Ann Thorac Surg 2005;80:183-188
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
Effect of Training in Mitral Valve Repair Surgery on the Early and Late Outcome
Christos Alexiou, PhD, FRCS*,
George Doukas, FRCSI,
Mehmet Oc, MD,
Bahar Oc, MD,
Leon Hadjinikolaou, MD,
Tomasz J. Spyt, MD, FRCS
Department of Cardiac Surgery, University Hospitals of Leicester NHS, Glenfield Hospital, Leicester, United Kingdom
Accepted for publication January 10, 2005.
* Address reprint requests to Dr Alexiou, Department of Cardiac Surgery, Glenfield Hospital, Groby Rd, Leicester LE3 9QP, United Kingdom (Email: alexiou486{at}aol.com).
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Abstract
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BACKGROUND: Preservation of the native mitral valve provides important advantages over valve replacement. The aim of this study was to evaluate the effect of training for mitral valve repair on the outcome.
METHODS: Between 1997 and 2004, 471 patients underwent mitral valve repair procedures in a single firm. Of these procedures, 300 (64%) were performed by a consultant (TJS) (consultant group) and 171 (36%) by trainees supervised by the same consultant (trainees group).
RESULTS: Atrial fibrillation was more prevalent in the consultant group (p = 0.02) but there were no significant differences in the demographics, etiology of mitral regurgitation, and other comorbidity between the groups. Posterior leaflet prolapse was more prevalent in the trainees group (p < 0.0001) and anterior leaflet prolapse (p < 0.0001), bileaflet prolapse (p = 0.003), and Barlow’s syndrome (p = 0.0003) in the consultant group. The consultant performed a higher proportion of concomitant coronary artery bypass grafting (p = 0.04), aortic valve replacement (p = 0.02), procedures, and nonelective cases (p = 0.03) with shorter bypass (p = 0.01) and ischemic times (p = 0.0004) than trainees. The complication rate was similar in the two groups (26% vs 22%), but the consultant had a higher operative mortality than the trainees (5% vs 0.6%) (p = 0.01). A similar proportion in the two groups exhibited recurrent mitral regurgitation (8% vs 9%). Kaplan-Meier five-year freedom from reoperation (95.6 ± 1.6 vs 95.7 ± 2.2%) (p = 0.7) and survival (82 ± 4% vs 88 ± 4%) (p = 0.09) were similar in the two groups.
CONCLUSIONS: With appropriate patient selection, cardiothoracic trainees can be taught mitral valve repair surgery without a negative effect on the early or late outcome.
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Introduction
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Preservation of the native mitral valve (MV) provides important early and late advantages over valve replacement including better left ventricular geometry and function, reduced need for anticoagulants with their attendant bleeding complications, significantly lower incidence of thromboembolic events and endocarditis, and improved long-term survival [1–3]. In the current cardiac surgical practice, therefore, broad familiarity with and competence in MV repair surgery is essential.
In the United Kingdom, the implementation of the Calman report in 1993 [4] introduced a structured six-year training program for specialist registrars in cardiothoracic surgery reducing the length of training. More recently, the European Working Time Directive (EWTD) [5] further shortens the time a trainee can spend in the hospital during his or her training program. At the same time, the consultant trainers are under considerable pressure generated by the growing demands for improved clinical results, while operating on higher risk patients, and the intense public scrutiny of their clinical performance. There are concerns that together these factors may adversely affect the quality of education and the hands-on experience provided to cardiothoracic trainees.
Previous studies [6–12] have addressed issues related to the training in coronary artery bypass grafting (CABG), and aortic and mitral valve replacement procedures, whereas a recent report [13] examined the impact of training residents in MV surgery (repair or replacement) on the early morbidity and mortality. The purpose of this study was to evaluate the feasibility of resident training in MV repair surgery and its effect on the early morbidity and mortality, recurrence rate of mitral regurgitation, need for reoperation, and survival.
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Patients and Methods
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Between 1997 and 2004, 471 consecutive patients underwent primary MV repair procedures in a single surgical firm at Glenfield Hospital, Leicester, UK. Of these procedures, 300 (64%) were performed by a senior consultant cardiac surgeon (Professor Tomasz J. Spyt) (consultant group), and 171 (36%) by specialist registrars supervised by the same consultant (trainees group) (Table 1). The national specialist registrars participate in a six-year training program in cardiothoracic surgery rotating to the units of Leicester, Nottingham, and Sheffield. The senior consultant involved in this study has a major interest in MV surgery and the registrars are usually attached to his firm during the second half of their training period. The two groups were compared with regard to the preoperative clinical profile, types of operations carried out, and early and late postoperative outcome. Patients undergoing redo cardiac surgery and MV repair with left ventricular remodeling procedures were not included in this study.
