Ann Thorac Surg 1997;64:1495-1498
© 1997 The Society of Thoracic Surgeons
How To Do It
Technique for Complete Subcoronary Implantation of the Medtronic Freestyle Porcine Bioprosthesis
Albert H. Krause, Jr, MD
Department of Cardiac Surgery, Legacy Portland Hospitals, Portland, Oregon, and Southwest Washington Medical Center, Vancouver, Washington
Accepted for publication June 2, 1997.
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Abstract
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Nonstented porcine bioprostheses offer the surgeon a larger implant option with better hemodynamics than stented counterparts by eliminating the space occupied by the frame. A secondary benefit may be improved durability related to reduction of leaflet stresses created by the frame. The Medtronic Freestyle stentless porcine aortic root can be implanted as a root replacement, as a miniroot cylinder within the aorta, or as a partially or completely scalloped valve replacement. This report describes an easy, reliable, and reproducible technique of completely scalloped valve replacement performed in a population of 75 patients with Freestyle implants and uses the anatomy of the Freestyle and human aortic roots to facilitate the implant technique.
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Introduction
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See also page 1498
Potential benefits of stentless versus stented bioprosthesis include: (1) larger valve implant diameters with reduced transvalvular gradients resulting in improved left ventricular function and (2) improved durability afforded by more physiologic valve suspension and use of calcium mitigating treatments [1].
The Medtronic Freestyle porcine aortic root bioprosthesis is a versatile implant option. The device can be modified for (1) root replacement with coronary ostial reimplantation, (2) mini-root inclusion cylinder aortic valve replacement, (3) partial scalloped subcoronary implantation, or (4) completely scalloped subcoronary aortic valve replacement. Techniques for some of these implant options have been described previously [2, 3]. This report describes a reliable reproducible technique for complete subcoronary implantation used in the majority of 75 patients receiving a Freestyle implant at our Food and Drug Administration-approved implant sites. This method uses the anatomic properties of the human and porcine aortic roots so that difficulties of implantation can be minimized.
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Technique
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Characteristics of the Freestyle Root
The Freestyle valve is provided as a glutaraldehyde-treated porcine aortic root with ligated coronary arteries and a cuff of thin Dacron velour covering the inflow margin and muscular septum under the right coronary sinus. The cloth covering has markers of green suture that define (1) locations at 120 degrees along the inflow and (2) the safe area along the inflow margin for suture placement. The 120-degree markers are generally at the porcine commissures but due to sinus asymmetry may not be precisely at each commissure. The root is fixed in buffered (0.2%) glutaraldehyde at 40 mm hydrostatic pressure to maintain aortic shape and proportions while leaflets are 0 pressure-fixed in a neutral position. The valve is also treated with a calcium mitigating compound, alpha-amino-oleic acid.
Anatomic Considerations and Rationale for Prosthetic Rotation With Implantation
The normal human aortic valve resides within three sinuses, the noncoronary usually being the largest of the three. In the porcine aortic root the right sinus is the largest. Additionally, the porcine right sinus includes well-developed ventricular septal muscle that displaces the right coronary origin cephalad compared with that of the left (Fig 1
). With orthotopic implantation (right sinus sutured to right sinus) this vertically increased dimension of subsinus tissue and Dacron in the Freestyle valve must be placed under the patient's right coronary ostium. To obviate these potential suturing difficulties, rotation of the right porcine sinus 120 degrees into the patient's noncoronary sinus is helpful.
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Fig 1. . Freestyle valve with cephaladly displaced right coronary artery above Dacron-covered ventricular septal muscle. (LCA = ligated left coronary artery; RCA = ligated right coronary artery.)
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Technique of Implantation
Cardiac exposure, cardiopulmonary bypass, left ventricular venting, and cardiac protection are established as with other methods of aortic valve replacement. It is helpful to mark the planned aortotomy location on the aortic root while it is still distended. Exposure of the valve is through a transverse aortotomy that includes two thirds to three fourths of the circumference of the aorta and is about 1 to 2 cm above the sinotubular ridge. This location maximizes exposure and avoids a suture line at the level of valve implantation. The diseased valve is excised and the annulus debrided. Traction sutures at the commissures facilitate exposure. Both coronary arteries must be visualized to assure that implantation is feasible and that significant coronary anomalies do not exist. Sizing is performed with the sizers provided for the valve, with consideration given to the size at both the annulus and sinotubular ridge. A larger diameter measured at the latter or uncertainty based on annular diameter would favor upsizing to the next larger valve.
