Stentless root bioprosthesis for repair of acute type A aortic dissection

ACQUIRED CARDIOVASCULAR DISEASE Stentless root bioprosthesis for repair of acute type A aortic dissection Craig R. Smith, MS, Sotiris C. Stamou, MD, PhD, Robert L. Hooker, MD, Charles C. Willekes, MD, John C. Heiser, MD, Lawrence H. Patzelt, MD, and Edward T. Murphy, MD Objective: The superior hemodynamics and excellent long-term clinical performance of stentless xenografts are well described. However, the early and midterm clinical outcomes of stentless valves in patients with acute type A dissection are widely unknown. The current study evaluated the early and midterm clinical outcomes of stentless bioprosthesis for repair of acute type A aortic dissection. Methods: Between May 2005 and December 2009, 24 of 80 patients underwent root replacement using the Medtronic Freestyle xenograft (Medtronic Inc, Minneapolis, Minn) at the Meijer Heart Center. Prospective data collection was used for retrospective review. Univariate comparisons of preoperative, intraoperative, and postoperative variables were performed between patients who underwent stentless root bioprosthesis for the correction of acute type A aortic dissection (n ¼ 24). Results: The mean age of patients was 57 years, with 15 patients aged less than 65 years. Axillary and femoral artery cannulation were used in 16 patients (67%) and 7 patients (29%), respectively. Median crossclamp and cardiopulmonary bypass times were 198 minutes (92-480 minutes) and 288 minutes (109-588 minutes), respectively. Median circulatory arrest time was 28 minutes (24-50 minutes). Operative mortality rate was 25%. Actuarial 5-year survival was 62.5%. No patients required redo aortic root replacement. Conclusions: Stentless valve implantation can be accomplished with satisfactory early and midterm clinical outcomes and is a valuable option in patients with acute aortic dissection who require root replacement. (J Thorac Cardiovasc Surg 2013;145:1540-4) Acute aortic dissection of the ascending aorta is commonly a life-threatening condition that requires emergency surgical intervention. 1 Standard surgical therapy consists of replacing the ascending aorta with resection of the entry tear. There is still a debate regarding the preferable surgical approach in patients who require aortic root replacement. A variety of aortic root replacement techniques have been explored to identify the best approach. The gold standard has been the Bentall procedure in which the root is replaced by a mechanical valve-conduit. The Freestyle stentless aortic root bioprosthesis (Medtronic Inc, Minneapolis, Minn) was approved for clinical use in November 1997 and has been associated with superior hemodynamic performance, durability, and survival compared with stented xenograft valves. 2-4 The stentless root allows for a larger effective orifice area, thereby producing lower gradients and decreasing the likelihood of aortic regurgitation. 5 Although the hemodynamic performance of the stentless root is well documented, there is a paucity of studies investigating its use in patients with type A aortic dissection. Our From the Department of Thoracic and Cardiovascular Surgery, Meijer Heart Center, Butterworth Hospital, Grand Rapids, Mich. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication Feb 6, 2012; revisions received April 3, 2012; accepted for publication May 15, 2012; available ahead of print June 14, 2012. Address for reprints: Sotiris C. Stamou, MD, PhD, Meijer Heart Center, 100 Michigan Ave, Suite 8830, MC 103, Grand Rapids, MI 49503 (E-mail: cvsisfun@hotmail. com). 0022-5223/$36.00 Copyright Ó 2013 by The American Association for Thoracic Surgery doi:10.1016/j.jtcvs.2012.05.029 study sought to examine the early and midterm clinical outcomes of aortic root replacement with stentless aortic root bioprosthesis in patients with type A aortic dissection. PATIENTS AND METHODS Patients The database of the Division of Cardiothoracic Surgery at the Meijer Heart Center was queried and identified 24 of 80 patients who underwent repair of acute type A dissection and aortic root replacement with the Freestyle stentless root bioprosthesis between May 2005 and December 2009. Of the 80 patients who had repair of aortic dissection at the Meijer Heart Center, 39 had aortic root replacement (stentless root ¼ 24, mechanical valved or tissue valved conduit ¼ 15), 4 had aortic valve replacement, 22 had aortic valve resuspension, and 15 had ascending aortic replacement only without intervention in the aortic valve. Computed tomography (CT) angiogram or transesophageal echocardiography was used to make the diagnosis of