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Eur J Cardiothorac Surg 2003;23:360-367
© 2003 Elsevier Science NL
6)
Department of Cardiology and Cardiac Surgery, University ‘G. D'Annunzio’, S. Camillo de' Lellis Hospital, via C. Forlanini, 50, 66100 Chieti, Italy
Received 9 September 2002; received in revised form 13 November 2002; accepted 27 November 2002.
* Corresponding author. Tel.: +39-0871-358-653; fax: +39-0871-402-239
e-mail: calafiore{at}unich.it
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Abstract |
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 Top Abstract 1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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6) who underwent isolated myocardial revascularization with and without cardiopulmonary bypass (CPB). Methods: From November 1994 to December 2001, 1266 patients with EuroSCORE6 underwent isolated myocardial revascularization. Among them, applying the propensity score, we were able to select 1020 patients operated on without CPB (group A, n=510) and with CPB (group B, n=510) with the same preoperative characteristics. The only differences were the higher incidence of patients with age between 61 and 65 years (9.4% in group A vs. 13.9% in group B, P=0.025) and the lower number of anastomoses/patient in group A (1.8±0.9 vs. 2.8±0.9, P<0.001). EuroSCORE were identical in both groups (7.8%). Results: Thirty-day mortality was higher in group B (5.9 vs. 3.1%, P=0.035). Group A showed a lower incidence of cerebrovascular accidents (CVAs) (0.6 vs. 3.1%, P=0.003), whereas incidence of acute myocardial infarction (AMI) was similar (2.0% in group A vs. 2.5% in group B, P=ns). Early negative primary end-points and early major events incidences were higher in group B (8.2 vs. 3.9%, P=0.004, and 14.5 vs. 7.1%, P<0.001, respectively). Stepwise logistic regression confirmed that CPB was an independent predictor for higher early mortality (Odds ratio (OR) 2.0) and CVA, negative primary end-points and early major events incidences (OR 4.6, 2.3 and 2.4, respectively). Five-year freedom from the events explored (death due to any cause, cardiac death, AMI, AMI on a grafted area, redo/percutaneous transluminal coronary angioplasty (PTCA), redo/PTCA on a grafted area, target cardiac events (cardiac death, AMI in a grafted area and redo/PTCA in a grafted area) and any event were similar in both groups. Conclusions: In high risk patients myocardial revascularization without CPB shows better early outcome and similar clinical late results.
Key Words: Off pump surgery • High-risk • Myocardial revascularization
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1. Introduction |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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Recently, an European score (EuroSCORE) was introduced [7,8] to evaluate the expected 30-day mortality after cardiac surgery. According to it, mean mortality after isolated coronary bypass grafting was 3.4% [7]. It seemed reasonable to us to define ‘high risk’ as any patient who had an expected mortality of 6 or higher. In these patients the impact on early and late outcome of myocardial revascularization with and without CPB was evaluated.
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2. Material and methods |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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2.1. Patient selection
Candidates for myocardial revascularization without CPB were patients (a) with suitable anatomy (epicardial vessels, with a size 1.2 mm, not calcified), (b) with high risk for perioperative or postoperative organ dysfunction (kidney, brain, liver, etc.). Ejection fraction per se was not a contraindication; however, dilated hearts, in our opinion, would not tolerate the verticalization in order to expose the lateral wall. Contraindications to the procedure were (a) unfavorable anatomy (small vessel disease, intramyocardial vessels or vessels with diffuse calcifications), (b) marginal branches in redo surgery, as epicarditis and fibrosis often does not allow to open correctly a lateral vessel also with CPB and cardiac arrest, (c) electric and/or mechanical instability.
2.2. Surgical techniques
Patients were anesthetized as usual. A pulmonary catheter was seldom used.