Operative Techniques
After median sternotomy, normothermic cardiopulmonary bypass (37°C) with cannulation of the ascending aorta and both vena cavae was established. Myocardial protection was afforded with antegrade or retrograde warm blood cardioplegia. In isolated MV surgery, access to the MV was obtained through the left atrium. If tricuspid valve surgery was also undertaken a transeptal approach was employed. The repair was tailored to each patient’s circumstances but certain general principles applied. Thus, posterior leaflet prolapse was managed with quadrangular resection, anterior leaflet prolapse with insertion of artificial chordae, and bileaflet prolapse with combination of the two techniques. An edge-to-edge repair [14] was utilized for cases of bileaflet prolapse in the setting of Barlow’s syndrome. In most patients with ischemic mitral regurgitation (MR) an annuloplasty band alone was used. In rheumatic valves, fused commissures, chordae, and papillary muscles were freed, and more recently an autologous pericardial patch was used to extend a short but relatively pliable anterior leaflet as described by Acar and colleagues [15]. In infective endocarditis, vegetations were removed and leaflet perforations closed with autologous pericardium. In all cases, a Cosgrove-Edwards (Baxter Healthcare, Irvine, CA) annuloplasty band was inserted to support the repair and prevent further annular dilatation. Tricuspid valve repair was accomplished with the insertion of a Cosgrove-Edwards annuloplasty band. When myocardial revascularization was required, the distal anastomoses were completed before MV surgery. In patients who were in atrial fibrillation, the left atrial appendage was oversewn in a linear fashion from within. Transesophageal echocardiography was used routinely in the perioperative period.
Follow-Up
The patients were seen regularly in the outpatient clinics by surgeons and cardiologists. In each visit they had a clinical examination, a 12-lead electrocardiogram, and a chest radiograph. Echocardiograms were performed approximately each year as part of the follow-up or if clinically indicated. Data were collected from the departmental database and the patient case notes.
Statistical Analysis
Continuous variables are expressed as means values ± standard deviation and the proportions as percentages. The differences between the groups for the categorical variables were compared with 
2 or Fisher’s exact test. The continuous variables were compared with an unpaired Student’s t test or a nonparametric test (Kruskal-Wallis). Freedom from reoperation and survival for the two groups were calculated with the Kaplan-Meier method and compared with the log-rank test. A p value of less than or equal to 0.05 was considered statistically significant. Statistical analysis was performed using commercially available software (SPSS, version 11, Chicago, IL).
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Results
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Preoperative Clinical Profile
There were no significant differences between the two groups with regard to the demographics, etiology of MR, prevalence of mixed MV disease, or moderate to severe tricuspid regurgitation, and proportion of patients having left ventricular impairment (left ventricular ejection fraction < 60%) (Table 2). Associated risk factors such as hypertension, hypercholesterolemia, diabetes mellitus, chronic obstructive airways disease (combination of chronic bronchitis and various degrees of emphysema), renal impairment (preoperative serum creatinine concentration > 200 µmol/L), and cerebrovascular disorders were evenly distributed (Table 3). Also, the groups had similar mean New York Heart Association and Canadian Cardiac Society functional class scores, and a similar predicted operative risk according to the Parsonnet scoring system. Atrial fibrillation, however, was significantly more prevalent in the consultant group (Table 3).
Mitral Valve Lesions and Operative Data
The two groups differed markedly in the types of MV lesions and the MV repair procedures they had (Tables 4 and 5). Posterior leaflet prolapse was the most common lesion in both groups, but it was significantly more prevalent in the trainees group. Inversely, the patients operated by the consultant had a significantly higher proportion of MR secondary to the prolapse of the anterior or both the anterior and posterior leaflets, and due to Barlow’s disease (Table 4). Consequently, in comparison with the consultant-supervisor, the trainees were significantly more likely to perform a quandrangular resection of the posterior leaflet, less likely to use an edge-to-edge (Alfieri stitch), sliding plasty, or insertion of artificial chordae type of repair, and as likely to implant an annuloplasty band (Table 5).
Concomitant tricuspid valve repair was carried out at similar rates, but the patients operated by the consultant underwent a significantly higher proportion of CABG and aortic valve replacement (AVR) procedures. Trainees operated on a significantly lower number of nonelective (urgent or emergency) cases with longer bypass and ischemic times than the consultant-supervisor (Table 5).
