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Ann Thorac Surg 2001;71:537-542
© 2001 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Vienna General Hospital, University of Vienna, Vienna, Austria
Accepted for publication May 12, 2000.
Address reprint requests to Dr Grimm, Department of Cardiothoracic Surgery, Vienna General Hospital, Waehringer Guertel 18-20, A-1090 Vienna, Austria
e-mail: michael.grimm{at}akh-wien.ac.at
| Abstract |
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Methods. We investigated 44 patients over 75 years, matched for preoperative risk and left ventricular function, who underwent coronary artery bypass grafting either with or without cardiopulmonary bypass (CPB). We analyzed patients characteristics, Parsonnet score, EuroSCORE, short as well as midterm outcome and quality of life (freedom from recurrence of angina, antianginal therapy, sf36 test).
Results. Perioperative mortality was higher in the patient group operated with CPB (15.9) as compared to patients operated without CPB (4.5%, p = 0.0226). Patients operated with cardiopulmonary bypass received more grafts (3.1 ± 0.1) than patients operated without cardiopulmonary bypass (1.6 ± 0.1, p = 0.0001) and and were more likely to undergo complete revascularization (with CPB 100%, without CPB 63.6%, p = 0.0010). Perioperative complications were more frequent and midterm survival was worse in the patient group operated with CPB (log rank p = 0.0228). Quality of life was comparable in both groups.
Conclusions. The concept of incomplete target vessel revascularization of the culprit lesion seems to be a promising option for selected high-risk patients, predominantly due to lower perioperative mortality.
| Introduction |
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Recent studies have shown that mortality and morbidity in patients with high operative risk can be reduced if surgery is performed without cardiopulmonary bypass (CPB) [4]. Complete revascularization of all diseased vessels, however, is not feasible in all cases [5, 6]. The long-term outcome and freedom from recurrence of angina may therefore be affected by incomplete revascularization. Whether this has an impact in the elderly patient group with limited life expectancy has not yet clearly been defined.
The aim of this study was to evaluate the perioperative outcome of selected elderly, high-risk patients undergoing either CABG with CPB with complete revascularization of all diseased vessels, or CABG without CPB focusing on target vessel revascularization of the culprit lesion. Furthermore, we investigated whether the operative technique affects quality of life and recurrence of angina in a midterm follow-up period.
| Patients and methods |
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Outcome
We studied preoperative patient characteristics, and postoperative as well as midterm outcome. Preoperative patient characteristics included all features building up the EuroSCORE and Parsonnet score as well as number of diseased vessels [7, 8]. Postoperative outcome was defined by number of grafts, complication rate, and length of hospitalization. Perioperative myocardial infarction was defined as any new Q-wave or loss of R in the electrocardiogram, significant creatinine kinase (CK)/CK-MB elevation (CK-MB >40 U/l) or infarction validated at autopsy. Cardiac failure was defined as prolonged need for inotropes (>1 day) or need for intraaortic balloon counterpulsation. Renal failure was defined as need for hemofiltration, and respiratory failure as need for prolonged ventilatory support (>5 days). Also evaluated were perioperative stroke, abdominal complications, sepsis, and local wound infections. Postoperative bleeding was defined as bleeding requiring rethoracotomy.
Blood levels of creatinine, blood urea nitrogen, CK, CK-MB, CK-MB fraction, C-reactive protein, hemoglobin, hematocrit, and leucocytes were compared preoperatively, immediately postoperatively on intensive care unit (ICU) admission, and on postoperative days 1, 2, and 7.
Midterm follow-up was defined by means of survival, freedom from recurrence of angina (Canadian Cardiovascular Society score), freedom from rehospitalizations and reinterventions, as well as need for antianginal medication. Quality of life was evaluated with the sf36 questionnaire.
Anesthesia and surgical technique
Patients were premedicated with midazolam. All patients received a standardized totally intravenous anesthesia with midazolam, etomidate, fentanyl, and pancuronium. Ventilation was performed with oxygen in air.
In all patients, surgical access was performed via median sternotomy. The patient was heparinized systemically after harvesting of arterial and venous grafts.
CABG with CPB
Patients undergoing CABG with CPB underwent normothermic CPB with intermittent cold blood cardioplegia with a hot shot before opening of the cross-clamp. The CPB circuit consisted of a hollow-fiber oxygenator (Bard HF 5701, C.R. Bard Inc, Havorhill, MA) and a lining system primed with Ringer lactate, mannitol, heparine, and aprotinine. Flow during CPB was maintained at 2.5 l/min/m2. Blood cardioplegia was administered in a 4:1 ratio. Hematocrit was kept above 20% with packed red blood cells if necessary. Perfusion pressure during CPB was kept above 50 mmHg with phenylephrine if necessary. Heparine was antagonized with protamine sulfate until preoperative activated clotting time was achieved. Mean arterial pressure after CPB was kept above 60 mmHg with volume and vasoactive drugs as appropriate. ICU treatment was performed according to institutional standards.
