Secondary Logo

Share this article on:

Geometric Ring Annuloplasty for Aortic Valve Repair During Aortic Aneurysm Surgery: Two-Year Clinical Trial Results

Rankin, J. Scott, MD*; Mazzitelli, Domenico, MD; Fischlein, Theodor, MD; Choi, Yeong-Hoon, MD, PhD§; Pirk, Jan, MD; Pfeiffer, Steffen, MD; Wei, Lawrence M., MD*; Badhwar, Vinay, MD*

Innovations:Technology and Techniques in Cardiothoracic and Vascular Surgery: July/August 2018 - Volume 13 - Issue 4 - p 248–253
doi: 10.1097/IMI.0000000000000539
Original Articles

Objective An aortic annuloplasty ring could be useful for aortic valve repair. This trial evaluated intermediate-term outcomes of internal geometric ring annuloplasty for repair of trileaflet and bicuspid aortic insufficiency associated with ascending aortic and/or aortic root aneurysms.

Methods Under regulatory supervision, 47 patients with aortic insufficiency and ascending aortic (n = 22) and/or aortic root (n = 25) aneurysms were managed with aortic valve repair and aneurysm resection. Valve repair was performed using trileaflet (n = 40) or bicuspid (n = 7) internal geometric rings, together with leaflet reconstruction. Ascending aortic and/or remodeling root replacements were accomplished with Dacron grafts 5 to 7 mm larger than the rings. An Echo Core Lab provided independent echocardiographic assessments, and changes over time were evaluated by Friedman tests.

Results Mean ± SD age was 60 ± 14 years, 57% (27/47) were male, 15% (7/47) had bicuspid valves, 87% (41/47) had moderate-to-severe aortic insufficiency, and 13% (6/47) had mild aortic insufficiency. All patients had annular dilatation, with a mean ± SD of 26.5 ± 2.6 mm before repair, and mean ± SD ring sizes were 21.7 ± 1.7 mm. Follow-up was 42 months (mean = 27 months). No operative mortality or valve-related complications occurred. Two patients died beyond 1 year from nonvalve-related causes. One patient required valve replacement for repair failure. Survival free of complications or valve replacement was 94% at 2 years. Significant reduction in aortic insufficiency and New York Heart Association class were observed (P < 0.0001), and valve gradients remained low. No heart block or direct ring complications occurred.

Conclusions In preliminary regulatory studies, aortic ring annuloplasty seemed safe and effective during aortic aneurysm surgery. This approach could help standardize aortic valve repair.

From the *Department of Cardiovascular and Thoracic Surgery, West Virginia University Heart and Vascular Institute, Morgantown, WV USA;

Department of Cardiac Surgery, Klinikum Bogenhausen, Munich, Germany;

Department of Cardiovascular Surgery, Klinikum Nürnberg, Paracelsus Medical University, Nürnberg, Germany;

§Department of Cardiac and Thoracic Surgery, University of Köln, Köln, Germany; and

Department of Cardiac Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic.

Accepted for publication June 15, 2018.

Supported by BioStable Science and Engineering, Inc, Austin, TX USA ( This multicenter clinical trial of the HAART 300 and 200 rings was performed in Europe, the HAART 300 device is now clinically approved in Europe (CE 613269), and both are approved in the United States by the FDA (21 CFR 870.3800).

The information in this article was generated in a prospective regulatory clinical trial of aortic ring annuloplasty ( NCT01400841, NCT01732835, and NCT02071849).

Disclosures: J. Scott Rankin, MD, is a consultant for BioStable Science and Engineering, Inc, Austin, TX USA, and AtriCure, West Chester, OH USA. Theodor Fischlein, MD, is a consultant for BioStable Science and Engineering, Inc, Austin, TX USA, and LivaNova, London, UK. Domenico Mazzitelli, MD, and Yeong-Hoon Choi, MD, PhD, are consultants for BioStable Science and Engineering, Inc, Austin, TX USA. Jan Pirk, MD, Steffen Pfeiffer, MD, Lawrence M. Wei, MD, and Vinay Badhwar, MD, declare no conflicts of interest.