2.2.1. Group A
In this group 156 patients had a left anterior small thoracotomy (LAST) operation (148) or a posterolateral thoracotomy (8). In the remaining 354 a median sternotomy was used. In this latter group mechanical stabilization was obtained with the CTS stabilizers (initially OPCABTM Midline Multi-Vessel System, CTS, Cupertino, CA, USA, later Acces UltimaTM System, Guidant Corporation, Cupertino, CA, USA). The heart was verticalized using different techniques. First only four slings were used; later a single Lima stitch was added [9]. More recently, the verticalization of the heart was obtained with the XposeTM (Guidant Corporation, Cupertino, CA, US) (apical suction) and a single Lima stitch with a single additional sling if necessary. Hemodynamic stability was obtained with Trendelenburg position, adding volume and with small boluses of a vasopressor when needed (metaraminol or diluted norepinephrine).
2.2.2. Group B
When CPB was used, normothermic perfusion and intermittent warm blood cardioplegia was used in all the patients but 19, where the aorta was not cross clamped and the procedure was performed under circulatory assistance.
After each single procedure, flow in the grafts was measured using two different flowmeters (Transonic, Ithaca, NY, USA and Medi-Stim, Oslo, Norway). Recently, a new imaging system was added (Novadaq Technologies Inc., Toronto, Canada).
2.3. Postoperative course
All the patients were admitted in intensive care unit (ICU) and subsequently to the regular ward. All the patients were discharged home on a regimen of oral diltiazem 60 mg three times a day for 1 month and aspirin 100 mg a day. They were followed up in our outpatient clinic 3, 6 and 12 months after surgery and thereafter at yearly intervals. The more recent information was obtained by calling the patient or the referring cardiologist. Follow up was 100% complete; its dead line was June 30, 2002.
2.4. Methodology of the study
End point of this study was the impact of CPB on early or midterm outcome of high risk patients. For this purpose 30-day incidence of mortality, of acute myocardial infarction (AMI), of cerebrovascular accidents (CVA), of early negative primary end points and early major events was recorded. After 30 days from surgery, deaths and its causes, AMI, AMI in grafted areas, need of surgical redo or percutaneous transluminal coronary angioplasty (PTCA), in all the areas or in grafted areas, incidence of target cardiac events and any event were recorded. All the data were analyzed using a variety of risk factors (see Appendix A).
2.5. Definition of terms
Mortality included death due to any cause. Cardiac mortality included any death for cardiac causes and sudden deaths. CVA was defined as global or focal neurological deficit, lasting less (transient ischemic attack, (TIA)) or more (stroke) than 24 h, that could be evident after emergence from anesthesia or after first awaking without any neurological deficits. CVA was diagnosed by a neurologist and confirmed by a brain computed tomography (CT) scan. AMI was defined as enzymatic elevation, electrocardiogram (EKG) sign of necrosis, new akinetic segment(s) at echocardiogram, ventricular arrythmias non-K+ related. Early major events (EME) were defined as the sum of death due to any cause, CVA, AMI, low output syndrome (defined as need of intra aortic balloon pumping (IABP) and or inotropic drugs for more than 12 h), need of mechanical ventilation for more than 24 h in absence of low output syndrome, acute renal insufficiency (defined as blood creatinine level 2.0 and two times the preoperative value), acute renal failure (need of ultrafiltration or hemodialysis), gastrointestinal complications with or without related surgery. Early negative primary end points were defined as death due to any cause, AMI and CVA, a patient included only once; target cardiac events as cardiac death, AMI in the grafted area and redo or PTCA in the grafted area, a patient included only once; any event as death due to any cause, AMI any territory, redo or PTCA any territory, a patient included only once.
2.6. Statistical analysis
Results are expressed as mean value±SD unless otherwise indicated. Statistical analysis comparing two groups was performed with unpaired two-tailed t testing for the means or 
2 test for categorical variables. Logistic regression was used to realize a model to calculate the propensity score (the probability to be selected for on-pump coronary artery bypass graft (CABG) given a set of preoperative risk factors listed in appendix A). The goodness of model was evaluated using the Hosmer and Lemeshow goodness-of-fit statistic and residual analysis. Each off-pump CABG patient was matched with the on-pump patient with the closest propensity score. Stepwise logistic regression analysis was used to select the independent variables that could predict the end points of this study and included all the univariate variable with a P value 
0.2. In the final regression model, independent variables were expressed as odds ratio (OR) with the 95% confidence limit (CL); the related P value was also reported. Actuarial survival curves were obtained with the Kaplan–Meier method. The statistical significance was calculated with the log–rank test. Cox analysis was used to evaluate the independent risk factors for reduced late survival. In the Cox analysis model independent variables were expressed as hazard ratio (HR) with the 95% CL; the related P value was also reported. The SPSS software (Chicago, IL, USA) was used. P values0.05 were considered significant.
