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Ann Thorac Surg 2006;82:2133-2138
© 2006 The Society of Thoracic Surgeons

Original Articles: Cardiovascular

Results of Aortic Valve Replacement With a New Supra-Annular Pericardial Stented Bioprosthesis

Daisy Pavoni, MD*, Luigi P. Badano, MD, Sergio F. Musumeci, MD, Romeo Frassani, MD, Pasquale Gianfagna, MD, Enzo Mazzaro, MD, Ugolino Livi, MD

Department of Cardiopulmonary Sciences, A.O. S Maria della Misericordia, Udine, Italy

Accepted for publication July 6, 2006.

* Address correspondence to Dr Pavoni, Cardiology Unit, Echo-lab, Department of Cardiopulmonary Sciences, A.O. S Maria della Misericordia, P. le S Maria della Misericordia 15, Udine 33100, Italy (Email: daisy_pav{at}libero.it).


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
BACKGROUND: The stented Soprano valve (Sorin Biomedica S.pA., Saluggia, Italy) is a pericardial tissue valve designed for a totally supra-annular implant with the aim of improving hemodynamic performance, particularly in patients with a reduced aortic annulus. However, its hemodynamics and early clinical outcome are poorly understood.

METHODS: Seventy-seven patients (mean age 76 ± 5 years, 56% males) underwent aortic valve replacement with the Soprano valve. All patients were monitored with clinical examination and serial echocardiography at 1, 6, and 12 months and yearly afterward.

RESULTS: At preoperative echocardiography, average left ventricular outflow tract diameter was 2.1 ± 0.2 cm. At operation, 35% of patients received a 20-mm valve, 54% a 22-mm valve, and 11% a 24-mm valve. At 6-month follow-up, peak and mean transprosthetic gradients were 18 ± 8 and 9 ± 4 mm Hg, respectively; effective orifice area (EOA) and EOA index were 1.84 ± 0.6 cm2 and 0.9 ± 0.2 cm2/m2, respectively. Incidence of patient-prosthesis mismatch (ie, EOA index < 0.85 cm2/m2) was 23%, with no case of severe mismatch (ie, EOA index < 0.6 cm2/m2). In addition, left ventricular hypertrophy showed a significant regression (mass index from 214 ± 98 g to 129 ± 41 g; p = 0.001), and ejection fraction increased (from 58% ± 17% to 67% ± 8%; p = 0.001). Cumulative follow-up was 7.9 months per patient. Thirty-day mortality rate was 2.6% (2 of 77). Cumulative survival at 6, 12, and 24 months was 92% ± 3.7%, 85% ± 5.7%, and 85% ± 5.7%, respectively. Two patients experienced embolic episodes. One case of anticoagulant-related bleeding occurred.

CONCLUSIONS: In our series, the Soprano bioprosthesis showed a good hemodynamic performance, low incidence of patient-prosthesis mismatch, and favorable early clinical results.


   Introduction
Top
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
For patients with severe and symptomatic aortic stenosis, the only effective treatment for changing their natural history is surgical valve replacement. The aim of aortic valve replacement is to relieve the stenosis, improve clinical status, and reduce left ventricular (LV) hypertrophy and dilatation, thus improving LV systolic and diastolic function. However, notwithstanding the impressive technological progress in the design and construction of prosthetic valves, their hemodynamic performance does not yet match that of the native valve, and a residual gradient may remain, especially in small valve sizes.

In elderly patients, tissue valves are the preferred prostheses owing to their improved durability and hemodynamic performance, patients’ relatively shorter life expectancy, and reduced bleeding complications from short-term anticoagulation therapy [1]. However, among patients with stented aortic bioprostheses, the reported incidence of patient-prosthesis mismatch has been reported to be as high as 52% [2, 3]. Several surgical options are available to try to avoid patient-prosthesis mismatch: first use of stentless prostheses; however, their implantation is technically demanding and extensive calcification of the aortic root may preclude their use. Mechanical hemidisc prostheses carry the risk of bleeding complications related to the chronic anticoagulation therapy required and are recommended only for elderly patients otherwise anticoagulated. Surgical enlargement of the aortic root may be another option; however, there are unsolved issues about the safety of this procedure. Finally, the supra-annular implantation of stented bioprostheses is a procedure that is gaining popularity because it is easy to perform, and it should result in a maximization of blood flow [4].

