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Ann Thorac Surg 2005;79:807-812
© 2005 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Heart Center, University of Leipzig, Leipzig, Germany
b Division of Cardiovascular Surgery, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada
Accepted for publication June 2, 2004.
* Address reprint requests to Dr Bucerius, University of Leipzig, Heart Center, Department of Cardiac Surgery, Strümpellstr 39, D-04289 Leipzig, Germany (E-mail: bucerj{at}medizin.uni-leipzig.de).
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Abstract |
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METHODS: Data were prospectively gathered on 2,182 consecutive female patients undergoing CABG either with or without cardiopulmonary bypass from 1996 to 2001. The associations between OPCAB surgery in addition with 22 further preoperative patient-related or treatment-related variables and 26 perioperative outcome variables were assessed with multivariable logistic regression analysis.
RESULTS: One hundred fifty-two (7.0%) female patients underwent OPCAB surgery during the study period. Women undergoing OPCAB had higher ejection fractions and received fewer coronary artery bypass grafts than CABG patients. Surgery using OPCAB was associated with shorter hospital stays, less bleeding, less transfusion requirements, and lower mortality than CABG. Furthermore, OPCAB surgery was independently associated with a lower prevalence of high perioperative transfusion requirement, postoperative respiratory insufficiency, postoperative renal insufficiency, and dialysis. Prevalence of postoperative blood loss of at least 500 mL was significantly higher after OPCAB surgery.
CONCLUSIONS: OPCAB in female patients undergoing coronary artery bypass surgery is safe and seems to be beneficial with regard to perioperative outcome as compared with conventional on-pump CABG. For that reason, off-pump surgery may be an effective method of lowering morbidity and mortality in these relatively high-risk patients.
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Introduction |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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A major recent development in CABG surgery is the avoidance of cardiopulmonary bypass (CPB), ie, standard use of off-pump CABG (OPCAB). The technique of OPCAB has been suggested to decrease morbidity and mortality by avoiding the deleterious effects of CPB, particularly in high-risk patients. The potential benefit of OPCAB with regard to the prevalence of adverse perioperative outcome in women undergoing CABG has not yet been fully assessed.
The purpose of this study was to determine whether OPCAB surgery is associated with a decreased risk of perioperative adverse outcomes in female patients undergoing CABG surgery both with and without CPB.
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Material and Methods |
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Surgery
Coronary artery bypass graft surgery was performed in a standard fashion in both groups. During on-pump surgery crystalloid cardioplegic arrest (HTK solution, Köhler Chemie, Alsbad, Germany) or blood cardioplegia were applied. Surgery with OPCAB was performed using commercially available devices applying pressure and suction. Choice of the type of procedure was made by the individual surgeon appointed for the case. This decision was made individually according to patient characteristics and on the basis of personal experience of the surgeon. Evaluation was performed according to the technique finally applied.
Data Collection
Perioperative data were recorded prospectively using an online database system as described previously (Medwork Database Software; Lenz + Partner GmbH, Dortmund, Germany) [11]. All variables analyzed were entered in a prospective fashion to accomplish a complete data set for each patient. The validity of the data was routinely ensured by using this information to generate text documents that became the patient's "chart" while in hospital.
Twenty-two variables that were analyzed as potential preoperative risk factors for perioperative morbidity and mortality in addition to the type of CABG surgery are listed in Table 1. Table 2 lists the adverse outcomes in both OPCAB and CABG female patients that were analyzed by univariate analysis for differences in prevalence between both surgical procedures. Outcome variables significantly different between OPCAB and CABG surgery were consecutively analyzed in a multivariate fashion for evaluation of independent associations with preoperative risk factors in Table 1, in particular OPCAB surgery. For the purpose of this study, intensive care unit stay was defined as total time spent in the intensive care unit (with mechanical ventilation) plus the intermediate care unit (without mechanical ventilation). Perioperative stroke was defined as any new temporary or permanent, focal or global neurologic deficit, as suggested by published guidelines [12]. Postoperative delirium was defined in accordance with the American Psychiatric Association guidelines [13]. Postoperative renal dysfunction was defined as increased serum creatinine or urea levels requiring medical treatment with diuretics, for example. Postoperative infection was defined as an infectious disease requiring antibiotic therapy. Rethoracotomy was defined as any chest reopening, nearly always because of bleeding.