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3. Results |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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Expected mortality from EuroSCORE was higher than the observed one. Globally, 46 patients died during the first 30 days from surgery, whereas the expected deaths were 76.4 (P=0.006). The highest discrepancy between the expected and observed mortality was found in the group of patients with an EuroSCORE from 6 to 8 (n=729, 23 observed vs. 46.6 expected deaths, P=0.006). Patients with EuroSCORE from 9 to 11 and 12 or higher showed similar observed and expected mortality (respectively, n=238, 17 vs. 22.9, P=ns, and n=53, 6 vs. 6.9, P=ns).
Table 4 shows the comparison of observed and expected mortality in group A and B. It is evident that, even if there is a clear trend towards a lower observed than expected mortality, the major advantage in our experience is related to patients operated on without CPB with an EuroSCORE from 6 to 8. Mortality in group A was significantly lower than in group B, but when EuroSCORE was 6 to 8 (6/357 patients in group A vs. 17/372 patients in group B, P=0.043) or 12 or higher (0/27 vs. 6/26, P=0.027).
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Table 5 shows the results of stepwise logistic regression for higher incidence of early death, AMI, CVA, early negative primary end points and EMEs. CPB was found to be an independent risk factor for all of them but AMI and cardiac deaths.
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3.2. Midterm results
Follow up ranged from 6 to 91 months (mean 46±23). Eighty-five more patients died (8.7%), 48 (56.5%) from cardiac causes; 24 (2.5%) had a new AMI, 15 (1.5%) in the grafted area; 26 (2.7%) had a redo or PTCA, 16 (66.7%) in the grafted area; 66 (6.8%) had a target cardiac event and 116 (11.9%) any event. Table 6 shows 5 year actuarial results and Table 7 the independent risk factors identified by Cox analysis. CPB is no more a risk factor for any of the events considered in the analysis.
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4. Discussion |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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The possibility of EuroSCORE to predict the mortality risk for an individual center was explored by Sergeant et al. [13] who found that EuroSCORE overestimates the risk from 0 to 8, was equal from 9 to 11 and underestimated in the range 12 or higher. Nevertheless, globally the predictive capacity was reasonable. We analyzed the coherency between EuroSCORE and observed mortality and found that, globally the observed mortality was significantly lower than the expected one. However, this was due mainly to group A, that was able to avoid 28 expected deaths, whereas in group A there was still a reduction (12 deaths), but not significant.
Some previous study found a positive effect of avoiding CPB on early mortality, but only in subgroups of patients, as redo [14] in patients with single vessel disease or in patients with ventricular dysfunction [15,16]. However, other authors did not find any difference in mortality when CPB was avoided if compared with patients operated on with CPB in subgroups considered ‘high risk’, as redo [5,17–19], elderly [5,20–22], patients with preoperative renal failure [5,23], ventricular dysfunction [5,24]. Other authors that considered more objective scoring scale [6] did not find again any benefit in avoiding CPB. Riha et al. [12] did not find any improvement in mortality in off CPB high risk patients if compared with expected mortality by EuroSCORE.
On the contrary, many studies demonstrated a reduction of morbidity when CPB was not used in subgroups of high risk patients: less transfusion rate [4,5,14,18,21–23], ICU stay [4,18], postoperative in hospital length of stay [4,14,18,20,21], less inotropic requirements [23], lower incidence of postoperative stroke [19,23], less need for prolonged ventilatory support [14,21], less need of postoperative IABP [19].
