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Eur J Cardiothorac Surg 2007;32:301-307. doi:10.1016/j.ejcts.2007.05.008
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved
Department of Cardiovascular Surgery, University Hospital, Lausanne, Switzerland
Received 4 December 2006; received in revised form 26 April 2007; accepted 14 May 2007.
* Corresponding author. Address: Service de Chirurgie Cardio-Vasculaire, Centre Hospitalier Universitaire Vaudois, rue du Bugnon 46, CH-1011 Lausanne, Switzerland. Tel.: +41 21 314 2921; fax: +41 21 314 2278. (Email: Patrick.Ruchat{at}chuv.ch).
| Abstract |
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Key Words: Mitral regurgitation Mitral valve repair Risk factors Reoperation Univariate and multivariate analysis
| 1. Introduction |
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| 2. Patients and methods |
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Mitral valve was exposed through standard left atriotomy. Valve analysis after Carpentier's functional classification showed normal leaflet motion (type I) in 37 patients (21%). A majority of patients (n = 131, 75%) had posterior leaflet prolapse with rupture of one or more chordae (type II). Finally, restricted leaflet motion (type III) was diagnosed in seven patients (4%). Repair technique was basically standardized with quandrangular resection of prolapsing posterior leaflet and annulus plication with 3–0 Prolen suture without sliding plasty; annuloplasty was carried on with Carpentier–Edwards ring. An annulovalvuloplasty was performed in 122 (70%) patients, an annuloplasty alone in 35 (20%) patients, and valvuloplasty without a prosthetic ring in 18 (10%) patients because posterior annulus was found nondilated during routine valve inspection. In 57 patients (32%), another cardiac procedure was associated to MVR, 30 (17%) had coronary arterial bypass graft (CABG), 23 (13%) had a complementary valvular procedure, and 4 (2%) had both CABG and a valvular operation. In the immediate postoperative period, all patients were anticoagulated with moderate IV heparin dosage followed by oral anticoagulation with acenocoumarol (Novartis, Basel, Switzerland) for 3 months, unless patients had another prosthetic valve or chronic atrial fibrillation which indicated anticoagulation indefinitely. Operative events were defined as those occurring within 30 days after surgery or longer if it was during the same hospitalization. Quality of the repair was considered successful when the early transthoracic echocardiography showed only a trivial residual mitral valve incompetence (MVI) of 0–1/4, acceptable when the echo score was 2/4, and failed when the score was 3–4/4.
2.3 Follow-up
Data on long-term outcome were obtained by questionnaires addressed one-time to the physician in charge of the patients (response rate 82%) and by phone interview with all living patients and family or neighbors in case of death. Further information about complications was obtained from hospital reports and death certificates from the Swiss Federal Office of Civil Status. In the end, 8 among 175 patients were definitively lost. Follow-up was thus 95.4% complete and represented 728 patients-years with a mean of 8.7 years and a range from 2.3 to 18.1 years.
We used the published guidelines for reporting valve-related morbidity and mortality after cardiac valvular operation of the STS/AATS [7]. Adverse valvular events reported were all clearly cardiac, sudden death, or reoperations due to valve-related complications.
2.4 Statistical analysis
Data analysis was done on an intention-to-treat basis and was performed using a JMP statistical software package (JMP v. 5.1) from the SAS Institute Inc. (Cary, NC 27513, USA) on a Macintosh computer. Continuous variables were provided as mean ± SD and compared with Student's t-test for parametric and Wilcoxon for nonparametric variables. Categorical data were analyzed univariately by
2-test or Fischer's exact test. Actuarial survival and freedom from reoperation were calculated by the Kaplan–Meier method and were univariately compared using the log-rank statistic. To identify significant independent risk factors influencing late mortality, all factors with a significance less than 0.1 were entered into multivariate analysis. Risk ratio and 95% confidence intervals were calculated using a Cox proportional hazards model. A p-value of less than 0.05 was then considered statistically significant.
| 3. Results |
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3.2 Late mortality
The overall mortality was 12.6% (22/175). Six patients had died perioperatively which left 169 patients for long-term follow-up. There were 16 late deaths (9.1%). Kaplan–Meier actuarial analysis showed a 96 ± 1% 1-year survival, 88 ± 3% 5-year survival and a 69 ± 8% 10-year survival. Most patients who died were in NYHA class III and IV and 75% were cardiac-related deaths with eight terminal ischemic cardiopathies, two sudden deaths, and two cardiac failures (Fig. 2
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Significant factors for reoperation risks are summarized in Table 3 .
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| 4. Discussion |
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The main finding of this study is the identification of perioperative factors associated with a suboptimal long-term outcome, which help perioperative decision making to improve management in complicated settings. The etiology of MR plays a major role. We have shown that degenerative MR is a factor influencing positively late outcome, while ischemic (IMR) and functional mitral regurgitation (FMR) both act negatively on long-term prognosis. Ischemic mitral regurgitation is the second most common cause for mitral surgery in Western countries with a strong impact on late survival. In our cases, repair was performed because of annular dilation, while in patients with altered leaflet motion the valve had been replaced. IMR remains the subject of much debate and important insights have been gained only recently in the underlying pathophysiological mechanisms of the condition. It has been proved that annular dilation is only one of the causes of IMR, while leaflet tethering, papillary muscle displacement, and ventricular remodeling play major roles. In a study comparing repair versus replacement, late mortality was not statistically different with an overall survival probability of 67 ± 7% at 5 years after repair versus 73 ± 9% after replacement [6]. In fact, in IMR, the long-term survival is dependent on preoperative left ventricular conditions and underlying pathophysiologic mechanisms like preoperative ejection fraction and preoperative pulmonary hypertension, rather than the choice of operative procedure [13]. It is noticeable that revascularization alone does not eliminate the negative long-term effects of even mild IMR [14].
