Ann Thorac Surg 2000;70:48-51
© 2000 The Society of Thoracic Surgeons
Original articles: Cardiovascular
Stentless aortic valve replacement with freestyle or Toronto SPV: an early comparison
Robert D. Riley, MDa,
John W. Hammon, Jr, MDa,
Sandy M. Adair, RNa,
A. Robert Cordell, MDa,
Neal D. Kon, MDa
a Department of Cardiothoracic Surgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
Address reprint requests to Dr Kon, Department of Cardiothoracic Surgery, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157
e-mail: nkon{at}wfubmc.edu
Presented at the Forty-sixth Annual Meeting of the Southern Thoracic Surgical Association, San Juan, Puerto Rico, Nov 4–6, 1999.
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Abstract
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Background. Stentless aortic xenograft valves have been developed to overcome the disadvantages of conventional stented prostheses. We have implanted two new aortic bioprostheses: the Medtronic Freestyle and the St. Jude Toronto SPV. Early results are compared.
Methods. Forty-four Freestyle valves were implanted using a freestanding total root technique. Fourteen subcoronary Toronto SPV bioprostheses were implanted. Sixty-four percent of both groups (28 of 44 Freestyle and 9 of 14 Toronto SPV) underwent concurrent procedures.
Results. Ischemic time was 117 ± 21 minutes for Freestyle and 124 ± 19 minutes for Toronto SPV. There were no operative deaths or valve-related reoperations. Aortic valve area was 1.83 ± 0.51 cm2 for Freestyle and 1.80 ± 0.51 cm2 (p = 0.89) for Toronto SPV. Transvalvular gradient was 8.03 ± 4.09 mm Hg for Freestyle and 12.4 ± 1.82 mm Hg (p = 0.002) for the Toronto SPV. Aortic regurgitation was not experienced in any Freestyle patients, while Toronto SPV patients were graded as none to trace 79% (11 of 14), mild 14% (2 of 14), and moderate 7% (1 of 14).
Conclusions. Aortic valve replacement with the Freestyle and Toronto SPV required equal time for implantation and had equal effective orifice areas. Freestyle had lower transvalvular gradient and less aortic insufficiency without increasing morbidity or mortality.
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Introduction
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Aortic valve diseases, aortic stenosis or aortic insufficiency, are surgically correctable mechanical problems of the heart. Symptomatic aortic valve disease is associated with a markedly reduced life expectancy. At 8 years after diagnosis, most patients have expired [1]. Aortic valve replacement (AVR) is truly a medical triumph resulting in symptomatic improvement and survival. Survival, however, is not returned to baseline for age-matched controls. Conventional aortic valve prostheses, either mechanical or biologic, have a 60% to 70% 10-year survival [2–4]. Factors affecting survival include operative mortality, uncorrected myocardial dysfunction with congestive heart failure or sudden death from dysrhythmias, as well as valve prosthesis-related complications. Stentless aortic valve bioprostheses have been developed to help alleviate some of these problems. Touted benefits from stentless technology include larger effective orifice areas and subsequent lower transvalvular gradients, improved hemodynamic flow characteristics and annular mechanics, greater reduction in left ventricular hypertrophy and improved ventricular function, as well as potential longer durability [5–9].
Our institutional experience with stentless aortic valves, including the Freestyle Valve (Medtronic, Minneapolis, MN), pulmonary autograft, and the cryopreserved allograft has been excellent and encouraging. To expand our repertoire of readily available stentless aortic valves, we also became part of the investigational trial for implanting the Toronto SPV (St. Jude Medical, Inc, St. Paul, MN). This study is an early comparative analysis of AVR using these two xenograft stentless aortic valves (Freestyle and Toronto SPV) at a single center over the same 2-year time period.
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Patients and methods
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From May 1997 to May 1999, patients undergoing stentless AVR were evaluated. All procedures were consecutively performed at a single institution, Wake Forest University Baptist Medical Center. Two separate and simultaneous Food and Drug Administration (FDA) investigations were in place at the start of this series. Patients were initially enrolled as part of each respective FDA protocol. FDA approval was achieved for each valve during the study interval. Beginning with our first institutional implantation of a Toronto SPV and extending for a period of 2 years, 14 Toronto valves were implanted. During this same time interval, 44 Freestyle valves were also implanted. The Freestyle protocol investigation had been underway for several years before the dates of inclusion, while this was the start of the Toronto SPV protocol. The decisions to perform stentless AVR and the choice of valve implanted were based on surgeon preference and not valvular or aortic pathology, except when the sino-tubular junction was dilated, which precluded Toronto SPV insertion.
