Predictors, Causes, and Consequences of Conversions in Robotically Enhanced Totally Endoscopic Coronary Artery Bypass Graft Surgery

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1 ORIGINAL ARTICLES: SURGERY: The Annals of Thoracic Surgery CME Program is located online at To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal. Predictors, Causes, and Consequences of Conversions in Robotically Enhanced Totally Endoscopic Coronary Artery Bypass Graft Surgery Thomas Schachner, MD, Nikolaos Bonaros, MD, Dominik Wiedemann, MD, Eric J. Lehr, MD, Felix Weidinger, MD, Gudrun Feuchtner, MD, David Zimrin, MD, and Johannes Bonatti, MD University Clinic of Cardiac Surgery and University Clinic of Radiology II, Innsbruck Medical University, Innsbruck, Austria; and Division of Cardiac Surgery, Department of Surgery, and Division of Cardiology, Department of Internal Medicine, University of Maryland, Baltimore, Maryland Background. Totally endoscopic coronary artery bypass graft surgery (TECAB), using the da Vinci telemanipulator, has become a reproducible operation at dedicated centers. As in every endoscopic operation, conversion is an important and probably inevitable issue. Methods. We performed robotic TECAB in 326 patients (age, 60 years; range, 31 to 90 years); 242 were singlevessel and 84 were multivessel TECAB. Results. Forty-six of 326 patients (14%) were converted to a larger incision (minithoracotomy, n 5; sternotomy, n 41). Left internal mammary artery injury (n 7), epicardial injury (n 4), balloon endoocclusion problems (n 7), and anastomotic problems (n 18) were common reasons for conversions. Conversion rate was significantly less for single-vessel versus multivessel TECABs (10% versus 25%; p 0.001). Non learningcurve case (7% versus 21%; p < 0.001) and transthoracic assistance (11% versus 22%; p 0.018) were associated with lower conversion rates. In multivariate analysis, learning-curve case was the only independent predictor of conversion (p 0.005). Conversion translated into increased packed red blood cell transfusion in the operating room (3 versus 0 units; p < 0.001), longer ventilation time (14 versus 8 hours; p < 0.001), and intensive care unit stay (45 versus 20 hours; p 0.001). Hospital mortality was 0.6% in this series, with 1 patient in the conversion group (2.2%) and 1 patient in the nonconverted group (0.4%; not significant). Five-year survival was 98% in nonconverted patients and 88% in converted patients (p 0.018). There was no difference in freedom from angina or freedom from major adverse cardiac and cerebral events. Conclusions. Conversion in TECAB is primarily learning curve dependent and associated with increased morbidity, but does not significantly affect hospital mortality. Both nonconverted and converted patients show good long-term survival, which is comparable to patients undergoing open sternotomy coronary artery bypass grafting. Long-term freedom from angina or freedom from major adverse cardiac and cerebral events is not influenced by conversion. (Ann Thorac Surg 2011;91:647 53) 2011 by The Society of Thoracic Surgeons Accepted for publication Oct 26, Address correspondence to Dr Schachner, Department of Surgery, University Clinic of Cardiac Surgery, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria; thomas.schachner@i-med.ac.at. Robotic technology enables totally endoscopic coronary artery bypass grafting (TECAB) and facilitates minimal invasive coronary artery bypass grafting (CABG). Avoiding sternotomy is of value for the patient by permitting earlier return to routine physical activity [1]. Robotic technology facilitates CABG through a small thoracotomy and is the only reproducible method to perform totally endoscopic coronary surgery (working exclusively through thoracic ports). As the procedure and technology has matured, it is possible to successfully complete increasingly complex operations. Surgeons now routinely perform not only single and double bypasses using the right and left internal mammary artery in situ grafts, but the repertoire of an experienced robotic cardiac surgeon now includes triple bypass, Y grafts, sequential grafts, vein grafts, and hybrid approaches. Conversion to open surgery is an important issue in every type of endoscopic operation. However, information pertaining to conversions and its impact on long-term major adverse cardiac and cerebrovascular events (MACCE) in larger series is limited in TECAB [2 7]. We reviewed our entire series of patients undergoing TECAB procedures to determine the risk factors and specific causes for conversions to larger incisions (ster by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc doi: /j.athoracsur