CABG without CPB
A myocardial coronary artery stabilizer system (Cardio Thoracic Systems, Cupertino, CA; Octopus, Medtronic, Minneapolis, MN) was used in all cases. The patients were heparinized systemically. In the majority of cases, the left anterior descending coronary artery (LAD) was revascularized first. The vessel was stabilized and snared proximally and distally to the chosen anastomotic site. No test of tolerance for regional ischemia was performed. Afterwards, the left internal mammary artery anastomosis to the LAD was performed on the beating heart. Further distal anastomoses were performed in the same way. Proximal anastomoses of saphenous vein grafts were performed on the partially clamped ascending aorta. Heparine was antagonized with protamine sulfate until preoperative activated clotting time was achieved.
Statistical analysis
Comparison of both patients groups was performed for categoric variables with the chi-square test or Fishers exact test as appropriate and for continuous variables with the Students t test. Survival analysis and freedom from recurrence of angina were calculated by means of Kaplan-Meier analysis (SAS Institute Inc, Cary, NC).
| Results |
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Postoperative outcome
The overall mortality of all available patients before matching was 13.9%.
Postoperative outcome of the study patients after matching is shown in Table 2. Mean aortic cross-clamp time was 59 ± 22 minutes and mean CPB time was 95 ± 34 minutes in the patient group undergoing surgery with CPB. In the study patients, we did not find a correlation between cross-clamp time or CPB time and perioperative mortality. According to the preoperative strategy, patients operated with CPB received more grafts than patients operated without CPB. According to the diseased vessels in the preoperative catheter study, revascularization was complete in 100% of the patients operated with CPB, but only in 63.6% of the patients operated without CPB.
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Follow-up and quality of life
Mean follow-up was longer for patients operated with CPB as compared to patients undergoing surgery without CPB (Table 3).
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In sf36 quality of life scores, both patient groups showed an improvement of physical as well as emotional part, as compared to preoperatively. Nevertheless, neither preoperatively nor postoperatively was there a difference between both groups (Fig 2).
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| Comment |
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With an increase in life expectancy, the number of elderly patients with symptomatic coronary artery disease is growing [2, 9]. As compared to younger patients, the elderly generally have more significant comorbidities which results in an increased perioperative mortality and a higher complication rate [3, 10]. Despite these aggravations, and due to growing surgical experience, CABG of elderly and high-risk patients has become an accepted strategy with significant and cost-effective improvement in quality of life [11, 12]. In contrast to the majority of recently published studies, in our study, we focused on the very old patient with markedly increased operative risk [1012]. This high-risk profile is expressed in a high percentage of patients who were operated urgently (39.8%), and had significantly impaired left ventricular function (25%) or significant comorbidities. As to be expected by the consequently high preoperative risk scores (EuroSCORE = 8.3 points and Parsonnet score = 21.6 points), this resulted in a higher perioperative mortality and a higher complication rate as compared to other studies [13, 14]. This has to be seen in the light that, as the university hospital, a high percentage of patients are being admitted to our institution from a rather large area. A lot of these patients have been rejected from other smaller centers due to excessive comorbidities. The probable need for a prolonged ICU stay in these high-risk patients would often exceed or block the limited ICU capacities of these small centers. On the other hand, there are only a few publications reporting on patients who are as old as our patients [15, 16]. In these articles, mortality rates ranking from 15.5% to 17% are being reported.