aortic dissection that was confirmed at the time of operation. The same group of cardiac surgeons performed the operations for the study period. Baseline demographic, procedural data, and preoperative outcomes were recorded and entered prospectively in a prespecified database by dedicated data-coordinating personnel. The Society of Thoracic Surgeons national cardiac surgery database definitions were used for this study. Long-term survival data were obtained from the Social Security Death Index website (http://ssdi.rootsweb.ancestry.com). Patients were followed up on a regular basis at the office with repeat CT angiogram of the chest, abdomen, and pelvis, as well as transthoracic echocardiography. Study Design and Conduct This is a retrospective study of prospectively collected data from consecutive patients who underwent aortic root replacement and repair of acute type A dissection at the Meijer Heart Center. Study approval was sought and obtained from the institutional review board. Patient 1540 The Journal of Thoracic and Cardiovascular Surgery c June 2013

Smith et al Acquired Cardiovascular Disease Abbreviations and Acronyms AI ¼ aortic insufficiency CT ¼ computed tomography confidentiality was maintained at all times, consistent with the Health Insurance Portability and Accountability Act of 1996 regulations. Operative Technique A median sternotomy was performed, and patients were placed on cardiopulmonary bypass with venous cannulation of the right atrium and common femoral or right axillary artery cannulation. The axillary artery was cannulated by anastomosing a tube graft and inserting a cannula inside the tube graft. Myocardial protection was obtained with cold-blood cardioplegia solution given retrograde via the coronary sinus or antegrade directly down the ostia of the coronary arteries. A left ventricular vent was placed via the right superior pulmonary vein. Hypothermic circulatory arrest was used in most cases, and the arch was inspected for tears in those patients. The goals of surgery were to resect the intimal tear, replace the ascending aorta with a prosthetic graft, and restore the anatomy of the aortic root. This study included patients in whom the aortic root or valve was deemed to be involved beyond repair, necessitating aortic root replacement with a Medtronic Freestyle stentless root bioprosthesis and reimplanting the coronary buttons. The proximal and distal suture lines were reinforced with Teflon (polytetrafluoroethylene) strips, and in some cases biological glue (BioGlue surgical adhesive; Cryolife Inc, Kennesaw, Ga) was used to reapproximate the dissected layers. After completion of the distal anastomosis, antegrade aortic perfusion was established in both groups. The Freestyle root was sewn into the aortic annulus with interrupted sutures. Whenever the porcine ostia were aligned with the patient s coronary buttons, the left main button was implanted on the left coronary ostium of the porcine root and the right coronary button was implanted on the right coronary ostium of the porcine root. Whenever such an orientation was anatomically not possible, the Freestyle root was implanted in a heterotopic position with the left main button implanted on the right coronary ostium of the porcine root and the right coronary button implanted on a custom-made orifice created at the noncoronary sinus of the porcine root. Data Analysis Continuous variables were summarized using medians and ranges, and frequencies and percentages were reported for categoric variables. A Kaplan Meier curve to depict survival was created. RESULTS Preoperative Characteristics Preoperative characteristics are presented in Table 1. Nine women (37.5%) with acute type A aortic dissection underwent aortic root replacement using the Medtronic Freestyle xenograft. The median age for both men and women was 57 years (range, 43-82 years). Fifteen patients were aged less than 65 years (63%), and 5 of them were aged less than 50 years (21%). Operative Characteristics Operative patient characteristics of those who underwent stentless root bioprosthesis for repair of type A aortic dissection are presented in Table 2. Two patients (8.3%) required total arch replacement. Antegrade cerebral perfusion was used more commonly than retrograde cerebral perfusion. There were 5 patients with dissection involving the left coronary button; in 3 of them, BioGlue was used to approximate the layers. One patient had the coronary wall layers reapproximated with interrupted Prolene sutures, and reconstruction of the button was not feasible in 1 patient, who underwent vein bypass grafts to the left anterior descending and obtuse