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a Hôpital Bichat, Service de Chirurgie Cardiaque, 46 rue Henri Huchard, 75018 Paris, France
b Service de Cardiologie, Hôpital du Taaone, BP 1640, Papeete, Tahiti, France
Received 11 October 2007; received in revised form 28 January 2008; accepted 31 January 2008.
* Corresponding author. Tel.: +33 1 40 25 80 80; fax: +33 1 40 25 80 80. (Email: Thomas.joudinaud{at}bch.aphp.fr).
| Abstract |
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Key Words: Homograft Redo surgery Valve disease Aortic valve Surgical technique
| 1. Introduction |
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During reoperation, degenerative and infective lesions, such as scars and calcification of the aortic homograft implanted as a root, may be responsible for increased technical difficulties. Aortic valve replacement in patients who have undergone previous aortic root replacement with an aortic homograft remains a challenging reoperation. We therefore evaluated our experience with aortic homografts as a root redo surgery to determine reoperation events.
| 2. Patients and methods |
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Indications for repeat aortic surgery were homograft degeneration in 18 patients (90%) and endocarditis in two patients (10%). Five patients (25%) presented with a stenotic aortic homograft and a gradient of 33.2 ± 18 mmHg. Seven patients (35%) had aortic insufficiency (2.9 ± 0.6), and the remaining eight presented with mixed pathology. In all cases, the echocardiographic view of the aortic homograft showed either tears and/or calcifications of the cusps. Seven patients (35%) presented with complete aortic homograft calcification including the wall of the root.
Of the 20 patients, seven patients were undergoing their third or more operation. One patient had a mechanical aortic valve implanted on an aortic insufficiency, one patient had an aortic homograft implanted with the freehand technique, two patients underwent aortic valve repair, and the remaining three had a mitral valve repair prior to the implantation of the aortic homograft as a root. Homograft implantation was primarily performed in our institution in 13 cases. Indications for aortic homograft implantation were: endocarditis in 12 patients (60%), aortic insufficiency in seven patients (35%) and aortic dissection in one patient (5%). Endocarditis had occurred on a rheumatic aortic valve in eight patients (40%), on a mechanical valve in one patient (5%), on a previous aortic homograft implanted with the freehand technique in one patient (5%) and on a bicuspid aortic valve in two patients. The seven patients with aortic insufficiency suffered from rheumatic disease and the last patient with aortic dissection had Marfan disease. Patients characteristics are reported in Table 1 .
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In patients who presented flexible homograft wall, the homograft leaflets were excised and aortic valve prosthesis was sutured along the homograft annulus.
2.3 Follow-up and statistical analysis
Early follow-up was performed retrospectively by analyzing surgical files including echocardiography and long-term follow-up was carried out by mail or telephone contact.
Numerical variables were expressed as mean ± standard deviation. Ninety-five percent confidence intervals were computed for the categorical variables if suitable and statistical associations between categorical variables were analyzed with Fisher's exact test. Event free survival curves were made with the Kaplan–Meier method. A value of p < 0.05 was considered as significant.
| 3. Results |
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In patients who presented with major homograft wall calcifications or endocarditis, nine aortic root reconstructions were performed (Bentall-De Bono procedure n = 7; homograft implantation n = 2). Fig. 1 shows a picture of an explanted aortic homograft with major calcification. In case of a flexible homograft wall, stented prostheses (mechanical n = 10, bioprosthesis n = 1) were implanted along the homograft annulus. In one case, the surgeon could not reimplant the right coronary button and had to perform a right coronary bypass.
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Cardiopulmonary bypass time and aortic cross-clamp time were 163 ± 65 min and 104 ± 40 min, respectively. Characteristics of surgery and postoperative period are reported in Table 2 .
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Perioperative complications occurred in 35% of patients: sternal re-entry accident (10%); early reoperations for excessive bleeding and/or signs of cardiac tamponade (10%); reoperations for mediastinitis (5%); renal insufficiency necessitating dialysis (5%). One patient needed a permanent pacemaker for complete heart block (5%). Confidence intervals of 95% for postoperative complications are reported in Table 3 . We were not able to find any association between operative procedures and postoperative complications with Fisher's exact test (Table 3).
