Asian Cardiovasc Thorac Ann 2000;8:227-230
© 2000 Asia Publishing EXchange Pte Ltd
Rheumatic Mitral Valve Annuloplasty With Polytetrafluoroethylene Ring
Raja P Akhtar, FRCS,
Masud Ahmad Cheema, FRCS
Department of Cardiac Surgery
Punjab Institute of Cardiology
Lahore, Pakistan
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For reprint information contact: Raja P Akhtar, FRCS Tel: 92 42 666 1017 Fax: 92 42 758 1227 email: rajap{at}lhr.paknet.com.pk 107 B Cavalry Ground Extension, Street 12, Lahore Cantt., Lahore, Pakistan.
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Abstract
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Mitral valve annuloplasty was performed using a supporting strip or ring of polytetrafluoroethylene cut from a vascular graft. From October 1995 to September 1997, this material was used in 42 patients (mean age, 17.5 ± 5.9 years) with rheumatic mitral valve disease. The technique was found to be useful, easy, safe, cost effective, and it preserved the physiological function of the mitral valve annulus.
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Introduction
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Although mitral valve disease due to rheumatic fever is relatively rare in developed countries, it is still the main cause of mitral valve disease in underdeveloped countries such as Pakistan. There is a prevalence of rheumatic fever in rural areas where 75% of our population reside. Most studies on mitral valve repair have been performed in developed countries where mitral valve disease is pre-dominantly degenerative in nature. Recently, repair of rheumatic mitral valves with variable success was reported from South Africa, India, and Brazil.1–3 Mitral valve repair is now the established procedure of choice for correction of regurgitation. Most techniques are based on implantation of a ring device or posterior graft support.2 A limited number of studies have reported long-term results of repair of rheumatic mitral valves.4 A young and predominantly female population and the lack of adequate medical facilities in rural areas prompted us to be more aggressive in conservation of the mitral valve. This has been supported by encouraging long-term results in a 17-year follow-up.2 Satisfactory early results and low reoperation rates after valve reconstruction in children was reported by Kumar and colleagues3 who stressed the importance of proper rheumatic control. We retrospectively reviewed our experience in 42 patients who underwent mitral valve repair.
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Patients and Methods
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From October 1995 to September 1997, 42 patients with rheumatic mitral valve disease underwent mitral valve repair and annuloplasty with a polytetrafluoroethylene (PTFE) strip or ring. There were 32 females and 10 males with a mean age of 17.5 ± 5.9 years (range, 6 to 65 years), 18 patients were 15-years old or less, and mean body weight was 39 kg. The predominant lesion was mitral regurgitation due to rheumatic fever in 36 patients, with annular dilatation in 33, and mixed mitral valve disease in 6. The anterior and posterior leaflets were thickened in 38 patients, there was chordal elongation in 6, subvalvular fusion in 27, and prolapsing anterior and posterior leaflets in 15.
All patients underwent two-dimensional transthoracic echocardiography before the operation, immediately after surgery, and on follow-up at 3, 6, 12, and 24 months. The degree of mitral regurgitation was calculated from the ratio of the regurgitant jet to the left atrial area: grade I (mild), 0% to 20%; grade II (moderate), 20% to 40%; and grade III (severe), > 40%. Chamber size was obtained from M-mode findings. Atrial fibrillation was present in 19 patients (45%).
Ascending aortic and two-stage venous cannulation was carried out, or bicaval cannulation if the tricuspid valve was diseased. Cardiopulmonary bypass was established using a membrane oxygenator and moderate hypothermia with topical cooling and cold antegrade crystalloid cardioplegia. The left atrium was opened posterior to the interatrial groove and the mitral valve was accessed as described by Carpentier and colleagues.5,6 Corrective procedures consisted of the following alone or in com-bination: shaving of the thickened mitral leaflets (30); commissurotomy of fused commissures (10); quadrangular resection of redundant posterior leaflet or triangular resection of the anterior leaflet (6); reattachment of ruptured chordae, chordal transfer, or fashioning of new chordae from Gore-Tex (WL Gore, Flagstaff, AZ, USA) or Prolene (Ethicon, Edinburgh, Scotland, UK) suture (6); shortening of elongated chordae (5); dissection of fused chordae and dissection of subvalvular apparatus (32). These were followed by posteromedial or antero-lateral commissure plasty in 38 patients.