marginal coronary arteries. Postoperative Characteristics Postoperative characteristics are shown in Table 3. Operative mortality rate was 25%. The most common cause of death was cardiac. Of the 7 patients who had a stroke, 2 had femoral cannulation and 5 had axillary cannulation. Of the 3 patients who had neurologic death, only 1 presented with neurologic symptoms before surgery. Of the 7 patients who had stroke, 1 presented with stroke symptoms (left hemiplegia) before surgery, 3 had their dissection extending into the arch and underwent arch replacement, and 4 did not have arch replacement. Head CT findings included no acute ischemia in 1 patient, but with clinical evidence of stroke: chronic small vessel changes, middle cerebral artery infarct, and reduced attenuation of both hemispheres and density of the right cerebellum. Two patients never received a head CT but were diagnosed with stroke from clinical symptoms. Survival and Freedom From Structural Degeneration Follow-up was 100% complete. The mean follow-up time was 717 730 days. Two patients died 132 and 489 days after surgery. Survival at 1, 3, and 5 years was 66.7%, 62.5%, and 62.5%, respectively (Figure 1). Freedom from structural valve degeneration was 100%. The mean peak gradient at the end of the follow-up time was 6.5 2.1 mm Hg (median peak gradient, 6.5 mm Hg; range, 3.5-10 mm Hg) (Table 4). No patients required redo aortic root replacement. Thirteen patients had no aortic insufficiency (AI), 2 patients had mild AI, and 1 patient had mild to moderate AI at the end of the follow-up time. Six patients had patent false lumen, and 9 patients had thrombosed false lumen or no residual dissection. One patient had aneurysmal dilatation of the aortic arch, but she refused arch replacement. DISCUSSION To the best of our knowledge, the current study is the first to report the use of the Medtronic Freestyle stentless aortic root bioprosthesis in the specific repair of patients with type A aortic dissection. Past studies have shown the stentless root bioprosthesis to be an excellent choice in the repair of aortic root disease. 6-8 Superior flow patterns, durability, and increased survival compared with stented xenograft valves have gained the stentless root bioprosthesis The Journal of Thoracic and Cardiovascular Surgery c Volume 145, Number 6 1541

Acquired Cardiovascular Disease Smith et al TABLE 1. Preoperative patient characteristics Age (median, range in years) 57 (43-82) Female gender 9 37.5 Diabetes 2 8.3 Congestive heart failure 14 58.3 Hypertension 20 83.3 Chronic renal insufficiency 1 4.2 Hemodialysis 0 0 Chronic obstructive lung disease (moderate/severe) 1 4.2 History of myocardial infarction 2 8.3 History of cerebrovascular accident 1 4.2 Arrhythmia 3 12.5 No. of diseased vessels 1 1 4.2 2 0 0 3 3 12.5 Numbers are expressed as or as median and range. TABLE 3. Postoperative patient characteristics Hemorrhage-related reexploration 2 8.3 Deep sternal wound infection 1 4.2 Acute renal failure 7 29.2 Postoperative hemodialysis 3 12.5 Prolonged ventilation (>24 h) 17 70.8 Cardiac arrest 3 12.5 Pericardial tamponade 2 8.3 Atrial fibrillation 6 25 Cerebrovascular accident 7 29.2 Length of stay in days (median/range) 13.5 (1-45) Prolonged length of stay (>14 d) 12 50 Operative mortality 6 25 Cause of operative mortality Cardiac 2 33 Pulmonary 1 17 Neurologic 3 50 widespread acceptance. 2,4 A possible drawback of the stentless root bioprosthesis is the more difficult mounting compared with stented xenografts and the more limited durability compared with the mechanical valveconduit. 2,7,8 Root replacement with the Freestyle stentless valve has been shown to be effective in the treatment of adults of all ages, including those with small aortic roots. 6,8-11 Our study specifically shows that acceptable results can be obtained through the use of the stentless TABLE 2. Operative patient characteristics Coronary artery bypass grafting 2 8.3 Mitral and tricuspid valve replacement 1 4.2 Implantation of left ventricular assist device 1 4.2 Total arch replacement 2 8.3 Intraoperative blood transfusion 19 79.2 Postoperative blood transfusion 20 83.3 Crossclamp time (median/range) 198 (92-480) Perfusion time (median/range) 288 (109-588) Circulatory arrest time (median/range) 28 (24-50) AI Trivial 3 12.5 Mild 5 20.8 Moderate 2 8.3 Severe 7 29.2 None 6 25 Arterial cannulation Aorta 1 4.2 Axillary 16 66.7 Femoral 7 29.2 Hemodynamic instability 3 12.5 Retrograde cerebral profusion 3 12.5 Antegrade cerebral perfusion 10 41.7 Use of biological glue 15 62.5 Numbers are expressed as or as median and range. AI, Aortic insufficiency. root bioprosthesis for root replacement in patients with type A aortic dissection. Operative Mortality and Morbidity We conducted an observational study within the Meijer Heart Center to examine the result of stentless root bioprosthesis in the repair of acute type A aortic dissection. On the basis of our findings, stentless root bioprosthesis is a feasible option in patients with ascending aortic root dissection who require aortic root replacement. There were 2 late deaths 132 and 489 days after surgery. The operative mortality rate in this study was comparable to the rates recorded in the literature for type A dissection (20%-37.5%). 