During valve washing, the inflow suture line is developed with a total of 15 to 21 vertical sutures of 3 0 Ti-cron (Sherwood Davis & Geck, St. Louis, MO) placed below the patient's annulus in the subannular tissue. The intent is to create a suture line that is in a flat plane that lies under the commissures but approaches or resides on the annulus in the midportion of each sinus remnant (Fig 2). This plane is flat to conform to that of the bioprosthesis. Suturing under the right-noncoronary commissure should be cephalad to conduction system near the membranous septum. The valve is trimmed with generous buttons of aortic tissue removed from each sinus, leaving only the "crown" or top of the valve and a 2- to 3-mm porcine aortic remnant along either side of each leaflet into which the outflow suture line will be placed (Fig 3).
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Fig 2. . Placement of subannular interrupted sutures. Note sutures under annulus at commissure and near or into annulus at midpoint of sinus.
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Fig 3. . Removal of generous buttons of porcine aorta leaving "crown" or top of valve and aortic remnant for outflow suture line.
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The Ti-cron inflow sutures are now placed symmetrically into the inflow Dacron cuff of the bioprosthesis (Fig 4) with orientation of it so the porcine right sinus lies within the patient's noncoronary sinus. The valve is seated and the sutures are tied and cut.
The porcine root should now sit as a cylinder within a cylinder. The valve, if properly sized and seated, should sit within the aorta undistorted.
The commissural posts of the bioprosthesis are now positioned within the patient's aorta. This is easily accomplished as the crown of the valve "positions" the commissural posts to their proper location. One of three 4-0 polypropylene sutures is placed above each commissural post as a horizontal mattress suture (Fig 5). These untied sutures define the likely final location of the valve commissural posts after implantation is complete. Once these positioning commissural post sutures are in place, the crown or top of the bioprosthesis is no longer needed and may be excised* (Fig 6). The outflow suture line is performed next. This seals the upper porcine aortic remnant to the patient's aorta and thus is an important hemostatic barrier to prevent paravalvular aortic insufficiency. Care must be taken to avoid needle or instrument injury to the leaflets. Three 4-0 polypropylene 36-inch (90 cm) sutures with RB1 or RB2 needles are used, each started in the base of the left, right, and then noncoronary sinuses suturing up to the commissural posts of that respective sinus. These sutures are then passed to the outside of the aorta to be tied in pairs after completion of the sinus closures (Fig 7). The "positioning sutures" can either be tied or removed. No polypropylene knots are within the aorta, as they may injure the valve leaflets due to abrasion. The aortotomy is closed and standard methods of cardiac resuscitation and deairing are performed (Fig 8).
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Fig 5. . Positioning sutures placed to define locations of commissural posts within the patient's aorta.
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Comment
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The described technique is simple and provides an implant method that is easily reproducible, avoiding some of the technical problems of orthotopic partial subcoronary implantation. This technique has been used in the majority of our Freestyle implantations, resulting in excellent hemodynamics and a low risk of aortic insufficiency. Hemodynamic benefit of stentless compared with other stented valve implants has been documented [4, 5]. Benefit regarding durability must await long-term follow-up.
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Footnotes
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Address reprint requests to Dr Krause, 2222 NW Lovejoy, Suite 315, Portland, OR 97210.
* Miniroot inclusion aortic valve replacement may be performed by leaving the valve crown and suturing sinuses and crown to the patient's aorta. 
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References
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- Piwnica A, Westaby S. Surgery for acquired aortic valve disease. Oxford: Isis Medical Media, 1997:83–101.
- Kon ND, Westaby S, Amarasena N, Pillai R, Cordell AR. Comparison of implantation techniques using Freestyle stentless procine aortic valve. Ann Thorac Surg 1995;59:857–62.[Abstract/Free Full Text]
- Barratt-Boyes BG, Christie GW, Raudkivi PJ. The stentless bioprosthesis: surgical challenge an implications for long term durability. Eur J Cardiothorac Surg 1992;6(Suppl 1): S39–43.[Medline]
- Sintek CF, Fletcher AD, Khonsari S. Stentless porcine aortic root: valve of choice for the elderly patient with small aortic root? J Thorac Cardiovasc Surg 1995;109:871–6.[Abstract]
- Westaby S, Amarasena N, Long V, et al. Time-related hemodynamic changes after aortic replacement with the Freestyle stentless xenograft. Ann Thorac Surg 1995;60:1633–9.[Abstract/Free Full Text]
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Abstract
Introduction