Address correspondence and reprint requests to J. Scott Rankin, MD, Department of Cardiac and Thoracic Surgery, WVU Heart and Vascular Institute, West Virginia University, 1 Medical Center Dr, Morgantown, WV 25605 USA. E-mail:

“To be most useful, an operation needs to be standardized and reproducible, so that any good surgeon can achieve excellent results.” John W. Kirklin, Ward Rounds, 1970.

Cardiac valve repair is now well established and usually consists of a combination of annuloplasty plus leaflet reconstruction.1 For mitral and tricuspid valves, ring annuloplasty provides stable outcomes, but development of an aortic valve ring has been difficult because of complex geometry. The availability of high-resolution computed tomography (CT) angiography allowed a detailed understanding of aortic valve annular and leaflet geometry,2 and from that work, internal geometric annuloplasty rings were developed for both trileaflet and bicuspid aortic valves.3,4 Early operative outcomes for these devices have been published elsewhere,4–9 including adjunctive leaflet repair techniques that were successfully applied.10 This analysis was undertaken to assess the final 2-year outcomes of a clinical trial of aortic ring annuloplasty for aortic insufficiency (AI) associated with ascending aortic and/or aortic root aneurysms.

Back to Top | Article Outline


Because this was the first application of aortic ring annuloplasty for aortic valve repair (AVr), the German Federal Competent Authority required the protocol to be split into an initial pilot component and then two pivotal components. All three phases were prospective multicenter regulatory protocols ( NCT01400841, NCT01732835, and NCT02071849), and after informed consent, a total of 47 patients underwent aortic valve reconstruction for AI associated with aortic aneurysms.4,9 The population included predominantly symptomatic male and female subjects, with inclusion criteria of moderate to severe AI accompanied by aortic annular dilation and a ventricular ejection fraction of 35% or more. Less severe AI was allowed when the primary indication was aneurysm size. Emergency status, endocarditis, active infections, recent myocardial infarction, and multiple valve surgeries were excluded. Minor stable coronary disease was allowed. All patients had concomitant ascending aortic and/or aortic root aneurysms and were the subjects of this analysis. Forty of the aneurysm patients had trileaflet valves and seven had bicuspid anatomy, for 47 patients in total. There were 22 ascending aortic and 25 aortic root aneurysms, and three patients had Marfan syndrome. Standard criteria were employed for diagnosis of aneurysms.11 All protocols were approved by the German Federal Regulatory body (Bundesinstitut für Arzneimittel und Medizinprodukte or BfArM) and local ethics committees. Every patient was counseled extensively and provided signed informed consent.

Both trileaflet [Hemispherical Aortic Annuloplasty Reconstructive Technology (HAART) 300] and bicuspid (HAART 200) annuloplasty rings were developed from mathematical analyses of human CT angiograms.3,4 The base geometry of the trileaflet ring was elliptical (2:3 diameter ratio), and the bicuspid ring was circular.4 Because the aortomitral curtain shifts with systole, both rings were machined in diastolic geometry,5 with the goal of moving the annuli centrally to recruit leaflet for coaptation height. Both had 10-degree outwardly flaring subcommissural posts, spaced equidistant on the base circumference (Fig. 1). Intraoperatively, trileaflet ring diameter required for valve competence was determined by measuring free-edge length of all three leaflets and dividing by 1.5. If leaflet free-edge length varied by one size, the smaller size was chosen to downsize the ring. If the lengths varied by two sizes, the intermediate size was chosen. Bicuspid rings were sized by dividing the nonfused leaflet length by 1.8 and also to keep intercommissural distance constant.4 The low-profile rings were fabricated by computerized milling from titanium blocks and covered with a thin layer of polyester to promote endothelialization. Ring suture technique involved nine transannular 4-0 Prolene horizontal mattress sutures for both rings, positioning the rings below the valve annulus, and tying the sutures above the annulus over fine polyester pledgets. The annular tissue used for ring suturing was exactly the same as for prosthetic valve replacement. Fixing the annular suture knot towers downward to the lateral aspect of the pledgets was very important to prevent leaflet-suture contact.4,9 Detailed technical information and early results were provided elsewhere, including leaflet pathology encountered and methods of leaflet reconstruction.3,4,7,9



After ring placement, the leaflets were inspected. The most common defect was leaflet prolapse requiring central leaflet plication,8,12,13 and approximately 20% of these had ruptured commissures, holes, or other structural abnormalities. Major structural leaflet defects usually were repaired with autologous pericardial techniques, and retracted Noduli were released using an ultrasonic device.10 After valve repair, concomitant ascending aortic and/or aortic root aneurysms were managed with ascending aortic and/or remodeling root replacement, using Dacron tube or Valsalva remodeling grafts that were 5 to 7 mm larger than ring size. Specific details about operative technique are provided elsewhere.8 Anticoagulation with warfarin was avoided for patients in sinus rhythm, and all patients were maintained on aspirin for at least 3 months.