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2 or Fisher's exact test. Preoperative patient-related or treatment-related variables including OPCAB surgery were entered into a stepwise (backward Wald) multivariable logistic regression analysis to determine the risk-adjusted effect of OPCAB surgery. Statistical significance was defined at the p less than 0.05 level and all p values were two-tailed. All statistical analyses were performed using SPSS statistical 9.0 (SPSS Inc, Chicago, IL). |
Results |
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Furthermore, CABG patients were significantly more likely to be undergoing urgent operations and to be suffering from preoperative myocardial infarction. In contrast, women undergoing OPCAB surgery suffered significantly more often from preoperative cardiogenic shock, whereas the prevalence of impaired left ventricular ejection fraction (<0.30) failed to be statistically significantly different between OPCAB and CABG (Table 1). History of pulmonary disease was higher in women undergoing OPCAB surgery without reaching statistical significance. Age at the time of surgery as well as all other preoperative variables were comparable in both surgical groups (Table 1).
Prevalence of adverse outcomes in OPCAB versus CABG patients are shown in Table 2. Prevalence of 5 of the listed 26 adverse outcomes was significantly higher in CABG patients (intraoperative red blood cell transfusion 
1,000 mL, postoperative renal insufficiency, renal dialysis, postoperative respiratory insufficiency, and 30-day mortality), whereas one adverse outcome showed a significantly higher prevalence in women undergoing OPCAB (postoperative blood loss 500 mL; Table 2). Multivariate analysis confirmed that OPCAB surgery was independently associated with a protective effect against those five adverse events as shown in Table 3. However, OPCAB surgery was an independent risk factor for one adverse postoperative outcome (postoperative blood loss 500 mL; Table 3).
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Comment |
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Off-pump coronary artery bypass surgery is a recently developed surgical technique avoiding the deleterious consequences of CPB. It has been suggested that high-risk patients most likely benefit from OPCAB inasmuch as these patients are at highest risk to develop complications related to the use of CPB [15, 16]. Given the results of several previously published studies of increased morbidity and mortality in female patients, we therefore decided to examine the effect of OPCAB in women. We compared outcomes for OPCAB versus standard CABG surgery in our subset of female patients.
We found that OPCAB was associated with significantly lower prevalences of postoperative respiratory insufficiency, postoperative renal insufficiency and dialysis, and perioperative high transfusion requirement, as well as 30-day mortality, than conventional CABG. However, the prevalence of increased postoperative blood loss was significantly higher in women undergoing OPCAB.
Several previously published studies found prolonged postoperative ventilation as a consequence of respiratory insufficiency to be significantly more frequently required in female patients as compared with male patients undergoing coronary revascularization [17–20]. This may be related to the greater comorbidity of women in comparison to male patients, especially to a significantly higher incidence of preoperative chronic obstructive airway disease as compared with men [10, 17, 21]. Furthermore, as suggested by Koch and associates [20], it may be related in part to the amount of narcotics and benzodiazepines administered intraoperatively. However, in agreement with Brown and associates [16] we found that in women OPCAB surgery was associated with a significantly lower prevalence of postoperative respiratory insufficiency as compared with conventional CABG. This is interesting, as the prevalence of preoperative pulmonary disease was higher in women undergoing OPCAB surgery. The results therefore indicate a beneficial effect of avoiding CPB even in the subgroup of female patients with an additional important risk factor for postoperative respiratory insufficiency.
