Eight-Year Results of Aortic Root Replacement With the Freestyle Stentless Porcine Aortic Root Bioprosthesis

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1 Eight-Year Results of Aortic Root Replacement With the Freestyle Stentless Porcine Aortic Root Bioprosthesis Neal D. Kon, MD,* Robert D. Riley, MD, Sandy M. Adair, RN, Dalane W. Kitzman, MD, and A. Robert Cordell, MD Department of Cardiothoracic Surgery and Section of Cardiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina Background. Stentless porcine aortic valves offer several advantages over traditional valves. Among these are superior hemodynamics, laminar flow patterns, lack of need for anticoagulation, and perhaps improved durability. Methods. One hundred four patients were operated on from September 17, 1992, to October 31, 1997, as part of a multicenter worldwide investigation of the Medtronic Freestyle stentless porcine bioprosthesis. All patients received a total aortic root replacement. The patients were evaluated postoperatively at discharge, at 3 to 6 months, and yearly by clinical examination and color flow Doppler echocardiography. Results. Operative mortality was 3.9%. No patient experienced structural valve deterioration, nonstructural deterioration, perivalvular leak, or unacceptable hemodynamic performance. At 8 years, survival was 59.8%. Freedom from thromboembolic complications was 83.3%. Freedom from postoperative endocarditis was 96.9%. Freedom from reoperation was 100%. Mean systolic gradients did not change over the time period studied. They were mm Hg at 1 year and mm Hg at 8 years. Correspondingly, effective orifice area was cm 2 at 1 year and cm 2 at 8 years. The incidence of any aortic insufficiency also did not change over the length of follow-up. At 1 year, 98% of patients had no or trivial aortic insufficiency and 2% had mild aortic insufficiency. At 8 years, 100% of patients evaluated were free of any aortic insufficiency. Conclusions. The Medtronic Freestyle aortic root bioprosthesis can be used safely to replace the aortic root or aortic valve for aortic valve and aortic root pathology. Total root replacement allows optimal hemodynamic performance with no significant aortic regurgitation. Results up to 8 years show excellent survival and no signs of degeneration. Further follow-up is still needed to determine valve durability. (Ann Thorac Surg 2002;73: ) 2002 by The Society of Thoracic Surgeons Stentless porcine aortic valves offer superior hemodynamic performance when compared to their stented counterparts [1]. Flow patterns are remarkably similar to normal native aortic valves [2]. In addition, they are silent, do not require the use of anticoagulants, and, in an elderly population, promise suitable durability. The greatest drawback to the use of stentless porcine aortic valves appears to be the technical demands associated with implantation [3]. Various techniques have been described, but are often associated with longer ischemic times and a surgeon s fear of aortic valvular incompetence at the conclusion of the operation [4, 5]. Similar technical difficulties and fears were observed with the use of aortic allografts. Many surgeons adopted the use of a root replacement technique to ensure aortic Presented at the Forty-eighth Annual Meeting of the Southern Thoracic Surgical Association, San Antonio, TX, Nov 8 10, *Recipient of the 2001 Southern Thoracic Surgical Association President s Award. Address reprint requests to Dr Kon, Department of Cardiothoracic Surgery, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC ; nkon@wfubmc.edu. valve competence when using an aortic allograft [6, 7] or pulmonary autograft [8, 9]. Therefore, we preferentially chose the full root technique when we began implanting stentless porcine valves in The present study evaluates our results with the initial Food and Drug Administration trial population of Medtronic Freestyle aortic root bioprosthesis during the past 8 years. Patients and Methods Wake Forest University Baptist Medical Center was selected in 1992 to serve as one of the US study centers to begin implanting the Freestyle investigational valve. Before initiation of the study at our center, the institution s internal review board approved the study design. Written informed consent was obtained for each patient before operation. This study evaluates the 104 total aortic root replacements submitted from our institution as part of Medtronic, Incorporated s submission to the Food and Drug Administration (FDA) for premarket approval of this valve. These 104 patients also make up a part of Medtronic s postmarket approval study required by the 2002 by The Society of Thoracic Surgeons /02/$22.00 Published by Elsevier Science Inc PII S (02)

