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Ann Thorac Surg 2006;81:502-508
© 2006 The Society of Thoracic Surgeons
Section of Cardiothoracic Surgery, James W. Riley Hospital for Children and Indiana University School of Medicine, Indianapolis, Indiana
Accepted for publication August 22, 2005.
* Address correspondence to Dr Brown, Section of Cardiothoracic Surgery, Indiana University School of Medicine, 545 Barnhill Drive, EH 215, Indianapolis, IN 46202-5123. (Email: jobrown{at}iupui.edu).
Presented at the Fifty-first Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 2–4, 2004.
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Abstract |
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METHODS: Since June 2002, 8 patients (7 female and 1 male) between 12 to 46 years of age with outgrown mechanical valves (n = 3) failed MV repair for rheumatic or congenital MV disease (n = 4) and irreparable bileaflet myxoid prolapse (n = 1), underwent PA-MVR. The pulmonary autograft was harvested and replaced using a pulmonary homograft. The autografts were mounted within a woven Dacron graft 6–8 mm greater in diameter than the autograft annulus diameter on a preoperative echocardiogram. The graft's external surface was covered with fresh autologous pericardium.
RESULTS: There were no deaths. Intraoperative echocardiography confirmed a mean MV gradient of 4 mm Hg with trivial (n = 7) or mild (n = 1) regurgitation. Follow-up (range, 13 to 36 months) echocardiography in 4 patients showed no increase in MV gradient or regurgitation. One patient with severe myxoid degeneration and one patient with rheumatic disease, both with systemic hypertension, developed progressive regurgitation due to stretching of a single autograft leaflet producing prolapse. One patient developed a moderate gradient due to retention of excessive native mitral leaflet and subannular chordal tissue. Three of 4 patients have required PA-MVR replacement with mechanical valves 6 to 14 months post-PA-MVR. One asymptomatic patient with mild to moderate mitral regurgitation is being followed after treatment of her systemic hypertension.
CONCLUSIONS: Pulmonary autograft mitral valve replacement offers selected patients a potentially lifelong autologous valve without the need for long-term anticoagulation. The PA-MVR technique deserves careful consideration in younger patients in sinus rhythm. Postoperative systemic hypertension should be treated aggressively to prevent excessive stress on the pulmonary autograft particularly in the early postoperative months.
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Introduction |
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Feasibility of pulmonary autograft aortic and mitral valve replacement was shown by Lower and colleagues in dog studies in 1959 and 1961 [2, 3]. In 1967, Ross, in his original paper [4], described replacement of the aortic valve (Ross I) as well as replacement of the mitral valve (Ross II) with a pulmonary autograft (PA). Yacoub and colleagues [5, 6], after the initial lead of Ross, reported a large series of MVRs using aortic homografts and utilizing a "top hat" surgical technique. Yacoub and colleagues placed the aortic homograft in a short tube of woven Dacron and inserted a pericardial skirt around the proximal end to suspend the supported aortic homograft to the lateral walls of the left atrium, thus creating a false floor in the left atrium.
Kabbani and colleagues [7, 8] modified the Ross-Yacoub technique in 2001 and eliminated the "hat brim" or "skirt-like," "false floor" in the left atrium, using pericardium only to cover the Dacron tube [7, 8]. This obviated the need to suspend the pulmonary autograft above the level of the mitral annulus with a pericardial skirt. Later, the pericardial sleeve was omitted altogether [9]. Due to the concern that soft varieties of Dacron tend to cause obstruction by kinking, it was recommended that the stiffness of the Dacron graft be increased by saturating it with 25% albumin, followed by autoclaving for 10 minutes [10]. The focus of most of Kabbani's recent modifications has been to simplify the technique and yet maintain the normal geometry of the pulmonary valve placed above the mitral annulus.
The excellent durability of the pulmonary autograft aortic valve replacement in several series, including our own [11], coupled with limited but good experience of the PA-MVR by Ross and Kabbani, encouraged us to offer PA-MVR to select patients who have an adequate-sized pulmonary valve (> 18 mm), who have a dilated left atrium(> 5 cm), and who require MVR. The aim of this study is to review our initial experience with PA-MVR.
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Material and Methods |
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Postoperatively, patients received aspirin (81 mg) and low dose coumadin (INR 2) for 6 to 8 weeks. Patients in preoperative atrial fibrillation (patient No. 7 in our series) would undergo a concomitant radiofrequency left-sided Maze procedure before placement of the PA-MVR.