2 648 SCHACHNER ET AL Ann Thorac Surg CONVERSIONS IN TECAB 2011;91: Table 1. Demographic Data for 326 Patients Undergoing Totally Endoscopic Coronary Surgery Variable Total (n 326) Conversion (n 46) No Conversion (n 280) p Value Age (y) 60 (31 90) 61 (41 82) 60 (31 90) Male sex 243 (74%) 32 (70%) 211 (75%) EuroSCORE 2 (0 8) 2 (0 7) 2 (0 8) Body mass index (kg/m 2 ) 27 (14 47) 27 (21 36) 27 (14 47) History of smoking 95 (29%) 13 (29%) 82 (30%) Diabetes mellitus 61 (19%) 9 (20%) 52 (19%) Hypercholesterinemia 201 (62%) 26 (58%) 175 (63%) Arterial hypertension 243 (75%) 31 (69%) 212 (77%) Previous PCI 75 (23%) 13 (29%) 62 (22.4%) History of myocardial 87 (27%) 16 (36%) 71 (25.6%) infarction Preoperative unstable angina 28 (9%) 4 (9%) 24 (9%) Preoperative ejection fraction 0.60 ( ) 0.60 ( ) 0.60 ( ) Preoperative NYHA class 3 (1 4) 3 (1 4) 3 (1 4) Peripheral vascular disease 8 (2.5%) 1 (2.2%) 7 (3%) Preoperative serum 0.98 ( ) 0.98 ( ) 0.97 ( ) creatinine (mg/dl) History of transient ischemic 10 (3%) 3 (7%) 7 (3%) attack History of stroke 3 (1%) 0 3 (1%) Chronic obstructive pulmonary disease 31 (10%) 4 (9%) 27 (10%) EuroSCORE European system for cardiac operative risk evaluation; NYHA New York Heart Association; PCI percutaneous coronary intervention. notomy or minithoracotomy. We also assessed the consequences of conversion (morbidity, mortality, and longterm outcome). CPB, Edwards Lifesciences, Irvine, CA, or Estech, San Ramon, CA) [8, 9]. Distal leg perfusion was monitored by near-infrared spectrometry [10]. In beating-heart pump- Patients and Methods Demographic data are listed in Table 1. The operations were performed by 3 different surgeons (J.B., T.S., N.B.) at Innsbruck Medical University and the University of Maryland. All patients gave informed consent for the procedure, which had received institutional review board approval at Innsbruck Medical University. Patient data were entered into a common Innsbruck Maryland database that was also approved by the institutional review board of the University of Maryland School of Medicine. Operative Technique All 326 patients underwent TECAB surgery using the da Vinci surgical telemanipulation systems (Standard, S, and Si models; Intuitive Inc, Sunnyvale, CA) from 2001 to The operations performed are listed in Table 2. The number of grafts was one in 247 patients, two in 77 patients, and three in 2 patients. The operative technique has been described previously [4, 6]. In brief, a camera port and two working ports were introduced into the left (or, if the right coronary artery was grafted, into the right) hemithorax under single-lung ventilation and carbon dioxide insufflation (6 to 10 mm Hg). In arrested-heart TECABs, the left femoral vessels were cannulated for the heart-lung machine using an aortic endoocclusion balloon catheter (Endo Table 2. Types of Totally Endoscopic Coronary Artery Bypass Graft Surgery Procedures (n 326) Performed Procedure Type Arrested heart TECAB LIMA to LAD 198 Arrested heart TECAB LIMA to marginal branch 34 and RIMA to LAD Beating heart (pump standby or pump-assisted) 24 TECAB LIMA to LAD Arrested heart TECAB LIMA to LAD and 22 diagonal branch jump Beating heart TECAB LIMA to LAD 16 Beating heart TECAB (pump standby or pumpassisted) RIMA to LAD and LIMA to marginal 9 branch Others a 23 a Others include beating-heart TECAB RIMA to LAD and LIMA to diagonal branch (pump standby or pump-assisted), beating-heart TECAB LIMA to LAD and axillocoronary saphenous vein graft to marginal branch (pump standby or pump-assisted), beating-heart TECAB LIMA to LAD and axillocoronary saphenous vein graft to marginal branches 1 2 jump (pump standby or pump-assisted), arrested-heart TECAB RIMA to right coronary artery, arrested-heart TECAB LIMA to LAD and saphenous vein graft to right posterior descending coronary artery, arrestedheart TECAB LIMA to marginal branch and ramus intermedius jump, arrested-heart TECAB RIMA to LAD and LIMA to marginal branches 1 2 jump, and arrested-heart TECAB LIMA to LAD and axillocoronary saphenous vein graft to marginal branch and ramus intermedius jump. LAD left anterior descending coronary artery; LIMA left internal mammary artery; RIMA right internal mammary artery; TECAB totally endoscopic coronary artery bypass graft surgery. n