2 1818 KON ET AL Ann Thorac Surg EIGHT-YEAR RESULTS WITH FREESTYLE PORCINE ROOT 2002;73: Table 1. Distribution of Valve Size Implanted Valve Size All Patients (n 104) No. Implanted % of Total 19 mm 6 5.8% 21 mm % 23 mm % 25 mm % 27 mm % Table 3. Incidence of Concomitant Procedure Procedures No. % of Total Coronary artery bypass % Ascending aorta replacement/repair % Myomectomy 3 2.9% Isolated aortic root replacement % Patients may have more than one concomitant procedure. Food and Drug Administration at the time of approval for general use. From September 17, 1992, to October 31, 1997, 104 patients received a Freestyle aortic root bioprosthesis. Forty-seven of the patients (45%) were men and 57 (55%) were women. The mean age was 72 years, with a range of 48 to 87 years. Eighty-seven percent of the patients were more than 65 years old and 77% were in New York Heart Association functional class III or IV preoperatively. All five available sizes were implanted (19, 21, 23, 25, and 27 mm). The distribution of use is shown in Table 1. Table 2 lists the various preoperative risk factors in this elderly patient population. The incidence of performing a concomitant procedure is listed in Table 3. The freestanding total aortic root replacement technique was chosen in all 104 patients. We have previously described the details of this technique [10]. Valve rotation was not performed at any of the operations in this group. All available patients were evaluated at discharge, at a 3- to 6-month interval, and again yearly by clinical examination and color flow Doppler echocardiography. Preoperative and postoperative data at each clinical examination and at each echocardiographic evaluation Table 2. Preoperative Risk Factors (n 104) Risk Factors a All Patients %of Total History of chronic lung airway disease % Diabetes mellitus % Myocardial infarction 6 5.8% Carotid artery disease 8 7.7% History of TIA CVA % Multiple occurrences 3 2.9% TIA CVA thrombotic TIA CVA hemorrhagic 1 1.0% TIA CVA embolic 1 1.0% TIA CVA indeterminate 7 6.7% Coronary artery disease % History of arrhythmias % Atrial arrhythmias % Ventricular arrhythmias 9 8.7% Congestive heart failure % Left ventricular dysfunction % Hypertrophy % Dilation % History of endocarditis 1 1.0% a Patients may have more than one risk factor. were tabulated and placed in the Freestyle database at Medtronic, Incorporated, in Minneapolis, Minnesota. Descriptive statistics were used to summarize the preoperative, operative, follow-up clinical, and hemodynamic data. The number of patients, mean, and standard deviation are provided for categorical data. The life table method is used to estimate survival and freedom from adverse events. Results Initial patient improvement in New York Heart Association functional class for congestive heart failure after operation is shown in Table 4. Mean aortic cross-clamp times for patients with isolated aortic root replacement were 110 minutes, whereas those who also had an additional concomitant procedure were minutes. Operative mortality (30-day or in hospital) was 3.9%. The actuarial survival rate at 8 years was 59.8% (Fig 1). Freedom from aortic valve reoperation and freedom from structural valve deterioration at 8 years were both 100%. The freedom from postoperative endocarditis at 8 years was 96.9% (Fig 2), whereas freedom from thromboembolic complications at 8 years was 83.3% (Fig 3). No patient suffered clinical hemolysis, nonstructural dysfunction, or unacceptable postoperative hemodynamic performance of the Freestyle aortic valve. The mean aortic valve gradients and effective orifice areas for each valve size are shown in Table 5. The mean aortic valve gradient and effective orifice areas for all sizes combined at each follow-up interval are shown in Table 6. There was no significant change in valve gradient or orifice area overall or for any size from the time of implant throughout the entire 8-year follow-up period. No patient exhibited any significant aortic regurgitation at any time interval studied for 8 years postoperatively (Fig 4). There were no observable changes in aortic valve function during the 8 years. Table 4. Change in NYHA Class From Preoperative NYHA Class Preoperative No. of Patients (%) 3 6 mo Postoperative No. of Patients (%) I 2 (1.9%) 94 (96.9%) II 22 (21.2%) 2 (2.1%) III 69 (66.3%) 1 (1.0%) IV 11 (10.6%) NYHA New York Heart Association.