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Results |
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Follow-up ranges from 19 to 36 months (mean, 25.0 ± 6.2 months). Serial echocardiograms in four patients showed no increase in MV gradient or regurgitation (Table 1). Patient No. 2 with severe myxoid degeneration and one patient with rheumatic disease (No. 6) developed progressive regurgitation due to prolapse of a single stretched leaflet of the PA. Both had untreated systemic hypertension that was not well-controlled medically and both required PA-MVR replacement with mechanical valves 6 to 8 months post-PA-MVR. Another patient (No. 5) had worsening of a gradient across the PA-MVR (mean 14 mm Hg) and the autograft was replaced. At reoperation, patient No. 5's annular suture line was stenotic due to retention of excessive native mitral leaflet and subannular tissue. The autograft looked and functioned normally. This unsatisfactory outcome appeared to be the result of technical error at the time of implantation.
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Comment |
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The attention directed to mitral valve repair techniques has significantly decreased the need for mitral valve replacement worldwide [8, 12]. However, reconstructive techniques have far from eliminated the necessity for MVR in patients with complex congenital mitral abnormalities or in patients with rheumatic mitral disease who have either failed repair or are not candidates for repair.
Currently available mitral valve prostheses have many limitations. Bioprosthetic mitral substitutes do not require chronic anticoagulation in patients with normal sinus rhythm, but they are relatively contraindicated in young patients because of their very limited durability and lack of growth potential. In our practice, xenograft valves are reserved for patients beyond 70 years of age or in patients in whom chronic anticoagulation is contraindicated. Mitral valve homografts have not been durable in younger age patients [13]. Bioprosthetic valves also have the relative disadvantages of a high profile stent, and limited effective orifice area in smaller valve sizes. They protrude into the left ventricular outflow in smaller hearts and can cause turbulence, obstruction, and arrhythmia. Mechanical valves are durable, but they require lifelong anticoagulation and, even in spite of therapeutic anticoagulation, have a significant thromboembolic and bleeding rate 25% to 35% over the first 12 to 15 postoperative years. Mechanical valves may also develop pannus formation on the atrial and ventricular surfaces of the sewing ring, which can result in prosthetic valve stenosis (patients No.1, No. 4, and No. 9 in our series) and up to 10% become dysfunctional on follow-up out to 15 years.
Pulmonary autograft aortic valve replacement (Ross I) has given younger patients an option for a potentially lifelong aortic valve prosthesis that does not require anticoagulation and has growth potential. Recently, such a substitute for the mitral position came to our attention when Ross and Kabbani reintroduced the PA-MVR in 1997.
Ross first reported success using the pulmonary autograft for MVR in 1967 in 2 patients [4]. He used the PA-MVR in 6 additional patients employing Dacron collars and a variety of stents to support the autograft in the mitral position, but never reported his expanded experience or patient follow-up until he collaborated with Kabbani in 1997 [1]. In a 1997 paper, he stated that 4 of the original 8 PA-MVR patients had survived for more than 10 years without symptoms or need for any further surgical intervention. Two patients developed subacute bacterial endocarditis and required autograft replacement [7]. No additional patients received a PA-MVR between 1972 and 1997. When questioned why, Ross stated that after 1971 other mechanical and xenograft valve options became available for MVR, making PA-MVR less attractive.
Yacoub and Kittle, in 1969 [5], modified the technique of Ross and placed an aortic homograft rather than a pulmonary autograft inside a Dacron tube for MVR. They placed this short conduit into the left atrium above the mitral annulus and attached the upper end of the conduit to the inside of the left atrium by means of a pericardial skirt [5]. Yacoub and colleagues published these results using this technique using aortic allografts in 1983 in more than 300 patients [14]. The durability of the aortic homograft in the mitral position was not satisfactory in most patients beyond 8 years [6]. Yacoub continued aortic homograft MVR for several more years and implanted this prosthesis in more than 1,000 patients (personal communication).
In the mid-1980s, Elkins replaced the mitral valve with the pulmonary autograft utilizing the Ross technique in 3 patients [12]. All 3 patients survived initially and one lived for more than 13 years before dying of unrelated acute asthmatic respiratory failure. At autopsy, this valve was found to be a nonstenotic, nonregurgitant, viable PA in the mitral position. This supported Ross's observation that the pulmonary autograft placed in a Dacron tube remains viable in the mitral position and has histologically normal appearing endothelium and connective tissue.