Clinical evaluations and transthoracic echocardiograms were performed at screening, discharge, 3 months, 6 months, 1 year, and 2 years. Survival status, complications, and New York Heart Association (NYHA) Class were recorded throughout. Serial echocardiograms were read in a blinded fashion by an independent Echo Core Lab (MedStar Research, Washington, DC USA), and AI grade and mean systolic valve gradients were assessed. Using standard echocardiographic definitions,14 estimates of AI severity (0–4 scale) were documented as follows: none and trivial, grade 0; mild, grade 1; moderate, grade 2; moderately severe, grade 3; and severe, grade 4. Missing baseline screening data and missing discharge data were imputed as the average of the other patients' values at the same time points, and subsequent missing data were imputed by the last value forward technique.9 This was a conservative approach, because patients requiring aortic valve replacement for repair failure recorded their worst AI grade and NYHA class for all subsequent examinations, permanently penalizing reoperation for valve replacement.

In examining Core Lab AI and gradient estimates, 4% of data points were missing, along with 5% of values for NYHA class. Data points were missing because of reoperative valve replacement, death, patient withdrawal/lost from the study, or lost echocardiogram. All patients in the last three categories had grade 0 or 1 AI at the last echo examination. In the analysis, Friedman test (nonparametric analysis of variance) evaluated changes in AI, mean systolic valve gradients, and NYHA class over time. Continuous variables were presented as means ± SD, and categorical variables as percentages. Analyses were performed using Prism 7 (GraphPad Software, Inc, La Jolla, CA USA), and a P value of less than 0.05 was considered significant.

Back to Top | Article Outline


In the 47 aneurysm patients, mean ± SD age was 60 ± 14 years (range = 25–77 years), 57% (27/47) were male, 15% (7/47) had bicuspid valves, 87% (41/47) had moderate-to-severe AI, and 13% (6/47) had mild (n = 5) or no (n = 1) AI (these were operated primarily for aneurysm size). Relative to leaflet free-edge length, all patients had significant annular dilatation, based on the validated formula: (for trileaflet valves) leaflet free-edge length/1.5 equals the annular diameter required for competence2,3 or (for bicuspid valves) nonfused leaflet free-edge length/1.8.4 Mean ± SD annular diameter was 26.5 ± 2.6 mm before repair, and mean ± SD required ring size was 21.7 ± 1.7 mm. An illustration of ring position after annuloplasty is provided in Figure 2. No operative mortality or early/late valve-related complications were observed. Two significant postoperative complications occurred: one was an early reoperation for bleeding with no positive findings and the second was a patient who required repair revision 5 days postoperatively. There were no strokes, sternal wound infections, renal failure, or major respiratory complications.



Two patients died beyond 1 year from alcoholic liver failure and pancreatic cancer. Neither had significant AI premortem. One patient required late prosthetic valve replacement for repair failure. On re-review of the original operative video, one size too large a ring probably was implanted, producing inadequate long-term coaptation. Thus, survival free of complications or valve replacement was 94% at 2 years (Fig. 3). On serial transthoracic echocardiograms, prolonged and clinically significant AI reduction was observed (P < 0.0001) (Fig. 4A). Mean valve gradients increased slightly early after annuloplasty (P = 0.001), consistent with a modest reduction in annular area.7,9 However, subsequent gradient changes were not clinically or statistically significant, and gradients remained low throughout follow-up in every patient (Fig. 4B). Improvement in NYHA class for congestive heart failure also was significant (P < 0.0001) (Fig. 5). In the aneurysm population, 57% of patients had grade 3 or 4 AI at screening, and that number was 2% at 2 years after repair (the single patient requiring reoperation). No new heart block or direct complications of the rings occurred. More detailed descriptions of the patient populations, surgical techniques, and early outcomes to 1-year postoperative have been published previously.4,9







