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Ann Thorac Surg 2000;70:21-24
© 2000 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, University of Lübeck, Lübeck, Germany
Address reprint requests to Dr Leyh, Department of Cardiothoracic and Vascular Surgery, Medizinische Hochschule zu Hannover, Carl Neuberg Str 1, 30625 Hannover, Germany
| Abstract |
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Methods. From 1992 to 1998, 20 patients with acute type A dissection received a valve-sparing aortic root replacement. Two different types of aortic valve-sparing operations were performed: the remodeling technique in 11 patients and the reimplantation technique in 9 patients. Patients were followed for 26 ± 18 months. Echocardiographic studies were performed every 6 months.
Results. There were 2 early postoperative deaths and no late death, no reoperation, and no thromboembolic events. The latest echocardiographic studies of the 18 survivors showed a competent valve in 12 and a trivial aortic valve insufficiency in 6 patients. The mean aortic valve pressure gradient was 4.3 ± 1.3 mm Hg.
Conclusions. These midterm results support the surgical strategy of valve-sparing aortic root replacement in patients with acute type A dissection.
| Introduction |
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Recent modification of operative techniques (remodeling/reimplantation) for repair of chronic aortic root aneurysm with macroscopically intact leaflets have focused on the sinotubular junction and sinus of Valsalva and their replacement [1418]. These techniques are extremely appealing in patients with acute type A dissection as the sinus is frequently involved in the disease process and can be completely replaced by prosthetic material using the aforementioned techniques. This technique provides the advantages of avoiding the shortcomings of the standard surgical techniques, and maintaining the functional integrity of the left ventricular outflow tract, aortic root, and ascending aorta. Because these repair techniques are more demanding than the standard techniques the applicability in the extremely sick patients with acute type A dissection remains debatable and results are limited. The present study was performed to evaluate the midterm results of these new techniques of aortic valve-preserving aortic root replacement in patients with acute type A dissection.
| Patients and methods |
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Postoperatively all patients were evaluated clinically in 6-month intervals at our hospital.
Operative technique
For cardiopulmonary bypass the femoral artery was cannulated in all patients. Standard cardiopulmonary bypass with a membrane oxygenator (Hollow Fiber Oxygenator, Spiral Gold, Baxter, Puerto Rico) at deep hypothermic circulatory arrest (18°C nasopharyngeal temperature) was used in all patients. After performing an open distal anastomosis cardiopulmonary bypass was reestablished after placing an arterial cannula in the prosthesis to establish antegrade flow. Cold crystalloid cardioplegia (St. Thomas Hospital solution) was used for myocardial protection, and retrograde cerebral perfusion for brain protection in 6 patients.
The operative techniques are described in detail elsewhere [1418]. Reimplantation technique in brief: after excision of the sinuses the aortic valve was implanted inside a straight, not tailored, Dacron tube (Hemashield Gold, Meadox Medicals, Oakland, NJ), similar to the implantation of an aortic valve homograft followed by reimplantation of the coronary ostia. Remodeling technique in brief: after excision of the diseased sinuses the end of the sized Dacron tube was trimmed to produce three separate tongue-shaped extensions that were fixed to the aortic annulus at the line of attachment of the cusps followed by reimplantation of coronary ostia. No reduction annuloplasties were performed except for the patient with annuloaortic ectasis who needed plication of the intervalvular trigone between the noncoronary and left coronary sinus. The size of the prosthesis was selected according to the average distance between the commissures. The operations were performed by two senior surgeons (R.G.L. and H.H.S.). The operative data are summarized in Table 2.
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Maximum velocities across the aortic valve were obtained by continuous-wave Doppler using the apical five-chamber view demonstrating the aorta and the left ventricular outflow tract. With pulsed-wave Doppler the sample volume was placed just below the aortic leaflets and recorded at 0.5-cm intervals to the midventricular level where the dropoff of aortic velocities occurred in order to measure velocities and velocity time integrals in the left ventricular outflow tract. The peak systolic gradient across the valve was calculated using the simplified Bernoulli equation:
, where
P is the peak systolic gradient and V the peak systolic velocity across the aortic valve. Pulsed-wave Doppler was also used for mapping the left ventricular outflow tract to assess aortic regurgitation.
Aortic regurgitation was assessed by color-flow Doppler techniques in the standard transthoracic and transesophageal views and graded as follows using the ratio of jet height (JH)/left ventricular outflow tract height (LVOH) [19]:
| Results |
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Patients were followed up from 1 to 75 months (mean, 26.2 ± 18.6 months; median, 21 months). During the follow-up period there were no deaths or reoperations for aortic valve failure or thromboembolic events. Three of 28 patients operated on during the same period with supracommissural tube graft replacement were reoperated on because of acute redissection or aneurysm in the sinus of Valsalva with 1 operative death. In all of these patients the diameter of the aortic root was judged to be normal and the sinus of Valsalva had to be reconstructed using GRF glue during the initial operation, leaving the diseased tissue in place.