Annuloplasty was performed in all cases to protect the repair. The valve was tested for regurgitation and coaptation of the leaflets by injecting saline into the left ventricular cavity using a syringe. If the repair was satisfactory, annuloplasty was carried out using an encircling PTFE strip or ring prepared from a Gore-Tex vascular graft (WL Gore, Flagstaff, AZ, USA) and sterilized with ethylene oxide. The strip was 15 cm in length, 5 mm in width, 0.6 mm thick, and the center was premarked. It was secured by continuous sutures of 2/0 Ethibond (Ethicon, Edinburgh, Scotland, UK) on 25-mm needles, starting at the center and working towards each end. Excess strip was excised and the slack was removed; the valve was tested again before tying the suture. Such a strip was used in the first 10 patients and a ring was used in the other 32 as it was easily reproducible and measurement was more accurate. The ring is available in 26, 28, 30, 32, and 34-mm sizes. The choice of ring size was based on restoration of the 3:4 ratio between the anteroposterior and transverse diameters of the normal annulus. The ring was sized by measuring the inter-commissural distance, not the intertrigonal distance as with the Duran ring. Carpentier-Edwards sizers (Baxter Healthcare Corp., Edwards CVS Division, Irvine, CA, USA) were used. When the correct size was established, the ring was fixed using multiple 2/0 Ethibond interrupted sutures on 25-mm needles. The left atrium was closed and routine deairing of the heart was carried out before release of the crossclamp. The patient was weaned from cardiopulmonary bypass in the usual manner.
The repair was assessed by palpation of the thrill on the left atrium, measurement of left atrial pressure, and the pattern of the pressure wave. The mean left atrial pressure was 10.8 mm Hg. The mean aortic crossclamp time was 63.9 ± 13.2 min (range, 46 to 101 min) and mean cardiopulmonary bypass time was 95 ± 18 min (range, 63 to 134 min). Associated procedures were tricuspid valve repair in 4 patients, 2 aortic valve replacements, 1 aortic valve repair, and 1 aortic valve assessment. Patients were transferred to the intensive care unit where standard invasive monitoring and ventilation were carried out. Transthoracic echocardiography was performed prior to discharge or in the intensive care unit if indicated, then at 3, 6, 12, and 24 months. Thromboembolic prophylaxis was instituted with warfarin for 3 months with the International Normalized Ratio kept between 2 and 2.5. Afterwards, antiplatelet therapy was prescribed. All patients were started on standard rheumatic prophylaxis with long-acting penicillin injections; in spite of patient education, compliance is a continuing concern.
Data are presented as mean ± standard deviation. Pre-operative and postoperative left atrial size and left ven-tricular diastolic and systolic internal dimensions were compared using Wilcoxon matched-pairs signed-rank tests. If the p value was < 0.05, it was considered significant.
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Results
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The mean intensive care unit stay was 42 hours and mean hospital stay was 8 days. There were 3 hospital deaths (7.14%): a 32-year-old woman with severe mitral and tricuspid regurgitation, died from refractory ventricular fibrillation; a 20-year-old man with severe heart failure preoperatively, died of low cardiac output syndrome; and an 18-year-old woman died of bronchopneumonia. There were 3 late deaths (7.14%): a 14-year-old boy died 6 weeks postoperatively due to arrhythmias secondary to an episode of acute rheumatic endocarditis; an 11-year-old boy died 3 months postoperatively due to cerebral and multiple peripheral emboli secondary to endocarditis; and a 12-year-old boy died 3 months postoperatively from severe mitral regurgitation due to repair failure secondary to endocarditis. Four patients were lost to follow-up. The mean duration of follow-up was 35.22 ± 1.06 months. There were no incidences of thrombo-embolism or reoperation.
Postoperative echocardiography showed trivial-to-mild regurgitation in the majority of patients (Table 1
). Mitral valve areas ranged from 2.8 to 3.4 cm2. There were statistically significant differences between the cardiac dimensions measured postoperatively by transthoracic echocardiography and the preoperative findings (Table 2). Thirty-one patients (74%) were in New York Heart Association functional class I and 6 (14%) were in class II postoperatively, compared to 24 in class III and 18 in class IV preoperatively.