3 Ann Thorac Surg KON ET AL 2002;73: EIGHT-YEAR RESULTS WITH FREESTYLE PORCINE ROOT 1819 Fig 1. The linearized rate of freedom from death after aortic root replacement. The open circles represent the estimated survival for 72-year olds in the United States in The data are from the National Vital Statistics Report, Vol. 47, No. 28, December 13, The vertical line is 95% confidence interval of survival for the Freestyle patients. Comment Aortic valve replacement with stentless porcine bioprostheses as a group has been associated with excellent hemodynamics and excellent clinical outcomes [11 14]. As has been described for aortic valve replacement with aortic allografts and pulmonary autografts, the Freestyle stentless porcine aortic root bioprosthesis can be implanted using one of several surgical techniques: the complete or modified subcoronary technique, the root inclusion technique, or a free-standing total aortic root replacement technique. When the multicenter clinical evaluation of the Freestyle stentless porcine aortic root bioprosthesis began in 1992, we elected to use the free-standing total aortic root replacement technique. This stentless aortic valve replacement technique was chosen for all patients with either aortic valve or aortic root pathology. It was our belief at the time, and has been subsequently demonstrated that this technique offers the best hemodynamic performance and the Fig 2. The linearized rate of freedom from endocarditis after aortic root replacement. Fig 3. The linearized rate of freedom from thromboembolic events after aortic root replacement. lowest incidence of aortic regurgitation when compared to other implantation techniques [4, 15]. The anticipated disadvantages of the full root replacement technique include prolonged myocardial ischemic times and increased intraoperative bleeding complications. Several lessons have been learned with our experience during the past 8 years using the Freestyle valve. Myocardial ischemic times have not been sufficiently prolonged to result in increased morbidity or mortality. Some previous studies have demonstrated longer ischemic times for root replacement than for the modified subcoronary technique [4, 15], whereas other studies have shown similar cross-clamp times for the two techniques [14, 16]. An aortic root replacement with a stentless valve involves an inflow suture line, two coronary artery reimplantation suture lines, and an aortic reapproximation suture line. A stented aortic valve replacement involves only an inflow suture line and an aortic closure suture line in the uncomplicated situations. Thus, in most instances, a stented valve is quicker to implant. Therefore, although a stentless root replacement may be similar in operative time to a stentless subcoronary implant, it is in no way as quick as a valve replacement with a stented valve. This has not, however, resulted in increased morbidity or mortality. We have also not seen a difference in bleeding complications despite the increased number of suture lines and operative complexity. The root replacement technique most reliably maintains root geometry for the stentless porcine leaflets. This is documented not only by studies showing the least incidence of aortic insufficiency with this technique, but also by having the lowest early gradients [4]. Late follow-up in this study, up to 8 years, shows no increase in gradients, no decrease in effective orifice area, and no increase in the incidence of aortic insufficiency over time. In contrast, a recent study evaluating the late follow-up for the Toronto stentless porcine valve, implanted with the subcoronary technique, has been associated with progressive dilatation of the sinotubular junction resulting in increased incidence of aortic insufficiency [17]. Other studies from the Freestyle database have shown somewhat more favorable hemodynamics, a lower pre-