Back to Top | Article Outline


As with repair of other cardiac valves,15,16 aortic valve reconstruction seems to be associated with lower-risk–adjusted operative mortality,17 fewer late valve-related complications18,19 and improved long-term survival.20 Linearized mortality rates after repair may be half of those observed with standard prosthetic valve replacement.20 Moreover, late outcomes with aortic valve prostheses seem suboptimal, whether comparing tissue or mechanical valves21 or original versus modern tissue valves.22 Annuloplasty is an important component of AVr,23,24 and several annuloplasty techniques have been useful, including subcommissural annuloplasty,25 external annuloplasty with reimplantation grafts,26–29 external aortic rings,30 and external circumferential suture annuloplasty.31 In virtually all studies, annuloplasty has been associated with improved late results.

However, disadvantages also exist with current annuloplasty techniques, including a higher late failure rate with commissural annuloplasty, requirement for deep external root dissection with reimplantation, and probably less than adequate annular reduction with external bands or sutures (designed to reduce annular diameter only by 1 size or to 25 mm, respectively). With the external devices, a potential risk also exists for eventually cutting through the aorta. Finally, none of these techniques are based on objective anatomic criteria, and all are predicated on circular annular geometry. From the present analysis, geometric ring annuloplasty seemed effective, at least to the intermediate term, and reduced annular diameter from an average of 26.5 to 21.7 mm. Operative and late mortalities were low, valve-related complications were negligible, and hemodynamic improvements were significant and sustained to 2 postoperative years (Figs. 3–5).

One anatomic advantage of geometric ring annuloplasty was more physiologic remodeling of the aortic annulus. With trileaflet valves, the annulus was reduced in circumference with a sizing protocol based on leaflet free-edge length, with free-edge length/1.5 yielding the proper annular diameter for competence. This technique was simple, objective, and very accurate. Annular geometry also was restored to a normal elliptical shape, which improved leaflet coaptation, as in the mitral valve. Physiologic outward commissural flare was maintained, raising leaflet effective height to a better level and increasing coaptation area. Over the long term, valve geometry was maintained from top to bottom by the commissural posts, rather than involving just one segment, such as the basal ring or sinotubular junction. Several technical advantages also existed. Annular geometry and leaflet configuration were restored as the first step, and the aneurysm procedure was completed at the end. Deep aortic root dissection was not required, and the procedures may have been simpler than with reimplantation techniques.8

The pathologic bicuspid annulus also was elliptical but with the long axis in the sinus-to-sinus dimension.4 Remodeling bicuspid annular circumference to a circle reduced the annulus and moved the sinuses toward each other. This assisted in migrating the leaflets centrally and again improved leaflet coaptation height and area. Because the bicuspid leaflet is slightly larger relative to annular diameter, the formula for ring sizing was nonfused leaflet free-edge length/1.8.4 An additional benefit of the bicuspid ring was remodeling the annulus to a 50% to 50% commissural geometry. A 180-degree commissural configuration facilitated central valve opening and laminar flow and simplified leaflet reconstruction, during which leaflet free-edge lengths and effective heights were equalized. Induced gradients, injuries from the rings, and pannus formation did not occur, and the annular suture lines were stable, because annular suture placement was the same as for aortic valve replacement. Thus, it is possible that ring annuloplasty for AVr functions much the same as mitral ring annuloplasty, the only difference being the shape of the ring.7

Of course, annuloplasty is just one component of valve repair. In patients with moderate-to-severe AI, up to 80% also had leaflet defects, usually leaflet prolapse.9 In two-thirds, prolapse seemed to involve the isolated right coronary leaflet, and in the remainder, prolapse was divided equally among the other cusps. Approximately a fifth of patients can have major leaflet defects, such as commissural rupture, holes, or extensive fenestrations.10 Thus, familiarity with aortic leaflet repair techniques is essential, including nodular release, autologous pericardial leaflet reconstruction, and pericardial leaflet replacement. A mastery of leaflet reconstruction was especially important in patients without aneurysms, who tended to have worse leaflet defects.9

In conclusion, AVr using internal geometric ring annuloplasty seemed safe and effective for reconstruction of trileaflet and bicuspid AI associated with aortic aneurysms to 2 years of follow-up. Survival free of valve-related complications was excellent, gradients were low, and AI reduction was significant and stable over the intermediate term. This approach could simplify and standardize AVr and valve-sparing procedures, but more experience will be required for full validation.