3 Ann Thorac Surg SCHACHNER ET AL 2011;91: CONVERSIONS IN TECAB assisted TECABs, the femoral artery or the left subclavian artery was prophylactically connected to the heart lung machine with percutaneous femoral venous cannulation to permit cardiopulmonary bypass support in case of hemodynamic instability. Early in the series, the internal mammary artery (IMA) was harvested in a semiskeletonized fashion, but we began skeletonizing the IMA in 2008 to gain additional graft length, especially for multivessel TECAB [11]. After removal of the pericardial fat pad and pericardiotomy, the coronary anastomoses were all performed in a handsewn running technique using a 7-0 polypropylene suture. In double-vessel TECAB, the lateral and back walls of the heart were exposed using an endoscopic suction stabilizer [12]. Intraoperative quality control by graft angiography or Doppler flow measurement was performed as previously described [13]. Conversions Conversions were defined as cases that required a larger thoracic incision (ie, minithoracotomy or sternotomy) and could not be finished in a totally endoscopic fashion. In general, a sternotomy was performed to convert to the most standard procedure. When a planned hybrid case required conversion, all diseased coronary arteries were revascularized. In 5 patients, the conversion was performed through a minithoracotomy. We routinely performed quality control of the bypass grafts (intraoperative angiography or Doppler flow measurement), and conversion was liberally carried out if graft angiography showed a doubtful result. Learning-Curve Cases We previously published learning curves for endoscopic IMA takedown and for single-vessel left IMA to left anterior descending coronary artery (LAD) TECABs [6, 11]. After 20 cases, the learning curves tend to flatten, which seems to be a reasonable cutoff to classify a new procedure version as being out of the steep learning curve. The different types of TECAB operations we performed are listed above in the operative technique section of the methods. The learning curve for each individual surgeon was considered for all of the variations of TECAB. We compared 158 cases within the learning curve (case number for a new procedure version 20) with 168 cases in which an experience of 20 cases per surgeon existed. An MACCE was defined as a postoperative myocardial infarction, cerebrovascular accident (transient ischemic attack, stroke), coronary intervention (percutaneous coronary intervention or CABG on any coronary artery), or death of any cause. Patients or their referring physicians were contacted by telephone interview to obtain long-term follow-up. Median duration of follow-up was 20 months (range, 1 to 96 months), and the follow-up was complete in 306 of 326 patients (94%). Statistical Analysis The statistical software program SPSS 15.0 (SPSS, Chicago, IL) was used for statistical analysis. Numbers are displayed as median and range for continuous variables, and as number and percentage for categorical variables. Associations among categorical variables were calculated using the 2 test. Associations between conversion and continuous variables were assessed using the Mann- Whitney test. For multivariate analysis of risk factors for conversion, the significant predictors of univariate analysis were entered into a binary logistic regression model. The probability value, the Wald coefficient, and the hazard ratio with the 95% confidence interval are displayed. Long-term survival and freedom from angina were calculated using life tables and Kaplan-Meier analysis with log-rank testing. A probability value of less than 0.05 was regarded as statistically significant. Results 649 Overall, 46 of 326 (14%) TECAB procedures required conversion to a larger incision, which was a minithoracotomy in 5 cases (2%) and a sternotomy in 41 cases (12%). The reasons for conversions were as follows: Anastomotic problems (bleeding, stenosis in intraoperative graft angiography, technical difficulties owing to blood flow in the target vessel, traction injury caused by stabilizer or instruments; n 18; 39% of conversions) Internal mammary artery problems (injury, intramural hematoma, too-short length of right IMA to LAD; n 7; 15% of conversions) Problems with remote access perfusion (arterial line pressure too high, balloon rupture, severe kinking of the iliac arteries preventing guidewire placement; n 7; 15% of conversions) Epicardial lesion (n 4; 9% of conversions) Intraoperative signs of ischemia in non target vessel regions in hybrid interventions (n 3; 7% of conversions) Inadequate target vessel exposure (n 3; 7% of conversions) Intramyocardial LAD (n 1; 2% of conversions) Retrograde aortic dissection (n 1; 2% of conversions) Bleeding from right atrial injury in redo case (n 1; 2% of conversions) Severe kinking of a jump graft (n 1; 2% of conversions) Operative times and intraoperative events are listed in Table 3. Conversion was less frequent in single-vessel compared with multivessel TECABs (10% versus 25%; p 0.001). In cases within the learning curve, the conversion rate was significantly higher than for procedures that the surgeon had performed at least 20 times (21% versus 7%; p 0.001). Transthoracic assistance decreased conversion rates (22% versus 11%; p 0.018). Multivariate analysis showed that the learning-curve case was a significant independent predictor of conversion (p 0.005; hazard ratio, 0.185; 95% confidence interval, to 0.592; Wald coefficient, 8.069; Table 4).

