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Ann Thorac Surg 2003;75:467-471
© 2003 The Society of Thoracic Surgeons

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Original article: cardiovascular

Valved stentless composite graft: clinical outcomes and hemodynamic characteristics

^a Herz- und Gefaess-Klinik, Bad Neustadt, Germany

Accepted for publication August 21, 2002.

* Address reprint requests to Dr Urbanski, Herz- und Gefaess-Klinik, Salzburger Leite 1, 97616 Bad Neustadt, Germany
e-mail: urbanski{at}kardiochirurg.de

	Abstract

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
BACKGROUND: The valved stentless composite graft has become well established in our hospital for replacement of the ascending aorta and aortic valve in elderly patients and those with contraindication for lifelong anticoagulation. This study was conducted to evaluate the postoperative hemodynamic characteristics and clinical outcomes after implantation of this device.

METHODS: Between November 1998 and February 2001, 45 consecutive patients with a mean age of 69 years underwent implantation of a composite graft using a stentless valve prosthesis (Toronto SPV) incorporated in a collagen-coated Dacron tube (InterGard). The indication for surgery was aortic valve disease with an accompanying true aneurysm of the ascending aorta in 42 patients and a dissection of the aortic wall in 3 patients. Postoperative echocardiographic examinations were performed before discharge from the hospital and at the time of the follow-up. Mean follow-up duration was 18 months (range 3 to 30 months).

RESULTS: There was no perioperative mortality. During follow-up, there were two noncardiac, nonvalve-related deaths. Echocardiographic evaluation before discharge and at follow-up demonstrated favorable hemodynamics of the valve prosthesis with mean transvalvular gradients of 8.5 ± 2.9 mmHg and 8.0 ± 3.1 mmHg, respectively. No regurgitation across the valve and no contact of the cusps with the Dacron tube were seen in any case.

CONCLUSIONS: A stentless composite graft for replacement of the aortic valve and ascending aorta offers excellent hemodynamic results and is a suitable device for patients in whom anticoagulation should be avoided.

	Introduction

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
The increasing number of elderly patients with complex diseases of the aortic valve and the ascending aorta stimulates the search for an ideal biological transplant [1, 2]. Homologous transplants are well suited for the replacement of the ascending aorta but their availability is limited. Biological conduits with a stented valve prosthesis on the other hand are rarely used because of the concern that eventual structural valve deterioration would require complete conduit replacement in a technically demanding operation [3, 4].

With the introduction of stentless biological valve prostheses, another alternative has emerged. These devices are readily available in various sizes without limitations and, in the case of structural valve deterioration requiring reoperation, only the cusps need to be replaced [5–7]. In addition, improved fixation techniques of the biological material encourages the expectation of prolonged durability [8, 9].

In 1998, we introduced a procedure to assemble, intraoperatively, a composite graft consisting of a stentless valve prosthesis incorporated in a sealed woven Dacron (InterVascular, La Ciotat, France) tube [10, 11]. The resulting device has since become well established in our hospital and is routinely used for replacement of the aortic valve and ascending aorta in patients in whom anticoagulation should be avoided. In this study, the postoperative hemodynamic characteristics and midterm clinical results after implantation of this valved composite graft are evaluated.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
Between November 1998 and February 2001, 45 consecutive patients, in whom anticoagulation was not desirable or contraindicated, underwent implantation of a stentless valved composite graft for replacement of the aortic valve and the ascending aorta. All operations were performed by the same surgeon (P.P.U.) The group included 25 men and 20 women with a mean age of 69.0 years (range, 24 to 79 years). A 24-year-old female patient with Turner’s syndrome was the exceptional case among the otherwise elderly group. Preoperative patients characteristics are shown in Table 1.

In the remaining 16 operations, we undersized the valve prosthesis in relation to the Dacron graft. In our study population, tube sizes 30, 28, 26, 24, 22, and 20 were chosen in 2, 25, 13, 2, 2, and 1 patients, respectively.

