Ann Thorac Surg 1999;68:2147-2151
© 1999 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
The Edwards Prima stentless valve: hemodynamic performance at one year
Uberto Bortolotti, MDa,
Giovanni Scioti, MDa,
Aldo Milano, MDa,
Giancarlo Borzoni, MDa,
Carmela Nardi, MDb,
Giuseppe Tartarini, MDb
a Section of Cardiac Surgery, Department of Cardiology, Angiology and Pneumology, Pisa, Italy
b University of Pisa Medical School, Pisa, Italy
Address reprint requests to Dr Bortolotti, U.O. Cardiochirurgia, Ospedale Cisanello, Via Paradisa 2, 56124 Pisa, Italy;
e-mail: u.bortolotti{at}cardchir.med.unipi.it
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Abstract
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Background. The Edwards Prima stentless valve (EPSV) is a porcine aortic root cylinder with resected coronary ostia, fixed in glutaraldehyde at low pressure. The purpose of this study was to evaluate the hemodynamic performance of the EPSV 1 year after aortic valve replacement.
Methods. From December 1994 to February 1996, 29 patients underwent aortic valve replacement with EPSV used in the subcoronary position (group 1, n = 23) or as a root replacement (group 2, n = 6). Hemodynamic performance of EPSV was assessed by two-dimensional Doppler echocardiography at 1 week, 6 months, and 1 year by calculating peak transprosthetic velocity, peak and mean gradients, effective orifice area, degree of aortic regurgitation, and regression of left ventricular hypertrophy.
Results. There were no operative deaths. One patient in group 2 died after 3 months at reoperation for endocarditis. In group 1 early mean gradient (25 ± 5 mm Hg for 23 mm and 19 ± 5 mm Hg for 25 mm) decreased at 6 months and 1 year in the 23-mm size (17 ± 7 mm Hg and 15 ± 4 mm Hg, p < 0.01) and at 1 year in the 25-mm size (14 ± 4 mm Hg, p = 0.03) without modifications of the effective orifice area in both sizes. A significant reduction in left ventricular hypertrophy occurred at 6 months and 1 year in both sizes. In group 2 lower early gradients were recorded with subsequent improvement at follow-up; reduction in left ventricular hypertrophy occurred as well.
Conclusions. The EPSV used in the subcoronary position has shown high early gradients, which partially regressed at 6 months, with further improvement at 1 year. Gradients are attributed to inward folding of the Dacron cloth at the right coronary ostium, being more evident in patients with aortic stenosis without dilatation of the aortic root and coronary ostia close to the annulus. In such patients a better early hemodynamic result can be obtained by using the EPSV as a root replacement.
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Introduction
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Stentless bioprostheses are gaining increasing popularity as cardiac valve substitutes, mainly because they are considered to have a superior hemodynamic performance when compared to stented xenografts [1]. We have used the Edwards Prima stentless porcine valve (EPSV) for aortic valve replacement (AVR) in the subcoronary position in a series of patients in whom high transvalvular gradients were observed early postoperatively [2]. For this reason this device was subsequently used as root replacement in patients requiring AVR. This article updates our clinical experience with the EPSV by reporting the hemodynamic data at 1 year and comparing patients operated on using two techniques.
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Material and methods
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Characteristics of the edwards prima stentless porcine valve
The EPSV (Baxter Healthcare Corp, Edwards CVS Division, Irvine, CA) is a porcine aortic root cylinder with resected coronary ostia. The tissue is fixed in 0.625% buffered glutaraldehyde at low pressure. A Dacron cloth around the annulus facilitates placement of sutures; a large piece of Dacron is also present outside the valve conduit mainly below the right porcine coronary ostium (Fig 1).
Clinical data
A total of 29 patients underwent isolated AVR with an EPSV. From December 1994 to August 1995, in 23 patients the EPSV was implanted in the subcoronary position (group 1), and from September 1995 to February 1996, 6 patients had root replacement with the same device (group 2). Main preoperative clinical data are summarized in Table 1. In group 1 there were 4 men and 19 women with a mean age of 75 ± 4 years; 15 patients (65%) were in New York Heart Association functional class III and 4 (17%) in class IV; in group 2 there were 6 women with a mean age of 79 ± 6 years; 4 (67%) were in class III and 2 (33%) in class IV. In both groups aortic stenosis was the predominant valvular lesion.