Functional mitral regurgitation, defined as the failure of the mitral valve to prevent systolic backward flow in the absence of significant structural or intrinsic valvular disease, has been associated in 11 (48%) out of 23 patients with aortic valve replacement for aortic stenosis. Few papers deal with this problem. Ruel et al. [15] showed that significant FMR (>2+), increased aged, decreased ventricular function, and atrial fibrillation all had independent adverse effects on mortality. This demonstration pleads for a major part of increased risk of mortality found in our study with FMR.
Our study also confirms that despite preservation of the mitral apparatus, left ventricular dysfunction remains a major cause of poor short-term evolution for older patient suffering from bad cardiac function represented by low LVEF or residual functional class III and IV, and lower late survival by old patient with associated valvular operation or coronaropathy [16].
4.2 Reoperation
In patients with degenerative mitral valve disease, valve repair using Carpentier's technique is the gold standard for surgical correction of mitral regurgitation and has provided excellent long-term results. Braunberger et al. [5] recently reported the very long-term results of valve repair in non-rheumatic mitral valve insufficiency. In patients with isolated posterior leaflet prolapse, 10- and 20-year freedom from reoperation was 98.5% and 96.9%, respectively. In those with isolated anterior prolapse, it was 86.2% and 86.2%, respectively. Finally, in bileaflet prolapse, it was 88.1% and 82.6%, respectively. These data confirm the excellent results of Carpentier's standard techniques of repair and their stability over a long period of time. As this study reflects the beginning of our experience, most repair was done in isolated posterior prolapse and chordal rupture. Our good results are comparable with those of Perier et al. [17]. Although repair durability is good in these patients, some will require late reoperation for recurrent mitral valve dysfunction. Causes of failed mitral valve repair may be classified as procedure-related (suture dehiscence, incomplete initial operation, rupture of previously shortened chordae) or valve-related (progressive disease, endocarditis). Numerous studies have documented a high proportion of procedure-related repair failure and few like Flameng et al. [18] reported on valve-related linearized rate of failure. These authors showed that only 50% of patients remain free from more than trivial mitral incompetence at 7 years after repair. Their linearized recurrence rate of regurgitation >1/4 of 6.9% per year and of regurgitation >2/4 of 2.5% per year were comparable with our rate of recurrence >2/4 of 1.6% per year. These findings strongly suggest a progression of the degenerative process with time. This is not surprising because myxoid changes are not entirely acquired but also genetically determined. Pathophysiological findings like glycosaminoglycans content of valve cells may help to explain why a progressive incidence of MR is found after initial adequate repair [19].
Residual regurgitation at intraoperative echocardiography has been identified by Mohty et al. [10] as an important factor associated with significantly increased risk of reoperation. In the present study, we found that residual regurgitation larger than grade 1/4 at routine postoperative TTE, absence of prosthetic ring insertion during the procedure and age younger than 60 years old were all independent predictors of late redo mitral valve surgery. Albeit, all patients who needed a reoperation had a degenerative etiology, this factor was not an independent predictor in our multivariate analysis. In the beginning of our experiment we did not check repair with perioperative ETO, and only failure were given in postoperative echocardiographic investigations. Since 1992, routine use of perioperative ETO helped the surgeon to select patients for mitral valve repair and gave immediate checking for quality of repair. Anterior leaflet prolapse was recognized in Carpentier series as an independent risk for reoperation. As this study reflects our early experience in MVR, operators were very cautious in selecting patients for valve repair. We used the somewhat pragmatic definition by Fasol and Mahdjoobian [20] which is based on gross appearance of the valve. Though we made an attempt to define the different forms of degenerative valve disease, mainly Barlow disease and fibroelastic deficiency. As we performed repair only if degenerative process involved less than 50% of leaflets (50% rule of thumb), we had only anecdoctical anterior leaflets repair avoiding statistical analysis of this subgroup.
Gerbode valvuloplasty without annulus reinforcement by a prosthetic ring is also a marker of reoperation. Our choice was given to the Carpentier ring, but tight anchorage of any type of annulus reinforcement prevented a high rate of mitral regurgitation progression and subsequent need for reoperation as described in a recent German study [21].
In our collective, all reoperated patients suffered from degenerative mitral regurgitation, all had trivial to acceptable residual MR at 7 days postoperative echocardiographic control, and all were younger than 60 years at first operation time.
Even if to our knowledge no reoperated patient had Marfan syndrome or trait of fibro-elastic deficiency, we can not exclude, due to the statistically higher reoperation rate by younger patients seen in our multivariate analysis, that a hereditary disease predisposed them to progression of the regurgitation after surgery because of the bad quality of their tissues [22].
4.3 Limitation of the study
The major limitation of the present study is that most information was collected retrospectively, a process that may reduce the validity of some data. However, particular attention was paid to the methods used in the follow-up by thorough examination of hospital files and precising questionnaires with a doubled interview with physicians. Special emphasis was brought to define accurately the cause of late death, because most of the deceased patients had no necropsy [23]. Statistical power, when analysing covariates in certain subgroups such as endocarditis, was low because of small numbers of patients and events. Furthermore, the findings of this study, as with any observational cohort, may not necessarily be generalizable to all patients with mitral valve repair.
| 5. Conclusion |
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2+), and the absence of prosthetic ring implantation.
| References |
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