Operative Mortality and Complications
Operative (30-day) mortality in the consultant and trainee groups was 5% (15 deaths) and 0.6% (1 death) (p = 0.01), respectively. Causes of death in the consultant group were low cardiac output (8), pneumonia (2), stroke (2), intestinal sepsis (2), and adult respiratory distress syndrome (1). The only death in the trainees group occurred in a patient with ischemic MR due to low cardiac output. With regard to the type of MV pathology, operative mortality in the consultant group for degenerative MR was 2.2% (4 deaths), for ischemic MR 10.6% (9 deaths), and for rheumatic MR 7.4% (2 deaths). Operative mortality among all study patients (consultant and trainees groups included) was 3.3% (1.4% for degenerative, 7.4% for ischemic, 4.8% for rheumatic, and 0% for infective MR). The patients in the two groups that survived the operation sustained a comparable number of cardiac, respiratory, neurological, renal, gastrointestinal, and other complications spending a similar time in the intensive care unit and the hospital (Table 6).
Late Outcome
At follow up, 22 patients (5%) from the consultant group and 15 from the trainees group (6%) exhibited grade II or III MR. Eight (3%) and 4 (2%) patients from each group, respectively, had grade III MR and underwent a MV reoperation. In the consultant group, the underlying MV pathology of those having a reoperation was degenerative in 4, rheumatic in 2, ischemic in 1, and Barlow’s syndrome in 1. In 4 patients the severe recurrent MR was accompanied by hemolysis and in 2 patients by left outflow tract obstruction due to systolic anterior leaflet motion. They all underwent MV replacement. In the trainees group, 3 of those requiring a reoperation had degenerative MR and 1 had ischemic MR. Hemolysis was present in 1 patient with degenerative MR. Two of the patients in the trainees group had MV replacement and 2 had repeat successful MV repair performed by the consultant-supervisor. Kaplan-Meier 5-year freedom from reoperation for the consultant group was 95.6 ± 1.6% versus 95.7 ± 2.2% for the trainees group (p = 0.7) (Fig 1).
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Fig 1. Kaplan-Meier freedom from reoperation in the two groups (p = 0.7). Numbers in parentheses denote patients remaining at risk in each group.  = trainees; — = consultant. (MV = mitral valve.)
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There were 14 late deaths (5%) in the consultant group and 9 (5%) in the trainees group. Overall 5-year Kaplan-Meier survival for the consultant and trainees group was 82 ± 4% versus 88 ± 4% (p = 0.09). Five-year survival for the consultant and trainees groups in patients having degenerative MR was 87 ± 5 versus 97 ± 4% (p = 0.11), and for those having MR of ischemic etiology it was 65 ± 10 versus 75 ± 9%, respectively (p = 0.36) (Figs 2 and 3).
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Fig 2. Kaplan-Meier survival for degenerative MR (mitral regurgitation) in the two groups (p = 0.11). Numbers in parentheses denote patients remaining at risk in each group. (- - - = trainees; — = consultant.)
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Comment
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The recognized benefits of MV repair are reflected in its increasing use over time. According to the Society of Thoracic Surgeons national cardiac database, the MV repair procedures performed in the USA in 1990 comprised 23% of all types of MV surgical cases and in 1999 this proportion rose to 32% [16]. Unlike the observed decline in CABG, MV repair surgery is likely to expand further for the management of the growing population of the elderly patients with degenerative valvular disease and the patients developing MR in the setting of heart failure of ischemic origin. At present, in our institution MV repair is the procedure of choice for the surgical treatment of MR of any etiology.
The modern cardiac surgeon ought to be conversant with all surgical options available for the treatment of a dysfunctional MV. To achieve this, provision of good quality training to cardiothoracic residents is needed. In the UK, this need is appreciated but is increasingly difficult to fulfill because of the reduced time trainees can spend in the hospital (as a result of the implementation of the Calman report and the EWTD), and the pressure exerted on the consultant-trainers by the public scrutiny of their individual clinical performance [4, 5]. In such an atmosphere, concerns of a higher operative morbidity and mortality could easily lead to a reduction of the training opportunities.