Fifty-eight patients underwent aortic valve replacement with one of the two available types of stentless porcine valves either as an isolated procedure or as part of a combined operation. Preoperative patient characteristics are summarized in Table 1. The groups are similar with respect to age, body surface area, and the presence of hypertension or diabetes mellitus. The groups represent an older population of valve patients, with an average age of 72 to 74 years and a life expectancy of less than 15 years given their age and comorbidities. Other preoperative comparisons of the two groups for left ventricular function, New York Heart Association (NYHA) functional class, and valve pathology are also listed. Significant differences between groups were seen in the categories of gender, left ventricular ejection fraction, and NYHA class IV. The etiology of valve lesions was primarily senile calcific degeneration (79% Freestyle and 65% Toronto SPV) with rheumatic, congenital bicuspid, myxomatous degeneration, failed prior prosthesis, or infective endocarditis listed as other etiologies. Echocardiographic evaluation was performed routinely preoperatively, intraoperatively, before hospital discharge, and again at 3 to 9 months in follow-up.
The surgical technique used for Freestyle valve implantation as a freestanding total root replacement has been previously described [5]. Similarly, the technique for Toronto SPV subcoronary implant is described elsewhere [6]. Intraoperative transesophageal echocardiography was available for all valve replacements. Concomitant procedures were performed simultaneously.
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Results
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Forty-four patients underwent Freestyle aortic root replacement and 14 patients had the Toronto SPV implanted. Six-month follow-up data are complete for all patients. Operative information and postoperative results are summarized in Table 2. Sixty-four percent of both groups (9 of 14 Toronto and 28 of 44 Freestyle) underwent concurrent procedures. Most patients had coronary artery bypass grafting, but some also required mitral valve repair or replacement or ascending aortic replacement or tailoring. As shown, implantation time was similar for both groups. All available sizes of the Freestyle valve, from 19 to 27 mm, were implanted. Only the larger Toronto valve sizes, 25 to 29 mm, were used, which is consistent with the concept of oversizing this type of valve.
Postoperative patient functional evaluation at 3 to 9 months as determined by NYHA class is also shown in Table 2. Valvular function at 3- to 9-month follow-up is summarized with respect to valvular insufficiency. Duplex echocardiography data are summarized in Table 3. Results of mean transvalvular gradient and effective orifice area measurements determined at hospital discharge and in follow-up at 3 to 9 months are shown for comparison. There was only one paravalvular leak noted on follow-up echocardiogram in a Toronto SPV patient, who later died from congestive failure and supraventricular dysrhythmias. Other complications were minimal and similar between groups. Thromboembolic complications manifested as transient ischemic attacks or cerebrovascular accidents (TIA or CVA), occurred in 1 (7%) of the Toronto SPV patients and 1 (2%) of the Freestyle patients. Bacterial endocarditis developed in 1 patient in each of the groups: a Toronto SPV patient at 1 month and the Freestyle patient at 20 months, which probably contributed to the death of each patient. No valves in either group required reoperation for any structural or nonstructural degeneration at any time during the study period. There were 2 patients in the Freestyle group who required reoperation for bleeding but neither was bleeding from the aortic root.
There were a total of four deaths over the 2 years of the study. There were no operative deaths in either group. Perioperative mortality, defined as in-hospital or within 30 days, was 3.4% overall. There were two in-hospital deaths in patients receiving the Toronto SPV for a perioperative mortality of 14.3%. One patient died at 30 days with bacterial endocarditis, and is the only Toronto SPV patient to develop endocarditis during the study period, and 1 died at 4 months from complications after a small bowel obstruction without ever leaving the intensive care unit. The Freestyle group had no (0%) perioperative deaths, which has significance at p = 0.01. Late mortality for the groups combined was 3.6% and not significantly different between groups, 2.3% Freestyle versus 8.3% Toronto SPV (p = 0.39). The one late Freestyle death occurred 20 months after implant, from myocardial infarction and sepsis from presumed endocarditis although not documented on transesophageal echocardiogram. The Toronto SPV patient who died late was previously mentioned and died 2 months postoperative from congestive heart failure and malignant supraventricular dysrhythmias.