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3.3 Survival
Follow-up was complete. Mean duration of follow-up was 2.1 ± 1.9 years (range: 74 months; 6 months). Fig. 2
shows Kaplan–Meier curves of the free-from-event survival for all patients as well as for survivors at the time of surgery. Cumulative free-from-event survival was 84.7% for all patients and 94.4% for the survivors at 74 months. One patient was reoperated on three months after redo procedure. An aortic homograft had been implanted in this patient for a Bartonella endocarditis. He presented a degenerated homograft with tears of the right coronary leaflets and was reoperated on 54 months later. The redo procedure consisted of implanting a stented bioprosthesis sutured along the homograft annulus. Three months later the patient presented with a large paravalvular leak necessitating a reoperation. The surgery consisted of the implantation of a stentless aortic valve (Cryolife, OBrien 23) inside the homograft root. The patient was also treated for active Bartonella endocarditis with no bacteriological evidence. At 2 years, the patient was free from reoperation. There were no others complications during follow-up.
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| 4. Discussion |
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Suboptimal durability is the most important factor leading to reoperation. Homograft degeneration is a long-term process and usually leads to leaflet perforation, fibrosis and calcification [10]. Patient's young age or donors older than 65 years were identified as the two risk factors that most likely contribute to degeneration [4,11]. Aortic stenosis or insufficiency due to calcification and tears are the usual degenerative ways and were common among our patients [12,9]. Most of the authors recommend early surgery of the failing homograft in order to limit the consequences on the left ventricle [11–14] and thus, regular follow-up of the patient is needed to assess left ventricular function. Table 4 shows reoperation causes of aortic homografts in the literature [4,10,12,15,16]. Our study results support these reports, and indicate that the degenerative process was the primary reason for reoperation. As in our patients, infection is the second cause of aortic homograft reoperation.
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The best surgical technique to avoid failure of an aortic homograft is to implant it as a functional unit (e.g. root replacement). This method decreases the risks of geometrical distortion due to technical error [4,6,17]. However, reoperating an aortic homograft implanted as a root may present technical difficulties. Besides the sternum reentry, the difficulties of the reoperation are due to the homograft calcification [18]. The calcification may affect the cusps, the homograft annulus and the homograft wall. Calcification can be so extensive that the aortic root becomes completely rigid. Thus, the strategy of the reoperation depends on the degree of homograft calcification. Eleven patients in our series presented minor calcifications of the root. In these cases, it was possible to dissect the flexible wall of the homograft and replace the aortic valve in the homograft. In case of major calcifications and a rigid wall of the homograft, the surgeon has to perform a root replacement (e.g. Bentall-DeBono procedure) [8,13,18]. We applied this strategy in seven patients who presented major calcifications of the root. Interestingly, as previously reported, the coronary buttons which constituted the native aortic wall, were never calcified and always remained flexible [12].
The indications of redo surgery (degeneration or endocarditis) and numerous other factors (such as timing of reoperation, emergency surgery, age of the patient, comorbidities, associated procedures and left ventricular function) influence the prognosis of redo aortic valve replacement. In the literature, redo aortic valve replacement presents less risk than redo aortic root replacement [19,20]. Davierwala et al. [19] reported 1.7% mortality in redo elective aortic valve replacement and in their study; mortality was not statistically related to redo surgery. In aortic root re-replacement, mortality between 8% and 12% was reported [21,22]. In the literature, perioperative mortality for aortic homograft redo surgery is reported as between 3% and 8% [9,11–13]. Kumar et al. [13] did not identify in their series an association between perioperative mortality and homograft redo surgery. In our series, we report two perioperative deaths (10%) and seven patients who presented perioperative complications. This high percentage of complications might be explained by the concomitant procedures. However, we did not find any statistical relationship between operative procedural characteristics and postoperative complications. The 95% confidence intervals computed for reopening surgeries or for all complications according to the procedure performed were always very large. Thus, these negative results were mainly a consequence of the small number of patients and clinical relevant difference cannot be excluded.
We reported two sternal re-entry accidents. In each patient, the saw blade tore the aorta adherent to the sternum. The femoral vessels were cannulated and the chest opened under hypothermia (18 °C) during circulatory arrest. This technique is described for the surgery of a false aneurysm of the ascending aorta [15]. In some cases, a CT scan or a lateral chest X-ray shows the retro-sternal space and allows the surgeon to adapt his strategy [12].
The aortic homograft redo-surgery remains a high-risk procedure compared to an elective aortic valve re-replacement. The degeneration of any aortic homograft is inevitable and at the time of initial implantation the surgeon must anticipate the reoperation. When comparing aortic homograft and mechanical prostheses, Kilian et al. [16] reported a higher rate of redo surgery in the homograft group.