10,12,13 Implantation of a stentless root bioprothesis requires more operative time than stented root xenografts. Studies have shown that although the stentless root replacement takes longer to complete, the operative time has not resulted in increased morbidity or mortality. 4,8 Likewise, a study by Kon and colleagues 4 showed no significant difference in bleeding complications associated with the stentless root bioprosthesis despite the increased operative complexity. Bach and colleagues 5 demonstrated operative risk and mortality to be reduced substantially by increased surgeon experience. Higher operative mortality was generally associated with prolonged myocardial ischemia, increased risk of bleeding complications, and more technically challenging implant of the stentless root, which may be the reason some surgeons favor root replacement with stented xenograft or mechanical valve conduit. 4,8,14-16 Another issue is the durability of the stentless root bioprosthesis in younger patients with type A dissection. In the current study, the mean age of the patient cohort was 57 years, and 15 patients were aged less than 65 years. Desai and colleagues 17 examined the durability of the Medtronic stentless root bioprosthesis in younger patients for a variety 1542 The Journal of Thoracic and Cardiovascular Surgery c June 2013

Smith et al Acquired Cardiovascular Disease FIGURE 1. Actuarial 5-year survival curve for patients who had root replacement with stentless root bioprosthesis for repair of acute type A aortic dissection (Kaplan Meier survival estimates). The number at risk is adjusted taking into account mortality along with variations in length of follow-up time. of aortic root conditions. They found the stentless root bioprosthesis to have excellent durability along with decreased anticoagulant-related bleeding compared with mechanical roots at 5 and 10 years of follow-up. 17 There was no noticeable difference in early or midterm mortality between the stentless and the mechanical valve conduit. 17 This success is likely attributable to the superior hemodynamics and durability of the stentless bioprosthesis seen in older patients. 2,4,17 The study by Desai and colleagues 17 is in agreement with previous studies showing the stentless root bioprosthesis in young patients to have excellent durability and clinical outcomes at 12 years of follow-up. 18 Clinical Implications This study is among the first in the literature to describe the use of the Freestyle stentless aortic root bioprosthesis in the specific repair of patients with type A aortic dissection. Data were prospectively acquired on a cohort of patients with the assistance of meticulous data-management personnel. Our results suggest that stentless root bioprosthesis may be used for aortic root replacement with acceptable early outcomes and midterm survival in patients with type A dissection. Freestyle stentless root bioprosthesis also may be TABLE 4. Mean peak gradients Size of bioprosthesis (mm) Total (%) Dp Mean (mm Hg) ± SD All 100 6.5 2.1 23 8 9 0 25 17 6.8 3.3 27 25 5.8 1.4 29 50 6.4 1.8 Values are expressed as % or as mean SD. SD, Standard deviation. considered as a choice for root replacement in patients with type A dissection who are aged less than 65 years and do not want to take warfarin (Coumadin; Bristol- Myers Squibb, New York, NY). Stentless roots allow the removal of more diseased aortic tissue (dissected sinuses) and in some cases can actually simplify this operation and result in decreased bleeding complications. In the current study, no patients required redo aortic root replacement with a median follow-up time of 875 days (range, 1-2035 days). Study Limitations Limitations of this study include those inherent in a retrospective single-institution methodology. The fact that more than 1 surgeon operated on the patients in this study may have introduced bias. Investigation into the causes of midterm mortality was not available during our study. The small sample size (n ¼ 24), due mainly to the infrequency of