Kabbani first published his personal series of PA-MVRs in 1999 [15] and has continued the series to now include more than 80 patients. He has continued to modify and simplify the technique. In 2001, he reported eliminating the pericardial "top hat" and placed the pericardium directly over the woven Dacron graft. He stated that this modification saved time and eliminated the dead space under the pericardial collar, which could fill up with clotted blood and eventually distort the autograft. He conjectured that any future valve replacement would be simpler without the fibrosis that could develop in the "dead space" under the false left atrial floor [8]. In 2004, Kabbani and colleagues [9] reported eliminating the pericardial cover altogether and anticoagulated their patients for 3 months to allow the Dacron to be covered with neoendocardium. If they were in chronic atrial fibrillation they received coumadin chronically. Kabbani's recent report describes his personal series of more than 80 patients operated between 1998 and 2004 in Damascus, Syria [9]. The average age of his patients was 39 years and all but 2 of the patients had rheumatic valvular heart disease. None had prior cardiac surgery. The operative and late mortality was 5% and 12%, respectively. Mean follow-up was 25 months with a range of 6 months to 6 years. At last follow-up 86% of surviving patients are New York Heart Association functional class 1. Six of 66 surviving patients (10%) have less than satisfactory results with moderate regurgitation in 4 and stenosis in 2.
Mitral valve replacement using a mitral valve homograft was introduced by Acar and colleagues [13] in France and enjoyed a brief period of success in the late 1980s and early 1990s. Mitral valve homograft MVR has subsequently faded from popularity due to limited durability secondary to progressive calcification resulting in valve stenosis and regurgitation [16].
The multiple potential advantages of PA-MVR enumerated by other authors are listed in Table 2. However, there are several limitations apparent with this technique. First is the lack of growth potential. The PA cannot grow in diameter inside the Dacron tube, thus eliminating the use of this technique for younger children. A pulmonary valve 16 mm in diameter placed in a 20 to 22 mm graft would give the patient a MV area of 2 cm2. Mitchell and colleagues [17] replaced a thrombosed St Jude Medical valve in a 3 year old child with the PA-MVR implanted inside an 18 mm polytetrafluoroethylene tube and that patient has done well for 4 years. The expected mitral valve area for different sized pulmonary valves is shown in Table 3. Our youngest patient to receive a PA-MVR was 12 years old and her 20 mm pulmonary valve was placed in a 28 mm graft giving her a calculated area of 3.1 cm2.
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Mitral regurgitation due to a connective tissue disorder is a third limitation of the PA-MVR. We would not recommend PA-MVR in patients with any connective tissue disorders such as Marfan or Ehlers-Danlos syndrome. We have been encouraged by the utility and durability of PA-MVR for our small series in all but two patients. The first is a 46 year old male with severe bileaflet prolapse secondary to myxoid degeneration, who underwent PA-MVR and initially had an excellent result. His preoperative afterload reduction was not continued postoperatively and he developed systemic hypertension. Over the next six months he developed a murmur and moderate regurgitation that was confirmed by echocardiography. His autograft was replaced with a mechanical valve because one autograft leaflet stretched and began to prolapse. Histology on the explanted autograft demonstrated myxoid degenerative change.
The other patient who developed significant regurgitation after PA-MVR was a 19 year old female with mitral valve rheumatic disease. She had trivial mitral regurgitation (MR) for the first 3 months postoperatively and at 6 months she had moderate MR. Her afterload reduction medication had been discontinued and she developed systemic hypertension and one of the 3 autograft leaflets elongated and prolapsed, resulting in moderate regurgitation. Her PA-MVR was replaced with a mechanical valve.
Another possible explanation for late development of MR is the fact that a Dacron graft 8 mm diameter wider than the valve was used to support the autograft. A smaller Dacron graft diameter (ie, 4 mm wider) would have given the autograft valve better support and might have prevented prolapse.
Prevention of systemic hypertension has been stressed to our patients after their first two unsatisfactory outcomes. We also plan to reduce the size of the Dacron support in future PA-MVRs.
In summary, we currently recommend PA-MVR for patients with congenital or rheumatic mitral valve disease who require valve replacement and have greater than a 20 year life expectancy, have isolated mitral valve pathology, and who have a left atrium greater than 5 cm in diameter. Presence of normal sinus rhythm or the potential for normal sinus rhythm with the application of a modified Maze procedure is also desirable. This technique for MVR has not been commonly utilized in North America, with only one reported case [15]. We have also used this surgical technique on 2 younger patients (age 6 months and 8 years) as a "bail out" procedure by substituting an aortic homograft for the pulmonary autograft since they had smaller than desirable pulmonary valves for PA-MVR (Yacoub technique).
