruck, Cardiac Surgery, Anichstrasse 35, Innsbruck 6020 Austria (Email: nikolaos.bonaros{at}uibk.ac.at).


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
BACKGROUND: Remote access perfusion and robotics have enabled totally endoscopic closure of atrial septal defect and patent foramen ovale. The aim of this study was to address learning curve issues of totally endoscopic atrial septal defect repair on the basis of a single-center experience and to investigate whether long cardiopulmonary bypass and aortic occlusion times influence intraoperative and postoperative outcomes.

METHODS: Seventeen patients (median age, 35 years; range, 16 to 55 years) underwent totally endoscopic atrial septal defect repair using remote access perfusion and robotic technology (da Vinci telemanipulation system). Learning curves were assessed by means of regression analysis with logarithmic curve fit. The effect of operative variables on clinical outcome was analyzed by linear regression using the Spearman's rho coefficient.

RESULTS: No operative mortality or serious surgical complications were observed. No residual shunt was detected at intraoperative or postoperative echocardiography. Significant learning curves were noted for total operative time: y(min) = 406 – 49 ln(x) (r2 = 0.725; p = 0.002); cardiopulmonary bypass time: y(min) = 225 – 42 ln(x) (r2 = 0.699; p = 0.003); and aortic occlusion time: y(min) = 117 – 25 ln(x) (r2 = 0.517; p = 0.04), x = number of procedures. Median ventilation time, intensive care unit stay, and hospital length of stay were 7 hours (range, 2 to 19 hours), 26 hours (range, 15 to 120 hours), and 8 days (range, 5 to 14 days), respectively. No correlation was detected between cardiopulmonary bypass time and intubation time (r2 = 0.283; p = 0.326), intensive care unit stay (r2 = –0.138; p = 0.639), or total length of stay (r2 = 0.013; p = 0.962).

CONCLUSIONS: Totally endoscopic atrial septal defect repair can be performed safely, and learning curves for operative times are steep. Longer cardiopulmonary bypass times had no negative impact on intraoperative and postoperative outcome.


   Introduction
Top
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
Surgical atrial septal defect (ASD) closure through minithoracotomy has gained significant acceptance within the cardiac surgery community [1]. The advent of totally endoscopic procedures using robotic technology has been reported to be a safe and effective method, with zero mortality and very low morbidity [2–5]. A rapid recovery of quality of life and lower pain levels as compared with both median sternotomy and minithoracotomy have been reported, whereas clinical results are still excellent [6].

On the other hand, totally endoscopic ASD repair (TEASD-R) remains a highly complex procedure, the performance of which requires experience with several nonroutine operative steps, such as remote access perfusion and robotic cardiac surgery [5]. Moreover anesthesia management of those patients has additional nonroutine steps as prerequisites, including single-lung ventilation and advanced transesophageal echocardiography for patient monitoring during remote access cardiopulmonary bypass (CPB) and endoaortic balloon occlusion. All studies published so far have shown that TEASD-R can be performed with excellent clinical results, but surgeons are required to invest in a time-consuming operative procedure, which includes long CPB and aortic occlusion times [2–5].

The aim of this study was to address learning curve issues of TEASD-R on the basis of a single-center experience and to investigate whether longer CBP and aortic occlusion times affect intraoperative and postoperative outcomes.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
After approval by the local university ethics committee and written informed consent, patients (n = 17) scheduled for TEASD-R by means of the da Vinci telemanipulation system (Intuitive Surgical, Sunnyvale, CA) were enrolled between March 2003 and December 2005 at the Department of Cardiac Surgery, Innsbruck Medical University. Patients presented with ASD of secundum type with a pulmonary-to-systemic ratio greater than 1.5, or patent foramen ovale with a documented neurologic event. Patients were excluded if single-lung ventilation or peripheral CPB could not be tolerated, or otherwise were considered poor candidates for a thoracoscopic approach.

Anesthesia
After induction of general anesthesia a left-sided double-lumen endotracheal tube was placed to allow for single-lung ventilation. Placement of central venous catheters included placement of a guidewire in the superior vena cava through the right internal jugular vein to facilitate intraoperatively cannulation of the superior vena cava. To monitor correct placement of perfusion cannulas and of the endoaortic occlusion balloon, transesophageal echocardiography and bilateral radial arterial blood pressure catheters were used.

