Ann Thorac Surg 2003;76:27-31
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Benefit to quality of life after Off-Pump versus On-Pump coronary bypass surgery
Franz F. Immer, MDa*,
Pascal A. Berdat, MDa,
Alexsandra S. Immer-Bansi, MDb,
Friedrich S. Eckstein, MDa,
Sascha Müller, MDa,
Hugo Saner, MDc,
Thierry P. Carrel, MDa
a Department of Cardiovascular Surgery, University Hospital, Berne, Switzerland
b Department of Anesthesiology, University Hospital, Berne, Switzerland
c Division of Cardiac Rehabilitation, University Hospital, Berne, Switzerland
Accepted for publication January 18, 2003.
* Address reprint requests to Dr Immer, Department of Cardiovascular Surgery, University Hospital, 3010 Berne, Switzerland.
e-mail: franzimmer{at}yahoo.de
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Abstract
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BACKGROUND: Whether the clinical outcome of off-pump coronary artery bypass graft (OPCABG) surgery is superior to on-pump coronary artery bypass graft (CABG) surgery is still a matter of debate. However with the considerable reduction of mortality associated with CABG surgery in recent years, more subtle outcome indicators such as quality of life (QOL) become more important. The aim of this study was to compare midterm QOL after OPCABG with that after CABG procedures and with an age- and sex-matched standard population.
METHODS: Quality of life was assessed using the Short-Form 36 Health Survey Questionnaire for 504 consecutive patients after CABG (n = 438) and OPCABG (n = 66) operated on between June 1999 and November 2000 at our institution.
RESULTS: Except for single-vessel disease, which was more frequent in OPCABG compared with CABG procedures (13.6% versus 6.8%; p <0.01), the preoperative variables were similar. Median EuroSCORE (European System for Cardiac Operative Risk Evaluation) was 3.2 ± 1.3 in the CABG group compared with 3.0 ± 0.8 in the OPCABG group (p = not significant). After a mean follow-up of 10.8 ± 0.5 months physical role function (73.5 ± 38.3 versus 45.3 ± 41.6; p <0.01) and emotional role function (75.3 ± 40.3 versus 61.0 ± 43.9; p <0.01) were significantly better in OPCABG than in CABG patients. Compared with a standard population, OPCABG patients were significantly impaired in emotional role function and CABG patients in physical and emotional role function.
CONCLUSIONS: Midterm QOL after myocardial revascularization is fairly well preserved compared with an age- and sex-matched standard population and is superior after OPCABG compared with CABG. Whether this is only due to avoidance of cardiopulmonary bypass remains to be elucidated.
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Introduction
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Although a certain decrease in mortality and morbidity has been demonstrated in subgroups of patients undergoing surgical myocardial revascularization, the overall benefit of off-pump coronary artery bypass graft (OPCABG) versus on-pump coronary artery bypass graft (CABG) surgery is still a matter of debate [1–3]. Especially the incidence of perioperative cerebrovascular accidents is discussed in a controversial way, although recent studies demonstrate that OPCABG may offer a substantial reduction in the perioperative risk of cerebrovascular accidents compared with CABG procedures [4–9].
Many risk factors associated with increased mortality after surgical myocardial revascularization have been well defined and several scores have been established, allowing a prospective risk stratification of perioperative mortality [10]. However with considerable reduction of mortality in coronary artery bypass surgery in recent years, other more subtle outcome indicators such as quality of life (QOL) gain more interest [11–14]. After CABG improvements in QOL have mainly been reported in patients with important preoperative health status deficits, whereas in less symptomatic patients and in those with preserved health status, improvements of QOL could not be demonstrated. Several studies have treated this subject and Van Dijk and colleagues [15] have recently published a randomized trial referring to the data of 181 patients looking at cognitive outcome and QOL 3 and 12 months after CABG and OPCABG surgery. They found no differences in terms of cognitive outcome between OPCABG and CABG surgery after a follow-up period of 12 months, which is in contradiction to other studies who demonstrated a clear benefit of neurologic [9] and neurocognitive outcome [16] in patients undergoing OPCABG surgery. Especially in less symptomatic patients with a more prognostic indication for myocardial revascularization, it is of great importance that QOL is preserved and comparable with that of an age- and sex-matched standard population.
The aim of this study was to assess midterm QOL in patients after OPCABG and CABG procedures and to compare the data with an age- and sex-matched standard population.
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Patients and methods
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Patients
Having been operated on for coronary artery disease at our institution between June 1999 and November 2000, 530 consecutive patients, 460 after CABG and 70 patients after OPCABG, were sent the Short-Form 36 Health Survey Questionnaire (SF-36). Nonresponders were contacted by phone. In-hospital mortality was 2.7% in the CABG group and 1.2% in the OPCABG group (p = not significant). During the follow-up period 2 patients (0.4%) died in the CABG group and no mortality was recorded in in the OPCABG group (p = not significant). Ten patients did not answer the SF-36: 8 patients had language problems and 2 patients refused to answer the questionnaire. There was no differences between the two groups. Of 445 survivors in the on-pump group, 438 patients answered the SF-36 (98.4%) and in the OPCABG group 66 of 69 survivors filled out the SF-36 (95.6%). Patient characteristics and perioperative data are summarized in Table 1.
