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Ann Thorac Surg 2008;85:513-519. doi:10.1016/j.athoracsur.2007.08.056
© 2008 The Society of Thoracic Surgeons
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Original Articles: Cardiovascular

Does Intensive Management of Cerebral Hemodynamics and Atheromatous Aorta Reduce Stroke After Coronary Artery Surgery?

Masanori Nakamura, MD, PhDa,*, Fumiyuki Okamoto, MD, PhDb, Katsuhiko Nakanishi, MD, PhDb, Ryushi Maruyama, MD, PhDb, Akira Yamada, MD, PhDb, Satoshi Ushikoshi, MD, PhDc, Shunsuke Terasaka, MD, PhDd, Satoshi Kuroda, MD, PhDd, Keisuke Sakai, MD, PhDb, Tetsuya Higami, MD, PhDa

a Department of Thoracic and Cardiovascular Surgery, Sapporo Medical University, Sapporo, Hokkaido, Japan
b Department of Cardiovascular Surgery, Teine Keijinkai Hospital, Sapporo, Hokkaido, Japan
c Department of Neurosurgery, Teine Keijinkai Hospital, Sapporo, Hokkaido, Japan
d Department of Neurosurgery, Hokkaido University Hospital, Sapporo, Hokkaido, Japan

Accepted for publication August 27, 2007.

* Address correspondence to Dr Nakamura, Department of Thoracic and Cardiovascular Surgery, Sapporo Medical University School of Medicine, South-1, West-16, Chuo-ku, Sapporo, 060-8543, Japan (Email: masanori{at}sapmed.ac.jp).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 
Background: Atheromatous aorta and carotid artery disease are known predictors for stroke after coronary artery bypass grafting (CABG). The clinical significance of intracranial cerebral artery disease is not known. This study was designed to determine whether a therapeutic strategy based on perioperative detection of intracranial and extracranial occlusive cerebrovascular disease and atheromatous aorta could reduce perioperative stroke.

Methods: We studied 485 patients who underwent isolated CABG. The control group was 247 patients who underwent standard-protocol CABG. The 238 subjects in the intervention group underwent preoperative magnetic resonance angiography of the head and neck and intraoperative epiaortic scanning. Cerebral hemodynamics were evaluated by single photon emission computed tomography and acetazolamide tests in patients with significant occlusive cerebrovascular disease. Surgical outcomes were compared.

Results: In the intervention group, magnetic resonance angiography detected significant intracranial or extracranial occlusive cerebrovascular disease, or both, in 40 patients. Prophylactic cerebrovascular interventions were performed in 7 patients who had disturbed cerebral hemodynamics. Aorta no-touch off-pump coronary artery bypass (OPCAB) was chosen intraoperatively in 37 patients with moderate to severe atheromatous aorta. The in-hospital stroke rate was 0.42% in the intervention group vs 2.8% in the control group (p = .068). A multivariate analysis revealed that the perioperative interventional protocol was the most powerful predictor of reduced risk of perioperative stroke (odds ratio, 0.023; 95% confidence interval, 0.001 to 0.469).

Conclusions: Prophylactic cerebrovascular interventions and the selective use of aorta no-touch OPCAB can significantly reduce the incidence of perioperative stroke. Careful vascular evaluation before and during CABG can improve surgical outcomes.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 
Stroke is one of the most devastating complications of cardiac surgery, causing poor functional outcomes and increased mortality, length of hospitalization, and need for long-term care [1]. Perioperative stroke has many causes. Microembolic and macroembolic events, systemic inflammatory response against cardiopulmonary bypass, and hypoperfusion may all play a role.

Atherosclerosis of the ascending aorta and the aortic arch is an important risk factor for stroke during aortic manipulation. Epiaortic scanning evaluates the walls of the ascending aorta for mobile atheromata that could potentially be dislodged [2, 3]. Embolic risk in such patients can be reduced by the use of off-pump coronary artery bypass (OPCAB), which involves less manipulation of the aorta. Comparative studies have shown that OPCAB reduces mortality and stroke in patients with severe aortic atherosclerosis [4]. Among OPCAB patients, the stroke risk for the no-touch aorta technique is lower than for use of a side clamp [5].