We have modified the conduct of the PA-MVR operation by harvesting and replacing the pulmonary autograft on an empty, beating heart, which greatly decreases myocardial ischemic time. We feel that PA-MVR deserves consideration in younger patients with isolated MV disease who meet the criteria mentioned above. The PA-MVR is a potentially permanent replacement for the mitral valve, which does not require anticoagulation and may be a valuable option for the management of patients throughout the world with mitral valve disease.
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Notice From the American Board of Thoracic Surgery Regarding Trainees and Candidates for Certification Who Are Called to Military Service Related to the War on Terrorism |
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If you have any questions about how this might affect you, please call the Board office at (312) 202-5900.
Carolyn E. Reed, MD
Chair
The American Board of Thoracic Surgery
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Discussion |
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DR BROWN: Thank you, Gus. It is really an inference. I wish I had more data. The numbers of failures are really quite small. I do know that this patient, when he first came back to see me, was hypertensive with a systolic pressure of 160. I asked his cardiologist to control his hypertension, but the patient wasn't very good about follow-up, which was one of the reasons I wanted to use a tissue valve to begin with. So I don't really know for sure.
My supposition is this: if you look at Ross's initial experience, four of his eight patients live more than 10 years with a functioning prosthesis, Ron Elkins has one or two, and now Kabbani has the majority of his patients, so it seems like the pulmonary valve can last in the mitral position, but there may be these individual variations. I blame myself for either oversizing the Dacron graft or allowing the patients to be hypertensive. I don't know which of those is most important.
DR MAVROUDIS: It is such an important issue that it might not be a bad idea to talk to Kabbani and together perform a multivariate analysis, because those of us who are trying to or are going to be doing this operation need to have that information, and I suspect that it is more than just the blood pressure postoperatively. Thank you very much.
DR ANDREW FIORE (St. Louis, MO): John, very nice presentation. Do you have any information comparing the effective orifice area of the autograft to a mechanical prosthesis?
DR BROWN: Thanks, Andy. The first discussion slide actually puts up the effective orifice area in these patients. It may be too difficult to get to, but an 18 mm valve gives you a 2.5 cm2 valve area; a 20 mm valve gives you almost a 3 cm2 orifice area. There is hardly any valve that we put in the mitral position, be it tissue or mechanical, that gives you a 3 cm2 orifice area. So you get the biggest bang for your buck with the autograft because it is obviously a stentless valve.
DR JAMES A. QUINTESSENZA (St. Petersburg, FL): John, that was an excellent presentation and I think you should be commended for this excellent work and also championing this technique, which truly is something better for our patients. The few patients that we have done, and the one we operated on together, now off coumadin, have a much improved quality of life; I think this should not be underestimated for these patients. I just wanted to compliment you.
DR BROWN: I think maybe it wasn't emphasized enough the fact that having a child or a young patient and a teenager without anticoagulation for the rest of their life is a major plus. We haven't worked out all the kinks with this operation yet but I think if enough of us continue to work, and based upon Kabbani's work, maybe we can learn enough to make this a very consistently successful procedure for the long term.
DR ABDULLA A. ATTUM (Louisville, KY): Why go all the way to the pulmonary valve? How about the stentless aortic valves that are available in the market and are easily available?
DR BROWN: That is a very good question. I think very definitely you could use the stentless, but it is only a temporary valve. What we are talking about is a lifelong valve, something that can last more than 15 years. I think a stentless aortic valve in the mitral position can work and I would use it.
In two of our patients we put an aortic homograft in the mitral position in a child. That will only last for a few years but allowed us to get out of the operating room with a patient that is alive. If you put a stentless aortic xenograft in the mitral position, it will last a period of years, but in a child, probably not 10 years. What I am looking for is a valve that is going to last a child 15 plus years, or for the rest of their life, without anticoagulation.
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References |
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This article has been cited by other articles:
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  A. S. Kumar, S. Talwar, and A. Gupta Mitral valve replacement with the pulmonary autograft: midterm results. J. Thorac. Cardiovasc. Surg., August 1, 2009; 138(2): 359 - 364. [Abstract] [Full Text] [PDF]
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 T. P. Graham Jr The Year in Congenital Heart Disease J. Am. Coll. Cardiol., June 20, 2006; 47(12): 2545 - 2553. [Full Text] [PDF]
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