The xenograft is placed inside the tube graft leaving a free margin of the tube of about 3 to 5 mm in length. The proximal suture ring of the valve prosthesis is fixed to the tube graft with a running mattress suture. Doing this, the small difference in circumference between the tube graft and the valve prosthesis has to be divided evenly to avoid tissue buckling or wrinkling (Fig 1). The free margin of the composite graft is then sewn to the aortic annulus with pledgeted interrupted mattress stitches. Following this, the upper circumference of the valve is sutured to the vascular prosthesis with a second running mattress suture. The graft is then fenestrated, and the coronary artery buttons are reimplanted. Finally, the tube graft is anastomosed to the distal aorta. This anastomosis was performed in an open arch technique in 16 patients using hypothermic circulatory arrest because of partial resection of the aortic arch. An additional coronary artery bypass grafting was performed in 10 patients: in 9 patients due to coronary heart disease, and in 1 because of calcification of the right coronary ostium which made its reimplantation impossible. In 1 patient, mitral valve repair, and, in another, mitral valve replacement, was performed. Tissue glue was used only in 1 patient with acute aortic dissection to approximate the dissected wall layers of the distal aorta. Operative data are shown in Table 3.

View larger version (48K): [in this window] [in a new window]   Fig 1. A virtual transversal view of the composite graft from the proximal end. (A) The outer diameter of the valve prosthesis is perfectly adapted to the inner diameter of the Dacron graft. (B) A possible wrinkling of the valve in case of oversizing (arrow). (C) A possible wrinkling of the tube in case of undersizing (arrow).

Statistical analysis
Values in the tables and text are expressed as mean ± standard deviation unless otherwise indicated. A Wilcoxon test was used to compare transvalvular gradients between patients receiving composite graft with oversized valve prostheses and those with undersized valve prostheses. Overall survival and freedom from valve-related events were estimated by the Kaplan-Meier method. The statistical analysis was performed with the SPSS software (SPSS Inc, Chicago, IL).

	Results

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
No patient died in the hospital or within 30 days after surgery. There was one rethoracotomy for bleeding located at the distal graft anastomosis. The mean blood transfusion requirement was 1.7 ± 1.6 units per patient. Two patients had perioperative neurologic events (minor stroke): 1 patient awoke with a cerebrovascular injury, and an embolic event on the 2nd postoperative day was the cause of a neurologic deficit in another patient. Other relevant early complications were pericardial effusion requiring drainage in 3 patients (6.7%), respiratory failure requiring tracheostomy in 1 patient (2.2%), and heart block or bradyarrhythmia requiring permanent pacemaker implantation in 4 patients (8.9%). The mean postoperative hospital stay was 16.4 ± 10.3 days.

Patient survival and late morbidity
Mean follow-up was 18.1 ± 8.5 months (range, 3 to 30 months) and was complete for all patients. During the follow-up period, there were two deaths caused by pneumonia and craniocerebral trauma, respectively. Of the 43 survivors, 81.4% (35 patients) were in New York Heart Association (NYHA) functional class I and 18.6% (8 patients) in NYHA II at the time of follow-up. Seventy-eight percent (32 patients) had sinus rhythm compared to 86.7% preoperatively. Seven patients (16.3%) were taking warfarin, and 25 patients (58.1%) were on antiplatelet therapy, usually aspirin. There were three thromboembolic events during the follow-up period, two minor and one major stroke. One event occurred early (2 days) and two events occurred late (3 months and 15 months) after surgery. All 3 of these patients had intermittent or permanent atrial fibrillation in common, and were not on anticoagulants at the time of the event. There were no reports of anticoagulant-related hemorrhage.

In 1 patient, prosthetic valve endocarditis was diagnosed 5 months postoperatively. The patient recovered completely after receiving antibiotic therapy and was in NYHA functional class I at the last follow-up.

There were no valve-related reoperations. In 1 case, coronary artery bypass grafting was necessary due to a progressive stenosis of the left main coronary artery.