Compromised cerebral circulation caused by extracranial and intracranial cerebral artery disease (CAD) is another risk factor for perioperative stroke. Intracranial CAD has also been implicated as an independent predictor [6]. Despite a high prevalence of both extracranial and intracranial CAD in Japanese patients [7, 8], routine preoperative assessment for intracranial CAD is not performed in Asia. Carotid artery duplex ultrasound can identify extracranial CAD, but magnetic resonance angiography (MRA) allows noninvasive identification of intracranial CAD [9].

Optimal surgical strategy for coronary artery bypass grafting (CABG) in patients with asymptomatic extracranial CAD, a known predictor of post-CABG stroke [10], has not yet been determined. Asymptomatic patients with reduced cerebral perfusion pressure and impaired reactivity to acetazolamide have been shown to have higher risk for ipsilateral ischemic stroke [11]. Normally, vasodilation of cerebral arteries allows the brain to tolerate a mild to moderate reduction of cerebral perfusion pressure. In patients with cerebrovascular occlusion, maximal autoregulatory vasodilation is already compensating for chronic circulatory insufficiency. Impaired reactivity to acetazolamide suggests that cerebral blood flow alters readily in response to changes in blood pressure. Such patients may tolerate perioperative reductions in cardiac output or blood pressure poorly, with increased risk of cerebral infarction, even when asymptomatic. Single photon emission computed tomography (SPECT) with acetazolamide may be a valuable noninvasive method to predict the risk of hemodynamic stroke in patients with extracranial and intracranial artery disease [11].

Wider application of these powerful vascular screening techniques may guide clinicians to the judicious use of prophylactic cerebrovascular interventions that might improve the post-CABG outcomes of high-risk patients. The present study evaluates the impact of targeted cerebrovascular intervention and selective use of aorta no-touch OPCAB on perioperative stroke. A multivariate logistic regression analysis was performed to assess the independent predictors of perioperative stroke.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 Acknowledgments
 References
 
Patients
This study was approved by the Institutional Review Board of Teine Keijinkai Hospital, with a waiver of individual patient consent. Consecutive patients who underwent isolated CABG in our hospital between January 1999 and October 2003 were studied. Control patients had surgery before November 2001, preceded by conventional preoperative examinations such as carotid artery ultrasound imaging and plain computed tomography (CT) of the chest and brain.

Conventional CABG was performed regardless of the results of preoperative and intraoperative examination, and no patients underwent further investigation and treatment before CABG. The ascending aorta was assessed manually during surgery. The intervention group underwent CABG after November 2001. Treatment strategies in the intervention group were driven by the results of the perioperative protocol, as described subsequently (Fig 1). Patients were excluded if a requirement for percutaneous cardiopulmonary support system prevented completion of preoperative cerebrovascular screening.


Figure 1
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  		Fig 1. Scheme of our perioperative protocol in intervention group (n = 238). (CABG = coronary artery bypass grafting; CPR = cerebral perfusion reserve; EAS = epiaortic scanning; MRA = magnetic resonance angiography; OPCAB = off-pump coronary artery bypass; SPECT = single photon emission computed tomography; US = ultrasound imaging.)

 
Surgical Procedures of Coronary Artery Bypass Grafting
Our methods for conventional CABG are described elsewhere [12]. Surgical methods did not change during the course of the study. Cardiopulmonary bypass (CPB) was used in a standardized fashion, with the use of a membrane oxygenator and a centrifugal pump. Myocardial protection using integrated myocardial management was performed under single aortic cross-clamping; side aortic clamping was not used in any case. Conventional CABG was selected in most patients.

All patients received 100 mg/day of aspirin, and warfarin was titrated to an international normalized ratio (INR) goal of 1.7 to 2.0 postoperatively. Many patients received continuous intravenous heparin from the day after surgery until an INR of 1.7 was achieved. Postoperative heparin level was analyzed as a predictor of perioperative stroke.

