Ann Thorac Surg 2004;78:60-65
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
The mitral pulmonary autograft: assessment at midterm
Sami S. Kabbani, MD, FACSa*,
Hisham Jamil, MDa,
Abdo Hammoud, MDa,
Jawad Abou Hatab, MDa,
Fawzi Nabhani, MDa,
Ryad Hariri, MDa,
Nada Sabbagh, MDa,
Donald Ross, FRCSa
a Damascus University Cardiovascular Surgical Center, Damascus, Syria
Accepted for publication August 7, 2003.
* Address reprint requests to Dr Kabbani, Damascus University Cardiovascular Surgical Center, Mezza St, PO Box 2837, Damascus, Syria
e-mail: dam-uncv{at}net.sy
Presented at the Video Session of the Fortieth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 26–28, 2004.
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Abstract
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BACKGROUND: There is a dire need, especially in emergent societies, for a mitral substitute that does not require anticoagulation, and is not affected by early degeneration.
METHODS: Between 1997 and 2003, 80 patients had successful mitral valve replacement with a pulmonary autograft. Fifty-five patients were female, and the mean age was 39.3 years. Seventy-eight patients had rheumatic mitral disease and 2 congenital. The autograft was placed inside a rigid Dacron tubing for support, and the right ventricular outflow was reconstructed with a xenograft or a homograft. Recently we have used microwave energy to ablate atrial fibrillation when present.
RESULTS: Intraoperative transesophageal echocardiography revealed adequate mitral valve areas (mean area 2.76 cm2) and acceptable mitral gradients (mean 4.3 mm Hg) in all 80 patients. There was no mitral regurgitation or trace amounts in 61 patients, and mild regurgitation in 19. Operative mortality was 5.0%, and late mortality clearly related to the procedure 6.25%. Follow-up was complete except for 2 lost patients, with a mean of 25 months, and echocardiographic findings were generally stable during follow-up. One patient developed uncritical mitral stenosis and another uncritical stenosis and insufficiency during 4 to 5.5 years. Four more patients had progression of mitral regurgitation from "mild" to "moderate" over a period from 8 months to 3 years. Uncritical xenograft pulmonic stenosis developed in 2 patients. Most of the surviving patients (83%) remain in class I status.
CONCLUSIONS: We believe the pulmonary autograft is a good mitral substitute at the disposal of cardiac surgeons, especially when patients are young and when life anticoagulation is contraindicated or impractical.
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Introduction
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Rheumatic heart disease is still rampant in most countries of the developing world, and the mitral valve is usually its main victim [1]. Attempts at rheumatic mitral valve repair have not been as successful as repair for other mitral pathologies [2], and most rheumatic mitral valves eventually require replacement. The classic substitute, the mechanical prosthesis, is not an ideal option in emergent societies due to the need for proper life-anticoagulation, a feat almost impossible to accomplish among young, poor patients with scanty health awareness [3]. Anticoagulation is also not advisable in pregnancy [4]. Additionally, the mechanical prosthesis has a bulky rigid contour which is not physiologic, and is obstructive in the smaller sizes. The other traditional alternative, the stented bioprosthesis, is notorious for early calcification and degeneration in the generally young rheumatic population [5].
In an attempt to find a suitable substitute for our patients, we have resorted to reviving the Ross concept of replacing the mitral valve with a pulmonary autograft, since July 1997 [6–8]. This report summarizes our experience to date.
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Patients and methods
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Between July 14, 1997, and April 22, 2003, a total of 83 patients with irreparable mitral valve disease underwent mitral replacement with a living pulmonary autograft at our center. Exclusion criteria included patients with associated significant aortic disease, extreme degrees of pulmonary hypertension (systolic pulmonary artery [PA] pressure more than 90 mm Hg), annular mitral calcification, poor left ventricular function (ejection fraction less than 30%), history of a previous cardiac operation and pericarditis found at operation. In 3 early patients the autograft was found to be stenotic at operative transesophageal echocardiography (TEE) and had to be sacrificed; so the total number of patients reviewed was 80. Fifty-five patients were female, and the age ranged between 4 and 64 years (mean 39.3 years).