4 1820 KON ET AL Ann Thorac Surg EIGHT-YEAR RESULTS WITH FREESTYLE PORCINE ROOT 2002;73: Table 5. Mean Systolic Gradient and Effective Orifice Area After Aortic Root Replacement Mean systolic Gradient (mmhg) Effective Orifice Area (cm 2 ) Discharge 2 yrs 5 yrs 7 yrs Discharge 2 yrs 5 yrs 7 yrs 19 mm (No.) Mean/SD mm (No.) Mean/SD mm (No.) Mean/SD mm (No.) Mean/SD mm (No.) Mean/SD valence of aortic insufficiency, and better New York Heart Association functional class on follow-up with the full root technique [18]. Utilization of the root replacement technique with aortic allografts also has been associated with greater durability when compared to the other implant techniques [19]. Another question regarding porcine root replacement concerns the fate of the aortic wall over time. In this study, we have routinely asked our echocardiographer to pay special attention to this detail. In no patient has excess aortic wall calcification been noted. Melina and associates [20] have compared aortic wall calcification in the Freestyle root to the aortic wall calcification in aortic allograft root replacements. Thus far calcification has remained lower in the Freestyle aortic wall than in the allograft aortic wall. No significant changes in the elastic properties of the aortic wall have been observed. Coronary orientation has posed some problems with aortic root replacement with Freestyle. The human coronaries are generally 120 to 160 apart, whereas the porcine coronaries are generally 90 to 110. The right porcine coronary artery sits in a superior plane compared to the left porcine coronary artery, and the Dacron inflow of the Freestyle valve comes up higher under the porcine right coronary artery than it does over the other two sinuses of Valsalva. In this study, to compensate for these differences in coronary anatomy, we opened the left coronary ostia toward the right to centralize the left sinus opening. The high right coronary artery still infrequently posed an alignment problem. This, in fact, may account for an increase in concomitant right coronary artery bypass grafting procedures in this study. We have subsequently learned that 120 rotation of the Freestyle valve has solved most of the coronary alignment problems. We now make the porcine noncoronary sinus the new left coronary sinus. The porcine left coronary sinus becomes the new right coronary sinus. Simply oversewing the porcine right coronary completes the new orientation of the porcine root. This maneuver readily allows the Freestyle valve to fit the human aortic root. Several studies with stentless valves intimate improved survival statistics after aortic valve replacement when compared to stented counterparts [21 23]. The true goal of aortic valve replacement in a patient with aortic valvular heart disease is to return that patient to both the lifestyle and the life expectancy of an age-matched patient without valvular heart disease. The high incidence of patients in New York Heart Association functional class I postoperatively in this study demonstrates significantly improved lifestyle. The superimposable natural life expectancy curve for a 72-year-old person with the survival of patients in this mean 72-year-old patient population demonstrates how close we are now coming to this goal (Fig 1). This is supporting evidence to continue using stentless porcine valves as root replacements for elderly patients with aortic valve and aortic root pathology. In conclusion, aortic root replacement is shown to be a safe replacement technique for aortic root and aortic valve pathology. Excellent valvular performance is ensured by optimal hemodynamics, perfect root geometry, no late aortic regurgitation, and no structural degeneration. Survival thus far is excellent and approaches that of an agematched population without valvular heart disease. Longer follow-up will help to determine true valve durability. Table 6. Mean Systolic Gradient and Effective Orifice Area for All Sizes Combined at Each Interval Examined Variable Discharge 3 6 mo 1 yr 2 yrs 3 yrs 4 yrs 5 yrs 6 yrs 7 yrs 8 yrs Mean systolic gradients (mm Hg) N Mean/SD Effective orifice area (cm 2 ) N Mean/SD

5 Ann Thorac Surg KON ET AL 2002;73: EIGHT-YEAR RESULTS WITH FREESTYLE PORCINE ROOT 1821 Fig 4. Incidence of aortic regurgitation after aortic root replacement. References 1. Yun KL, Jamieson WR, Khonsari S, Burr LH, Munro AI, Sintek CF. Prosthesis patient mismatch: hemodynamic comparison of stented and stentless aortic valves. Semin Thorac Cardiovasc Surg 1999;11(4 suppl 1): Kon ND, Adair SM, Kitzman DW, et al. Comparison of results using the Freestyle stentless porcine aortic root bioprosthesis with the cryopreserved aortic allograft. In: Huysmans HA, David TE, Westaby S, eds. Stentless bioprosthesis, 2nd ed. Oxford, United Kingdom: Isis Medical Media, 1999: Ennker J, Bauer J, Rosendahl U, et al. Simultaneous myocardial revascularization and aortic valve replacement: stentless versus stented bioprostheses. Semin Thorac Cardiovasc Surg 1999;11(4 suppl 1): 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: Doty DB, Cafferty