Preoperative Screening of Cerebrovascular Diseases
Expanded preoperative screening was performed in the intervention group to identify extracranial or intracranial CAD, or both. Examinations included carotid artery ultrasound imaging (SONOS 5500 Ultrasound Imaging System, HP ultra-band trapezoidal linear transducer, 3 to 11 MHz, Philips Holland), and MRA (Sigma Horizon 1.5T; GE Yokokawa Medical System, Tokyo, Japan). If MRA was contraindicated due to insertion of an intraaortic balloon pump (IABP) or implantation of a pacemaker, alternative modalities such as three-dimensional CT angiography (3D-CTA, Aquilion16; Toshiba, Tokyo, Japan) or four-vessel angiography were used. All images were evaluated by the qualified neurosurgeons (S. U., S. T., and S. K.).

Cerebral hemodynamics were evaluated by SPECT whenever severe stenosis (>75%) or occlusion of the major arteries was detected. Cerebral blood flow was measured before, and 15 minutes after intravenous injection of 10 mg/kg acetazolamide, using [123I] N-isopropyl-p-iodoamphetamine (123I-IMP) SPECT. This method has been described elsewhere [11, 13]. Ten healthy controls who were free of cerebrovascular disease provided normal control values of cerebral blood flow (mean ± standard deviation, 38.1 ± 5.4 mL/min/100 g) and cerebrovascular reactivity to acetazolamide (30% ± 8%) in the middle cerebral artery (MCA) territory. An abnormal test result was defined as any value falling outside of two standard deviations below the mean; for example, reduced cerebral perfusion reserve was defined as cerebrovascular reactivity of less than 14%.

CABG was performed without any cerebrovascular intervention when cerebral perfusion reserve was normal. Prophylactic cerebrovascular interventions in patients with reduced cerebral perfusion reserve included percutaneous transluminal angioplasty (PTA) [14], stent deployment, carotid endarterectomy (CEA), or superficial temporal artery (STA)-MCA anastomosis. Patients having staged surgeries had continuous heparin infusion or oral cilostazol (Otsuka Co, Osaka, Japan) until CABG was performed.

Preoperative and Intraoperative Screening of the Ascending Aorta
The intervention group had enhanced chest CT (Aquilion16) before the procedure, and intraoperative epiaortic scanning (SSA-340A; Toshiba, Tokyo, Japan), to evaluate the embolic potential of the ascending aorta. Epiaortic scanning was performed with a 7-MHz linear ultrasonic probe (PVF-745V; Toshiba) before harvest of the internal mammary arteries. The mediastinal cavity was filled with warm saline solution. The probe was then gently manipulated to obtain longitudinal and transverse views from the aortic valve up to the innominate artery.

Atherosclerotic disease in the ascending aorta was defined as normal/mild (aortic wall thickness <3 mm), moderate (aortic wall thickness 3 to 5 mm), and severe (aortic wall thickness >5 mm or the presence of marked calcification, or both, protruding or mobile intraluminal atheromatous portions, and ulcerated plaques), according to the classification of Wareing and colleagues [3]. If atherosclerotic disease in the ascending aorta was moderate or severe, the scheduled conventional CABG was converted to complete aorta no-touch method, using in situ bilateral skeletonized internal mammary arteries and right gastroepiploic artery.

Risk Factors and Outcomes
This study evaluated 23 clinical variables in all subjects, including age, gender, diabetes mellitus, hypertension, hyperlipidemia, smoking, obesity, family history, hyperuricemia, history of stroke, peripheral vascular disease, carotid artery stenosis, preoperative atrial fibrillation, emergency operation, unstable angina, old myocardial infarction, number of grafts, chronic hemodialysis, previous cardiac operation, use of IABP, use of postoperative heparin, postoperative low output syndrome, and perioperative management by conventional or interventional protocol (Appendix).

Perioperative stroke was defined as any new neurologic deficit lasting more than 24 hours or new cerebral lesions on CT or magnetic resonance image (MRI). Survival and functional recovery were noted.