Our analysis shows that in patients with EuroSCORE 6 or higher, CPB was an independent predictor of higher 30-day mortality (OR 2.0), higher incidence of postoperative CVA (OR 4.6), higher incidence of early negative primary end points (OR 2.3) and early major events (OR 2.4). This means that not only mortality, but also morbidity was reduced when CPB was not used. This is evident as mortality related to non-cardiac causes was lower in patients in group A. In particular, CVA incidence was reduced, but only because 341 patients had no aortic manipulation at all [25]. The global reduction of morbidity was the cause of reduced ICU stay and postoperative in hospital stay (Table 3).
Actuarial 5 year freedom from different events (Table 6) shows no more difference between groups, due to the peculiar mechanism at the basis of the actuarial model. Freedom from revascularization failure is higher, even if not statistically significant, in group B, but this is due to higher rate of progression of disease in group A, due to relatively high incidence of LAST operation. In fact failure of revascularization on grafted vessels is, conversely, slightly higher in group A, demonstrating that off CPB strategy does not affect negatively patency rate in the long term. That off CPB strategy is not related to higher adverse cardiac events is also shown by the similar incidence of freedom from cardiac target events in both groups.
In conclusion, patients with EuroSCORE6 who need myocardial revascularization have lower 30-day mortality and morbidity if operated on without CPB. Actuarial results after 5 years show similar outcome independently from the surgical strategy used, demonstrating that there is no price to pay in the long term for a better early results.
A limitation of this study is that, even if propensity score eliminated the great part of the differences between groups, extension of the disease was somehow different in the two groups. However, even if myocardial revascularization without CPB has its own indications and limits, as all surgical techniques, our study demonstrates that, when it is technically feasible, there is a clear evidence of a better early outcome. As use of cardiopulmonary bypass cannot be avoided in all the cases, only a careful selection of patients for one of the two strategies (that are complementary and not antagonist) will increase the global quality of the surgical results of myocardial revascularization in high risk patients.
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Footnotes |
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Appendix A |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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Appendix B. Conference discussion |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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Dr Calafiore: I gave the indication and the contraindication to the CPB. So perhaps the conclusion would better be said as following this indication and the contraindication, you can have better results if you can do the patient off pump. But not all the patients can be done off pump, some them must be done on pump.
Unfortunately, these patients, the so-called high-risk patients, have a higher morbidity because of the use of pump and everything is related; not very high, but it's still significant.
On the contrary, when you have a score, patients are divided according it and you compare patients with the same score. So this means that globally the amount of comorbidities is the same. So if you are able to operate on patients without CPB, you can have better results. But if you are not able to do this because they must be done on pump, you have the results I showed, because I could not operate on all the patients on pump. The problem is, are you able to do these cases on pump or off pump? If you are not able to do these cases on pump, you will have a little bit higher morbidity and mortality.
Dr Dion: When you consider the few truly randomized studies OPCAB versus CABG - let's take the paper presented by Puskas at the recent AATS - the results are different from yours: there is no outcome difference in neurology, infarction or survival. The only difference they found was a length of stay of one more day although the ICU stay was identical. So if I consider what you present here – 2.7% CVA in the CPB group versus 0.7 – I'm not convinced yet that a randomized study would have shown the same. I agree with you that if you can do apply OPCAB in high-risk patients with less morbidity, let us use it. I still wonder whether the groups were really comparable.
Dr Calafiore: Yes, I understand this point. But the problem with randomization is that, first of all, it's quite difficult to randomize patients. Second, you put in the randomization your biases, according to the technique you are using. So personally I prefer to consider all the patients I am doing, trying, of course, to have some selection of patients. Afterwards, using some more complex statistics, we can understand, not the truth, but something that can approach the truth.
Dr C. Alhan (Istanbul, Turkey): I'll not ask any question, but I'll make a comment. I'll be presenting more or less similar data on Wednesday, Fast Track Recovery in the High Risk Patient. And in our group of 158 patients, the mean EuroScore was 7.9 and the mortality rate was 3.2, and all of the patients were operated on pump. Interestingly, the mean number of distal anastomoses is more or less the same with you, and I think that the same results can be achieved on pump also.
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References |
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TopAbstract1. Introduction2. Material and methods3. Results4. DiscussionAppendix AAppendix B. Conference...References |
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