The Sorin Soprano valve (Sorin Cardio S.p.A., Saluggia, Italy) is a pericardial tissue valve designed for a totally supra-annular seating that is in widespread use in Europe and Asia. It has been marketed since May 2003. Nevertheless, only a preliminary report of its normal functioning has been published [5]. Therefore, the aim of this prospective study was to evaluate the clinical and hemodynamic performance of this stented bioprosthesis in elderly patients with degenerative aortic valve disease.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
The Soprano Valve
The Soprano valve is a new stented bioprosthesis that has been designed for totally supra-annular seating. The sewing ring is made of an acetal resin stent, a silicone core, and Carbofilm-coated (Sorin Biomedica S.pA, Saluggia, Italy) polyester fabric. Valve leaflets were manufactured in a unique two-sheet design using glutaraldehyde stabilized bovine pericardium posttreated with a detoxification process. This exclusive treatment with homocysteic acid neutralizes the residues of unbound glutaraldehyde groups left after tissue fixation process.

The prosthesis is then stored in a sterile and aldehyde-free solution. The final product does not contain glutaraldehyde residues; thus, the valve is ready to implant and does not require rinsing. This detoxification process has been applied since 2000 to Pericarbon More and Pericarbon Freedom Stentless, then applied to Soprano in 2003 and Freedom Solo in 2004. The valve stent shows a low profile, not having to interfere with the coronary ostia. The base of the Soprano sewing ring is flat.

Patient Population
This study was performed on 77 consecutive patients aged more than 65 years of age, candidates to receive a biological prosthesis, and with a small aortic annulus (ie, left ventricular outflow diameter 23 mm or less). They were implanted with the Soprano valve between May 2003 and December 2005. The study was designed in a prospective fashion to assess clinical and hemodynamic performance of the valve. Patient selection was not randomized. Exclusion criteria included emergency surgery, coexistent illness known to have a high mortality rate, or valve replacement other than aortic. All surviving patients underwent clinical assessment and postoperative echocardiographic study at 1 month, 6 months, and 1 year after surgery and yearly thereafter. This time frame was chosen to avoid the immediate postoperative hyperdynamic state of the left ventricle and to allow patients to compensate their postoperative relative anemia.

The study was approved by the Hospital Ethical Committee, and written informed consent to it was obtained from all patients.

Surgical Procedures
After median sternotomy, all patients underwent aortic valve replacement with Soprano prostheses under mild-to-moderate hypothermic cardiopulmonary bypass. Myocardial protection was achieved both by topical cooling and by intermittent infusion of cold crystalloid solution (St Thomas’ Hospital) directly into the coronary ostia or in a retrograde manner via the coronary sinus. With regard to sizing the prosthesis, the surgeon determined the largest size hosted by the annulus using the specific sizers provided by the manufacturer, without applying any force and without dilating the annulus. The final choice of the prosthesis size was based on the sizing of the patient’s annulus and the best fitting sizer at time of surgery. As the labeled size represents the valve internal orifice diameter, there is no hemodynamic benefit in oversizing the valve. Conversely, as the stent profile of the Soprano valve is relatively high, oversizing the valve could compromise coronary artery perfusion. The Soprano valve was implanted in supra-annular position using the technique of multiple, interrupted, noneverting pledgettes vertical mattress sutures. After surgery, all patients were treated with warfarin sodium (Coumadin) for 3 months; the target international normalized ratio (INR) was kept between 2.0 and 3.0. Afterward, patients were treated lifelong with antiplatelet agents.

Echocardiographic Studies
Complete M-mode, two-dimensional spectral Doppler and color-flow studies were performed, using commercially available ultrasound instruments (VIVID 7 Dimension; GE Healthcare, Horten, Norway). Two-dimensional cine-loops, M-mode, and Doppler tracings were digitally recorded, and all hemodynamic measurements were made off-line by two observers (D.P., L.P.B.) masked to prosthesis size, using a dedicated software for quantitative analysis (Compacs; MediMatic S.r.l., Genova, Italy) [5].

Definitions
Descriptions of valve-related events and deaths were based on guidelines for reporting morbidity and mortality after cardiac valvular surgery [6]. In accordance with these guidelines, valve-related events were defined as structural deterioration, thromboembolism, bleeding, prosthetic endocarditis, reoperation, and death related to the morbid events. Operative mortality was classified as early when it occurred during the hospitalization or within 30 days from the intervention, and as late when it occurred later than 30 days after surgery. Cause of death were described as valve related, cardiac not valve related, or noncardiac.