Statistical Analysis
Results were expressed as the mean ± standard deviation. Standard statistical tests, including unpaired two-tailed t test of the means and {chi}2 test or two-sided Fisher exact tests for categoric variables, were used for univariate comparisons. Multivariable logistic regression analysis was used to calculate risk-adjusted odds ratios to determine the independent predictors of perioperative stroke. Variables were considered for the multivariable models at a univariable value of at p < 0.25. All statistical analyses were completed using SPSS 11.0 J software (SPSS Inc, Chicago, IL).


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 Acknowledgments
 References
 
During the study period, 485 consecutive patients underwent CABG procedures. Conventional preoperative screening was performed on 247 controls. The expanded vascular screening protocol was performed on 238 patients in the intervention group. Baseline demographic data and cardiovascular risk factors are outlined in Table 1. The intervention group had significantly more patients aged older than 75 years. It also had a higher prevalence of prior stroke, carotid stenosis, and preoperative atrial fibrillation, but fewer smokers.


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  		Table 1 Comparison of Clinical Characteristics Between Control Group and Intervention Group
 
In the control group, 6.4% of patients had an abnormal carotid test result, although none of these underwent further workup or surgical therapy before CABG. Occlusive cerebrovascular disease was detected in 40 of 238 patients (16.8%) in the intervention group, of whom 20 had isolated ECAD, and 20 had intracranial CAD with or without extracranial CAD. SPECT studies revealed normal cerebral perfusion reserve in 29 of 40 patients, none of whom sustained a perioperative stroke. Cerebral perfusion reserve was reduced in 11 patients (4.6%), of whom 7 underwent prophylactic cerebrovascular interventions, including PTA of the vertebral artery in 1, stent deployments to the cervical or intracranial internal carotid artery (ICA) in 2 (Fig 2), CEA in 2, and STA-MCA bypass in 2. One patient had simultaneous CEA and CABG; the other 6 had staged CABG over 15 ± 8 days (range, 3 to 24 days). Follow-up SPECT studies confirmed improvement of cerebral perfusion reserve in all 7 patients.


Figure 2
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  		Fig 2. Radiologic findings of a 75-year-old man who was admitted due to unstable angina. (A) Coronal view of screening magnetic resonance angiography revealed that flow signals were decreased in the right carotid artery territory due to right internal carotid artery (ICA) stenosis (arrow). (B) Right carotid angiogram showed severe stenosis of the petrous portion of the right ICA (arrow). (C) Stent deployment effectively normalized the caliber of the right ICA (arrow). (D) Single photon emission computed tomography before and after intravenous injection of acetazolamide (ACZ) revealed that cerebral blood flow and cerebrovascular reactivity were reduced in the right cerebral hemisphere before stent deployment. (E) Preoperative stent deployment significantly improved cerebral blood flow and cerebrovascular reactivity.

 
An acute myocardial infarction occurred in 1 patient 4 days after STA-MCA bypass because of postoperative anemia. OPCAB performed 2 weeks later was complicated by ventricular fibrillation and hypotension, but no perioperative stroke. The remaining patients had uneventful postinterventional recoveries.

Prophylactic interventions were technically impossible in 4 of 11 patients. OPCAB without bypass of diseased left circumflex arteries was performed in 3 patients. OPCAB was precluded by ischemic cardiomyopathy in the fourth patient, who underwent conventional CABG using high-flow (80 mL/kg) and high mean aortic pressure (>70 mm Hg) perfusion. One patient had a STA-MCA bypass 3 months after OPCAB (new transient ischemic attack), but no perioperative strokes occurred.

Conventional CABG was performed in all but 3 controls, but 37 of 238 patients (15.5%) in the intervention group who had severe or moderate atherosclerosis in the ascending aorta on interoperative epiaortic scanning underwent ascending aorta no-touch CABG using in situ arterial conduits (OPCAB in 34 and on-pump beating CABG in 3 to maintain hemodynamic stability). Aorta no-touch OPCAB was performed in 19 of 238 due to single vessel disease or a contraindication to CPB. Thus, conventional CABG was performed in 182 of 238 patients (76.5%) without significant atherosclerosis in the ascending aorta.