Single-vessel disease was more frequent (13.6% versus 6.8%; p <0.01) and the mean number of distal anastomoses (2.6 ± 1.1 versus 3.4 ± 1.6; p <0.01) was significantly lower in OPCABG compared with CABG procedures. However median EuroSCORE (European System for Cardiac Operative Risk Evaluation) was 3.2 ± 1.3 in the CABG group compared with 3.0 ± 0.8 in the OPCABG group (p = not significant). Length of stay was significantly shorter for OPCABG than CABG (8.7 ± 4.8 versus 11.2 ± 7.8 days; p <0.05). All other variables were not different between the groups (Table 1).
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Table 1. Preoperative, Intraoperative, and Postoperative Data for Patients Undergoing CABG Surgery and Patients Undergoing Off-Pump CABG Surgery
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Methods
Preoperative, perioperative, and postoperative data of patients undergoing CABG and OPCABG surgery were retrospectively assessed. The EuroSCORE was calculated [10]. All patients were operated on through a full median sternotomy. A subgroup analysis of patients with triple-vessel disease was done. After a mean follow-up time of 10.8 ± 0.5 months all patients received a health-related SF-36, a validated standard questionnaire to assess the subjective quality of life supplemented with disease-specific questions for evaluation of their postoperative QOL. The method of the SF-36 has been published elsewhere [17, 18]. In brief, it consists of 36 short questions mirroring health and QOL in eight different aspects: bodily pain (BP, 2 items); mental health (MH, 5); vitality (VT, 4); social functioning (SF, 2); general health (GH, 5); physical functioning (PF, 10; and role functioning, both emotional (RE, 3) and physical (RP, 4). Role functioning reflects the impact of emotional and physical disability on work and regular activity (the person’s normal everyday role). Raw points are transformed into a score from 0 to 100 for each dimension, with 100 reflecting best functioning, correcting for age and sex, based on a Swedish normal population (n = 8,930). The researchers carrying out the SF-36 administration were blinded to the surgical approach.
Statistical analysis
Results were analyzed in accordance to the SF-36 manual and missing values replaced using the described algorithm [17, 18]. The SF-36 scores are presented as mean ± standard deviation. The Mann-Whitney U test and the 
2 test were used for comparison of continuous and nominal variables, respectively. A p value of less than 0.05 was considered statistically significant. All analyses were performed with StatView 4.1 statistical software package (Abacus Concepts, Berkeley, CA).
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Results
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Physical role (73.5 ± 38.3 versus 45.3 ± 41.6; p <0.01) and emotional role function (75.3 ± 40.3 versus 61.0 ± 43.9; p <0.01) were significantly better in OPCABG than CABG patients (Fig 1).
All other aspects tested were similar between the groups.
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Fig 1. Short-Form 36 (SF-36) Health Survey Questionnaire score for patients undergoing on-pump coronary artery bypass graft surgery ([CABG] open bars; n = 438) and off-pump CABG ([OPCABG] solid bars; n = 66), raw scores (not age- and sex-matched); maximum score 100 points. (BP = bodily pain; GH = general health; MH = mental health; PF = physical functioning; RE = emotional role functioning; RP = physical role functioning; SF = social functioning; VT = vitality.)
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In comparison with an age- and sex-matched standard population OPCABG patients were significantly impaired (score <85) in emotional role function (score 82.8 ± 23.2) and CABG patients in physical (score 58.1 ± 33.8) and emotional role function (score 69.1 ± 29.7), whereas the other aspects of QOL were not different between patients of the two groups and a standard population (Fig 2).
Similar results were found in a subgroup analysis of patients suffering from triple-vessel disease, in which OPCABG patients showed a significant impairment in emotional role function (score 79.3 ± 18.2) and CABG patients in physical (score 57.4 ± 28.9) and emotional role function (score 65.8 ± 25.3). Mean age was similar in both groups with 67.2 ± 8.2 years for CABG patients and 66.8 ± 10.4 years for OPCABG patients (p = not significant). The number of distal anastomosis in this subgroup analysis was 3.7 ± 1.2 in CABG patients and 3.3 ± 0.8 in OPCABG patients (p = not significant).
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Fig 2. Short-Form 36 Health Survey Questionnaire age- and sex-matched comparison with a standard population (range, 85 to 115) for patients undergoing on-pump coronary artery bypass graft surgery ([CABG] open bars; n = 438) and off-pump CABG ([OPCABG] solid bars; n = 66). Results below 85 (arrows) reflect a significant impairment. (BP = bodily pain; GH = general health; MH = mental health; PF = physical functioning; RE = emotional role functioning; RP = physical role functioning; SF = social functioning; VT = vitality.)