Operative Procedure
The patient was positioned in a 30-degree left lateral decubitus position, with the right arm tucked at the side and the pelvis relatively flat to facilitate femoral cannulation. After systemic heparinization (300 IU/kg), femoral vessels were accessed through an oblique incision along the inguinal crease. A 23F or 25F venous return cannula (Biomedicus; Medtronic, Eden Prairie, MN) was inserted through the right femoral vein into the inferior vena cava. The bypass circuit was completed by positioning a 17F or 21F remote access perfusion cannula with endoaortic balloon (ESTECH, Danville, CA) in the ascending aorta through the common femoral artery. The distal tip of the arterial cannula was passed under echocardiographic guidance into the ascending aorta, approximately 1 cm from the aortic valve. Additionally, a 17F cannula (Biomedicus; Medtronic) was percutaneously inserted in the superior vena cava under echocardiographic guidance.

After establishment of selective left lung ventilation, a port incision was made in the fourth intercostal space, in the midclavicular line, and a 12-mm endoscopic trocar (Ethicon, Sommerville, NJ) was placed into the right thoracic cavity. The endoscopic camera was inserted, and the pleural space was insufflated with carbon dioxide to a maximum pressure of 8 to 12 mm Hg. Additionally two 8-mm port incisions were made in the third and sixth intercostal spaces, in the right anterior axillary line, to allow insertion of the robotic instruments. Two additional port incisions (9 mm and 5 mm) were made in the fourth and fifth intercostal spaces, in the posterior axillary line, to enable transthoracic assistance and pump sucking, respectively.

The intrathoracic part of the operation began with pericardiotomy and placement of pericardial stay sutures. Caval snares were placed using a special long Endoflex clamp (Obtech Medical AG, Baar, Switzerland) to encircle the superior and inferior venae cavae to install total CPB. After CPB initiation and cooling to 32°C, the endoaortic balloon was insufflated under echocardiographic control, and cardiac arrest was achieved by delivery of an initial dose of adenosine (3 mg) and cold cardioplegic St. Thomas II solution. After snaring of the superior and inferior venae cavae, the right atrium was opened, and four stay sutures (4-0 Gore-Tex CV4, Flagstaff, AZ) were placed on the atrial roof to expose the ASD. Cardiotomy suction was passed through the posterior assistance port by the patient-side surgeon. Anatomic landmarks including the fossa ovalis, coronary sinus ostium, and eustachian valve were identified. According to the size of the defect, either a double-layer 4-0 Gore-Tex running suture or a Dacron patch was used. For longer suture lines, several 15-cm-long segments were required. After ASD closure the endoaortic balloon was deflated, and the patient was rewarmed. The atriotomy was closed using a single layer of running 4-0 Gore-Tex suture, and the patient was weaned from CPB. Integrity of the atrial septal closure was confirmed by transesophageal echocardiography, and protamine sulfate (1:1) was administered. After adequate hemostasis was achieved, the robotic arms were removed from the chest, and a 24F chest tube was inserted in the right pleural space through one of the port holes, after removing of the cannulas and reconstruction of the femoral artery.

Postoperative Management
Postoperatively patients were monitored at the intensive care unit overnight. Discharge to an intermediate care unit took place as soon as hemodynamics and spontaneous respiration had adequately stabilized. Chest drains were removed when drainage reached less than 100 mL/24 h. All patients underwent control transthoracic echocardiography immediately before discharge from hospital and at 3 months after the procedure.

Statistical Analysis
Data are given as median (range) or when appropriate as mean ± standard deviation. Regression models with logarithmic curve fit were used for learning curve analysis. Moreover, Spearman's rho was calculated. A probability value less than or equal to 0.05 was considered statistically significant. The statistical computer package SPSS 11.0.1 for Windows (Chicago, IL) was used for statistical analysis.


   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
Preoperative diagnosis and baseline data are presented in Table 1. No major technical failures attributed to the telemanipulator were experienced. There was no mortality and no serious life-threatening complication in this cohort. No conversions to minithoracotomy or median sternotomy were needed, and no patient underwent reoperation for bleeding. One patient required interposition of a short Gore-Tex graft and an additional bare-metal stent implantation after local dissection of the cannulation site in the femoral artery. Six months postoperatively, the patient is free of claudication without signs of intimal thickening at the reconstruction site. No case of lymphatic fistula was noted in the postoperative period. Total operative time, CPB time, and aortic occlusion times are shown in Table 2. No perioperative neurologic event was recorded and no residual ASD was detected on intraoperative transesophageal and on postoperative transthoracic echocardiography performed before discharge and at 3 months after the operation (Table 3). Because of the complexity of the procedure, the whole operation was divided into several single operative steps; the duration of each is presented in Table 4.