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Discussion
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Thanks to the work of Carpentier, Duran, and Cosgrove, there has been increasing interest in the repair of heart valves. Repair procedures on the mitral valve are reproducible and have almost become standardized. The prevalence of rheumatic mitral regurgitation in the young, especially young females, is a persistent source of concern for cardiologists, cardiac surgeons, the patients, and their families. Faulty anticoagulation control, particularly in patients in remote areas, recurrent attacks of rheumatic activity, and interrupted supply of vital medicines are the factors responsible for tragedies after apparently successful surgical results of valve replacement.
Mitral valve repair is technically more difficult in the rheumatic population, with a high rate of failure due to persistent rheumatic activity because of poor compliance with medical therapy and the inherent complexity of the disease process. In contrast to mitral valve repair in degenerative disease, there is a very high incidence of repair failure in rheumatic mitral valve disease, which is characterized by leaflet fibrosis and retraction. Numerous studies have examined repair procedures stabilized by a rigid ring.6,7,8 It was recently shown that the mitral valve annulus is a saddle-shaped structure that is higher at the anterior and posterior locations and lower at the com-missures. The annulus is a dynamic structure with a sphincter-like mechanism, with a reduction in systole to 80% of its diastolic dimension and counter-clockwise rotation of the posterior annulus.7 Recognition of this function has led to the development of flexible annulo-plasty systems.6,7,8 One of the considerations in developing countries is the high cost of cardiac surgery and prosthetic devices. In view of this, we used PTFE material to support the repair. Stabilization of the repair is of the utmost importance, especially in young patients who are exposed to recurrent attacks of rheumatic fever. The PTFE ring is completely flexible and will not change the saddle shape or inhibit the sphincter mechanism of the annulus. Although Kalil and colleagues2 suggested that rheumatic mitral regurgitation can be effectively repaired without a prosthetic annuloplasty ring, we disagree.
Rheumatic fever is a well-established risk factor for late failure of valve repair.4,9 A reoperation rate of 17.8% with a linearized incidence rate of 1.8% per patient-year was reported for patients with rheumatic mitral valve disease; the actuarial freedom from reoperation was 77.6% at 5 years compared to 94.4% for patients with degenerative disease, and freedom from reoperation at 15 years was 76% in rheumatic patients compared to 93% for those with degenerative lesions.8,10 The predominant cause of reoperation has been regurgitation; repair failure was noted to be due to progressive sclerosis and retraction of leaflets.9 The number of patients in this study was too small and the follow-up was too short to assess the risk of reoperation; there was only one repair failure in a 12-year-old boy who did not take regular rheumatic pro-phylaxis, he developed rheumatic carditis with severe mitral and tricuspid regurgitation and died 3 months postoperatively. Antunes and colleagues1 noted that the reoperation rate was higher below 12 years of age. Duran and colleagues10 reported a 23.6% higher incidence of repair in patients less than 20 years.
We concluded that the PTFE material is effective in supporting the annulus and sufficiently flexible to preserve the physiological function of the mitral valve. It is cheaper than the "physio-ring" or Cosgrove flexible annuloplasty system, which is an important factor in Third-World countries. Strict rheumatic prophylaxis through patient education is important for good long-term results.
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Acknowledgments
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The authors wish to thank Mr. Khawar Saeed, Data Control Manager, Shaukat Khanum Cancer Hospital and Research Centre.
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References
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Kalil RA, Lucchese FA, Prates PR, Sant’Anna JR, Faes FC, Pereira E, et al. Late outcome of unsupported annuloplasty for rheumatic mitral regurgitation. J Am Coll Cardiol 1993;22:1915–20.[Abstract]
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Kumar AS, Rao PN, Saxena A. Results of mitral valve reconstruction in children with rheumatic heart disease. Ann Thorac Surg 1995;60:1044–7.[Abstract/Free Full Text]
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Deloche A, Jebara VA, Relland JY, Chauvaud S, Fabiani JN, Perier P, et al. Valve repair with Carpentier techniques. The second decade. J Thorac Cardiovasc Surg 1990; 99:990–1002.[Abstract]
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Duran CG, Revuelta JM, Gaite L, Alonso C, Fleitas MG. Stability of mitral reconstructive surgery at 10–12 years for predominately rheumatic valvular disease. Circulation 1988;78(Suppl I):91–6.
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Abstract
Introduction