The published evidence, though, does not seem to substantiate these concerns. In a study originating from Cambridge trainees have performed, with various levels of consultant supervision, 44% of all isolated CABG operations under cardiopulmonary bypass (CPB) with no negative effect on operative morbidity, mortality, and hospital costs [6]. In a series of reports, the Bristol group have shown that trainees can undertake CABG surgery without the aid of CPB on large numbers of low, medium, and high risk cases with operative mortality and morbidity rates similar to those observed when these operations are performed by consultants [8–10]. These studies [6, 8–10] have been conducted after the application of the Calman report for specialist registrar training and overlap with the onset of implementation of the EWTD [4, 5]. This suggests that with good planning and intensification of the training program the problem posed by the EWTD can be overcome. Past studies from North America and Europe [6–12] have demonstrated the feasibility and safety of resident training in CABG and aortic or mitral valve replacement procedures. However, only one recently published study [13] examined the impact of resident training in MV repair (and replacement) on the early outcome, which indicates that exposure of trainees to this type of cardiac surgery may be limited. In this Canadian study [13], between 1998 and 2003 the residents performed 79 repair procedures with the staff surgeons performing 116 mitral repairs over the same period (proportion of resident cases 40.5%). Operative mortality for residents and staff surgeons was almost identical (3.8% and 4.3%, p = 1.0) [13].
In the present study, supervised trainees have carried out 36% of MV repair operations of the consultant caseload without apparent negative impact on the early or late outcome. The trainees group had a significantly lower operative mortality than the consultant group (0.6% versus 5%), and similar morbidity, intensive care, and hospital stay. These results can be readily explained by the significant differences between the two groups in the preoperative clinical profile, the types of MV lesions, and the operative procedures performed, all of which emphasize the careful case selection carried out by the consultant supervisor. Thus, the consultant was more likely to operate on patients that were in atrial fibrillation (an indicator of a more advanced MV disease stage), he performed a significantly higher number of concomitant CABG and aortic valve replacement procedures, and he operated more frequently on urgent and emergency cases. In the authors’ view, the similar preoperative mean Parsonnet score in the two groups should be viewed as a failure of this scoring system to accurately predict the operative risk of patients that had MV disease and required often concomitant CABG, tricuspid valve, or aortic valve surgery. A report from four cardiac surgery centers from the northwest of England has previously highlighted the limitations of the Parsonnet score to measure the preoperative risk-stratified mortality in patients undergoing a wide variety of cardiac surgical procedures [17].
The bulk of the cases performed by trainees in this series were MV annuloplasty and quadrangular resection of the posterior leaflet. On the other hand, most patients having prolapse of the anterior or both leaflets were operated by the consultant-supervisor, and few of these patients were operated by trainees. Our findings in this regard are different from the Canadian experience where residents were more likely to undertake anterior leaflet repair than the staff surgeons [13]. It seems logical to expose the trainee to the simpler types of repair before the more complex ones. We also feel that in this way a fair balance can be achieved between the provision of high quality care to the patient and appropriate training opportunities to the trainee. It is also important to protect the patient and the trainee from the traumatic experience of a poor result.
The trainees had significantly longer ischemic and bypass times than the consultant despite operating in less complex cases. Admittedly, longer operating times from the trainees are unavoidable but, provided that they do not compromise the patient outcome, they seem to be an acceptable price to pay for the training of future consultant cardiac surgeons.
The techniques of MV repair that have been developed over the years by pioneering surgeons [14, 18–21] are standardized and reproducible but there exist some controversies. It has been our policy to use an annulopasty ring in every case to support the repair and prevent further dilatation. We prefer to use a partial ring because the anterior MV annulus is part of the fibrous trigone of the heart and it does not dilate significantly. We feel that artificial chordae insertion is relatively easy and yields consistent results [20]. Also, we found that the edge-to-edge repair provides a simple and reliable solution to the complex problem of Barlow’s syndrome [14].
The overall results in this series are in keeping with those reported in the literature [22–24], confirming the low operative mortality, good late survival, and long durability of MV repair undertaken for degenerative MR as well as the higher operative risk and the reduced late survival that are observed after MV repair for ischemic MR. We have found no other studies on the effect of resident training in MV repair on the late outcome. In this respect, the observed rates of recurrent MR and the Kaplan-Meier freedom from reoperation and survival in the trainees group are encouraging. In conclusion, this study shows that with appropriate patient selection the cardiothoracic trainees can be taught MV repair surgery without a negative effect on the early or late patient outcome.
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Fig 3. Kaplan-Meier survival for ischemic mitral regurgitation in the two groups (p = 0.36). Numbers in parentheses denote patients remaining at risk in each group. - - - = trainees; — = consultant.
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Abstract
Introduction
