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Cardiac Surgery Unit, Cardiovascular Sciences Department, Glenfield Hospital, University of Leicester, Leicester, United Kingdom
Accepted for publication January 18, 2008.
* Address correspondence to Dr Galiñanes, Cardiac Surgery Unit, Cardiovascular Sciences Department, Glenfield Hospital, University of Leicester, Groby Rd, Leicester, LE3 9QP, United Kingdom (Email: mg50{at}le.ac.uk).
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Abstract |
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Description: Here we present a novel prefabricated stentless valved conduit incorporating sinuses of Valsalva and describe the technique of implantation. The BioValsalva (Vascutek Terumo, Renfrewshire, Scotland) valved conduit incorporates a stentless porcine aortic valve (Elan; Vascutek Terumo) suspended within a triple-layered vascular conduit (Triplex; Vascutek Terumo) constructed with sinuses of Valsalva.
Evaluation: The BioValsalva valved conduit was used in 12 patients with aortic regurgitation due to annuloaortic ectasia unsuitable for aortic valve repair and concomitant ascending aorta aneurysm, with no deaths and excellent functioned result.
Conclusions: The prefabricated, composite, stentless valved conduit is composed of material that is hemostatic and reduces bleeding. It is easy to implant, with a short ischemic time, and lends itself well to a variety of insertion techniques.
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Technology |
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To overcome this problem, woven prostheses with zero porosity were developed. The use of a xenograft root, which if necessary could be extended distally with a vascular graft, has also been proposed [1]; however, the xenograft aortic wall is prone to calcification. If reoperation were required, then replacement of the entire xenograft root would be necessary, compounding the risk of surgery [2]. The use of a mechanical valve in a composite graft requires long-term anticoagulation and is a disadvantage, especially in elderly patients, in patients unsuitable for anticoagulation, and in patients with extended aortic pathologies such as aortic dissection and thoracoabdominal aortic aneurysms.
Composite valved conduits using mechanical and bioprosthetic prostheses have traditionally been designed as straight tubes without incorporating the sinuses of Valsalva. The physiologic importance of the sinuses is beginning to be recognized. Vortices that form at this site improve blood flow to the coronary arteries and promote earlier and more gradual valve leaflet closure, thus reducing stress of the leaflet coaptation [3]. Furthermore, in the absence of the sinuses, there is a theoretic risk of collision of the valve leaflets with the vascular graft, resulting in abrasive wear. Therefore, the ideal composite valved conduit used for replacement of the aortic valve, aortic root, and ascending aorta should possess the following characteristics:
Here we report a new bioprosthetic valved conduit, the BioValsalva (Vascutek Terumo, Renfrewshire, Scotland). It consists of the Elan valve (Vascutek Terumo), a stentless bioprosthesis that has been shown to afford excellent hemodynamics with performance [4], within a polyester and polytetrafluoroethylene (PTFE) triple-layered conduit that is hemostatic, has favorable handling properties, and incorporates sinuses of Valsalva (Fig 1). The selected porcine valves were predilated and preserved with low-pressure fixation in 0.5% buffered glutaraldehyde. They did not receive antimineralization treatment. Two sizes of the prosthesis were used, 26 and 28 mm for the conduit, and 25 and 27 mm for the valve. The diameters of the sinus of Valsalva for these conduits are 32 mm and 35 mm, respectively. Different implantation techniques can be used to accommodate one of these two prostheses sizes into a wide range of aortic anatomy.
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Technique |
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The sewing ring of the BioValsalva composite conduit was anastomosed to the aortic annulus using a variety of techniques, depending on the aortic anatomy. When the tissue was healthy, continuous and semi-continuous sutures were used, with or without pledget reinforcement. When the tissue quality was poor and the annulus calcified, interrupted mattress sutures were used. Interrupted mattress sutures were also used when a small aortic annulus was encountered, allowing the implantation of a larger root into the supraannular position; whereas everted mattress sutures reinforced with continuous sutures were used when there was a large annulus to allow a smaller root to be implanted in the intraannular position.
The vascular graft was fenestrated with a punch (5.6 mm), and the coronary buttons were anastomosed to the BioValsalva graft using 5-0 Surgipro (Syneture/Tyco Healthcare, Norwalk, CT). After completion of the coronary anastomoses, the tube graft was cut to length and an end-to-end anastomosis to the distal ascending aorta was fashioned using a continuous 3-0 Prolene (Ethicon, Somerville, NJ) suture reinforced with Teflon (DuPont, Wilmington, DE) felt and tissue glue (Glubran, GEM, Viareggio, Italy).
Patients with aneurysms extending distally underwent further ascending aorta and arch replacement with a 28-mm Dacron (DuPont) conduit. The distal anastomosis was performed under circulatory arrest with a tube graft inversion technique as described previously [5].
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The mean ± standard error of the mean (SEM) CPB time was 145 ± 28 minutes, and the mean aortic cross-clamp time was 95 ± 21 minutes. Deep hypothermic circulatory arrest (range, 20 to 22 minutes) was used in 3 patients for distal ascending aorta and arch replacement with a 28-mm Dacron conduit. There were no in-hospital deaths or reoperations for bleeding or tamponade.