Three patients were in New York Heart Association (NYHA) functional class I, 36 in class II, 38 in class III and 3 in class IV. All except 2 patients with congenital malformation suffered from rheumatic mitral involvement (31 with predominant mitral stenosis [MS], 11 from pure mitral insufficiency [MR] and 38 from combined stenosis and insufficiency). One of the congenital patients (age 4 years) had a stenotic parachute mitral valve, and the other (age 6 years) had bileaflet prolapse from elongated papillary muscles. Neither could be adequately repaired. Twenty-three patients had significant associated tricuspid regurgitation and 37 patients had insignificant (less than 1.5/4) associated aortic incompetence. Forty-four patients presented with atrial fibrillation. Table 1
depicts the preoperative echo/Doppler data. Twenty six patients underwent cardiac catheterization to rule out associated coronary artery disease.
Operation was carried out under cardiopulmonary bypass. Details of the operation were described in an earlier report [9]. To explore the mitral valve we used a Dubost transseptal approaches early in our experience, but now rely on a standard left atriotomy, except in those cases with a relatively small left atrium (smaller than 5 cm). Once the decision to replace the valve is made, the pulmonary autograft is taken down as in the classic Ross procedure. The prepared autograft is placed within a 2.5 cm tubing of nontreated rigid woven Dacron (C.R. Bard, Covington, GA), marked with 6 equidistant lines. (We presently use the Intraortic Woven Vascular Graft, Meadox, Oakland, NJ.) The distal and proximal ends of the autograft are sutured to the Dacron tubing with a running suture of 5-0 polytetrafluoroethylene or 4-0 polypropylene, using the six marks as guidelines (Fig 1). In the 2 congenital patients, the Dacron tubing was slit open along one side in the first patient and along two sides in the second, to allow for annular enlargement with the growth of the child.
The size of the Dacron tubing encasing the pulmonary autograft is chosen according to the "eye-balled" size of the pulmonary artery. If the pulmonary artery is estimated to be 27 or 29 mm, which is the case in the great majority of patients, a size 30 Dacron tubing is chosen. If the pulmonary artery is estimated to be 25 mm, a size 28 Dacron tubing is preferred. In the 2 children with congenital lesions size 26 tubings were chosen. Occasionally a severely dilated pulmonary artery would require a size greater than 30. In general, sizing has not been a problem, and in no case did we have to reconstruct the autograft/Dacron conduit because of disparity in size.
The mitral valve is excised, preserving valve-papillary muscle continuity as much as possible, and the distal end of Dacron-autograft conduit is sutured to the mitral annulus with interrupted 2-0 polyester sutures.
Early in the series we used autologous pericardium in a "top-hat" fashion to anchor the autograft/Dacron conduit to the atrial wall and cover foreign material. After our 36th patient, the pericardium was used only to cover the prosthetic components of the conduit in order to save operative time and avoid complications experienced with the top-hat model. We found that anchoring the Dacron tubing was not necessary and that a resilient Dacron tube was all that was needed to avoid kinking of the prosthesis [10]. In our last 33 patients, however, we have abandoned the use of pericardium altogether to simplify the operation, and have so far encountered no ill effects related to this latest modification. Figure 2
reveals an operative view of the seated PA autograft/Dacron conduit.
At the completion of procedure the left atrial appendage is excluded, the tricuspid valve is repaired if required and the left atriotomy closed. A transesophageal echocardiogram (TEE) is obtained when myocardial activity is restored. Figure 3
depicts a typical postoperative echocardiogram. Figure 4
reveals a typical postoperative continuous Doppler tracing.
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Fig 3. Transthoracic color Doppler echocardiogram showing laminar flow through mitral autograft in diastole. (AO = aorta; AUTO = autograft; LA = left atrium; LV = left ventricle; RV = right ventricle.)
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Fig 4. Continuous Doppler tracing, calculating mitral valve area by pressure half time method to be 2.6 cm2.
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The right ventricular outflow was reconstructed in our series with a pulmonary homograft in 29 patients, a pulmonary xenograft in 48 patients, and an aortic homograft in 3 patients. Tricuspid annuloplasty was performed in 21 patients. The aortic cross-clamp time varied between 78 and 275 minutes (mean 125 minutes) and has hovered around 100 minutes in the last 33 patients.