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  		Table 1. Baseline Characteristics
 

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  		Table 2. Intraoperative Data
 

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  		Table 3. Postoperative Data
 

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  		Table 4. Duration of Single Operative Steps in Totally Endoscopic Atrial Septal Defect Repair
 
Learning Curves
Operative times showed a statistically significant learning curve pattern with regard to total operative time, CPB time, and aortic cross-clamp time (Fig 1). Similarly, learning curves of basic intraoperative steps, such as ASD closure time (y(min) = 40 – 5*ln(x); r2 = 0.511; p = 0.04) and atriotomy suture time (y(min) = 55 – 11*ln(x); r2 = 0.34; p = 0.003) were also statistically significant. On the other hand, no significant reduction of the intubation time (r2 = 0.146; p = 0.6), intensive care unit (ICU) stay (r2 = 0.132; p = 0.64), and total length of hospital stay (r2 = –0.031; p = 0.93) were noted during the whole time course.


Figure 1
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  		Fig 1. Learning curves in 17 patients who underwent totally endoscopic atrial septal defect repair in terms of total operative (OR) time (A; y (min) = 406 – 49 x ln(x); r2 = 0.725; p = 0.002), cardiopulmonary bypass (CPB) time (B; y (min) = 225 – 42 x ln(x); r2 = 0.699; p = 0.003), and aortic occlusion (X-Clamp) time (C; y(min) = 117 – 25 x ln(x); r2 = 0.517; p = 0.04). The x axis shows consecutive atrial septal defect (ASD) case number.

 
Correlations of Cardiopulmonary Bypass and Aortic Occlusion Time With Clinical Variables
As shown in Table 2, CPB and aortic occlusion times reached less than 2 h and 15 min and 1 h and 10 min, respectively. Although CPB perfusion and aortic occlusion were longer as compared with those needed for a conventional operation through a sternotomy, none of them correlated with ICU stay and total length of stay in the hospital (Fig 2). Although long CPB and aortic occlusion times are associated with longer single-lung ventilation, none of them correlated with intubation time and blood gas variables such as partial oxygen and carbon dioxide pressures at the end of the operation, after extubation, and before ICU discharge (Table 5). Similarly, no correlation was detected between CPB or cross-clamp time and the duration of continuous positive airway pressure support therapy or bleeding. On the other hand, CPB and aortic occlusion times were positively correlated with the number of blood products used intraoperatively and the maximal levels of creatine kinase observed in the postoperative phase. However, there was no correlation with the level of myocardial damage as detected by maximal elevation of creatine kinase, cardiac isoenzyme (Fig 3).


Figure 2
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  		Fig 2. Linear correlations of cardiopulmonary bypass (CPB) time with intubation time (A; r2 = 0.283; p = 0.326), intensive care unit (ICU) stay (B; r2 = 0.138; p = 0.639), and hospital length of stay (C; r2 = 0.013; p = 0.962) after totally endoscopic atrial septal defect repair in 17 patients.

 

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  		Table 5. Correlations (Spearman's rho) Between Clinical Variables and Cardiopulmonary Bypass or Aortic Occlusion Times
 

Figure 3
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  		Fig 3. Linear correlations of cardiopulmonary bypass (CPB) time with maximal levels of creatine kinase (CK) elevation (A; r2 = 0.815; p = 0.007) and maximal levels of creatine kinase, cardiac isoenzyme (CK-MB) elevation (B; r2 = 0.084; p = 0.830) after totally endoscopic atrial septal defect repair in 17 patients.

 

   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
Various minimal access incisions have been described for ASD closure. These incisions allow the surgeon to use common exposures, cannulation techniques, and instruments. Whether parasternal upper partial sternotomy [1], lower partial sternotomy [7], or right minithoracotomy [8] is performed, these incisions leave obvious scars, which may have a negative influence on the psychology and quality of life of young adolescent or adult patients, who are usual candidates for ASD repair. In addition, patients operated on through a minithoracotomy experience significant pain levels in the immediate postoperative period, mainly attributed to intercostal nerve trauma [9].

The advent of robotic technology and remote access CPB has enabled a totally endoscopic approach to ASD repair through thoracic ports. As currently fewer than 100 TEASD-R cases have been reported worldwide, one should be cautious in drawing conclusions with regard to the efficacy of the method. However, on the basis of the safety and attractiveness of the technique for surgeons and referring cardiologists and because young adult patients appreciate a totally endoscopic procedure [10], we believe that installation of a TEASD-R program is worthwhile.