All patients underwent postoperative CT of the aorta and echocardiography before discharge. Figure 2 is a representative axial CT section and Figure 3 shows the valved conduit in a CT reconstruction. These confirm the presence of 3 distinct sinuses of Valsalva. The mean ± SEM peak gradient of the aortic valve prostheses was 18 ± 6 mm Hg. The mean ± SEM effective orifice area (EOA) was 2.2 ± 0.3 and 2.4 ± 0.4 cm2 for the 25- and 27-mm prostheses, respectively. In all cases, the valve prostheses were functioning well with no evidence of regurgitation.
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Comment |
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The Bentall procedure is the gold standard for repair of ascending aortic aneurysms and aortic regurgitation. Universal use of mechanical valves is limited by their need for anticoagulation and suboptimal hemodynamics. With improved durability of bioprosthetic valves coupled with their excellent hemodynamic profile, several groups have modified the Bentall procedure to incorporate stentless aortic valves [1, 6, 7]. These were constructed intraoperatively after sizing of the annulus. Intraoperative construction requires an extended cross-clamp time. In addition, imperfectly placed sutures can result in distortion of the valve that might only be identified by TEE upon discontinuation of CPB [8]. The new prefabricated BioValsalva valved conduit eliminates the ischemic time required for the construction of the valved conduit during the procedure and the risk of valve malfunction. Our results show a mean ischemic time of 95 minutes, which compares favorably with other series of Bentall operations [8].
Composite grafts constructed from the first-generation Toronto SPV valve (St. Jude Medical, St. Paul, MN) within a Dacron tube have been shown to have good hemodynamic performance accompanied by good medium-term clinical outcomes [3, 7]. The BioValsalva prosthesis uses an Elan stentless aortic valve that has also been shown to possess excellent hemodynamic performance and clinical results [4, 9].
Bleeding is a significant morbidity associated with the Bentall procedure and can result in the need for reoperation in more than 10% in some series. Earlier ascending aorta replacements were complicated by bleeding from needle holes and anastomotic lines. The BioValsalva prosthesis contains a Triplex vascular graft with an inner woven polyester layer and an outer PTFE layer. The superior hemostatic properties of this conduit can be seen where the valved conduit was anastomosed to a distal conduit in repairs involving the aortic arch; notably, bleeding occurred from the Dacron graft suture holes but not in the valved conduit. In our series, there were no reoperations and little mediastinal drainage.
An added benefit with this vascular graft material is the ease of fenestration with an aortic punch, avoiding the imprecise perforation with electrocautery. Nevertheless, care must be taken to ensure that the valve leaflets are not damaged by the punch, because surface tension can draw the leaflets onto the conduit wall.
Unlike mechanical valves, optimal functioning of biologic valves is affected by the anatomy of the aortic root. The sinuses of Valsalva, in particular, may play a role in enhancing durability of the valves. The presence of the sinuses theoretically reduces the impact of the valve leaflets on the conduit during valve opening, and on each other during valve closure, and may improve blood flow in the coronary arteries [3].
Another major advantage of the BioValsalva valved conduit is the relative ease for explantation if a reoperation is needed because the valve is not incorporated into the suture line of the prosthesis to the aortic annulus. Early bioprosthetic valved conduits were sutured in such a way that both the valve and the vascular graft were incorporated into the anastomosis [6, 10], and in this case, full explantation of the valved conduit is necessary when valve replacement is required. Compared with homograft and xenograft roots, the polyester vascular prosthesis is relatively resistant to calcification and dilation and would not require replacement. Reoperation could therefore be achieved through entering the graft and excising the stentless valve. A new stentless or stented valve could then be reimplanted into a suitable position.
In conclusion, the BioValsalva bioprosthetic valved conduit belongs to a new generation of prefabricated bioprosthetic valved conduits with excellent hemodynamic profiles and hemostatic properties incorporating sinuses of Valsalva. Our series showed that this versatile valved conduit could be implanted easily and safely, using a wide range of techniques, for the replacement of the aortic valve, aortic root, and ascending aorta, with good short-term clinical outcomes.
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This article has been cited by other articles:
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  S. A. LeMaire, S. Y. Green, K. Sharma, C. K. Cheung, A. Sameri, P. I. Tsai, G. Adams, and J. S. Coselli Aortic root replacement with stentless porcine xenografts: early and late outcomes in 132 patients. Ann. Thorac. Surg., February 1, 2009; 87(2): 503 - 513. [Abstract] [Full Text] [PDF]
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 K. Bochenek-Klimczyk, K. K.W. Lau, M. Galinanes, and A. W. Sosnowski Preassembled stentless valved-conduit for the replacement of the ascending aorta and aortic root Interactive CardioVascular and Thoracic Surgery, December 1, 2008; 7(6): 964 - 968. [Abstract] [Full Text] [PDF]
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