4 650 SCHACHNER ET AL Ann Thorac Surg CONVERSIONS IN TECAB 2011;91: Table 3. Intraoperative and Early Postoperative Data for 326 Patients Undergoing Totally Endoscopic Coronary Artery Bypass Graft Surgery Variable All Patients (n 326) Conversion (n 46) No Conversion (n 280) p Value Operative time (min) 270 ( ) 422 ( ) 262 ( ) Cardiopulmonary bypass time (min) 106 (0 444) 188 (3 428) 98 (0 444) Aortic occlusion time (min) 67 (0 239) 101 (25 231) 65 (0 239) Left internal mammary artery 37 (16 85) 40 (22 84) 37 (4 85) takedown time (min) Right internal mammary takedown 35 (19 95) 41 (30 95) 35 (19 72) time (min) Beating-heart TECAB 53 (16%) 11 (24%) 42 (15%) Multivessel TECAB 79 (24%) 20 (44%) 59 (21%) Hybrid revascularization 131 (40%) 15 (33%) 116 (43%) ICU stay (h) 20 ( ) 45 (14 384) 20 ( ) Ventilation time (h) 8 (0 349) 14 (4 288) 8 (0 349) Hospital stay (days) 6 (2 52) 8 (5 35) 6 (2 54) PRBC units transfused in operating 0 (0 19) 3 (0 17) 0 (0 19) room FFP units transfused in operating room 0 (0 21) 5 (0 13) 0 (0 21) Skeletonized IMA takedown 98 (30%) 10 (22%) 88 (32%) Transthoracic assistance 248 (76%) 27 (60%) 221 (80%) Intraaortic counterpulsation 5 (1.5%) 3 (7%) 2 (0.7%) Perioperative myocardial infarction 9 (2.5%) 3 (7%) 6 (2%) Postoperative TIA 1 (0.3%) 0% 1 (0.3%) Postoperative new stroke 6 (2%) 2 (4%) 4 (1%) Postoperative pneumonia 11 (3.4%) 4 (9%) 7 (2.5%) Postoperative long-term ventilation 3 (0.9%) 3 (6.5%) 0% requiring tracheostomy Postoperative renal failure requiring 2 (0.6%) 2 (4%) 0% hemofiltration Deep thoracic wound infection 1 (0.3%) 1 (2.2%) 0% Hospital mortality 2 (0.6%) 1 (2.2%) 1 (0.3%) FFP fresh-frozen plasma; ICU intensive care unit; IMA internal mammary artery; PRBC packed red blood cell; TECAB totally endoscopic coronary artery bypass graft surgery; TIA transient ischemic attack. Conversion translated into a higher rate of transfusions of packed red blood cells and fresh-frozen plasma units in the operating room (p 0.001) as well as in a longer ventilation time (p 0.001) and intensive care unit stay (p 0.001; Table 2). Hospital mortality was 0.6% in this series with 1 patient in the conversion group and 1 patient in the nonconverted group (2.2% versus 0.3%; p 0.147). Additional details concerning postoperative morbidity are provided in Table 3. Long-term survival was 99%, 98%, and 98% at 1, 3, and 5 years, respectively, in nonconverted patients, whereas it was reduced (94%, 88%, and 88%, respectively) in converted patients (p 0.018; Fig 1A). Causes of death are listed in Table 5. Long-term freedom from angina was 89%, 85%, and 85% at 1, 3, and 5 years, respectively, in nonconverted patients, whereas it was 97%, 97%, and 86%, respectively, in converted patients (p 0.362; Fig 1B). The vast majority of angina recurrence was attributable to progression of native coronary artery disease or reinterventions in hybrid revascularization cases. Overall, the freedom from target vessel reintervention was 98% at 5 years. Long-term freedom from MACCE was 84%, 84%, and 81% at 1, 3, and 5 years, respectively, in the whole series, Table 4. Multivariate Analysis for Risk Factors of Conversion in 326 Totally Endoscopic Coronary Artery Bypass Graft Surgery Patients Variable p Value Wald Coefficient Hazard Ratio 95% Confidence Interval No learning-curve case Multivessel TECAB Transthoracic assistance TECAB totally endoscopic coronary artery bypass graft surgery.