aortic root replacement for type A aortic dissection, is another limitation of our study. The small sample size did not allow comparison between the Freestyle root and the non- Freestyle root replacement and will be a focus of future studies. More studies are required to confirm the durability, freedom from structural valve degeneration, and midterm clinical outcomes of this subset of patients. CONCLUSIONS Full-root stentless valve implantation is a valuable option in patients with acute aortic dissection who require root replacement. Although this method is technically a more challenging operation, it is associated with acceptable early and midterm clinical outcomes. The authors thank Dr Alan Davis for the invaluable contribution to the statistical analysis of the article. References 1. Svensson LG, Crawford ES. Techniques for dissection involving the proximal aorta. In: Svensson LG, Crawford ES, eds. Cardiovascular and Vascular Disease of the Aorta. Philadelphia, PA: WB Saunders Company; 1997:296-335. 2. Kon ND, Cordell AR, Adair SM, Dobbins JE, Kitzman DW. Aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis. Ann Thorac Surg. 1999;67:1609-16. 3. David TE, Puschmann R, Ivanov J, Bos J, Armstrong S, Feindel CM, et al. Aortic valve replacement with stentless and stented porcine valves: a case match study. J Thorac Cardiovasc Surg. 1998;116:236-41. 4. Kon ND, Riley RD, Adair SM, Kitzman DW, Cordell AR. Eight-year results of aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis. Ann Thorac Surg. 2002;73:1817-21. 5. Bach DS, Cartier PC, Kon ND, Johnson KG, Deeb GM, Doty DB. Impact of implant technique following freestyle stentless aortic valve replacement. Ann Thorac Surg. 2002;74:1107-13. 6. Ennker IC, Albert A, Dalladaku F, Rosendahl U, Ennker J, Florath I. Midterm outcomes after aortic root replacement with stentless porcine bioprosthesis. Eur J Cardiothorac Surg. 2011;40:429-34. 7. Kon ND, Westaby S, Amarasena N, Pillai R, Cordell AR. Comparison of implant techniques using the Freestyle stentless porcine aortic valve. Ann Thorac Surg. 1995;59:857-62. 8. Dapunt OE, Easo J, H olzl PPF, Murin P, S udkamp M, Horst M, et al. Stentless full root bioprosthesis in surgery for complex aortic valve-ascending aortic The Journal of Thoracic and Cardiovascular Surgery c Volume 145, Number 6 1543

Acquired Cardiovascular Disease Smith et al disease: a single center experience of over 300 patients. Eur J Cardiothorac Surg. 2008;33:554-9. 9. Piccardo A, Regesta T, Zannis K, Gariboldi V, Pansini S, Tapia M, et al. Outcomes after surgical treatment for type A acute aortic dissection in octogenarians: a multicenter study. Ann Thorac Surg. 2009;888:491-7. 10. Mehta RH, O Gara PT, Bossone E, Nienaber CA, Myrmel T, Cooper JV, et al. Acute type A aortic dissection in the elderly: clinical characteristics, management, and outcomes in the current era. J Am Coll Cardiol. 2002;40:685-92. 11. Stamou SC, Hagberg RC, Khabbaz KR, Stiegel MR, Reames MK, Skipper E, et al. Is advanced age a contraindication for emergent repair of acute type A aortic dissection? Int Cardiovasc Thorac Surg. 2010;10:539-44. 12. Hata M, Sezai A, Niino T, Yoda M, Unosawa S, Furukawa N, et al. Should emergency intervention be performed for an octogenarian with type A acute aortic dissection? J Thorac Cardiovasc Surg. 2008;135:1042-6. 13. Shrestha M, Khaladj N, Haverich A, Hagl C. Is treatment of acute type A aortic dissection in septuagenarians justifiable? Asian Cardiovasc Thorac Ann. 2008; 16:33-6. 14. Doty DB, Cafferty A, Cartier P, Huysmans HA, Kon ND, Krause AH, et al. Aortic valve replacement with Medtronic Freestyle bioprosthesis: 5 year results. Semin Thorac Cardiovasc Surg. 1999;11(4 Suppl 1):35-41. 15. Edmunds LH Jr, Clark RE, Cohn LH, Grunkemeier GL, Miller DC, Weisel RD. Guidelines for reporting morbidity and mortality after cardiac valvular operations. J Thorac Cardiovasc Surg. 1996;112:708-11. 16. Cartier PC, Dumesnil JG, Metras J, Desaulniers D, Doyle DP, Lemieux MD, et al. Clinical and hemodynamic performance of the Freestyle aortic root bioprosthesis. Ann Thorac Surg. 1999;67:345-51. 17. Desai ND, McCarthy F, Moser W, Szeto WY, Zeeshan A, Brown D, et al. Durability of porcine bioroots in younger patients with aortic root pathology: a propensity-matched comparison with composite mechanical roots. Ann Thorac Surg. 2011;92:2054-61. 18. Bach DS, Metras J, Doty JR, Yun KL, Dumesnil JG, Kon ND. Freedom from structural valve deterioration among patients aged<or ¼ 60 years undergoing Freestyle stentless aortic valve replacement. J Heart Valve Dis. 2007;16: 649-55. 1544 The Journal of Thoracic and Cardiovascular Surgery c June 2013