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Ann Thorac Surg 2006;81:568-572
© 2006 The Society of Thoracic Surgeons
Department of Cardiothoracic Surgery, St George's Hospital, London, United Kingdom
Accepted for publication July 18, 2005.
* Address correspondence to Dr Chandrasekaran, Department of Cardiothoracic Surgery, St. George's Hospital, Blackshaw Rd, London SW17 0QT, United Kingdom (Email: v.chandra{at}fsmail.net).
Presented at the Poster Session of the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.
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Abstract |
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 Top Abstract IntroductionMaterial and MethodsResultsCommentReferences |
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METHODS: All 251 OPCABG cases performed by one service over an 18-month period were analyzed. The 83 operations (33%) performed by two trainees under supervision were compared with the 168 operations (67%) performed by an experienced consultant surgeon. Patient and disease characteristics, intraoperative and postoperative data, morbidity and mortality were analyzed using univariate and multivariate analysis. Data were extracted from a prospective database.
RESULTS: Patients operated on by the consultant were more likely to have had unstable angina (p = 0.003, odds ratio [OR] = 3.5), impaired left ventricular function (ejection fraction <0.3; p = 0.005, OR = 2.4), or previous cardiac surgery (p = 0.03). They were more likely to receive three or more grafts (p = 0.017, OR = 2.0). Operative mortality was 2.4% (consultant) and 0% (trainees; p = 0.31). Postoperative morbidity, such as reoperation for bleeding (consultant 3% versus trainees 1.2%), stroke (0.6% versus 1.2%), and hemofiltration (3.6% versus 0%) was similar between the two patient groups. Stay in the intensive care unit was not significantly different in the two groups.
CONCLUSIONS: In our experience, trainee surgeons are less likely to operate on patients with unstable angina or cardiac dysfunction. Operative morbidity and mortality are, however, similar in patients operated on by either an experienced consultant surgeon or trainees. We believe OPCABG can be taught safely to trainees under supervision.
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Introduction |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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Performing OPCABG is undoubtedly demanding technically as the surgeon is faced with a beating heart and not a bloodless field that contrasts with conditions in on-CABG. The potential clinical advantages of OPCABG and the advances made in surgical technology have made this procedure an essential part of a cardiothoracic training program. The aim of this study is to review clinical data of patients undergoing OPCABG and compare clinical outcomes after procedures performed by a consultant surgeon or a trainee as the primary operator over an 18-month period.
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Material and Methods |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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The clinical data were collected prospectively in line with the appended Minimum Dataset (MDS) defined by The Society of Cardiothoracic Surgeons. The current MDS, and its associated definitions, is compatible with all existing initiatives in the United Kingdom such as the UK Heart Valve Registry, the Central Cardiac Audit Database, and the British Cardiac Intervention Society database. The definitions and data fields are also compatible with evolving European initiatives, The Society of Thoracic Surgeons, the American College of Cardiology, and the Healthcare Financing Administration in the United States [2]. Local validation of the collected data is performed regularly, and external validation is being performed by the Society on a 3- to 5-yearly cycle.
Anesthetic and Operative Techniques
The anesthetic and operative techniques used for OPCABG at our institution have been described in a separate study report [8]. Briefly, anesthetic premedication included morphine (10 mg) and hyoscine (0.3 mg) administered intramuscularly 2 hours before the operation. Anesthesia was introduced with midazolam (100 to 200 µg/kg), fentanyl (150 to 200 µg), and pancuronium (50 to 100 µg/kg), and sustained with propofol (5 to 10 mg · kg–1
· hour–1). Anticoagulation was achieved using 150 U/kg of heparin. The activated clotting time was maintained above 300 seconds. Heparin was reversed completely with protamine sulphate at the end of the procedure. The operation was performed through median sternotomy using the Guidant Acrobat SUV Vacuum Stabilizer System (OM-9000; Santa Clara, California). The exposure of the target vessel was facilitated by the use of swabs in the transverse sinus (deep pericardial stay sutures were not used), allowing the right side of the pericardium down and proximal vessel occlusion by a soft bulldog clamp. All distal anastomoses were constructed with 8-0 polypropylene and the proximal onto the aorta with 6-0 polypropylene. Mean arterial blood pressure was maintained between 50 and 70 mm Hg during the procedure by maintaining optimal preload, repositioning the heart, and selective use of vasoconstrictors, such as metaraminol and norepinephrin.
Training Method
The two trainees participating in this study had surgical experience equivalent to year 3 and 4 of the UK National Training Program. Both had received previous training in on-pump CABG involving more than 100 cases each. In our institution, approximately one third of coronary surgery is done off pump. The training consultant performs 85.5% of revascularization operations off pump. The trainees during the study period performed exclusively off-pump CABG. The patients operated upon by the trainees were selected by assessing their suitability for training taking into account the urgency of the operation, their co-morbidities, the quality of the coronary arteries, and the number of grafts required. Patients with poor left ventricular function and unstable hemodynamics were not used for training purposes. Training in OPCABG focused, therefore, on teaching the technique of handling the heart, positioning the stabilizer, and performing the anastomoses at the front of the heart initially. Furthermore, the training progressed to gradually increasing levels of complexity and responsibility according to the surgical abilities of the trainee. More specifically, arterial and venous conduits were used as indicated and sequential and Y-graft anastomoses were included in the teaching. All the training took place under the supervision of the same consultant surgeon, who assisted in the majority of cases and allowed the trainees to perform the operations on their own at the final stages of the training period with the trainer being in the vicinity of the operating room. The sequence of grafting consisted of the left anterior artery grafted first if it was critically diseased, followed by the vessels of the left side of the heart and the vessels of the posterior wall.