Statistical Analysis
Statistical analysis was performed with the SPSS statistical software package (SPSS 12, Chicago, Illinois). Values are expressed as mean value ± SD, and they were compared with nonparametric tests (Mann-Whitney). The categorical variables were compared with contingency tables and the {chi}2 test (corrected with the Yate’s formula when necessary) or the Fisher exact test. Values of p less than 0.05 were considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
Between May 2003 and December 2005, 77 patients with aortic valve disease underwent valve replacement with a Soprano valve. The preoperative demographics and clinical characteristics of the study patients are summarized in Table 1. Forty-two patients (56%) were aged more than 75 years, and 14 (17%) were aged more than 80 years. Eighteen patients (22%) were obese (body mass index ≥ 30 kg/m2). Preoperatively, 35 patients (44%) were in New York Heart Association functional class 3 and 4 (Fig 1). On average, preoperative left ventricular (LV) systolic function was normal (Table 1). However, 7 patients (9%) showed mild LV dysfunction (ejection fraction between 45% and 55%), 9 patients (11%) showed moderate LV dysfunction (LV ejection fraction 30% to 45%), and only 3 patients had a preoperative ejection fraction of 30% or less. At the time of aortic valve replacement, 47% of patients underwent concomitant surgical interventions (Table 2). Early postoperative complications are summarized in Table 2.


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  		Table 1. Demographics and Preoperative Characteristics of the 77 Study Patients
 

Figure 1
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  		Fig 1. Preoperative and postoperative New York Heart Association (NYHA) functional class in patients implanted with the Soprano valve.

 

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  		Table 2. Intervention Data, Postoperative Clinical and Left Ventricular (LV) Function Data in 77 Patients Implanted With the Soprano Valve
 
Follow-up information was obtained in the majority of cases from outpatient clinical visit (80%). Mean follow-up time was 13 ± 9 months, and cumulative follow-up was 7.9 months per patient. At the time of follow-up, New York Heart Association functional class was significantly improved in comparison with the preoperative status (p < 0.001), and only 9% of patients remained in class III to IV functional impairment (Fig 1). During the follow-up period, 8 deaths (10%) occurred: 2 early within 30 days (1 cardiac tamponade during the hospital stay, and 1 sudden unexplained death at home), and 6 late. None of the late deaths was valve related. There was only 1 cardiac death (1.2%), and the cause of the fatal event was sudden unexplained death, in the others 5 patients, the cause was noncardiac (3 severe respiratory failure, 1 cerebral tumor, and 1 polytrauma). Cumulative survival at 6, 12, and 24 months was 94% ± 2.8%, 88% ± 4.7%, and 85% ± 5.7%, respectively (Fig 2). Among the 77 patients, 2 (2.6%) showed thromboembolic events during the early postoperative course. In 1 patient, both cerebral ischemia and anterior myocardial infarction occurred. One case of anticoagulant-related bleeding occurred. No case of infective endocarditis and no structural valve dysfunctions were observed during the follow-up period.


Figure 2
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  		Fig 2. Cumulative survival in patients implanted with the Soprano pericardial tissue valve.

 
The data about hemodynamic performance of the valve at 6 months after surgery are summarized in Table 3. On average, mean transprosthetic flow rate was 224 ± 70 mL/s, and peak and mean transprosthetic gradients were 18 ± 8 mm Hg and 9 ± 4 mm Hg, respectively. The effective orifice area was 1.84 ± 0.6 cm2, and the effective orifice area index was 0.9 ± 0.2 cm2/m2. On average, valve resistance was 583 ± 271 dyne/s · cm–5. The effective orifice area increased significantly with increasing valve size (Table 3). Hemodynamic determinants did not change significantly during the follow-up period (Table 4).