In this series, OPCAB surgery was significantly associated with a lower prevalence of postoperative renal insufficiency as well as renal failure requiring dialysis. This is in concordance to findings of Brown and associates [16], who found lower prevalence of both acute renal failure as well as renal complications in women undergoing OPCAB. However, in contrast to our series, both postoperative outcome variables failed to reach statistical significance [16]. Prevalence of postoperative renal morbidity such as anuria has been reported by some to be higher in women as compared with a matched cohort of men undergoing CABG surgery, indicating a potentially higher risk for postoperative renal complications in women undergoing CABG surgery [20]. However, as previously shown in several series of both female and male patients undergoing CABG surgery, OPCAB seems to be beneficial with regard to postoperative renal function [22–24]. This may be mainly because of the avoidance of the deleterious effects of CPB such as hemodilution by the priming volume, nonpulsatile flow, renal hypoperfusion, or hypothermia [22]. Furthermore, it has been shown that preoperative renal dysfunction is one of the most important risk factors of postoperative renal morbidity [22]. However, despite several indicators for an impact of female gender on postoperative renal function, no significant differences in the incidence of preoperative renal dysfunction have been reported for women undergoing CABG [10, 17, 25]. One study exists, reporting a higher incidence of preoperative renal dysfunction in women in a large study population of more than 2,500 patients [4].
Koch and associates [20] reported a higher perioperative transfusion requirement in women undergoing CABG surgery as compared with male patients. We found OPCAB surgery to be beneficial with regard to this postoperative complication in female patients. This may be related to a lower risk profile in OPCAB patients as a result of selection bias leading to more-stable postoperative conditions. In contrast, postoperatively increased blood loss was—surprisingly—significantly lower in women undergoing conventional CABG. However, the requirement for high red blood cell transfusion was significantly lower in women undergoing OPCAB in our series.
Previous literature on the impact of female gender on perioperative mortality has yielded conflicting results. Although some reported a higher in-hospital mortality for women, others could not find a significant difference between female and male patients [2, 4, 6, 10, 17, 20, 21, 26–29]. Similar to our results, Brown and associates [16] found a 42% lower mortality rate in women undergoing OPCB than women undergoing on-pump CABG. This is in accordance to findings of Mack and associates [15] revealing a significantly lower postoperative mortality after OPCAB surgery in a large study population of male and female patients undergoing CABG surgery, although the mean predicted risk profile was significantly higher in OPCAB patients.
Our study revealed excellent results in female patients undergoing OPCAB surgery, despite potential concerns about beating heart revascularization in patients with small coronary arteries related to a small body surface area. However, in a series of 1,939 consecutive patients, Mickleborough and associates [30] found women not to be more likely to have vessels larger than 1.5 mm in size, but to be less likely to have diffuse coronary artery disease as compared with men. In our study, as well as in previously published series, female OPCAB patients had shorter intensive care and hospital stays than female CABG patients despite both time periods having been shown to be significantly longer in women as compared with men [16–18]. It is for these reasons and despite some of our differences maybe having been related to selection bias that we can say with confidence that OPCAB can be safely performed in female patients.
Because of the retrospective design of our study and the lack of randomization, selection bias may have accounted for some of the observed differences between the surgical groups. That is, lower-risk female patients may have been selected to undergo OPCAB surgery. It should be noted that women undergoing OPCAB surgery had a higher mean left ventricular ejection fraction and received fewer coronary artery bypass grafts than female CABG patients. These differences may be related to selection bias. The possibility of selection bias, as for all nonrandomized studies, therefore is the main limitation of our study. However, it is important to note that the OPCAB group did not have the lowest prevalence of each of the potential preoperative risk factors, especially with regard to preoperative prevalence of impaired cardiac performance (left ventricular ejection fraction < 0.30). We therefore believe that despite the named limitations of our study, reliable suggestions regarding a beneficial effect of OPCAB surgery in women can be raised.
In conclusion, OPCAB is a safe technique for myocardial revascularization even in female patients. Surgery with OPCAB seems to have beneficial effects on several outcome variables after CABG surgery in women. For that reason, off-pump surgery may be an effective method for lowering morbidity and mortality in these relatively high-risk patients.
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