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Comment
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AVR with stentless xenograft technology holds promise as a viable option for all types of aortic valve pathology. This series compares not only two different stentless aortic xenografts, the Medtronic Freestyle and the St. Jude Toronto SPV, but two different implant techniques as well, the total root replacement and the subcoronary implant. Both a subcoronary valve implant and a total root replacement are valid alternatives for aortic valve replacement. The Freestyle total root and the Toronto SPV both require longer times for insertion over conventional stented prosthesis. In the current series, there was no difference in cross-clamp or cardiopulmonary bypass time between the two groups. The additional ischemia time is not manifested in adverse outcomes such as death or perioperative morbidity. Some investigators have suggested that this may be related to improved postoperative hemodynamics with these stentless valves that result in beneficial changes to the myocardium [10–12]. No perioperative mortality for the Freestyle group in the current series is less than that reported in our larger population of Freestyle root replacements (3.6%) [5]. This demonstrates the excellent results that can be achieved with this operation. Our perioperative mortality for the Toronto SPV group of 14.3% is higher than that reported by David and the investigators for this valve at 2.6% [12]. Conclusions should not be drawn regarding mortality because this represents only two deaths and is exaggerated by the small sample size. In addition, one of these was not valve related or cardiac in origin. Postoperative morbidity was low in both groups and comparable with AVR with stented prostheses. Specifically, there were no cases that required exploration for bleeding from the site of valve insertion, either the aorta or root.
Hemodynamic data favor the Freestyle total root replacement over the Toronto SPV subcoronary implant in the current series. We measured lower transvalvular gradients and larger effective orifice areas in the Freestyle group despite implanting larger size valves in the Toronto SPV group. It has been noted previously using the Freestyle valve that valve gradients are lower with the freestanding root replacement technique than in the subcoronary position [13, 14]. The freestanding position, which allows larger valves to be employed without impingement, and the consistent anatomical relationship of the total porcine root, may contribute to the hemodynamic advantage. The regurgitant flow across some of the Toronto SPV valves may introduce error into the echocardiographic calculations and overestimate gradients and orifice areas. Aortic regurgitation was nonexistent in the Freestyle group. More valvular insufficiency was noted in the Toronto SPV group, but this amount is consistent with published reports (none, 79% vs 85%; 1+, 14% vs 7%; 2+, 7% vs 5%; 3+ and 4+, 0% vs 0.8%, respectively) [12]. This is not unique to the Toronto SPV and has been reported with the subcoronary implant technique using cryopreserved allograft and Freestyle in this position as well [11]. Those valves that leak early tend to deteriorate with time, and these early functional results correlate with valve durability [15].
There are several limitations to this report. This is a retrospective comparative analysis of two independent prospective trials. The patient enrollment was therefore nonrandomized and subject to the selection bias. Due to our prior success with the Freestyle root replacement, a substantial, but undetermined number of referrals were specifically in reference to this valve. Overall study sample size, especially for the Toronto SPV group, was small and may be related to this. The Toronto SPV series, again, is the start of our experience with this particular valve, and therefore our respective locations on each learning curve are substantially different. This may be demonstrated by the fact that our first patient in the Toronto SPV series developed the most aortic insufficiency postoperatively. Group matching was biased against the Toronto SPV, with more of these patients having worse NYHA functional status and ventricular dysfunction.
The study population needs further addressing. Our Toronto SPV results vary from those published by the Toronto SPV investigation group, likely due to the group population differences [12]. Compared with this reference group, a high percentage of patients in the current series had poor left ventricular function with left ventricular ejection fraction less than 40%, and a significantly higher percentage were preoperatively in NYHA class IV (21.4% vs 8%), with a more striking difference found when combining class III and IV (86% vs 50%). More of our patients also required concomitant coronary artery bypass grafting (64% vs 42%) or mitral valve repair (14% vs 1%). The question should therefore be, in the sicker patient, is there more potential benefit with a stentless valve or is the operation too complex making a simpler and shorter operation better? Perhaps, these more difficult patients should receive a stentless valve only after the surgeon has progressed through a sufficient learning curve.
