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J Thorac Cardiovasc Surg 2003;126:777-781
© 2003 The American Association for Thoracic Surgery
Surgery for acquired cardiovascular disease |
a Division of Cardiovascular Surgery of Toronto General Hospital and the University of Toronto, Toronto, Ontario, Canada
Read at the Twenty-eighth Annual Meeting of The Western Thoracic Surgical Association, Big Sky, Mont, June 19-22, 2002.
Received for publication July 10, 2002; revisions received September 3, 2002; revisions received September 18, 2002; accepted for publication October 3, 2002.
* Address for reprints: Dr Christopher M. Feindel, Peter Munk Cardiac Centre, Toronto General Hospital, 200 Elizabeth Street—14EN-205, Toronto, Ontario,Canada M5G 2C4
Chris.Feindel{at}UHN.on.ca
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Abstract |
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 Top Abstract Patients and methodsResultsDiscussionDiscussionReferences |
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METHODS: Mitral valve surgery was performed in 54 patients (28 men and 26 women, mean age 63 ± 14 years) with mitral regurgitation and extensive mitral annular calcification. Most patients (78%) were in New York Heart Association classes III and IV, 14 had coronary artery disease, and 9 had prior mitral valve replacement in which the calcium bar was not removed. The calcium bar was excised and a new mitral annulus was created by suturing a strip of pericardium onto the endocardium of the left ventricle from lateral to medial fibrous trigones and to the endocardium of the left atrium. The mitral valve was repaired in 12 patients and replaced in 42. In 23 patients the intervalvular fibrous body was reconstructed and the aortic valve was also replaced. Mean follow-up was 4.1 ± 3.7 years and was complete.
RESULTS: There were 5 operative deaths and 11 late deaths. Five-year survival was 73 ± 7%. Four patients needed reoperation and each survived. Freedom from reoperation at 5 years was 89 ± 6%. Three patients had a stroke and 4 had anticoagulation-related hemorrhage, one of which was fatal. Five-year freedom from valve-related mortality or morbidity was 75 ± 8%. Most survivors were in New York Heart Association functional classes II and III.
CONCLUSIONS: Resection of the calcium bar and creation of a new annulus with pericardium provided good clinical results in patients with extensive calcification of the mitral valve.
This study reviews our experience with mitral valve surgery in patients with extensive calcification of the mitral annulus in whom the calcium bar was removed and the annulus reconstructed with either fresh autologous or glutaraldehyde-fixed bovine pericardium.
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Patients and methods |
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TopAbstractPatients and methodsResultsDiscussionDiscussionReferences |
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In 31 patients the calcium bar was limited to the posterior part of the mitral annulus. If the mitral valve was thought to be nonrepairable, it was excised and the calcium bar removed by sharp en bloc dissection. The atrioventricular junction was then reconstructed with a strip of untreated autologous or glutaraldehyde-preserved bovine pericardium by suturing it to the endocardium of the left ventricle with a continuous 3-0 polypropylene suture. The valve sutures were passed through this patch at a level that corresponded to the mitral annulus posteriorly and to the intervalvular fibrous body superiorly. Before a prosthetic valve was implanted, the proximal part of the patch was secured to the left atrium.
For the 12 patients in whom the mitral valve was thought to be repairable, the posterior leaflet was completely detached from the calcium bar from commissure to commissure. The calcium bar was excised by en bloc dissection and the atrioventricular groove was reconstructed with fresh untreated autologous pericardium. The prolapsed section of the posterior leaflet was resected, repaired, and then sutured to the pericardial patch that was used to reconstruct the posterior mitral annulus. Prolapse of anterior leaflet, when present, was corrected by chordal replacement with expanded polytetrafluoroethylene sutures. A flexible annuloplasty ring or a posterior band was used in all patients and was secured to the pericardial patch and leaflets.
Twenty-three patients required circumferential reconstruction of the mitral annulus because of intervalvular fibrous body calcification. The aortic valve was diseased or had been previously replaced in 17 of these patients and was normal in 6. The operation was performed through the aortic root and dome of the left atrium. The aortotomy was extended into the anterior leaflet of the mitral valve and the dome of the left atrium, exposing both the left ventricular inflow and outflow tracts. After complete excision of the calcium bar and the calcified intervalvular fibrous body, a large strip of glutaraldehyde bovine pericardium patch was sutured to the endocardium of the left ventricle from the medial to the lateral fibrous trigones as well as to the left atrium. Approximately two thirds of the circumference of a prosthetic mitral valve was secured to the patch. Then a triangular patch of Dacron or bovine pericardium was sutured to the lateral and medial fibrous trigones, to the remaining superior aspect of the prosthetic mitral valve, and then to the aortic root with a continuous 3-0 polypropylene suture. A separate patch was used to close the dome of the left atrium. An aortic prosthetic valve was implanted in the aortic position by securing it to the native aortic annulus and to an additional patch on the right side of the aortic root. Further technical details including illustrations of these operative procedures have been previously published.2,3
Table 2 summarizes the operative data.