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Comment
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Overall QOL after surgical myocardial revascularization is fairly well preserved in both groups and comparable with that of a standard population in most aspects. General and mental health, vitality, physical and social functioning, and bodily pain were not negatively affected by surgery irrespective of the procedure chosen. However in emotional and even more in physical role function CABG patients were significantly impaired in comparison with both OPCABG patients and a standard population. These facets of QOL assess problems occurring during daily activity. Patients typically complain about problems assuming daily workload and analyzing complex situations and are handicapped at work, owing to emotional problems. These subtle impairments in the person’s normal everyday role may reflect neuropsychological deficits known to occur after major surgery and especially after CABG [6, 13, 14]. However most authors emphasize that the reported deficits do not affect the patient’s individual functionality. Nevertheless two studies reported a small proportion of patients with intellectual dysfunction or memory deficits becoming sufficiently disabled to prevent them from returning to work [6]. However of those patients returning to work postoperatively after CABG 38% showed a significant impairment in emotional role function and 26% in physical role function in our study.
In contrast OPCABG patients had a significantly better QOL compared with CABG patients concerning physical and emotional role function. In comparison with a standard population, OPCABG patients were only slightly impaired in emotional role function with only 9% of the patients reporting a significant impairment in this aspect whereas all other aspects of QOL were as good as in a standard population. Similar results were found in a subgroup analysis looking only at the SF-36 in patients with triple-vessel disease.
The reason for this significantly better QOL after OPCABG compared with CABG remains speculative. Whether the reduced physical and emotional role function after CABG is due to a more pronounced structural brain damage induced by cardiopulmonary bypass with increased cerebral embolic load [5, 8], brain edema, inflammatory response [19], inhomogeneous nonpulsatile cerebral perfusion, and perioperative hypothermia and hyperthermia is currently not known. Thus reducing the improvements in QOL only to avoiding cardiopulmonary bypass seems rather simple. On the other hand comparing our data with those of Van Dijk and colleagues [15], who found no differences in cognitive outcome 12 months after CABG and OPCABG surgery, we have to take into account that those patients were younger (61 versus 66 years) and less frequently had diabetes (13% versus 18.4%) and triple-vessel disease (20% versus 78.8% in the OPCABG group and 27% versus 82% in the CABG group). Looking at these data one may assume that the extent of arteriosclerosis is much more severe in our study population compared with the patients randomized in the Dutch trial and may impair postoperative outcome and have a negative impact on QOL. Especially age and diabetes have been shown to be important risk factors for the occurrence of cerebrovascular accidents [20], which may lead to impairment of postoperative neurocognitive functions. We recently reported a decrease in the aspects of role emotional and role physical, especially in older patients undergoing surgery for ascending aortic aneurysms probably due to cerebral embolisms [21]. According to these data we think that high-risk patients may benefit the most from OPCABG surgery. The significant reduction of cerebral microembolisms, which has been documented in several studies, may improve neurocognitive outcome and QOL after myocardial revascularization especially in the elderly patient [15, 20, 22]. In low-risk and younger patients however the use of cardiopulmonary bypass still allows the performance of CABG surgery with excellent results and as the results from Van Dijk and coworkers [15] show, without impairment in neurocognitive outcome and QOL.
One limitation of the study may be its retrospective nature without randomization of patients for OPCABG versus CABG surgery. As our experience in the field of OPCABG was limited at the beginning of this study, only patients thought to be suitable candidates for OPCABG were selected. Nevertheless factors that may affect postoperative QOL such as left ventricular function, functional classification according to the New York Heart Association, age, and cardiovascular risk factors did not differ significantly between the two groups. Preoperative risk stratification according to EuroSCORE was similar in both groups. As the SF-36 allows to perform an age- and sex-matched comparison with a standard population, older age in the on-pump group is methodologically corrected and does not influence the results. A subgroup analysis including only patients with a triple-vessel disease showed no differences in the results of the SF-36 in comparison with the results obtained in the total collective. Therefore we can assume that the two groups are suitable for comparison. Furthermore owing to the retrospective nature of the study, QOL could only be assessed postoperatively and therefore relative changes in QOL from preoperative to postoperative could not be evaluated. Comparisons with a standard population may partly counterbalance this lack under the premise that patients with coronary artery disease may not differ substantially from a normal age- and sex-matched population concerning QOL.
We conclude that QOL after myocardial revascularization is fairly good in comparison with an age- and sex-matched standard population. Quality of life is better preserved in two of eight aspects after OPCABG compared with CABG surgery. We believe that high-risk patients may benefit the most from OPCABG surgery. In low-risk patients the use of cardiopulmonary bypass still allows CABG surgery to be performed with excellent results without impairment in neurocognitive outcome and QOL.
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References
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Abstract
Introduction