A, Kon ND, Huysmans HA, Krause AH Jr, Westaby S. The Medtronic Freestyle Multicenter Clinical Trial Centers. Medtronic Freestyle aortic root bioprosthesis: implant techniques. J Cardiac Surg 1998;13: O Brien MP, McGriffin DC, Stafford EG. Allograft aortic valve implantation techniques for all types of aortic valve and root pathology. Ann Thorac Surg 1989;48: Daicoff GR, Botero LM, Quintessenza JA. Allograft replacement of the aortic valve versus the miniroot and valve. Ann Thorac Surg 1993;55: Kouchoukos NT, D Avila-Roman VG, Spray TL, et al. Replacement of the aortic root with a pulmonary autograft in children and young adults with aortic-valve disease. N Engl J Med 1994;330: Elkins RC, Santangelo K, Stelzer P, et al. Pulmonary autograft replacement of the aortic valve: an evolution of technique. J Cardiac Surg 1992;7: 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: David TE, Pollick C, Bos J. Aortic valve replacement with stentless porcine bioprosthesis. J Thorac Cardiovasc Surg 1990;99: Del Rizzo DF, Goldman BS, Joyner CP, et al. Initial clinical experience with the Toronto stentless porcine valve. J Cardiac Surg 1994;9: Westaby S, Amarasena N, Long V, et al. Time-related hemodynamic changes after aortic replacement with the Freestyle stentless xenograft. Ann Thorac Surg 1995;60: Cartier PC, Metras J, Dumesnil JG, et al. Clinical and hemodynamic performance of the Freestyle aortic root bioprosthesis. Ann Thorac Surg 1999;67: Doty DB, Cafferty A, Cartier P, et al. Aortic valve replacement with Medtronic Freestyle bioprosthesis: 5-year results. Semin Thorac Cardiovasc Surg 1999;11(4 suppl 1) Riley RD, Hammon JW Jr, Adair SM, Cordell AR, Kon ND. Stentless aortic valve replacement with Freestyle or Toronto SPV: an early comparison. Ann Thorac Surg 2000;70: David TE. Dilation of sinotubular junction: SPV bioprosthesis. Presented at The 81st annual AATS Plenary Scientific Session, San Diego, CA, May Bach DS, Cartier PA, Dumesnil JG, Kon ND, Doty DD. Impact of implant technique on clinical outcomes following freestyle stentless tissue aortic valve replacement - Presented at the American Heart Association Scientific Sessions Nov 2000: Lund O, Yacoub M, Chandrasekaran V, et al. Primary aortic valve determinants of outcome. J Thorac Cardiovasc Surg 1999;117: Melina G, Rubens MB, Amrani M, Khaghani A, Yacoub MH. Electron beam tomography for cusp calcification in homograft versus Freestyle xenografts. Ann Thorac Surg 2001; 71(5 suppl):s David TE, Puschmann R, Ivanov J, et al. Aortic valve replacement with stentless and stented porcine valves: a case-match study. J Thorac Cardiovasc Surg 1998;116: Del Rizzo DF, Abdoh A, Cartier P, Doty D, Westaby S. The effect of prosthetic valve type on survival after aortic valve surgery. Semin Thorac Cardiovasc Surg 1999;11(4 suppl 1): Westaby S, Horton M, Jin XY, et al. Survival advantage of stentless aortic bioprosthesis. Ann Thorac Surg 2000;70: DISCUSSION DR W. STEVES RING (Dallas, TX): Dr Kon, these are excellent results. We are finally starting to see some of the long-term outcome with this new valve. Could you describe a little bit about your technique? Many of these patients have an extremely calcified annulus, frequently with calcium extending into the septum and the mitral annulus. Do you alter your technique for implanting the Freestyle bioprosthesis in the presence of a heavily calcified aortic annulus? DR KON: Initially, we thought that calcification around the coronaries and in the sinuses of Valsalva might be a contraindication to doing a root replacement. But what we actually found is that it is an indication to do a root replacement. What we do is try to clean up all of the calcium and excise all of the heavily diseased tissues. One of the beauties of doing a total root replacement in this setting is that you end up with excess tissue, therefore you do not end up with tension on any suture lines and you remove most, if not all, of the severely diseased tissues. We debride extensively everything and almost take out the entire annulus, if necessary, because we can seat the valve conduit a little bit lower in the left ventricular outflow tract when calcification in the annulus is extensive. If necessary, we have also endarterectomized the coronaries to reimplant them or left a larler rim of normal sinus of Valsalva tissue to aid in reimplantation. So, in summary, I believe the awful situation of extensive calcification can be handled quite nicely when using a root replacement technique.