Calculations of learning curves issues and operative times play a major role for the acceptance of such a program, especially in the setting of a busy university clinic. According to a previous study from our group this could be successfully initialized by using a stepwise approach, whereby the total operative procedure was split into several modules, including dry-laboratory training, ASD closure through minithoracotomy and remote access perfusion, and after gaining parallel experience with the totally endoscopic coronary artery bypass grafting on the arrested heart [5]. This approach has been used by other authors to implement other complex surgical procedures such as totally endoscopic coronary artery bypass grafting [11–13].

Clinical results were quite encouraging in this patient series, as in all cases the operation could be performed safely, without any major surgical complication, and with no need for conversion to full sternotomy or minithoracotomy or residual shunt in intraoperative and follow-up echocardiography. Conversion rates in TEASD-R seem to be lower in comparison to the ones reported for the totally endoscopic coronary artery bypass grafting procedure [4, 10, 14]. Especially, the fact that all operations were completed in a totally endoscopic fashion may be attributed to the experience of the operating group with complex robotically assisted surgery and remote access perfusion [15] and detailed patient evaluation by means of preoperative computerized tomographic scans before enrollment.

Residual shunts requiring reoperations have only been reported in patients who underwent direct defect closure [1, 4]. Limited experience is available regarding patch closure in TEASD-R (2 patients operated on by our group and 2 patient from the Frankfurt group [3]), more probably owing to careful patient selection [6] (smaller longitudinal defects with sufficient overlapping tissue, which allow tension-free closure) and less because of the aim to use direct closures for the sake of time. According to our experience, the second TEASD-R case using patch closure was completed in a little more than 4 hours, whereas 6.5 hours were needed for the first case performed on the third patient of this series.

In this context, we experienced statistically significant learning curves in terms of total operative times, which also reflected similar curves with regard to single steps of the operation, such as CPB and aortic occlusion times and duration of ASD closure and atriotomy suturing as well. This fact shows that operative learning curves are extremely steep as fewer than 10 cases were needed to achieve procedure times of less than half of the initial experiences. This is consistent with the experimental [16] and clinical experience of other groups with regard to robotically assisted totally endoscopic coronary artery bypass grafting [13] or endoscopic lead placement [17], whereas published data concerning TEASD-R are too preliminary.

Undoubtedly procedure duration, as well as CPB and aortic occlusion times, is longer than the ones reported for conventional ASD repair operations through sternotomy or minithoracotomy. Total duration of the procedure and CPB times were comparable with the experience of other groups. Aortic occlusion times of approximately 60 minutes confirmed the results reported from other authors with the exception of Argenziano and colleagues [4], who observed aortic occlusion times of approximately 30 minutes in a series of 17 patients operated on using direct suture closure in all cases.

With regard to postoperative results, we experienced no reduction of intubation time, ICU stay, and total length of stay on the course of our series. This may mainly be attributed to previous experience of the ICU and intermediate care unit teams with totally endoscopic procedures, which allows rapid extubation and early mobilization of the patient. Length of stay reached the usual levels reported in most public European centers, which is significantly higher as compared with the U.S. experience, mainly because of the European health system. In our previous experience with totally endoscopic coronary artery bypass grafting patients, longer operative and CPB times were associated with delayed extubation and longer ICU stay [11]. Interestingly, this fact was not observed in TEASD-R-patients, which can be attributed to the younger age and lower incidence of comorbidities and especially pulmonary disease of this patient group. Long duration of single-lung ventilation did not negatively affect intraoperative or postoperative oxygenation variables or increase the need for continuous positive airway pressure therapy.

On the other hand, longer CPB times were associated with higher rates of intraoperative blood transfusions. Nevertheless, these did not exceed a median of one unit of packed red blood cells and one unit of fresh-frozen plasma, whereas no transfusion was required thereafter. The fact that longer CPB times correlated with higher creatine kinase but not with higher creatine kinase, cardiac isoenzyme, levels indicated that it may be associated with phases of inadequate leg perfusion of the leg distal to the cannulation site. We addressed this problem by using selective perfusion of the superficial femoral artery distal to the cannulation site, as described by Greason and associates [18].