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  		Table 3. Hemodynamic Measurements of the Soprano Valve According to Valve Size
 

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  		Table 4. Left Ventricular (LV) Geometry and Function, and Hemodynamic Measurements of the Soprano Valve Changes During the Follow-Up Period
 
Compared with the preoperative data, postoperative left ventricular ejection fraction showed a significative improvement (from 58% ± 17% to 67% ± 8%, p = 0.001), both end-diastolic and end-systolic volumes decreased (111 ± 47 mL to 86 ± 29 mL, p = 0.0001, and 51 ± 34 to 29 ± 15 mL, p = 0.0001, respectively), and left ventricular mass showed a significant regression (from 396 ± 189 g to 224 ± 70 g, p = 0.0001). The incidence of valve prosthesis-patient mismatch (effective orifice area index ≤ 0.85 cm2/m2) was 23%, and no patients showed severe (effective orifice area index ≤ 0.6 cm2/m2) valve prosthesis-patient mismatch.


   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
Our study was designed to assess hemodynamic and functional results in patients who were implanted with the Soprano valve in supra-annular aortic position. In our study population of elderly patients with stenosis of the native aortic valve, supra-annular implant of this valve was associated with a good hemodynamic performance of the bioprosthesis, early improvement of left ventricular systolic function and patient functional class, and significant regression of left ventricular hypertrophy.

Owing to the increasing number of elderly patients requiring aortic valve replacement and the persistent risk of thromboembolic and bleeding complications in patients with mechanical prostheses, the use of bioprostheses has continuously increased during the last decade. Accordingly, there is a renewed interest in the hemodynamic performance of bioprostheses because survival may be affected by the influence of prosthesis-patient mismatch on left ventricular mass regression, especially in patient with a small aortic root [7]. Indeed, senescent calcification of the aortic valve is not associated with dilatation of the aortic valve annulus or proximal ascending aorta. The aortic valve annulus is frequently small, especially in women who have a small body surface area, and 19-mm or 21-mm valve sizes are frequently implanted in these patients. The small aortic annulus presents the potential for iatrogenic "valve prosthesis-patient mismatch" [7].

To warrant satisfactory postoperative hemodynamic results in small aortic roots, new technologies in heart valve manufacturing have been introduced. The construction of stented bioprostheses designed for complete supra-annular implant has gained wide acceptance because their implant is easy to perform, and by allowing a precise alignment of the valve orifice to the patient’s tissue annulus, it should result in a maximization of blood flow. The Soprano valve has been designed for a totally supra-annular implant.

The valves implanted in our patients were small, with 89% 20-mm or 22-mm sizes. This small size was mainly due to prevalence of pure aortic stenosis (70%) and the high percentage of women (44%) in our study population. However, it is also because the manufacturer labeled the bioprosthesis following the ISO International Standards Document, released on March 01, 2005, that indicates that the labeled valve size of all supra-annular models must correspond to the "valve internal orifice diameter."

Our results showed a favorable hemodynamics of the Soprano valve, especially in small size (20 mm). That bioprostheses in supra-annular position show a better hemodynamic performance than prostheses in intra-annular position has been reported previously [5]. Badano and colleagues [5] showed that, compared with the same prosthesis in intra-annular position, the implant of the Soprano valve in supra-annular position was associated with an increase by 23% of the effective orifice area, a reduction by 58% of both peak and mean transprosthetic gradients, and a reduction by 54% of valve resistance to flow. Good hemodynamic performance of the Soprano valve has been already reported; however, the gradients measured in our study are even lower than those reported by Botzenhardt and coworkers [8]. The difference may be due to their having used a simplified formulation (4vmax valve 2) instead of the modified (4 · (vmax valve 2 – vmax LVOT 2)) Bernoulli equation to calculate peak and mean transprosthetic gradients, and did not take into account of the velocity of flow in the left ventricular outflow tract (LVOT). However, the simplified formulation of Bernoulli equation can be used only for flow that is through a restrictive orifice (ie, inertial component is negligible) and when vmax valve is much higher than vmax LVOT. Since new normofunctioning prosthetic valves show non-restrictive orifices and low vmax valve values, using the simplified Bernoulli equation to assess transprosthetic gradients of these valves may cause a significative overestimation of calculated gradients also in patients with vmax LVOT less than 1 m/s [5, 8].