Statistical Methods
Contingency tables for categorical data were compared between the two groups using Pearson's 
2 test or Fisher's exact test. Distributions of continuous data were observed and t tests or Mann-Whitney U tests were performed accordingly for comparisons of groups. When no normal distribution of data was detected, variables were presented as median with 25th and 75th percentiles (interquartile range). The European System for Cardiac Operative Risk Evaluation (EuroSCORE) was used to analyze patients according to predicted risk for operative mortality [9]. Odds ratios with 95% confidence intervals were calculated for all compared variables. Logistic regression was used to correlate preoperative patient and disease characteristics with postoperative outcomes. All p values less than 0.05 indicate a statistically significant difference between patient groups. All analyses were carried out using the statistical software SPSS 11.0 (SPSS, Chicago, Illinois).
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Results |
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The demographic and preoperative clinical characteristics of the two patient groups are presented in Table 1. The two groups' characteristics were similar with the exception of age (older in the trainee group, p = 0.034), angina Canadian Cardiovascular Society class (higher in the consultant group, p = 0.001) and left ventricular ejection fraction (lower in the consultant group, p < 0.005). All nine reoperations included in the study, were performed by the consultant (p = 0.03). The predicted mortality risk, as calculated by EuroSCORE, was identical in the two patient groups.
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Comment |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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It is commonly believed that operations allocated to trainees involve patients with low predicted operative risk. In our study, patients in the trainee group were significantly older but had, overall, lower angina class and higher left ventricular ejection fraction. Operative risk scoring, as assessed by the EuroSCORE, demonstrated median scores of four in both groups, with a 75th percentile of four in the trainee group versus six in the consultant group. The EuroSCORE is an additive risk prediction system, similar in concept to the Parsonnet score, and was constructed using data from 128 European cardiac surgical centers [9]. It was developed using mainly on-CABG patients and has undergone extensive external validation with satisfactory discrimination and calibration [10]. The EuroSCORE also showed satisfactory prediction properties for OPCABG patients [11]. Our study suggests that overall average predicted risk does not differ between patients operated on by trainees as compared with consultants, although particularly high risk operations are performed by a consultant surgeon. It is possible that patients with particularly diffuse coronary artery disease and small coronary vessels were more likely to undergo operation by the consultant, although it would be difficult to quantify this statement.
Small sample size is the main limitation of our study. Low rates of outcome measures, such as mortality and morbidity, precluded our regression analysis from detecting correlation between patient characteristics and outcome. Low complication rates were, nevertheless, encouraging. A nonsignificant trend for cases performed by trainees to develop fewer postoperative complications reinforces the notion that trainees can be taught to operate safely off-CPB. Analysis of higher numbers of OPCABG cases performed by a variety of trainees should be performed in future studies to reconfirm the main findings of this trial. Long-term follow-up of patients will also be of interest.
The effect of training on clinical outcome after cardiac surgery has been the subject of previous publications. Some authors attempted to compare outcome between consultant and trainee cases directly and also by accounting for possible treatment selection bias. Oo and associates [12] adjusted for case mix by using propensity score and concluded that when trainees operate on lower risk cases, they produce better clinical outcome than their trainers. In their study, CABG was performed off-CPB only in 26.3% of cases. and trainees operated on merely 9.9% of the total patient population. Mean EuroSCORE was 2.9 for trainees and 3.5 for consultants. In a trial conducted in a UK center, hospital costs were not increased when trainees performed the surgery [13]. When trainees operated on higher risk on-CABG cases than the trainers, in a separate study, they achieved equally satisfactory results [14]. The same group also showed that it is safe to train junior surgeons in the performance of complex cardiac procedures, such as mitral valve repair [15]. Trainees performed 79 mitral valve repairs with a hospital mortality of 3.8% versus 4.3% for staff surgeons. Similarly, propensity score-matched cases showed no significantly different complication rates in the two patient groups. These findings are significant, as few trainee surgeons have the opportunity to gain substantial experience under supervision in mitral valve repair.
The need to provide junior surgeons with adequate exposure to cardiac surgical techniques without CPB has been recognized in the literature over the last few years. The experience of a single resident in OPCABG training was presented in an early report [16]. In this publication, the trainee tended to use the OPCABG technique for cases that required, on average, a smaller number of grafts than on-CABG cases performed during the same training period. Only 56% of these patients received a circumflex artery anastomosis. The same group conducted a postal survey assessing the exposure of the North American cardiac surgical residents to OPCABG. Response at the time (1999) suggested that the majority of residents would not reach proficiency in performing OPCABG during their residency [17]. It is likely that training in the technique has become more sufficient by the year 2005.
In the United Kingdom, experience of training in OPCABG has been previously reported by a small number of cardiac surgical departments. Jenkins and coworkers [18] reported findings of five patients who underwent OPCABG by a trainee and consented to early postoperative coronary angiography. This revealed 17 satisfactory (100%) distal anastomoses. The concept and outcome of training in OPCABG in a single UK cardiac surgical center has been presented comprehensively in a series of publications, all largely concerning the same patient population [19–22]. The last report of the series summarizes outcome on 990 CABG cases performed by trainees, of which 474 were OPCABGs. These operations were compared with those performed by an experienced consultant surgeon. Predicted and observed risk of death or serious complications was similar for trainee and consultant operations. The authors conclude that it is safe to teach OPCABG to trainee surgeons, and that continuous performance monitoring for trainees is possible and desirable.
In summary, the results of this study suggest that trainees can be taught to perform OPCABG safely under supervision with low rate of complications, including in patients with triple-vessel disease and grafting to the posterior wall of the heart. These findings are in agreement with previous literature reports. We believe the trainees should be given sufficient exposure to operate on patients undergoing OPCABG after adequate exposure to on-CABG surgery. Patients should be reassured that safety is not compromised by the presence of a trainee as the primary operator in their surgery.
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