In conclusion, AVR can be accomplished using stentless aortic bioprostheses with acceptable morbidity and mortality. Stentless valves have more favorable hemodynamics, a greater reduction in left ventricular mass index, and hopefully less myocardial dysfunction and dysrhythmias. Long-term follow-up will determine if the differences seen in this study have bearing upon how long each of these valves will last and the niche each will occupy for valve replacement.
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References
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Kon N.D., Adair S.M., Kitzman D.W., et al. Comparison of results using the Freestyle stentless porcine aortic root bioprosthesis with the cryopreserved aortic allograft. In: Huysmans H.A., David T.E., Westaby S., eds. Stentless bioprostheses. Oxford: Isis Medical Media, 1999:127-133.
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Cohn L.H., Collins J.J., Rizzo R.J., Adams D.H., Couper G.S., Aranki S.F. Twenty-Year follow-up of the Hancock modified orifice porcine aortic valve. Ann Thorac Surg 1998;66:S30-S34.
-
Poirier N.C., Pelletier L.C., Pellerin M., Carrier M. 15-Year experience with the Carpentier-Edwards pericardial bioprosthesis. Ann Thorac Surg 1998;66:S57-S61.
-
Banbury M.K., Cosgrove D.M., Lytle B.W., Smedira N.G., Sabik J.F., Saunders C.R. Long-term results of the Carpentier-Edwards pericardial aortic valve. Ann Thorac Surg 1998;66:S73-S76.
-
Kon N.D., Cordell A.R., Adair S.M., Dobbins J.E., Kitzman D.W. Aortic root replacement with the Freestyle stentless porcine aortic root bioprosthesis. Ann Thorac Surg 1999;67:1609-1616.[Abstract/Free Full Text]
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Christakis G.T., Campbell D.J., Morgan C.D., et al. Left ventricular mass regression early after aortic valve replacement. Ann Thorac Surg 1996;62:1084-1089.[Abstract/Free Full Text]
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Bach D.S., David T., Yacoub M., et al. Hemodynamics and left ventricular mass regression following implantation of the Toronto SPV stentless porcine valve. Am J Cardiol 1998;82:1214-1219.[Medline]
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Jin X.Y., Zhang Z.M., Gibson D.G., Yacoub M.H., Pepper J.R. Effects of valve substitute on changes in left ventricular function and hypertrophy after aortic valve replacement. Ann Thorac Surg 1996;62:683-690.[Abstract/Free Full Text]
-
Maselli D., Pizio R., Bruno L.P., Di Bella I., De Gasperis C. Left ventricular mass reduction after aortic valve replacement. Ann Thorac Surg 1999;67:966-971.[Abstract/Free Full Text]
-
David T.E., Puschmann R., Ivanov J., et al. Aortic valve replacement with stentless and stented porcine valves. J Thorac Cardiovasc Surg 1998;116:236-241.[Abstract/Free Full Text]
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Kon N.D., Westaby S., Amarasena N., Pillai R., Cordell A.R. Comparison of implantation techniques using Freestyle stentless porcine aortic valve. Ann Thorac Surg 1995;59:857-862.[Abstract/Free Full Text]
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David T.E. The Toronto SPV bioprosthesis. Ann Thorac Surg 1999;68:S9-S13.
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Westaby S., Huysmans H.A., David T.E. Stentless aortic bioprosthesis. Ann Thorac Surg 1998;65:235-240.[Abstract/Free Full Text]
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Dumesnil J.G., LeBlanc M.H., Cartier P.C., et al. Hemodynamic features of the Freestyle aortic bioprosthesis compared with stented bioprosthesis. Ann Thorac Surg 1998;66(Suppl):130-133.
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David R.E., Bas J. Aortic valve replacement with stentless porcine aortic valve. Semin Thorac Cardiovasc Surg 1999;11:9-11.[Medline]
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Abstract
Introduction