5 Ann Thorac Surg SCHACHNER ET AL 2011;91: CONVERSIONS IN TECAB Fig 1. (A) Long-term survival of 326 patients undergoing totally endoscopic coronary surgery. (B) Freedom from angina of 326 patients undergoing totally endoscopic coronary surgery. (C) Freedom from major adverse cardiac and cerebrovascular events (MACCE) of 326 patients undergoing totally endoscopic coronary surgery. with no difference between nonconverted and converted patients (p 0.644; Fig 1C). Comment 651 Totally endoscopic coronary artery bypass graft surgery using the da Vinci telemanipulator has become a routine procedure for coronary revascularization at dedicated centers. Nevertheless, conversion to a larger incision remains a challenge. In this series of 326 TECAB patients, conversion to sternotomy was necessary in 12%, and conversion to minithoracotomy in 2%. We included all TECAB operations ever performed at both centers, including all learning-curve cases. We previously described a clear drop in conversion rates for arrested-heart single-vessel TECAB from 28% for the first 25 cases to 4% to 8% for the remaining 75 cases [6]. De Cannière and coworkers [7] report a 28% conversion rate in a multicenter series of 228 TECAB procedures (90% singlevessel TECAB). This paper also showed a learning-curve effect, which brought down the conversion rates of offpump TECAB operations into the 20% range and into the 10% range in on-pump TECAB operations [7]. Srivastava and associates [5] experienced a conversion rate of 13.8% in 108 patients scheduled for beating-heart TECAB. Both papers report conversion rates that are in accordance with our results. Conversion is a clinical reality in all endoscopic surgical procedures. Kauvar and colleagues [14] recently reported a 6% conversion rate in 315 laparoscopic cholecystectomies. In general surgery, Giulianotti and coworkers [15] report a 10% conversion rate for robotic-assisted laparoscopic pancreatic operations, which are long, demanding procedures (mean operative time, 331 minutes). Schumacher and associates [16] describe their results of robotic cystectomy, which is another complex endoscopic procedure in which longer operative times (mean, 501 minutes) are necessary and conversion to open surgery can occur (16%). We also sought to determine the risk factors for conversion in TECAB. Interestingly we found no significant associations between a variety of demographic variables and conversion. The surgical problems leading to conversion were left IMA injury, epicardial injury, problems with the balloon endoocclusion system, and anastomotic problems. It is worth noting that with increased experience, some problems that initially led to conversion can now be managed endoscopically. Balloon rupture can be tackled by reinsertion of a new balloon catheter while being on-pump. Left IMA injury can be managed by shortening the vessel if the lesion is in the distal portion or by taking down the right IMA as an alternative graft. A short pedicle was a potential reason for one conversion in multivessel TECAB. Skeletonized endoscopic IMA takedown provides additional graft length. In 1 patient, endoscopic construction of a Y graft of the right IMA to the left IMA successfully prevented conversion. Transthoracic assistance (using an endoscopic forceps inserted through a parasternal stab incision) significantly improved the quality of anastomotic suturing, minimized anastomotic errors, and, in turn, decreased the conver-

6 652 SCHACHNER ET AL Ann Thorac Surg CONVERSIONS IN TECAB 2011;91: Table 5. Causes of Perioperative and Late Deaths Among 326 Patients Who Underwent Totally Endoscopic Coronary Artery Bypass Graft Surgery Patient Number Time From Operation to Death Cause of Death Conversion Status 1 In hospital Intracerebral bleeding during venovenous Not converted ECMO for ARDS 2 In hospital Sudden cardiac death with pulseless Converted electric activity 3 4 months Sudden cardiac death Not converted 4 4 months Myocardial infarction Converted 5 23 months Myocardial infarction Not converted 6 24 months Prostate cancer Converted ARDS acute respiratory distress syndrome; ECMO extracorporeal