None of the patients was on anticoagulation treatment. All patients were in New York Heart Association class I at the latest follow up. Table 3 shows the degree of aortic insufficiency preoperatively and at the latest follow up. None of the patients had more than grade I aortic insufficiency. The mean aortic valve pressure gradient was below 4.3 ± 1.3 mm Hg in all patients. Structural changes of the aortic leaflets were not detected.
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| Comment |
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Supracommissural tube graft replacement of the ascending aorta in conjunction with glue or suture fixation of dissected segments of the sinus in acute type A dissection is the simplest form of repair restoring valve competence and can be achieved in up to 90% of patients [2, 6, 7]. Aneurysms of the sinus of Valsalva and annuloaortic ectasia are contraindications for supracommissural tube graft replacement requiring complete replacement of the aortic root with a composite graft as the surgical standard technique under these circumstances [8, 9].
The validity of supracommissural tube graft replacement has been proven by several authors inasmuch as the freedom from reoperation for aortic valve dysfunction was 91% to 82% after 10 years [2, 7]. Nevertheless, high reoperation rates after supracommissural tube graft replacement have been published recently [10]. Moreover, the incidence of moderate to severe aortic insufficiency after this technique varies between 20% and 45% [6, 7]. There is a growing body of evidence that progression of the disease with subsequent aortic root dilatation may lead to aortic regurgitation due to maladaptation of the aortic leaflets [1012]. In addition, Simon and coworkers [11] found a development of sinus of Valsalva aneurysm in 29% of patients after supracommissural tube graft replacement for acute type A aortic dissection within 44 ± 22 months after operation. The pathophysiologic cause of this phenomenon is not well established so far and may be manifold. In an in vitro study Simon and coworkers [20] showed that prosthetic replacement of the ascending aorta leads to increased stress in the sinus of Valsalva. In conjunction with cystic medial necrosis, which is present in a high proportion of patients with acute aortic dissection, this mechanism may contribute to acceleration of the disease in the aortic root [21].
In a substantial number of patients presenting with acute type A dissection the dissection is not confined to the ascending aorta and involves the sinus of Valsalva. The most common surgical approach of gluing the sinus tissue with GRF glue is a symptomatic approach not dealing with the underlying pathologic problem. Fukunaga and coworkers [22] showed that gluing of dissected tissue is not always a safe method and carries the risk of redissection or aneurysm formation particularly in the proximal part of the aorta necessitating further operation. These results are confirmed by our own series in which a high incidence of aortic root redissection and aneurysm formation within 3 years after supracommissural tube graft replacement of the ascending aorta necessitating emergency reoperations. Concerning this problem we believe that the diseased wall of the aortic root should be resected completely and replaced in patients with acute type A dissection.
Valve-preserving techniques (remodeling/reimplantation) have gained increasing interest in elective cases with aortic root aneurysm and intact valve leaflets. Applying these methods to patients with acute aortic dissection seems to be attractive as these techniques focus on replacing the sinus of Valsalva and the entire ascending aorta, eradicating all diseased tissue. Thus the drawbacks of replacement of the aortic root using a composite graft with mechanical or biological valve substitutes are avoided [8, 9]. Furthermore, long-term anticoagulation mandatory after mechanical aortic valve replacement may impair the spontaneous clotting of the false lumen distal to the repair and thus influence long-term outcome [13, 23, 24].
We demonstrated that in type A dissection and combined root pathology (dissection and/or dilatation) valve-sparing aortic root replacement is feasible with a low combined morbidity and mortality. Two hospital deaths occurred that were unrelated to the surgical technique itself, as echocardiographic studies in these 2 patients performed immediately after the operation demonstrated excellent aortic valve function. The midterm results with respect to valve function and functional capacity are excellent and comparable to electively performed operations. One concern of these novel valve-sparing operations is related to the risk of reoperations due to valve failure, which might be propagated by the disease process involving the leaflet tissue as well as by the stress characteristics after the reconstruction. In a recent study we demonstrated that the aortic root distensibility as well as the opening and closing characteristics are more physiologic after the remodeling technique than after the reimplantation technique [25], which might have consequences on leaflet stress distribution, thus influencing the longevity of the repair. However, the valve function was excellent in all patients regardless of which technique was applied. In this regard the freedom from aortic valve replacement after valve-sparing operations is reported to be up to 97% ± 2% after 6 years [16] and 89% ± 0.5% after 10 years [18].
In conclusion, our data support the surgical strategy of valve-sparing aortic root replacement in patients with acute type A dissection. The intermediate clinical results and aortic valve function were excellent and the rate of reoperation due to newly developed root pathology seemed to be reduced, indicating that this operative method is a valuable alternative to the standard technique. For final judgment of this operative method long-term results are necessary.
| References |
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