We conclude that TEASD-R can be safely implemented and performed in the setting of a medium-size university clinic in acceptable operative times without significant perioperative morbidity or mortality, and no residual shunts, despite the presence of an initial learning curve. Learning curves are steep for operative, CPB, and aortic occlusion times and for major parts of the operation such as ASD closure and atriotomy suture. Long CPB times during the initial implementation phase translate into increased blood product use but otherwise do not compromise the clinical outcome. Atrial septal defect closure is apparently adequate.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Doll N, Walther T, Falk V, et al. Secundum ASD closure using a right lateral minithoracotomyfive-year experience in 122 patients. Ann Thorac Surg 2003;75:1527-1531.[Abstract/Free Full Text]
  2. Toracca L, Ismeno G, Quarti A, Alfieri O. Totally endoscopic atrial septal defect closure with a robotic systemexperience with seven cases. Heart Surg Forum 2002;5:125-127.[Medline]
  3. Wimmer-Greinecker G, Dogan S, Aybek T, et al. Totally endoscopic atrial septal repair in adults with computer-enhanced telemanipulation J Thorac Cardiovasc Surg 2003;126:465-468.[Abstract/Free Full Text]
  4. Argenziano M, Oz MC, Kohmoto T, et al. Totally endoscopic atrial septal defect repair with robotic assistance Circulation 2003;108(Suppl 2):191-194.
  5. Bonaros N, Schachner T, Oehlinger A, et al. Experience on the way to totally endoscopic atrial septal defect repair Heart Surg Forum 2004;7:E440-E445.[Medline]
  6. Morgan JA, Peacock JC, Kohmoto T, et al. Robotic techniques improve quality of life in patients undergoing atrial septal defect repair Ann Thorac Surg 2004;77:1328-1333.[Abstract/Free Full Text]
  7. Black MD, Freedom RM. Minimal invasive repair of atrial septal defects Ann Thorac Surg 1998;65:765-767.[Abstract/Free Full Text]
  8. Ryan WH, Cheirif J, Dewey TM, Prince SL, Mack MJ. Safety of minimally invasive atrial septal defect closure Ann Thorac Surg 2003;75:1532-1534.[Abstract/Free Full Text]
  9. Walther T, Falk V, Metz S, et al. Pain and quality of life after minimally invasive versus conventional cardiac surgery Ann Thorac Surg 1999;67:1643-1647.[Abstract/Free Full Text]
  10. Bonaros N, Schachner T, Oehlinger A, Friedrich G, Laufer G, Bonatti J. Assessment of heath-related quality of life after coronary revascularization Heart Surg Forum 2005;8:E380-E385.[Medline]
  11. Bonatti J, Schachner T, Bernecker O, et al. Robotic totally endoscopic coronary artery bypass. Program development and learning curve issues J Thorac Cardiovasc Surg 2004;127:504-510.[Abstract/Free Full Text]
  12. Falk V, Diegeler A, Walther T, et al. Total endoscopic computer enhanced coronary artery bypass grafting Eur J Cardiothorac Surg 2000;17:38-45.[Abstract/Free Full Text]
  13. Kappert U, Schneider J, Cichon R, et al. Development of robotic enhanced endoscopic surgery for the treatment of coronary artery disease Circulation 2001;104(12 Suppl 1):102-107.[Abstract/Free Full Text]
  14. Kappert U, Cichon R, Schneider J, et al. Technique of closed chest coronary artery surgery on the beating heart Eur J Cardiothorac Surg 2001;20:765-769.[Abstract/Free Full Text]
  15. Schachner T, Bonaros N, Feuchtner G, Muller L, Laufer G, Bonatti J. How to handle remote access perfusion for endoscopic cardiac surgery Heart Surg Forum 2005;8:E232-E235.[Medline]
  16. Maniar HS, Council ML, Prasad SM, Prasad SM, Chu C, Damiano RJ. Comparison of skill training with robotic systems and traditional endoscopyimplications on training and adoption. J Surg Res 2005;125:23-29.[Medline]
  17. Jansens JL, Jottrand M, Preumont N, Stoupel E, De Cannière D. Robotic-enhanced biventricular resynchronizationan alternative to endovenous cardiac resynchronization therapy in chronic heart failure. Ann Thorac Surg 2003;76:413-417.[Abstract/Free Full Text]
  18. Greason KL, Hemp JR, Maxwell JM, Fetter JE, Moreno-Cabral RJ. Prevention of distal limb-ischemia during cardiopulmonary support via femoral cannulation Ann Thorac Surg 1995;60:209-210.[Abstract/Free Full Text]



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