membrane oxygenation. sion rate. Most epicardial lesions caused by instrument maneuvers can now be repaired endoscopically by placing a reinforced suture or a local hemostatic agent. Lastly, anastomotic problems were solved by placing endoscopic repair stitches or resuturing the anastomosis. Our intraoperative conversion rate for anastomotic problems identified by intraoperative angiography was higher than one would initially expect. However, early anastomotic failures are generally underreported in the literature because surgeons typically do not perform routine intraoperative angiography, but instead follow a symptomatic approach. Routine angiography after standard CABG identified complete graft occlusion in 1.3% and an anastomotic stenosis of at least 50% in 7.8% of patients at 10 days postoperatively [17]. In minimally invasive direct CABG with left IMA to LAD grafting, the graft occlusion is 6% and an anastomotic stenosis of more than 50% is found in 10% [18]. It is therefore expected that we identified a number of graft problems as a result of angiographic quality control. Conversion in these cases probably was a positive factor, as the anastomotic problem was corrected immediately. Unlike off-pump CABG, in which conversion to onpump surgery is associated with an increased hospital mortality in the 10% range [19], conversion in TECAB did not adversely affect perioperative survival. Some converted patients had postoperative low cardiac output syndrome requiring intraaortic balloon counterpulsation, renal failure requiring hemofiltration, and respiratory issues that led to increased ventilation times and intensive care unit stays in converted patients. These problems, however, did not translate into a significantly increased hospital mortality, which remained within the predictions of the EuroSCORE. Late mortality, however, was higher in converted patients compared with nonconverted patients. Six patients (3 converted, 3 nonconverted) died during the follow-up period, including the 2 hospital deaths. In the conversion group, 1 of 3 deaths was attributable to cancer, which may explain the decreased long-term survival of converted patients. The overall survival rates of 98%, 97%, and 97% at 1, 3, and 5 years, respectively, in our series (converted and nonconverted patients taken together) is very comparable to mortality data in the published literature for open CABG. Goy and colleagues [20] published a 5-year survival rate of 97% in patients undergoing single-vessel CABG to the LAD, and Hannan and associates [21] reported a 92% survival rate at 3 years after CABG in two-vessel disease. In our series freedom from angina was 85% at 5 years postoperatively in converted and nonconverted patients, which compares favorably with data from the ARTS (Arterial Revascularization Therapies Study II) trial [22] and the COURAGE trial (74% in the percutaneous coronary intervention arm) [23]. Freedom from target vessel reintervention was 98% at 5 years. The majority of patients with recurrence of angina had a planned hybrid revascularization concept or a progression of their native coronary artery disease. The overall MACCE rate was 16% at 1 year and 19% at 5 years. In comparison, the 1-year MACCE rates in the SYNTAX (Synergy between percutaneous coronary intervention with Taxus and Cardiac Surgery) trial were 12.4% in the CABG arm and 17.8% in the percutaneous coronary intervention arm, and the 5-year MACCE rate was 21.1% in the CABG arm of the ARTS II trial [22, 24]. In conclusion, our series demonstrates learning-curve cases to be the most important independent predictor for conversion in robotic TECAB. Conversion to larger incisions does not significantly increase hospital mortality, but is associated with increased postoperative morbidity. Long-term survival in converted patients seems to meet the standards of CABG through sternotomy, but may be lower than in nonconverted patients. Freedom from MACCE and freedom from angina are similar in converted and nonconverted patients. References 1. Bonaros N, Schachner T, Wiedemann D, et al. 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