Since December 2002, we have used microwave energy to ablate atrial fibrillation either endo- or epicardially (AFx, Inc, Fremont, CA). Four of 5 patients with atrial fibrillation were converted to sinus rhythm by this method.
Follow-up visits were scheduled 1, 3, and 6 months after operation, and then yearly afterwards. We continue to anticoagulate our patients for the first 3 months after operation. Subsequently no form of anticoagulation is used, except in those patients who persist in having atrial fibrillation, where an INR of 2.0 to 2.5 is sought. We also give prophylactic long-acting penicillin to all postoperative patients younger than the age of 40 years.
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Results
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Table 2
depicts our findings at intraoperative TEE. Of a total of 5 early patients demonstrating graft obstruction due to kinking of the soft Dacron tubing encasing the autograft, 2 could be surgically corrected [10], and 3 had to have re-replacement with a mechanical valve. Once we were aware of this potential complication, it did not recur, and we presently employ a Dacron tubing of suitable resilience to prevent it. TEE in all remaining patients revealed adequate mitral valve areas and acceptable gradients. In 2 early patients we had to go back on cardiopulmonary bypass to repair a flail pericardial collar.
Table 3
summarizes intensive care data and events. Two early patients sustained myocardial infarction, one of whom required intraaortic balloon assistance, and is now, 4 years later, the only class IV patient in the series. Intraaortic balloon assistance had to be used on another patient with low cardiac output, who is presently, 5.5 years postoperatively, in class II status. Four patients died in the intensive care due to the causes listed, for an operative mortality of 5.0%. No reason for the cerebrovascular accident in a young man about to be discharged from the intensive care unit (ICU) could be elicited, nor was it possible to obtain an autopsy, but he was one of the patients who had to have postoperative repair of a flail pericardial collar. It is possible that the accident was caused by embolization of a shred of pericardium. There has been no operative mortality or major complication in the last 23 patients.
The median hospital stay was 7 days. Echocardiography before discharge revealed findings similar to those of the intraoperative TEE. The mean estimated PA systolic pressure at discharge was 25.6 (± 9.5 mm Hg). There was only one major wound infection in the series.
Follow-up was complete except for 2 patients who were lost to follow-up because of change of address. The mean follow-up period was 25 months. Events during follow-up included one late (2 months) wound infection, one late (1 month) episode of pericarditis with tamponade, and three episodes of major arrhythmia: atrial fibrillation with rapid ventricular response that temporarily caused acute renal failure; atrial flutter; and supraventricular tachycardia. All these complications were successfully managed.
There were 9 late fatalities. Three patients died of subacute bacterial endocarditis at 1, 6, and 8 months after operation. One patient died of inadvertent bleeding at reoperation for a paravalvular leak 6 months after the procedure, and one patient died of acute cardiac tamponade secondary to excessive anticoagulation 1 month after her procedure. Two patients died of causes apparently unrelated to the operation (septic shock secondary to a urinary tract infection, and excessive vomiting causing a fatal arrhythmia), and 2 died of undetermined causes, 3 and 5 years after their operation. Echocardiography at the last outpatient visit had been reported adequate for the last 2 patients.
Table 4
reveals the last outpatient echocardiographic findings of our surviving patients (excluding the 2 patients lost to follow-up). It is evident that most continue to have adequately functioning autograft valves, with acceptable PA pressures. These findings have remained more or less stable during the period of follow-up, reaching up to 5 8/12 years, except for the following patients. One patient, a 28-year-old woman, has demonstrated, on echocardiography, decreasing measurements of her mitral valve area (from 2.4 to 1.5 cm2), starting one year postoperatively and over a period of 3 years. She remains in NYHA class I, with low mitral gradients and normal pulmonary artery pressures, and in fact became pregnant and uneventfully delivered an infant 2.5 years after her operation. The second patient, a 29-year-old man, had mild MR on intraoperative TEE that progressed to moderate MR starting 2.5 years postoperatively and over a period of 3 years, while his mitral valve area decreased from 2.5 to 1.8 cm2. He also remains in NYHA class I status. Neither of these 2 patients showed clinical or laboratory evidence of rheumatic activity during these changes. Four more patients had some progression of their immediate postoperative MR from mild to moderate over a period from 8 months to 3 years. Two of them have remained in class I status, one patient is presently in class II and one patient in class III. Figures 5A and 5B
depict the actuarial curves for freedom of the PA autograft from MS and MR.