In contrast to these selected high-risk patients, the concept of complete surgical revascularization of all diseased vessels is still the gold standard for the majority of patients [17]. In a large series of younger patients (mean age 57 years; 2,057 patients complete, 803 patients incomplete), Jones and Weintraub [18] demonstrated a better survival for completely revascularized patients at 12-year follow-up. The patients with incomplete revascularization carried a higher preoperative risk (prior myocardial infarction, impaired left ventricular function, more diseased vessels, more totally occluded vessels). In multivariate analysis, they showed that completeness of revascularization was an independent predictor for survival, whereas for recurrence of angina, a difference was found only in univariate analysis. No differences at all were found for myocardial infarctions and need for reinterventions. In view of our study cohort, it is important that the survival benefit of complete revascularization will not become evident due to the per se limited life expectancy. From controversial discussions in interventional cardiology, we know that a long-term survival benefit and freedom from reintervention following complete interventional revascularization is still uncertain [1921]. Bell and colleagues [20] have shown that incomplete target vessel revascularization in sicker patients (advanced age, poorer left ventricular function, more severe angina status) is not a significant predictor for late outcome as compared to complete revascularization in less sick patients. On the other hand, Tan and associates [22] showed that incomplete interventional revascularization in patients with a mean age of 73 years (range 70 to 83) is associated with poorer long-term outcome. However, this study is limited by the fact that incomplete revascularization is defined as unsuccessful complete revascularization. In our patients, the decision which is the culprit lesion was based on accurate clinical investigation including angiograms, electrocardiograms, and scan techniques. Regarding the latter interventional data, we interpret the good midterm cardiac event-free survival in our patients with target vessel revascularization without CPB as predominantly related to low perioperative mortality. Quality of life (sf36 test, comparable need for antianginal therapy and reinterventions) improved in both of our patient groups. This supports that both surgical techniques may be comparable if symptomatic relief is to be achieved as the primary goal in selected elderly patients with limited life expectancy. Nevertheless, a longer follow-up of our patients will be needed to prove equality of long-term survival for the two surgical strategies.
When comparing percutaneous transluminal coronary angioplasty to CABG in the elderly, CABG is frequently associated with higher perioperative mortality and complications but improved long-term outcome (survival and freedom from recurrence of angina) [23, 24]. The introduction of CABG without CPB into clinical routine led to a significant reduction of major complications in high-risk patients undergoing surgical coronary revascularization [4]. This may relate to the reduction of the systemic inflammatory response syndrome [25, 26] and renal failure, which is partly induced by the foreign surfaces of the CPB system. It is well accepted that use of aortic cross-clamping and cardioplegic cardiac arrest results in an increased leakage of CK-MB, troponine I, and myoglobine, even in uncomplicated cases as compared to CABG without CPB [2628]. Also in our study, CK-MB levels are lower in the patient group operated without CPB, thus indicating a reduction in myocardial damage. The reduction of neurologic complications may be explained by the predominant use of only internal mammary artery grafts without proximal anastomoses, thus avoiding manipulation at the generally sclerotic ascending aorta of the elderly.
Since revascularization of the posterior wall is a certain limitation for CABG without CPB, patients receive less grafts than patients undergoing surgery with CPB [29]. Previously, short- and long-term survival of patients following CABG without CPB has been shown to be comparable to conventional CABG with CPB [4, 29]. In a recent study, Boyd and coworkers [30] compared CABG with and without CPB in the elderly (mean age = 74 years). They could demonstrate a significantly lower postoperative morbidity for patients operated without CPB. Mortality was comparable between the 2 groups. In our study, in-hospital mortality was higher. However, our patients were markedly older (mean age = 80 years) and carried a much higher Parsonnet score than described by Boyd and colleagues [30]. Since perioperative mortality most steeply rises at an age of 75 years, our patients are more likely to represent the high-risk geriatric population with significant comorbidities [3]. This suggests a critical role of the use of CPB in CABG in selected old patients with high operative risk.
The most important limitation of the study arises from the fact that we investigated nonrandomized patient groups.
The experience of the surgical community is continuously growing. This retrospective analysis reflects a certain time period when CABG without CPB was in an earlier state of clinical application. This continuous learning process is also reflected by the fact that, in this retrospective patient cohort, there is a trend towards a lower number of diseased vessels in the patient group undergoing CABG without CPB. Due to our recent experience, complete revascularization without CPB also continues to gain clinical importance. In the study cohort, we did not try to achieve complete revascularization, and which surgical strategy to use was the decision of the individual surgeon.
The mean follow-up of the study patients operated without CPB is shorter than of patients operated with CPB; this may mimic a decrease in quality of life and freedom from angina after 2 years in these patients. Finally, the number of patients over 75 years undergoing coronary revascularization without CPB is still low.
Taking the above-mentioned limitations into consideration, our results show that target vessel revascularization without CPB in very old and high-risk patients leads to a significant reduction of in-hospital mortality and major postoperative complications. Furthermore midterm survival and quality of life is not negatively affected. Therefore, we consider target vessel revascularization of the culprit lesion without CPB a promising alternative to CABG with CPB in selected old and high-risk patients. Nevertheless, a prospective randomized study is needed to determine if CABG without CPB provides a benefit for elderly, high-risk patients.
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