Back to Top | Article Outline


This trial was registered at the German Federal Competent Authority (Bundesinstitut für Arzneimittel und Medizinprodukte or BfArM). Because this was the first evaluation of an internal aortic annuloplasty ring, the trial was required to be split into a pilot component and then two pivotal components ( NCT01400841, NCT01732835, and NCT02071849). All aspects were approved by the Federal Competent Authorities and the local ethics committees, and surgery was performed under full regulatory monitoring with patient informed consent. The HAART 300 ring currently is CE Marked in Europe (CE 613269) and is approved by the FDA (21 CFR 870.3800). The HAART 200 ring is FDA-approved, but is still under review in Europe.

Back to Top | Article Outline


1. Carpentier A. Cardiac valve surgery - the “French correction”. J Thorac Cardiovasc Surg. 1983;86:323–337.
2. Rankin JS, Bone MC, Fries PM, Aicher D, Schäfers HJ, Crooke PS. A refined hemispheric model of normal human aortic valve and root geometry. J Thorac Cardiovasc Surg. 2013;146:103–108.
3. Crooke PS, Beavan LA, Griffin CD, Mazzitelli D, Rankin JS. Design characteristics of a three-dimensional geometric aortic valve annuloplasty ring. Innovations. 2013;8:364–370.
4. Mazzitelli D, Pfeiffer S, Rankin JS, et al. A regulated trial of bicuspid aortic valve repair supported by geometric ring annuloplasty. Ann Thorac Surg. 2015;99:2010–2016.
5. Mazzitelli D, Rankin JS, Lange R. The use of a rigid ring in aortic valve repair. Ann Thorac Surg. 2015;99:1108–1112.
6. Mazzitelli D, Nobauer C, Rankin JS, et al. Early results after implantation of a new geometric annuloplasty ring for aortic valve repair. Ann Thorac Surg. 2013;95:94–97.
7. Mazzitelli D, Stamm C, Rankin JS, et al. Hemodynamic outcomes of geometric ring annuloplasty for aortic valve repair: a 4-center pilot trial. J Thorac Cardiovasc Surg. 2014;148:168–175.
8. Mazzitelli D, Nobauer C, Rankin JS, et al. Early results of a novel technique for ring-reinforced aortic valve and root restoration. Eur J Cardiothorac Surg. 2014;45:426–430.
9. Mazzitelli D, Fischlein T, Rankin JS, et al. Geometric ring annuloplasty as an adjunct to aortic valve repair: clinical investigation of the HAART 300 device. Eur J Cardiothorac Surg. 2016;49:987–993.
10. Mazzitelli D, Stamm C, Rankin JS, et al. Leaflet reconstructive techniques for aortic valve repair. Ann Thorac Surg. 2014;98:2053–2060.
11. Svensson LG, Adams DH, Bonow RO, et al. Aortic valve and ascending aorta guidelines for management and quality measures. Ann Thorac Surg. 2013;95(suppl 6):S1–S66.
12. Schäefers HJ, Aicher D, Langer F. Correction of leaflet prolapse in valve-preserving aortic replacementz; pushing the limits? Ann Thorac Surg. 2002;74:1762–1764.
13. de Kerchove L, Glineur D, Poncelet A, et al. Repair of aortic leaflet prolapse: a ten-year experience. Eur J Cardiothorac Surg. 2008;34:785–791.
14. Zoghbi W. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and doppler echocardiography. J Am Soc Echocardiogr. 2003;16:777–802.
15. Daneshmand MA, Milano CA, Rankin JS, et al. Influence of patient age on procedural selection in mitral valve surgery. Ann Thorac Surg. 2010;90:1479–1486.
16. Gammie JS, Sheng S, Griffith BP, et al. Trends in mitral valve surgery in the United States: results from the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Ann Thorac Surg. 2009;87:1431–1439.
17. Caceres M, Ma Y, Rankin JS, et al. Mortality characteristics of aortic root surgery in North America. Eur J Cardiothorac Surg. 2014;46:887–893.
18. Aicher D, Fries R, Rodionycheva S, Schmidt K, Langer F, Schafers HJ. Aortic valve repair leads to a low incidence of valve-related complications. Eur J Cardiothorac Surg. 2010;37:127–132.