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Table 1. Clinical Characteristics of Patients Undergoing Aortic Valve Replacement With the Edwards Prima Stentless Valve
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Prosthetic sizes were as follows: 21 mm (n = 1), 23 mm (n = 10), 25 mm (n = 10), and 27 mm (n = 2) in group 1; 23 mm (n = 4) and 25 mm (n = 2) in group 2. Two patients in group 1 (9%) and 1 of group 2 (16.5%) had associated procedures, which included coronary artery bypass grafting in all. Mean aortic cross-clamp time and mean bypass time were 69 ± 15 minutes and 82 ± 17 minutes in group 1, and 82 ± 25 and 87 ± 29 minutes in group 2, respectively (Table 2).
Surgical technique
Operation was performed with standard, moderately hypothermic cardiopulmonary bypass, a single dose of cold blood cardioplegia into the aortic root or coronary ostia, and topical cooling. When implanting the EPSV in the subcoronary position a technique similar to that proposed by Konertz and colleagues [3] was used. The aortic valve is exposed through a transverse aortotomy and excised; the annulus is debrided from calcific deposits and sized. A row of interrupted sutures of 3/0 Ethibond Extra (Ethicon Ltd, UK) is placed below the aortic annulus and then passed in the prosthetic Dacron rim. Once the valve has been seated it is trimmed by cutting the aortic wall remnants only above the two coronary ostia. The EPSV is then sutured to the native aortic wall by means of three continuous sutures of 3/0 Prolene (Ethicon), which are tied at each commissure outside the aorta over small Teflon felts or pledgets of autologous pericardium. In patients undergoing aortic root replacement the ascending aorta is completely transected a few millimeters above the commissural level. The valve is excised and the coronary ostia, detached with buttons of the aortic wall, are adequately mobilized. The EPSV is secured to the aortic annulus using multiple sutures of 2/0 Ethibond Excel (Ethicon) buttressed by small subannular Teflon pledgets. The coronary ostia are then connected to the prosthetic coronary orifices with a continuous suture of 4/0 Prolene (Ethicon). A similar running suture is used also for the distal aortic anastomosis.
Anticoagulant treatment with subcutaneous calcium heparin is started on postoperative day 1, gradually replaced by sodium warfarin; oral anticoagulants are maintained for approximately 3 months and then suspended unless clear indication for long-term anticoagulation is present.
Follow-up
All patients were followed in the outpatient clinic where they returned 1 month after operation and then at every 6-month interval. At each follow-up visit information was collected on the clinical status and incidence and type of postoperative complications, which were evaluated based on criteria recommended by recently revised guidelines [4]. Follow-up protocol for prosthetic valve recipients also includes a transthoracic two-dimensional color-Doppler echocardiographic study, which is usually performed immediately before discharge and planned every 6 months thereafter. All studies were done with commercially available equipment (Aloka SSD 2200; Aloka Co, Ltd, Tokyo, Japan; or Vingmed CFM 800; Vingmed Sound, Horten, Norway), using a 2.5-MHZ transducer and recorded continuously on 0.5-inch videotapes for subsequent analysis. The peak preprosthetic velocity was obtained from apical transducer position placing the sample volume of pulsed wave Doppler in the central region of the left ventricular outflow tract, just proximal to the area of preprosthetic flow acceleration. By continuous wave Doppler the peak transprosthetic flow velocity was registered from multiple transducer positions, including the right parasternal and suprasternal approach. The highest velocity registrations with a clearly defined envelope of the spectral curves were used for further calculations. Peak and mean transprosthetic gradients and prosthetic effective orifice area applying the Bernoulli and continuity equations were calculated for each patient. Measurements were averaged over three beats in patients with sinus rhythm and over five beats in those with atrial fibrillation. Aortic regurgitation was graded as absent (0), trivial (1+), mild (2+), moderate (3+), and severe (4+). In patients with pure or predominant aortic stenosis regression of left ventricular hypertrophy was studied by comparing the left ventricular mass, calculated using the Devereux and Reicheck formula [5] at discharge, at 6 months, and at 1 year.