The number of coronary grafts was significantly lower in the intervention group than in the control group (3.1 ± 1.1 and 3.7 ± 1.2, respectively; p < 0.001) because the number of patients with single-vessel disease (8.8% vs 2.0%, p < 0.001) and OPCAB (23.5% vs 1.2%, p < 0.001) was greater in the intervention group than in the control group and aorta no-touch OPCAB, using in situ arterial grafts, limited the number of potential grafts.

Perioperative Stroke and Mortality
Total in-hospital mortality did not differ between control and intervention groups overall (2.0% vs 2.5%, p = 0.768), or in the subset of elective cases (0.97% vs 0.94%, p = 1.000). Perioperative stroke occurred in 7 of 247 controls (2.8%), but only in 1 of 238 patients in the intervention group (2.8% vs 0.4%, p = 0.068, Fig 3), which trended towards significance. In controls, all events were cerebral infarctions, of which six occurred perioperatively (early stroke). One late stroke occurred 2 weeks after CABG. Hemodynamic ischemia, (ICA, MCA, or basilar artery occlusion) caused four events, and atheroembolic showers from the aorta caused three events. Two deaths occurred. One patient had good functional recovery and 4 were discharged with neurologic deficits. One patient had moderate carotid stenosis (50% by preoperative carotid ultrasound scan), and 2 others had had a prior stroke. In the intervention group, one patient had a perioperative stroke attributed to air embolism. Neurologic deficits resolved completely by discharge. Poor neurologic outcome at 3 months was significantly more frequent in controls than in intervention patients (2.4 vs 0%, p = 0.03; Fig 3).


Figure 3
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  		Fig 3. Bars show the incidences of perioperative stroke and disability at 3 months after coronary artery bypass grafting in the control group (clear bar) and intervention group (filled bar).

 
Predictors of Perioperative Stroke
Multivariate logistic regression modelling was conducted to clarify independent predictors of perioperative stroke. The perioperative interventional protocol, postoperative low output syndrome, and stroke history were the risk-adjusted independent predictors of perioperative stroke (Table 2). The odds ratio of the perioperative interventional protocol was 0.023. The odds ratios of stroke history and postoperative low output syndrome were 6.2 and 11.6, respectively.


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  		Table 2 Independent Predictors of Perioperative Stroke Among 485 Patients Who Underwent Coronary Artery Bypass Grafting
 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
Acknowledgments
 References
 
These results show that tailoring the surgical strategy according to the cerebrovascular and aortic evaluation reduced the neurologic morbidity of perioperative stroke associated with CABG. Many candidates for CABG had significant cerebrovascular disease. Decreased cerebral perfusion reserve was seen on SPECT and acetazolamide tests. The intensive preoperative protocol resulted in prophylactic treatment for cerebrovascular disease in 7 asymptomatic patients. Intraoperative epiaortic scanning results drove selection of aortic no-touch methods in 37 patients due to atherosclerosis of the ascending aorta.

Despite having more extracranial CAD, stroke history, advanced age, and preoperative atrial fibrillation, all of which are perceived risk factors for perioperative stroke [15] (Table 1), the intervention group had significantly less perioperative stroke. Our data suggest that the perioperative interventional protocol may have been crucial in preventing perioperative stroke by preventing hemodynamic ischemia during and after the CABG. Intraoperative detection of atheromatous aorta may allow selection of lower-risk surgery that can prevent distal embolism to the brain and other organs [2]. Multivariate analysis suggests that an aggressive perioperative interventional protocol may prevent strokes due to either mechanism.

Prophylactic cerebrovascular interventions were performed on the basis of cerebral perfusion reserve. Perioperative risk did not appear to be increased in the 29 patients with occlusive cerebrovascular diseases and normal cerebral perfusion reserve. Prophylactic cerebrovascular interventions included PTA with or without stenting, CEA, and STA-MCA bypass.

Although cerebrovascular intervention for asymptomatic patients is controversial, Gaudino and colleagues [16] reported that simultaneous CEA/CABG in patients with severe unilateral asymptomatic extracranial CAD confers significant neurologic protection during the ensuing years. A randomized clinical trial has also proven that CEA halved the net 5-year stroke risk in asymptomatic patients with more than 70% ICA stenosis [17]. Although previous randomized clinical trials have not shown the significance of STA-MCA bypass in preventing subsequent stroke [18], no strokes occurred in the 2 patients in this study who underwent STA-MCA bypass before CABG.

