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Ann Thorac Surg 2005;79:81-87
© 2005 The Society of Thoracic Surgeons
a Division of Cardiac Surgery, "G D'Annunzio" University, Chieti, Italy
b Division of Cardiac Surgery, University of Torino, Torino, Italy
Accepted for publication June 16, 2004.
* Address reprint requests to Dr Calafiore, Division of Cardiac Surgery, "S Giovanni Battista" Hospital, c.so Dogliotti 14, 10126 Torino, Italy (E-mail: calafiore{at}unich.it).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentReferences |
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METHODS: From November 21, 1994, to December 31, 2001, 4,381 patients underwent isolated coronary revascularization: among these patients, 274 (6.3%) underwent a redo. Applying the propensity score, 239 redo patients (group R) were matched with 239 who underwent the first revascularization (group F).
RESULTS: Early mortality was 2.1% (group F) and 4.2% (group R), not significantly different. Group R showed significantly higher creatine kinase myocardial band release, length of intensive care unit stay, and incidence of incomplete myocardial revascularization than group F. In group R, off-pump patients showed higher incidence of incomplete revascularization. Redo was a risk factor for abnormal (>19 IU/L) creatine kinase myocardial band release (odds ratio, 1.7; p = 0.0066) and incomplete myocardial revascularization (odds ratio, 2.4; p = 0.0060). Five-year clinical outcome was significantly worse in group R, except for freedom from redo or percutaneous transluminal coronary angioplasty. Redo was an independent variable for lower freedom from death of any cause, cardiac death, acute myocardial infarction, cardiac events, and any event. Patients with higher creatine kinase myocardial band release or incomplete myocardial revascularization showed lower freedom from cardiac-related events. Incidence of incomplete myocardial revascularization and creatine kinase myocardial band release were significantly higher in group R by both univariate and multivariate analysis. This could explain the worse late outcome of redo patients.
CONCLUSIONS: Complete revascularization without damaging the heart, whichever technique is used, is the target of redo surgery, to achieve the same quality of results obtained in the first operation.
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Introduction |
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Despite some authors reporting a reduced mortality and morbidity in redo, especially in patients operated on using off-pump procedures [4, 8, 9], the risk remains higher than in the first operation [10]. Furthermore, the long-term outcome seems to be worse than in patients who underwent the first revascularization [11–17].
The purpose of this study is to evaluate whether and why reoperative CABG can influence early and late outcomes of patients who undergo isolated CABG.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Patient Selection for On-Pump and Off-Pump
Allocation to off-pump surgery was on the basis of the vessel size (>1.2 mm) and the absence of diffuse coronary calcifications. In the presence of mechanical or electrical instability, the patient was selected preferably for on-pump surgery. The final decision was depending on the basis of the expertise of the surgeon responsible for the operation.
Surgical Technique
ON-PUMP
Cardiopulmonary bypass was instituted by cannulation of the ascending aorta and the right atrium. A standard circuit with a hollow-fiber membrane oxygenator and a roller pump was used. The body temperature was kept to 37°C. Myocardial protection was achieved by means of intermittent antegrade warm blood cardioplegia [18].
OFF-PUMP
The method of exposure of the target coronary vessel and of stabilization has already been reported [19]. In more recent years, apical suction was used to expose in particular the lateral and inferior walls (Xpose; Guidant Corporation, Cupertino, CA). When the coronary artery was exposed, stabilization was achieved with a pressure (Acces Ultima System; Guidant Corporation) or suction (Axius Vacuum 2 System; Guidant Corporation) stabilizer. The target vessel was occluded with a 4-0 polypropylene suture (Prolene; Ethicon, Somerville, NJ), passed on a small piece of silicone tubing and then gently snared.
Clinical Data Collection, Monitoring, and Definition
A set of perioperative data were collected prospectively for all patients undergoing CABG at our institution. The following were recorded and defined: Mortality included death of any cause. Cardiac mortality included any death for cardiac causes and sudden deaths. Cerebrovascular accident (CVA) was defined as global or focal neurologic deficit, diagnosed by a neurologist and confirmed by a brain computed tomography scan. Acute myocardial infarction (AMI) was defined as enzymatic elevation, electrocardiographic sign of necrosis, new akinetic segment(s) at echocardiogram, or ventricular arrhythmias that were not potassium related. Early negative primary end points were defined as death of any cause, AMI, and CVA. Early major events were defined as the sum of death of any cause, CVA, AMI, low output syndrome (need of intraaortic balloon pump and or inotropic drugs for >12 hours), need of mechanical ventilation for more than 24 hours, acute renal failure (postoperative blood creatinine 
2.0 mg/dL, if the preoperative value was normal [
1.4 mg/dL], or 1 mg/dL higher if pathologic), and gastrointestinal complications. Cardiac events were defined as the sum of cardiac deaths, AMI, and redo/percutaneous transluminal coronary angioplasty. Any event was defined as death any cause, AMI, and redo or percutaneous transluminal coronary angioplasty. To evaluate ischemic injury, the peak of the creatine kinase myocardial band (CK-MB), both as a continuous variable and as a cutoff (19 IU/L was the highest normal, according to our laboratory), was analyzed. Completeness of revascularization was defined as the revascularization of all coronary arteries with a stenosis equal or higher than 50% and with a size equal to or greater than 1.5 mm [20].