Statistical analysis
Data are expressed as mean ± standard deviation. Comparison between pre- and postoperative echocardiographic results was made by using the Student’s t test and p values less or equal to 0.05 was considered as statistically significant.
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Results
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Clinical data
There were no operative deaths. Two patients in group 2 experienced transient low output syndrome, which resolved with adequate inotropic support. Minor postoperative complications were observed in 2 patients consisting of episodes of supraventricular arrhythmias in 1 and pneumothorax in 1. One patient in group 2 was readmitted after 3 months because of prosthetic endocarditis. Reoperation was successfully performed but she died suddenly on postoperative day 7. There were no other late deaths. Follow-up of 28 current survivors ranges from 9 to 24 months (mean, 19 ± 5 months), with a cumulative follow-up of 542 patient-months. At last follow-up 22 of them (78.5%) are in functional class I and 6 (21.5%) are in class II. Only 2 patients are still on oral anticoagulants because of chronic atrial fibrillation; 1 of them experienced a minor anticoagulant-related hemorrhage.
Echocardiographic data
Echocardiographic studies were performed in all patients before discharge, in all survivors at 6 months (28 patients) and in 27 at 1 year from AVR. In group 1 there was a significant reduction in peak transprosthetic flow velocity, peak and mean transprosthetic gradients at 6 months and 1 year when compared to values at 1 week in the 23-mm EPSV (Table 3 ); in patients with a 25-mm EPSV, significant reduction in peak transprosthetic flow velocity, peak and mean transprosthetic gradients was observed only 1 year after AVR (Table 4). There was also an increase in effective orifice area in both sizes; however, this is not statistically significant. Trivial aortic regurgitation was noted in 6 patients.
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Table 3. Hemodynamic Data in Patients Undergoing Aortic Valve Replacement With the Edwards Prima Stentless Valve Implanted in the Subcoronary Position (23 mm, 10 patients)
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Table 4. Hemodynamic Data in Patients Undergoing Aortic Valve Replacement With the Edwards Prima Stentless Valve Implanted in the Subcoronary Position (25 mm, 10 patients)
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Left ventricular mass index decreased from 184 ± 41 g/m2 at 1 week to 163 ± 39 g/m2 at 6 months and 149 ± 35 g/m2 at 1 year (p < 0.01) in patients with the 23-mm EPSV (Fig 2 ); it decreased from 148 ± 23 g/m2 at 1 week, to 119 ± 19 g/m2 at 6 months and 117 ± 11 g/m2 at 1 year (p < 0.01) in those with a 25-mm EPSV (Fig 3).
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Fig 2. Reduction of the left ventricular mass index (LVMI) in patients with a size 23-mm Edwards Prima stentless valve (EPSV).
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Fig 3. Reduction of the left ventricular mass index (LVMI) in patients with a size 25-mm Edwards Prima stentless valve (EPSV).
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In group 2 patients, lower gradients were recorded at discharge in both prosthetic sizes when compared to group 1 patients; gradients further reduced and effective orifice area increased at 6 months and 1 year (Table 5). Left ventricular mass regression was observed also in this group at each follow-up interval with no cases of aortic regurgitation.
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Comment
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Use of stentless bioprostheses for AVR was first reported by Binet and colleagues [6] in 1965, but availability of commercially manufactured stented porcine valves contributed to the limited use of this valve substitute in subsequent years. Stented porcine bioprostheses have shown low thrombogenicity, limited durability due to progressive calcific structural degeneration, and a suboptimal hemodynamic performance in the small sizes [7–9]. Renewed interest in stentless bioprostheses has been recently stimulated by the reports of David and associates [1, 10, 11], who demonstrated their improved hemodynamics when compared to stented valves. Furthermore, the absence of a stent should also enhance valve durability by reducing the mechanical stress on the cusps and by more uniformly distributing it on the aortic wall [12].