The aortic homograft, due to its great resistance to infection, gives a clear advantage in endocarditis [5,23]. According to the literature, aortic homografts present a small but constant infection rate [24]. Only two patients in our series were reoperated on for homograft infection. They presented with an abscess of the homograft annulus and we chose to implant a new aortic homograft. In patients who present annular abscess or prosthetic infection, the left ventricular outflow tract and the aortic root can be reconstructed with the aortic homograft. An abscess along the aorto-mitral junction can also be covered by the appending mitral leaflet of the aortic homograft [23]. Considering these reports, aortic endocarditis with annulus abscess or extensive prosthesis infection should be the main indications for aortic homograft implantation.
| 5. Limitations of the study |
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| 6. Conclusion |
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Late reoperation for failing aortic homograft implanted as a root remains a high-risk procedure. Considerable debate has surrounded the ideal methods of homograft implantation, with root replacement predominating from 1990s. However, subcoronary technique allows preserving the native sinuses and may facilitate an inevitable redo surgery. This more demanding and time-consuming technique requires precise matching of the valve size and root to avoid early failure [6]. A recent report of subcoronary implantation of aortic homograft presented extremely favorable early and late mortality, freedom from surgical reintervention and freedom from endocarditis [25]. Considering this report and the difficulties in redo surgery of aortic root homograft, the debate about subcoronary implantation may start again. Endocarditis with annulus abscess or major prosthesis infection should be the main indications of aortic homograft implantation as a root.
| Appendix A |
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Dr C. Yankah (Berlin, Germany): I would like to stress the predictive factors for reoperation in relation to the patient and donor age as well as matching of the homografts. It appears you didnt analyze that. It is well established that younger age is a predictive factor for early calcific degeneration of allografts, whilst formation of clots between the homograft and the native aortic wall could also accelerate early degeneration. These three factors, younger age, homograft mismatch and clot formation accelerate structural deterioration and early reoperation.
Removal of the calcified allograft aortic root is the most challenging at reoperation and your resection technique using electrical cauter is applicable when there is soft tissue.
My first question is whether you experienced a-v block in your series with this resection technique. How many patients required pacemaker?
My second question: Did you have in your series allograft-patient size mismatches which could be a cause for early degeneration and whether this might also change your clinical practice in the selection of allografts according to age and size.
My third question relates to inflammatory tissue reaction or immune response, whether you are anticipating using anti-inflammatory drugs postoperatively to minimize or control postoperative inflammatory tissue reaction, which is also a factor for developing early degeneration.
Dr Joudinaud: For the first question, I actually agree with you, the younger the patient the faster is the degeneration. And our rate of degeneration, we had to reoperate on these patients seven years later, which is a little less than 10–15 years, because they were young.
For the use of an agent to reduce the degeneration of our homografts, I am not aware of any use of it. My report was mostly focused on how to perform the operation easier.
Dr Yankah: Of course in using this tissue one has to also know the risk and also the future development. I just want to ask you whether you will be anticipating using these drugs at least to delay early degeneration? I mean, you cant avoid degeneration but you might delay it, especially in the younger age group.
Dr Joudinaud: That is true.
Mr S. Westaby (Oxford, UK): Just a comment before John Pepper asks his question. I used to do a lot of aortic homograft surgery and enjoyed it a great deal. I have a homograft lab. But I have been extremely disappointed with the durability of aortic homografts given the early optimistic view of the durability of homografts. I can see Fred Mohr nodding his head. He seems to agree. What do you think, John? I will ask you a question.
Dr J. Pepper (London, UK): Yes, I think it is disappointing.
I enjoyed your analysis, but when you place the aortic valve inside the homograft where the calcification is very minimal, two questions related to that. One, do you critically assess the possibility of patient-prosthesis mismatch and do you think that that is a situation that would really be ideal for percutaneous aortic valve replacement, or I should say transcutaneous valve replacement?
Dr Joudinaud: The first question, for the mismatch, yes, we try to assess the mismatch. That is why we had to perform a Konno procedure on one of our patients. And the second question, I think to move on with a percutaneous valve and a transapical valve in patients who are 30 years old is probably a little bit too early. We are presently doing 90-year-old cases. We performed last week in Paris our first case of transapical aortic valve replacement and the patient was 93 years old, and it was a redo of coronary artery bypass grafting. So between these patients, most of them from Tahiti, who are living on a very small island in the remote part of the world, we cannot go for them with a percutaneous valve. There will be no follow-up, and I dont think it is ethical at that time. It may come, you know, it may come, and there is a lot of money being put that way, and it may happen. It will be the new surgery. I dont know.
Mr Westaby: I think we could possibly leave this paper with the question, given the excellent valve prostheses now available, is the aortic homograft and its questionable durability an ideal solution for primary aortic valve replacement? That question is open.
| Footnotes |
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Presented at the 21st Annual Meeting of the European Association for Cardio-thoracic Surgery, Geneva, Switzerland, September 16–19, 2007. | References |
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