The good hemodynamic performance of Soprano valve at midterm translated into favorable clinical results. The incidence of prosthesis-patient mismatch was 23%, and more important, no case of severe mismatch occurred. Accordingly, patients experienced improvement of left ventricular systolic function and early regression of left ventricular hypertrophy that were both statistically significant at 6 months after surgery. The latter may be related to the low transprosthetic gradients. Indeed, the extent of muscle mass regression has been shown to be highly dependent on the type and size of prosthesis used for valve replacement, as well as on their hemodynamic performance [9, 10]. Barner and associates [11] demonstrated that regression of LV hypertrophy after aortic valve replacement is better in patients with a prosthesis size greater than 21 mm (–21%) than in patients with a prosthesis of 21 mm or less [11]. Nishimura and colleagues [12] found that the mean wall thickness of the LV was directly related to the pressure gradient across the aortic prosthetic valve. In this context, it should be emphasized that left ventricular hypertrophy has long been recognized as an important risk factor and predictor of survival as well as a major determinant of systolic and diastolic function and exercise capacity [7].

Good hemodynamic results of the Soprano valve have been reported by others [8, 13]. However, Eichinger and colleagues [13] documented that the relatively high position of the valve in the aortic root may affect the coronary perfusion in patients with small aortic root. Careful sizing of the valve using the manufacturer sizer and avoiding oversizing may prevent this adverse event.

In addition to the good hemodynamic performance, there were also favorable clinical results. In our cohort, the actuarial survival at 24 months was 85%. This relatively high mortality rate at midterm was probably related to the advanced age of the analyzed patient group. The freedom from thromboembolism at 24 months was 97%, while the freedom from endocarditis, structural deterioration, and reoperation was 100% for all.

In conclusion, our study shows that the Soprano bioprosthesis offers little resistance to forward flow, even in patients with a small aortic annulus. Its favorable hemodynamic performance translates into early regression of left ventricular hypertrophy and improvement of left ventricular systolic function. Larger trials and a longer follow-up are needed to evaluate the impact of the improved hemodynamics of these findings on patient mortality and morbidity.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Task Force on Practice Guidelines (Committee on Management of Patients with Valvular Heart Disease) ACC/AHA guidelines for the management of patients with valvular heart diseaseA report of the American College of Cardiology/American Heart Association. J Am Coll Cardiol 1998;32:1486-1588.[Free Full Text]
  2. Pibarot P, Honos GN, Durand LG, et al. The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status Can J Cardiol 1996;12:379-387.[Medline]
  3. Pibarot P, Dumesnil JG, Lemieux M, et al. Impact of prosthesis-patient mismatch on hemodynamic and symptomatic status, morbidity and mortality after aortic valve replacement with a bioprosthetic heart valve J Heart Valve Dis 1998;7:211-218.[Medline]
  4. Badano LP, Zamorano JL, Pavoni D, et al. Clinical and hemodynamic implications of supra-annular implant of biological aortic valves J Cardiovasc Med 2006;7:524-532.
  5. Badano LP, Pavoni D, Musumeci S, et al. Stented bioprosthetic valve hemodynamicsHow much is the supra-annular implant better than the intra-annular one?. J Heart Valve Dis 2006;15:238-246.[Medline]
  6. Edmunds Jr LH, Clark RE, Cohn LH, et al. Guidelines for reporting morbidity and mortality after cardiac valvular operations Ann Thorac Surg 1996;62:932-935.[Abstract/Free Full Text]
  7. Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention J Am Coll Cardiol 2000;36:1131-1141.[Abstract/Free Full Text]
  8. Botzenhardt F, Eichinger WB, Bleiziffer S, et al. Hemodynamic comparison of bioprostheses for complete supra-annular position in patients with small aortic annulus J Am Coll Cardiol 2005;45:2054-2060.[Abstract/Free Full Text]
  9. Jin XY, Zhang ZM, Gibson DG, et al. 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]
  10. Krayenbuehl HP, Hess OM, Schneider J, et al. Left ventricular function and myocardial structure in aortic valve disease before and after surgery Herz 1984;9:270-278.[Medline]
  11. Barner HB, Labovitz AJ, Fiore AC. Prosthetic valves for the small aortic root J Card Surg 1994;9:154-157.[Medline]
  12. Nishimura RA, Pieroni DR, Bierman FZ, et al. Second natural history study of congenital heart defectsAortic stenosis: echocardiography. Circulation 1993;87(2 Suppl):I66-I72.[Medline]
  13. Eichinger WB, Botzenhardt F, Wagner I, et al. Hemodynamic evaluation of the Sorin Soprano bioprosthesis in the completely supra-annular aortic position J Heart Valve Dis 2005;14:822-827.[Medline]



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