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Interact CardioVasc Thorac Surg 2008;7:964-968. doi:10.1510/icvts.2008.184457 © 2008 European Association of Cardio-Thoracic Surgery
Preassembled stentless valved-conduit for the replacement of the ascending aorta and aortic root
a Department of Cardiac Surgery, Glenfield Hospital, University of Leicester, Groby Road, Leicester, LE3 9QP, UK Received 22 May 2008; received in revised form 30 July 2008; accepted 4 August 2008
Corresponding author. Tel.: +44 116 2563032; fax: +44 116 2502449.
Here we report the early clinical results of a new preassembled stentless valved-conduit incorporating artificial sinuses of Valsalva (BioValsalvaTM). This new composite conduit incorporates a stentless porcine aortic valve (Elan, Vascutek Terumo, UK) suspended within a triple-layered vascular conduit (TriplexTM, Vascutek Terumo, UK) constructed with sinuses of Valsalva. Between December 2006 and January 2008, 17 patients with the mean age of 65 years underwent aortic valve, root and ascending aorta replacement with the BioValsalvaTM valved-conduit. There was no perioperative mortality. There were no myocardial infarctions, cardiac failure or cerebrovascular events. Mean cardiopulmonary bypass time was 156±56 min and ischemic time was 112±33 min. Eight patients required deep hypothermic circulatory arrest for additional distal ascending aorta replacement. Mean mediastinal drainage was 499±262 ml. Postoperative transthoracic echocardiography and CT-scans of the aorta in all patients before discharge demonstrated well-functioning prosthetic aortic valves with small residual mean gradients, no regurgitation, and the presence of sinuses of Valsalva. In conclusion, the novel prefabricated, composite stentless valved-conduit BioValsalvaTM possesses excellent hemodynamic performance and can be implanted with low morbidity. In addition, the conduit material has good hemostatic properties which reduced bleeding, and is easy to implant with a variety of surgical techniques.
Key Words: Aortic valve replacement; Aortic root; Aortic operation; Valve disease
The replacement of the aortic root, ascending aorta and aortic valve with a valved-conduit, first reported by Bentall and De Bono [1], has become the standard procedure for the treatment of ascending aorta pathologies. Several modifications in techniques have been developed for a range of valved-conduits including mechanical valved-conduits, homografts, root allografts and conduits constructed manually at the time of operation [2, 3]. Today, both short and long-term results of the Bentall procedure are excellent [4, 5]. One of the main drawbacks of using a mechanical valved-conduit remains the need for anticoagulation with its associated complications. The need for bioprosthetic valved-conduits is even more compelling in the imminent era of percutaneous aortic valve replacement, where reoperations can be avoided through minimally interventional procedures. Alternatives to the mechanical valved-conduits include pulmonary autografts, allograft and xenograft aortic roots. Nevertheless, these grafts are limited in length and are not always suitable for replacement of the entire ascending aorta. They are also costly and in limited supply. Their implantation is technically demanding with steep learning curves, and re-operation for these patients poses additional challenges. Stentless aortic valves, on the other hand, are becoming more durable, and have hemodynamic performances which approximate the aortic homograft [6]. Therefore, it seems that a stentless-valved-conduit is the next step in the evolution for the improvement of the surgical outcome of the Bentall procedure. To date, most stentless bioprostheses have been constructed intraoperatively during the ischemic period of cardiopulmonary bypass (CPB), following sizing of the aortic annulus [7], although the use of composites such as the Shelhigh valved-conduit is being increasingly adopted. Manual suturing of the selected biological valve to a Dacron graft is devoid of quality control and vulnerable to technical errors, and is also time consuming, prolonging the ischemic period. The importance of the sinuses of Valsalva for optimal functioning of bioprosthetic valves is also increasingly recognised [8]. Hemodynamically, the sinuses optimise leaflet coaptation, reduce stress on the leaflet edges, help avoid impact of valve leaflets on the conduit wall, and improve coronary flow. Furthermore, the presence of sinuses extending outward helps reduce tension on the coronary button anastomosis. Therefore, a prefabricated, ready to use valved-conduit comprising a stentless bioprosthetic valve with good hemodynamic properties, within a state-of-the-art vascular prosthesis incorporating artificially constructed sinuses such as the BioValsalvaTM (Vascutek Terumo, UK), may represent the next generation for the Bentall procedure. Previously we have reported the design and construction of the BioValsalvaTM stentless valved-conduit [9] and here we report our clinical experience.