19. Price J, De Kerchove L, Glineur D, Vanoverschelde JL, Noirhomme P, El Khoury G. Risk of valve-related events after aortic valve repair. Ann Thorac Surg. 2013;95:606–613.
20. de Meester C, Pasquet A, Gerber BL, et al. Valve repair improves the outcome of surgery for chronic severe aortic regurgitation: a propensity score analysis. J Thorac Cardiovasc Surg. 2014;148:1913–1920.
21. Gaca JG, Clare RM, Rankin JS, et al. Risk-adjusted survival after tissue versus mechanical aortic valve replacement: a 23-year assessment. J Heart Valve Dis. 2013;22:810–816.
22. Ganapathi AM, Englum BR, Keenan JE, et al. Long-term survival after bovine pericardial versus porcine stented bioprosthetic aortic valve replacement: does valve choice matter? Ann Thorac Surg. 2015;100:550–559.
23. de Kerchove L, Mastrobuoni S, Boodhwani M, et al. The role of annular dimension and annuloplasty in tricuspid aortic valve repair. Eur J Cardiothorac Surg. 2016;49:428–437.
24. Aicher D, Kunihara T, Abou Issa O, Brittner B, Graber S, Schafers HJ. Valve configuration determines long-term results after repair of the bicuspid aortic valve. Circulation. 2011;123:178–185.
25. Cabrol AGG, Bertrand M. Le traitement de l'insuffisance aortique par l'annuloplastie aortique. Arch des Mal du Coeur. 1966;59:1305–1312.
26. David TE, Armstrong S, Maganti M, Colman J, Bradley TJ. Long-term results of aortic valve-sparing operations in patients with Marfan syndrome. J Thorac Cardiovasc Surg. 2009;138:859–864.
27. David TE, Feindel CM, Webb GD, Colman JM, Armstrong S, Maganti M. Long-term results of aortic valve-sparing operations for aortic root aneurysm. J Thorac Cardiovasc Surg. 2006;132:347–354.
28. de Kerchove L, Boodhwani M, Glineur D, et al. Valve sparing-root replacement with the reimplantation technique to increase the durability of bicuspid aortic valve repair. J Thorac Cardiovasc Surg. 2011;142:1430–1438.
29. Bavaria JE, Desai N, Szeto WY, et al. Valve-sparing root reimplantation and leaflet repair in a bicuspid aortic valve: comparison with the 3-cusp David procedure. J Thorac Cardiovasc Surg. 2015;149(suppl 2):S22–S28.
30. Lansac E, Di Centa I, Vojacek J, et al. Valve sparing root replacement: the remodeling technique with external ring annuloplasty. Ann Cardiothorac Surg. 2013;2:117–123.
31. Aicher D, Schneider U, Schmied W, Kunihara T, Tochii M, Schäfers HJ. Early results with annular support in reconstruction of the bicuspid aortic valve. J Thorac Cardiovasc Surg. 2013;145(suppl 3):S30–S34.
Back to Top | Article Outline


This trial evaluated intermediate-term outcomes of a new aortic valve annuloplasty ring for repair of both trileaflet and bicuspid aortic insufficiency associated with ascending aortic and root aneurysms.

Forty-seven patients underwent aortic valve repair using this novel annuloplasty ring, 22 with ascending aortic and 25 with aortic root aneurysms. Forty of the patients had trileaflet valves. The mean age was 60 years; most patients were male. The mean ring size was 21.7 mm. There were no operative mortalities or valve-related complications. At 2 years, survival free of complications for valve replacement was 94%. Significant reduction in aortic insufficiency and New York Heart Association functional class were observed, and the valve gradients remained low. The incidence of recurrent greater than 2+ aortic insufficiency was surprisingly low.

These are very encouraging midterm results from this small clinical trial. This approach could both simplify and standardize aortic valve repair in this patient population. Although more experience will be required for full validation, the investigators are to be congratulated for a promising two-year results.


Aortic annuloplasty; Aortic valve repair; Aortic root aneurysm; Aortic valve replacement

©2018 by the International Society for Minimally Invasive Cardiothoracic Surgery