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Statistical analysis
SAS 8.1 (SAS Institute, Cary, NC) was used for all statistical analyses. Descriptive data are reported as the mean ± SD for continuous variables and as proportions for categorical variables. As this is an observational, descriptive study of a complex operative procedure with relatively few patients, multivariable Cox regression analyses to determine the independent predictors of operative and late mortality were not performed. The Kaplan-Meier method was used to estimate long-term survival and freedom from morbid events.
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Results |
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TopAbstractPatients and methodsResultsDiscussionDiscussionReferences |
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There were 10 late deaths: 6 cardiac (congestive heart failure in 2, sudden death in 2, myocardial infarction in 1, and arrhythmia in 1), 1 valve-related (anticoagulation-related hemorrhage), and 3 noncardiac and nonvalvular causes. Survival was 65% ± 8% at 8 years as shown in Figure 1.
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Discussion |
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TopAbstractPatients and methodsResultsDiscussionDiscussionReferences |
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In its most characteristic form, mitral annular calcification manifests itself as a semilunar bar or ring of calcium within the fibrous annulus of the mitral valve. Although the base of the valve leaflet and the adjacent myocardium are affected, there is minimal involvement of the actual leaflet and chordae.1,6 Progressive calcification of the base of the posterior leaflet eventually restricts its mobility and also prevents contraction of the atrioventricular annulus. The submitral calcification pushes the posterior leaflet up toward the atria, often simulating a degree of prolapse, and causes increased traction on the chordae. This may in turn lead to insufficient coaptation of the mitral leaflets and result in further chordal elongation and possible rupture.1,4,9,10
Extensive calcification of the mitral annulus may present a formidable surgical challenge during mitral valve surgery. The patient is at risk from such potentially fatal complications as intractable hemorrhage, atrioventricular disruption, and ventricular rupture. Therefore, it is not surprising that a variety of different surgical techniques have been used to approach this difficult problem with varying results.
In those cases in which the mitral annulus is sufficiently dilated it may be possible to simply removed part of the valve and sew a prosthetic valve of adequate size into position without having to dissect the calcium away from the annulus. Although this may appear to be a safe approach, it is important to ensure that the new valve is sewn into relatively pliable tissues to avoid the development of a paravalvular leak and possible dehiscence. Securing the prosthetic mitral valve sewing ring directly to a calcium bar is almost certain to fail as it likely lead to paravalvular leak and/or dehiscence.
Another approach that may avoid an extensive annular dissection is the technique of intra-atrial insertion of a mitral prosthesis as described by Natafet and coworkers.11 The prosthesis in these patients is modified by enlarging the circumference of the sewing ring with a Dacron collar, which in turn is sutured to the left atrial wall. A limitation of this procedure is the transfer of high left ventricular pressure into the left atrium, which may in turn lead to severe hemorrhage or valve dehiscence. In Natafet’s series of 36 patients in whom the mitral annulus was destroyed due to endocarditis or calcification, the operative mortality was 36%. Furthermore, valve dehiscence subsequently developed in 4 of the 23 survivors.
Some authors have favored limiting the decalcification to the area of repair and reconstructing the fibrous annulus with nonpledget-supported vertical figure-of-8 sutures.12 However, this technique is limited to those cases in which the valve is repairable and the calcification is not extensive.
Annular reconstruction after complete decalcification has been described by different techniques. Carpentier and colleagues6 described reconstruction of atrioventricular junction by a series of figure-of-8 nonpledget-supported sutures placed into the atrial and ventricular edges and tied on the atrial wall. The posterior leaflet is sutured to this edge after valve repair.
In our series, we used a patch repair in all patients as described previously by us and by others.2-4,12,13 The patch technique has the advantage that it can be used when extensive repairs involving the posterior aspect as well the superior aspect of the annulus are necessary. Using this technique we have not seen any long-term failures such as aneurysm formation or dehiscence. Although any patch material can be used, because of their strength we have preferred the use of gluteraldehyde-fixed bovine pericardium or Dacron for reconstruction of superior annulus and intervalvular fibrous body. Repairs of the posterior annulus alone can usually be achieved using the patient’s own untreated pericardium.
As calcification spares the leaflets in most of the myxomatous valves, repair of the mitral valve should be attempted and is the preferred operation.6,12,14 However, severely fibrotic, calcified, and immobile leaflets, heavily deformed subvalvular apparatus, calcification of the entire annulus, and/or extremely fragile tissues remain contraindications for valve repair. In our series of 54 patients, repair was possible in only 12 cases and 2 of these patients required reoperation (16.7%) due to pannus formation and hemolysis. This is in contrast to the normally excellent long-term results with mitral valve repair without annular reconstruction.6,12 At the time of reoperation, the reconstructed annulus was found to be intact and no further decalcification or annular reconstruction was needed before valve replacement.