Follow-Up
All the patients were followed up in our outpatient clinic 3, 6, and 12 months after surgery and thereafter at yearly intervals. The most recent information was obtained by calling the patient or the referring cardiologist. Follow-up was 100% complete up to June 30, 2003.
Statistical Analysis
Results are expressed as mean ± standard deviation. Statistical analysis comparing the two groups was performed with unpaired two-tailed Student's t test for the means or 
2 test for categorical variables. Stepwise logistic regression was used to realize a model to calculate the propensity score [21]. Variables included in the stepwise logistic regression analysis were preoperative (age, age 75 years, female sex, body weight, history of hypertension, history of smoking, hypercholesterolemia, chronic renal failure, chronic hepatic failure, chronic obstructive pulmonary disease, unstable angina, chronic heart failure, AMI < 24 hours, preoperative intraaortic balloon pumping, previous atrial fibrillation, urgency, diabetes [insulin or oral treatment], redo, ventricular arrhythmias, extracoronary vasculopathy, previous CVA, previous AMI, left main disease, number of diseased vessels, ejection fraction, ejection fraction 0.35, inotropic agents, nitroglycerin i.v.) or perioperative (use of cardiopulmonary bypass, simultaneous carotid surgery, number of anastomoses, number of arterial anastomoses). The variable "surgeon" was eliminated as all the procedures were performed by one of three surgeons (A.M.C., G.d.G., G.T.), who had the same results. The definition of the variables was previously reported [22]. The goodness of fit was evaluated using the Hosmer and Lemeshow goodness-of-fit statistic and residual analysis. Each redo patient was matched with the first CABG patient with the closest propensity score. Variables at the basis of the model are shown in the Appendix. Stepwise logistic regression was used to select the independent variables that could predict the end points of this study and included all the univariate variables with a p value less than or equal to 0.2. In the final regression model, independent variables were expressed as an odds ratio with the related p value also reported. Five-year actuarial results were obtained with the Kaplan-Meier method and listed in the tables as percentages. The statistical significance was calculated with the log-rank test. Cox analysis was used to evaluate the independent risk factors for reduced late events. In the Cox analysis model independent variables were expressed as a hazard ratio with the related p value also reported. The SPSS software (Chicago, IL) was used. Probability values less than or equal to 0.05 were considered significant.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Group R showed significantly higher CK-MB release, length of intensive care unit stay, and incidence of incomplete myocardial revascularization than group F (Table 3). Stepwise logistic regression confirmed that redo was a risk factor for abnormal (>19 IU/L) CK-MB release (odds ratio, 1.7; p = 0.0066) and for incomplete myocardial revascularization (odds ratio, 2.4; p = 0.0060).
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The independent predictors for early events, identified by stepwise logistic regression, are shown in Table 4. Redo coronary surgery was not a risk factor for any of the explored events.
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19 IU/L (79, 41.1%, group R and 113, 58.9%, group F). Group H (high) included 286 patients (59.8%) whose peak CK-MB release was more than 19 IU/L (160, 55.9%, group R and 126, 44.1%, group F). Five-year actuarial results are shown in Table 8. Higher CK-MB release was related to lower freedom from cardiac deaths, cardiac events, and any event.
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Owing to these results, a further analysis was performed excluding patients with higher CK-MB release and incomplete myocardial revascularization. Five-year outcome in group F and group R showed no difference between the two groups of patients (Table 10).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Recently better angiographic results of the saphenous vein graft [6] than in the past [7] were reported, very likely owing to a wide use of the statins and aspirin. Furthermore, the great majority of patients operated on since the middle 1980s received a left internal mammary artery to left anterior descending coronary artery, which, as well known, increases the event-free period [23]. Therefore the prevalence of redo has reached a plateau in more recent years [5].