2.1. Patients The present study is a prospective, non-randomised, single-centre study. Between December 2006 and January 2008, 17 BioValsalvaTM stentless-valve composite grafts were implanted electively in 17 patients (11 males) by two surgeons (AWS and MG). Informed consent was obtained for all patients in accordance with the General Medical Council (UK) guidelines. The regional ethics committee has confirmed that ethical approval was not required under the NHS research governance guidelines. Patients' age ranged from 45 to 82 years (mean 65±10) and their characteristics are listed in Table 1.
2.2. Conduit The BioValsalvaTM prosthesis has been described in detail previously [9]. Briefly, it consists of a stentless porcine valve Elan (Vascutek Terumo, UK) pre-implanted within a conduit (TriplexTM, Vascutek Terumo, UK) incorporating sinuses of Valsalva. During this study only two sizes, the 26 and 28 mm conduits incorporating 25 and 27 mm prostheses were available. The corresponding diameters of the sinus of Valsalva for these conduits are 32 and 35 mm, respectively. 2.3. Anesthesia and surgical technique Standard anesthesia and surgical techniques were performed. Transesophageal echocardiogram (TOE) was performed routinely in all patients prior to and following separation from CPB.CPB was established between the right atrium and aortic arch with moderate hypothermia (28 °C), or deep hypothermia (17 °C) if circulatory arrest was required. Cold blood cardioplegia in a ratio of 4:1 was used for myocardial protection. A modified Bentall technique with complete resection of the ascending aorta and aortic valve, and reimplantation of the coronary buttons was used in all patients. The sewing ring of the BioValsalvaTM composite conduit was anastomosed to the aortic annulus using a variety of techniques depending on the aortic anatomy as previously described [9]. Briefly, continuous and semi-continuous sutures were used when the tissue was healthy. Interrupted mattress sutures were used when the tissue quality was poor and the annulus calcified. Interrupted mattress sutures were also used when a small aortic annulus was encountered, allowing the implantation of a larger root into the supraannular position; whilst 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 BioValsalvaTM graft using 5/0 SurgiproTM (Syneture, USA). Following 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 ProleneTM (Ethicon, USA) suture reinforced with Teflon felt strips and tissue glue (GlubranTM, GEM, Viareggio, Italy). Eight patients with aneurysms extending distally underwent further distal ascending aorta replacement with a 26 mm or a 28 mm conduit (GelweaveTM, Vascutek Terumo, UK). Continuous data were presented as mean±S.D. Categorical data were expressed as percentages.
3.1. Intraoperative A 26 mm BioValsalvaTM graft was implanted in eight patients and a 28 mm BioValsalvaTM conduit was implanted in the remaining nine patients. The intraoperative data for each patient are summarised in Table 2. The mean CPB time was 167±55 min, and the mean aortic cross-clamp time was 112±33 min. In the subgroup of patients who only underwent a planned Bentall procedure, the CPB time was 148±27 min and the mean aortic cross-clamp 103±27 min. Deep hypothermic circulatory arrest (range 20–41 min) was used in eight cases when extensive replacement of ascending aorta was required. One patient underwent reoperation for bleeding from the side-branch stump of the additional Dacron conduit used for the replacement of the distal ascending aorta.
One patient experienced difficulty weaning off CPB. She had a congenital bicuspid aortic valve with abnormal origin of the right coronary artery and, although there was no evidence of technical error, she was successfully weaned off CPB following placement of a coronary bypass graft to the right coronary artery. There were no intraoperative or 30-day mortality, myocardial infarctions, cardiac failure or cerebrovascular events. Median intensive care unit stay was 1.5±1 day, and in-hospital stay was 12.8±7.7 days (see Table 3). The mean postoperative mediastinal drainage was 499±262 ml. The mean volumes of transfusion for packed red cells, platelets and fresh frozen plasma were 1.4, 0.8 and 1.1 units per patient, respectively. By contrast, three patients did not require any blood product transfusion.