Two patients developed progressive pulmonary xenograft stenosis during follow-up. The 6-year-old child with congenital mitral insufficiency started with a PA gradient of 15 mm immediately after operation, which progressed to 55 mm in 1 year. She remains a class I patient. The second patient, a 45-year-old woman, started with a PA gradient of 20 mm immediately postoperatively, which became 49 mm 2 years later. Her clinical status has changed to class II.
Figure 6
reveals the change in clinical status after operation of all surviving patients (excluding those lost to follow-up). No reoperation on any of the patients was necessary.
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Comment
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We continue to believe that a tissue alternative to the classic mechanical prosthesis should be found in mitral valve replacement, especially in developing societies where anticoagulation is impractical, if not impossible, and where patients are relatively young and women are in child-bearing age [11]. The fact that about one half of the patients with mitral disease suffer from associated atrial fibrillation should not make us resign ourselves to a mechanical substitute, since the danger of thromboembolism from mechanical valves far outweighs that from lone atrial fibrillation. Furthermore, ablation of atrial fibrillation has become available through a variety of approaches [12–14].
Since stented heterografts have proven to be ill-suited for young patients with rheumatic (or congenital) mitral disease, a stentless substitute should be sought. The complete mitral homograft, although attractive, has not performed well over the medium term [15] and has now been discontinued by its chief advocate, Dr. Acar (personal communication, February 2003). Doctor Frater's quadrileaflet pericardial valve (the Quattro) seems to be fairing well at midterm [16], but is not yet commercially available.
We are convinced that the pulmonary autograft is a good option at the disposal of cardiac surgeons when anticoagulation is unsafe. The device is viable, nonthrombogenic, nonobstructive, and accommodates to the changes in contour of the mitral annulus with the cardiac cycle. Sizing has not been a problem, and opening the Dacron tubing along one or preferably two sides allows the autograft to grow with the patient if he or she were a child. Admittedly, it is a two-valve operation and requires a "learning curve," but so is the classic Ross procedure which has proven to be the best operation for young aortic patients. We think the best candidates for the Ross-Kabbani operation are those mitral patients with sinus rhythm, a left atrium greater than 5 cm in diameter, who are younger than 50 years (since beyond that age the quality of the pulmonary autograft maybe in question) and with the least amount of comorbid conditions. It may also turn out that this operation is the best alternative for infants and children with irreparable congenital mitral pathology.
Our follow-up data show that this autogenic substitute is generally stable over the medium term. It is possible that the one patient with progressive postoperative MS, and the other with progressive MS and MR were suffering from the effect of continuing rheumatic activity, known to influence a minority of young rheumatic patients undergoing the classic Ross operation [17], even though no clinical laboratory evidence of such activity had been detected, and even though the 2 patients had been on prophylactic penicillin. Furthermore, it is expected, that some autograft insufficiency will develop in a small percentage of patients at midterm, as is the case with the classic Ross operation [18, 19], and that an even smaller number of those would require reoperation. However, we believe that the development of autograft degeneration in a small proportion of patients should not deprive the majority of the benefits of this operation.
The fate of the right ventricular outflow graft should be the same as that in the classic Ross procedure [20]. It is encouraging that newer PA substitutes are becoming available and will one day delay, or cancel altogether, the need for right ventricular outflow reoperations [21–23].
It is our hope that we will, in the near future, be guided by the algorithm shown in Figure 7
with regard to choosing among the available mitral valve substitutes.
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Acknowledgments
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The authors gratefully acknowledge the assistance of Randa Jaafari in the preparation of this manuscript.
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Top
Abstract
Introduction
= preoperative; 
= postoperative.