Early mortality of redo CABG ranged from 1.8% to 16.7% [8, 24]. Although surgical risk is decreasing as a result of improved surgical experience and new technical strategies, many authors still report higher mortality and morbidity in redo than in the first operation [5, 11, 12, 25]. Long-term results are also consistently worse in redo patients than in patients who undergo the first revascularization [11–17].
However, redo patients present characteristics different from patients at the first operation. Generally they are older, with a lower ejection fraction and more comorbidities. To eliminate these differences, in this study we applied the propensity score, selecting a group of 239 patients at first operation who had preoperative and operative characteristics similar to a group of 239 redo patients. Regarding early clinical outcome, there were no significant differences, with the exception of CK-MB release and length of intensive care unit stay, which were significant higher in group R.
In a large series of 508 redo CABG, Salomon and associates [11] reported a 10-year survival of 66.5%, significantly lower if compared with 74.4% of 6,591 patients at first operation. In the same study only 30% of redo patients were alive and free from angina, AMI, and reoperation versus 50% of primary CABG patients. Many studies have demonstrated that different long-term outcome between the first operation and the reoperation had to be attributed to higher age [11, 13–16] and to more impaired left ventricular function of redo patients [11–14, 16, 17].
In our series, even if the clinical preoperative profile of the patients included in the study was made similar by using the propensity score, long-term results showed lower freedom from death of any cause, cardiac death, AMI, cardiac events, and any event in group R compared with group F. Cox analysis confirmed that redo was a risk factor for decreased freedom from all the events mentioned above, whereas there were no significant differences regarding freedom from redo or percutaneous transluminal coronary angioplasty both by univariate and multivariate analyses.
Although redo presents more technical difficulties, such as the potential for cardiac and conduit injury during dissection, availability of conduit, management of patent vein graft, myocardial protection, and bleeding [26], early outcome was similar between the two groups analyzed. As a consequence, worse midterm clinical results of redo patients cannot be related to higher incidence of perioperative complications.
In a previous study of ours, we demonstrated that peak CK-MB values above normal during the early postoperative period can impact negatively on midterm clinical results, especially on events that are cardiac related [22]. In this study we repeated the same analysis, with similar results. Patients who had abnormal CK-MB release showed worse midterm cardiac-related results both by univariate and multivariate analyses. As stepwise logistic regression showed that redo was a risk factor for increased CK-MB release, this could partially explain the negative influence on midterm outcome of redo coronary surgery.
Many studies demonstrated that incomplete myocardial revascularization affects negatively midterm [27, 28] and long-term [20, 28] follow-up. Another possible explanation for worse midterm outcome could be the higher prevalence of incomplete myocardial revascularization in group R if compared with group F (93.3% versus 85.4%; p = 0.005), confirmed by stepwise logistic regression. Patients with incomplete myocardial revascularization showed lower freedom from cardiac death, AMI, and cardiac events by both univariate and multivariate analyses.
The impact of off-pump procedures in long-term results is not uniform. Early results show a beneficial effect of off-pump procedures in group R, even if not statistically significant, in lowering mortality and incidence of CVA, AMI, early negative primary end points, and early major events. Furthermore, CK-MB release in patients without clinical AMI is significantly lower. All these aspects contribute to improve the quality of long-term outcomes. However, in group R off-pump patients show a high incidence of incomplete revascularization, and this, on the contrary, worsens long-term outcome. Even if it is difficult to give a weight to all these findings, which lead in opposite directions, we think that incomplete revascularization was a high price to pay to reduce early mortality and morbidity. The net result was a limitation of the benefit of the surgical procedure in group R.
That higher CK-MB release and higher incidence of incomplete revascularization are at least partially responsible of the worse outcome of group R versus group F is also suggested by Table 10. When group R and group F include only patients with normal enzymatic release and complete revascularization, long-term results are similar.
In conclusion, reoperative CABG does not seem to affect early results. Even if the patients in this study showed similar preoperative characteristics, long-term results are worse in group R than in group F. We suggest that higher CK-MB release and incompleteness of myocardial revascularization can be at the basis of this unsatisfying result. Complete revascularization without damaging the heart, whichever technique is used, is the target of redo surgery, to achieve the same quality of results obtained in the first operation.
Off-pump surgery has globally beneficial effects; however, in our experience it is related to a high incidence of incomplete myocardial revascularization, which negatively affects long-term outcome. We suggest that this strategy not be used indiscriminately, but only in selected cases: we should not sacrifice a long-term benefit to an early successful outcome.
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Appendix |
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References |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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