The EPSV has been available for clinical use since 1991 [13]. We have used this valve substitute for AVR in a small series of patients with good early clinical results. Some concern was raised, however, on the hemodynamic performance of this device implanted in the subcoronary position, as early high transprosthetic gradients were recorded; such gradients were significantly reduced at the 6-month follow-up evaluation only in a limited number of patients [2]. A similar behavior was observed by Pillai and colleagues [12] in reporting their experience with 31 patients undergoing AVR with the EPSV. By using mostly 25-mm valves they noted at 4 weeks lower gradients (average peak and mean transprosthetic gradients of 24 mm Hg and 9 mm Hg, respectively), which did not modify after 6 months. Dossche and associates [14] compared the hemodynamic properties of freehand allografts, EPSV, and Carpentier-Edwards stented porcine valve. They also recorded high transprosthetic gradients in patients with EPSV, which did not significantly change at 1 year; such gradients were equivalent to those of the stented Carpentier-Edwards porcine valve. Similar results were reported by Parry and colleagues [15], who studied 25 patients receiving the EPSV. Doppler assessment at 5 and 10 days after implantation showed peak transprosthetic gradients as high as 43 mm Hg and 38.5 mm Hg, respectively, being unrelated to the size of the prosthesis. We believe that such unusual hemodynamic findings may be at least in part explained by the peculiar design of the EPSV, which is provided with a high external Dacron fabric cloth below the right coronary ostium. When suturing the inferior rim of the prosthetic right coronary ostium below the patient’s right coronary ostium, the Dacron fabric will bend inward, creating a fixed obstacle in the left ventricular outflow at the valvular level; this was observed in 2 of our patients, not included in this series, in whom the EPSV was explanted intraoperatively for this reason [2]. This problem is more likely to occur when the coronary ostia are close to the annulus as in cases of pure or predominant aortic stenosis without dilatation of the aortic root. The mechanism is similar to that described by Westaby and associates [16] in some patients receiving the Medtronic Freestyle stentless valve. In their experience, however, gradients have been noted to regress with time, which has been ascribed to expansion and remodeling of the porcine root to fit the native aortic sinuses together with resolution of both perivalvular hematoma and inflammatory reaction [16]. To overcome this problem alternative implantation techniques have been suggested, such as clockwise rotation of the prosthesis so that the Dacron cloth corresponds to the noncoronary sinus or its use as root replacement [16]. In the last patients of our series the EPSV was implanted as root replacement. This is a technically more demanding procedure that, however, has provided better early hemodynamic results. Mean aortic cross-clamp and bypass times in patients receiving the EPSV in the subcoronary position were similar to those reported by other investigators [12, 17]. The longer ischemic time needed to implant the EPSV as a root replacement did not result in higher operative mortality or morbidity, despite the older mean age of the patients in this group.
By extending the follow-up of our patients we observed a further hemodynamic improvement at 1 year. This was associated with a significant reduction in left ventricular hypertrophy despite the fact that transprosthetic gradients remained above the figures expected for a stentless valve, at least in patients with a 23-mm EPSV. These results seem to support the concept of progressive remodeling of the porcine aortic root also in the EPSV, although in our experience this appears to occur more slowly than reported by other researchers [16]. Also at this follow-up interval the hemodynamic performance of the EPSV used as a root replacement seems to be superior to the subcoronary implantation, but the small number of patients does not allow a statistically significant comparison.
In conclusion, in our limited experience the EPSV implanted in the subcoronary position has been associated to high early transprosthetic gradients, which tend to regress at 6 months with further reduction at 1 year and concomitant regression of left ventricular hypertrophy. Patients with aortic stenosis, small aortic root, and a short distance between the annulus and the right coronary ostium are more prone to develop high postoperative gradients. In these patients a better early hemodynamic result can be obtained with alternative implantation techniques such as the use of the EPSV as root replacement.
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Accepted for publication May 4, 1999.
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Abstract
Introduction