Patients with extensive mitral annular calcification who require mitral valve surgery may present significant challenges to the surgeon. Although we recommend removal of the calcium bar, this is a major undertaking and should not be considered lightly. In our own institution, patients noted to have extensive mitral annular calcification on angiography are usually referred to the more experienced valve surgeons. If a surgeon is not comfortable with the reconstruction of the mitral annulus, then it might be safer to simply partially excise the valve leaflets and leave enough rim intact to which an adequate-sized prosthesis can be inserted. However, if the annulus is too small for an adequate-sized valve or if there is no remaining tissue to which a valve can be sewn, then patch reconstruction of the annulus will have to be considered. Patch reconstruction of the mitral annulus is an extremely useful adjunct to help avoid dreaded complications of atrioventricular disruption or valve dehiscence. On the basis of our experience we believe that a prosthetic mitral valve can be safely secured into a newly created annulus with very acceptable operative mortality and morbidity as well as good long-term results.
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Discussion |
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TopAbstractPatients and methodsResultsDiscussionDiscussionReferences |
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Older approaches using small prostheses without decalcification have been the conventional way. Large sutures passed through the calcium seemed to have worked fine but I think none of us knows the reoperation rate and the prevalence of paravalvular leakage. Historically, as Dr Feindel indicated there was an explicit prohibition against decalcification of the posterior mitral annulus. In Dr David’s group those methods, taken from treatment of annular abscesses and treatment of infective endocarditis, are used here to replace the annulus and cushion it.
The extent of the disease is indicated by the involvement of the aortic valve in at least 28 patients. Some of these may have had intrinsic aortic disease but at least 6 had normal aortic valves, yet aortic valve replacement was necessary and is a disadvantage of the procedure.
I have several questions: First, considering the extensive nature of this procedure, how does one make the decision to offer operation to such a patient? In the operating room, how does one make the decision to do this extensive decalcification rather than trying to put in a smaller valve with a bulky ring?
Second, there was a rather high incidence of bleeding. Does this reflect in particular disruption in any of the areas where the calcium was debrided, and were there any ventricular disruption patients who did not die but were treated successfully? Also, what is the prevailing attitude toward how to avoid coronary artery disturbance?
Heart block developed in 11 patients, which is an excessive number. What is the relationship of the complexity of the procedure and the calcium bar to heart block, and have the authors learned a way to avoid block in their later experience?
Dr Feindel. Thank you, Dr Karp. I will leave your first question, which I think is the toughest question, for later and answer the other ones, which are a little easier for me.
Most of the patients with the more complex procedures were the ones that required pacemakers, which was not surprising. We do not have any special techniques to avoid it. The main principle is to remove the calcium so as to be able to reconstruct the annulus safely. It is not surprising that heart conduction tissue will be damaged during that.
The other question you asked was about bleeding. In all cases the bleeding was due to coagulopathy because of the long pump runs. Earlier, we were not using aprotinin. We now find aprotinin very helpful in these cases.
The aortic valve was involved in some cases, and even when it was normal it sometimes had to be changed because of the involvement of the entire fibrous skeleton of the heart. We were forced into doing that in those cases.
The most difficult question I think is, When do you decide to do this operation? When you see an angiogram such as the one I showed you at the beginning of the talk, it raises concerns. In our group what tends to happen is that the other surgeons (there are 10 surgeons in our group) will ask either Dr David or me to have a look at the patient. Depending on the state of the patient’s physiology, it may be more appropriate to make an effort to implant a valve without doing any major dissection at all. The key in this situation is to not to do anything with the posterior leaflet, but as you well know we may have to take it out. Once we start working at the calcium bar, things start to fall apart pretty quickly and we are forced into excising the entire area. This also is obviously a major concern if the circumflex artery is in that territory. I have had 1 case in which I had to bypass the distal circumflex. Fortunately, intraoperative echocardiography detected the wall dysfunction and we were able to resolve the situation with bypass.
Dr Kent Jones (Salt Lake City, Utah). Dr Doty should be asking this question. He has more experience in it than I do. A lot of the patients that we see with mitral valve annular calcification do not have this discrete calcium bar that you describe, especially patients who have renal failure with a high calcium turnover. They almost have a calcified endocardium, with the calcium extending onto the atrial wall as well as down onto the ventricular wall. We have been using a high-frequency ultrasonic nebulizing device that the orthopedic surgeons use. It works quite well to decalcify that material, and it leaves the muscle and the annulus disturbed. One is able to decalcify the entire endocardium as well as the annulus and then insert a pericardial patch, as you have described. My question is, Have you had any experience with that type of device?
Dr Feindel. We certainly have not had experience with this device. I think that is an excellent idea. In those patients I admit we tend to try to insert a valve without dissecting anything because we believe that the heart is going to fall apart otherwise. However, I think this sounds like a superb idea. I am surprised that it comes out of the muscle that easily without much damage, although when we take calcium off the anterior leaflet of the mitral valve when doing aortic valve surgery, it tends to peel off quite well.
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