All patients underwent transthoracic echocardiography prior to discharge and computer tomography (CT) of aorta was performed 27±9.7 days after surgery (range 9–39 days). The echocardiographic studies revealed a mean gradient across aortic bioprosthesis of 9.5±3.5 mmHg that is similar to other stentless bioprostheses. In all cases the prosthetic valves were opening well and were fully competent. All CT images demonstrated satisfactory postoperative appearances of the BioValsalvaTM conduit with presence of three distinct sinuses of Valsalva and patent coronary arteries. Patients were followed-up for up to 17 months. As shown in Table 3, during this period there were no deaths, major adverse cardiovascular events (MACE) or conduit-related adverse events. One patient with a thoraco-abdominal aorta aneurysm successfully underwent subsequent repair of the aneurysm four months following the Bentall procedure. Three patients had CT-scan between 6–13 months after operation with satisfactory results and absence of periprosthetic hematomas.
The Bentall and De Bono procedure [1] is the treatment of choice for the management of pathologic conditions affecting the aortic valve, sinuses of Valsalva and ascending aorta. Here we are presenting the clinical results of a novel prefabricated biological valved-conduit which facilitates the implantation and relieves the need for anticoagulation. Early solutions to the problem of a need for Bentall operations with non-mechanical valves included intraoperative construction of a biological valved-conduit [7]. However, attaching a bioprosthesis to a vascular graft requires an extended ischemic cross-clamp time and is subject to technical errors. Indeed, there is no quality control on the de novo construct which represents an additional source of prosthesis dysfunction [10]. Therefore, prefabricated valved-conduit with strict in vitro quality control eliminates both the ischemic time required for the valved-conduit construction and the risk of valve malfunction following insertion. Our results with the BioValsalvaTM prosthesis show a short ischemic time in patients who underwent the Bentall procedure alone, and this compares favorably with other series of Bentall operations [4, 10]. In addition, our early clinical experience shows an excellent hemodynamic performance of the prosthesis that is consistent with the published literature on the Elan Valve [11]. We observed a perfect opening and closing of the prosthetic valve leaflets, without regurgitation and a minimal mean gradient. It may be possible that the presence of sinuses of Valsalva contributes to the optimal functioning of the prosthesis by reducing the impact of the valve leaflets on the vascular conduit during valve opening and on each other on coaptation during valve closure [8]. It has been reported that the presence of sinuses of Valsalva after a Bentall procedure results in improvement of the systolic component of coronary flow [12] and it is possible to argue that such an effect may play a role in enhancing the durability of the valves. Furthermore, the presence of sinuses in the BioValsalvaTM valved-conduit can also facilitate the surgical correction by reducing the need for extensive coronary artery dissection and relieving the tension on the coronary anastomoses. Bleeding from needle holes and anastomosis lines complicated earlier ascending aorta replacements and contributes to the morbidity associated with the Bentall procedure. Certainly, bleeding is the cause for reoperation in between 6% to over 10% in some series [13]. The BioValsalvaTM prosthesis utilises a TriplexTM vascular graft which has very low porosity [14] conferring superior hemostatic properties to the conduit as shown by the small blood volume lost during the postoperative period in the series presented here (mean of 499 ml of the total mediastinal bleeding). The little need for the transfusion of blood products (three patients did not require any) is also a reflection of the hemostatic properties of the conduit. However, one patient had to be reopened because of bleeding, although the source of the bleeding was identified in the side-branch stump of the additional distal Dacron tube and not in the sutures involving the BioValsalvaTM conduit. A potential major advantage of the stentless valved-conduit is the relative ease for explantation in the event a reoperation is required. Both mechanical valved-conduits and homograft/xenograft roots require full-explantation when valve replacement is required. This considerably increases the risk for reoperation [15]. However, since the conduit material is more durable than the valve, any structural deterioration should be corrected with a smaller operation of valve replacement rather than replacement of the entire valved-conduit. This is only possible if the valve leaflets could be separated from the conduit material, and are not incorporated into the anastomosis of 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 [7]. Importantly, the proximal anastomosis of the BioValsalvaTM valved-conduit includes only the vascular graft and, as the valve is not incorporated into the suture line, future explantation of the valve is unhampered. Therefore, reoperation could be a simple matter of entering the graft and excising the stentless valve. A new valve could then be reimplanted into a suitable position. In conclusion, the BioValsalvaTM bioprosthesis represents the prototype for a new generation of prefabricated bioprosthetic valved-conduits that facilitate the replacement of the ascending aorta and the aortic root and has excellent hemodynamic performance and hemostatic properties. Our early results show that this versatile valved-conduit can be implanted easily and safely using a wide range of techniques adapted to the anatomy of the aortic root.
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Abstract
1. Introduction