Actuarial survival and freedom from any valve-related complications are shown in Figures 2 and 3.

View larger version (9K): [in this window] [in a new window]   Fig 2. Overall survival after implantation of the valved stentless composite graft.

View larger version (9K): [in this window] [in a new window]   Fig 3. Freedom from any valve-related complications after implantation of the valved stentless composite graft.

At the time of follow-up, there was a slight but not significant decrease of the mean transvalvular gradient to 8.0 ± 3.1 mmHg, and no aortic incompetence. The valve cusps had no contact with the Dacron tube (Fig 4) and showed no signs of structural deterioration. The outside diameter of the Dacron prostheses determined by echoacardiography is 2 mm bigger on average than the inside diameter published by the manufacturer. Bearing in mind the thickness of the tube wall, this means that there is no relevant postoperative dilatation.

View larger version (86K): [in this window] [in a new window]   Fig 4. M-mode echocardiogram showing the opening of the cusps of the native aortic valve (A) in comparison with a postoperative echocardiogram (B), in which the cusps of the stentless bioprosthesis do not touch the wall of the aortic graft (arrowheads).

	Comment

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

In 1998, Westaby described replacement of the aortic root with a stentless xenograft and a Dacron graft extension to replace the ascending aorta [14]. This technique prompts two concerns. The first is that with a xenograft, as with a homograft, calcification may occur not only in the cusps, but also in the aortic wall, which will make reoperation difficult if a complete change of the valve prosthesis becomes necessary. Secondly, the anastomosis between the wall of the xenograft and the Dacron tube can cause bleeding problems, especially when performed under tension. To prevent this complication, other surgeons have proposed a reinforcement of the suture line with a strip of pericardium [15] or a biological adhesive [16]. These steps can reduce the risk of bleeding but do not facilitate reoperation, an option that the surgeon should always bear in mind, when using a biological conduit.

In the composite graft described in this article, the stentless valve prosthesis is located within a Dacron tube, thereby protecting the vulnerable tissue of the xenograft from tension forces and limiting the potential late calcification to the valve and not the tube graft. In addition, the supraannular placement of the graft allows implantation of tubes with relatively large caliber (89% of patients received tubes equal or larger than 26 mm). This could facilitate later potential valve re-replacement, because we believe that the feasibility of this valve re-replacement is similar to a valve replacement in a case of valve failure after valve-sparing root reconstruction [17].

The stentless biological valve prosthesis placed in a Dacron tube maintains its favorable hemodynamic characteristics without signs of degenerative changes during the follow-up period of up to 30 months. These results are similar to isolated aortic valve replacement with a Toronto SPV biological prosthesis [18].

Considerations for good and lasting postoperative results include the choice of a Dacron graft that does not dilate. Graft dilatation similar to dilatation of the sinotubular junction in the native aorta could lead to progressive aortic valve insufficiency [19]. When implanting the valve prosthesis into the Dacron tube, care has to be taken to avoid deviation of the commissures and tissue buckling or wrinkling as this could lead to progressive structural degeneration of the valve prosthesis [20, 21]. Correct implantation is simplified by the use of a stentless valve prosthesis and a tube graft with the smallest possible difference in diameter. However, small over- or undersizing of the stentless valve does not seem to have an impact on the hemodynamic outcome.

While replacement of the aortic valve and the ascending aorta with a conduit containing a mechanical valve prosthesis has become a standard procedure [22, 23], there is no general agreement on the type of conduit to be used for elderly patients and those with contraindication for lifelong anticoagulation. The composite graft with a stentless biological valve prosthesis, as described, offers an excellent hemodynamic performance and is a suitable device for patients in whom anticoagulation should be avoided.

	Acknowledgments

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 
We thank Silvia Martin for preparing the article and Monica Meyer for reviewing the article.

	References

Top Abstract Introduction Patients and methods Results Comment Acknowledgments References

 

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