Recent technologic advances have broadened the neuroradiologic treatment options for occlusive cerebrovascular diseases [19], but neither surgical nor radiologic interventions are risk-free in vasculopathic patients. The risk of stroke or death within 30 days of CEA was 3.1% in the Asymptomatic Carotid Surgery Trial (ACST) [17]. One myocardial infarction occurred in a patient who underwent prophylactic procedures, although the subsequent CABG outcome was good.

A team approach by surgeons, radiologists, and anesthesiologists is essential for the best results [14]. Recent OPCAB technique has been improved, and hypotension during anastomosis or conversion to CPB has been rare, but cardiac output can be decreased during bypass of left circumflex arteries. In the study, CABG after cerebral intervention was performed for the patients with reduced cerebral perfusion reserve. Further prospective randomized studies between OPCAB without cerebral intervention and CABG after cerebral intervention are needed for the patients with reduced cerebral perfusion reserve.

Postoperative heparin did not independently reduce perioperative stroke, despite a prior report that acute thrombosis may occur at the site of preexisting intracranial CAD after a cardiac operation [20]. Fluctuating blood pressure due to postoperative low output syndrome or atrial fibrillation, and increased thrombogenicity, are potential mechanisms of late stroke [15]. Further studies of postoperative anticoagulation are needed to determine optimal strategies to prevent thrombotic occlusion of preexisting intracranial arterial stenosis.

This study also evaluated a simultaneous strategy in which epiaortic scanning dictated the use aorta no-touch OPCAB with in situ arterial grafts in patients with moderate or severe atherosclerosis. Wareing and colleagues [3] reported that the stroke rate was 1.1% in normal or mild atherosclerosis, 3.0% in moderate, and 4.8% in severe atherosclerosis when conventional CPB was used. Our approach was informed by recent data that suggested that intraoperative screening of the ascending aorta could reduce perioperative stroke [2]. OPCAB reduces stroke risk by avoiding extracorporeal circulation and decreasing aortic manipulation [4] but may reduce the number of available sites for grafting. We have subsequently used proximal anastomosis assist devices, including Heart Strings (Guidant Inc, Natick, MA) or Enclose II (Novare Surgical Systems Inc, Cupertino, CA), to increase the number of potential grafts in OPCAB surgeries. Further studies are needed to clarify the advantages of these devices compared with side-clamp methods.

Limitations of the study include the small size of both groups. More specific analysis of each clinical risk factor may have been possible with a larger number of patients and might have allowed us to separate the benefits of aortic versus cerebral evaluation. However, enrollment in this study was sufficient to provide initial proof that significant improvements in neurologic outcome can be achieved. The enrollment of intervention patients was separate from and later than the enrollment of the control group, raising the possibility that other improvements in surgical or critical care might be responsible for part of the improved outcomes. A randomized clinical trial would have avoided this, but there is no evidence for any systematic disadvantage in the historical controls, and there were no major changes in surgical or postoperative care strategies. Our study population was a homogeneous population from a single medical center, which may limit the generalizability of our findings. Costs were not assessed. Further study should clarify the advisability of our approach in other populations, and determine if the costs of our approach are offset by the improvement in outcomes.

In conclusion, vascular risk assessment with preoperative screening of extracranial and intracranial CAD and intraoperative evaluation of the ascending aorta can guide targeted surgical treatment options that reduce perioperative stroke in patients undergoing CABG. Prophylactic cerebrovascular interventions reduced stroke risk in patients with poor cerebral perfusion reserve due to cerebrovascular atherosclerosis. Further study is required to determine the costs and benefits of a more aggressive approach to preoperative vascular evaluation in patients requiring CABG.


   Appendix
 
Variables Assessed in Predictive Models

• Diabetes mellitus: Hemoglobin A1c >5.6% or a history of diabetes treated with diet, oral hypoglycemic agents, or insulin
• Hypertension: a history of hypertension treated with medication
• Hyperlipidemia: Total cholesterol >220 mg/dL or a history of hyperlipidemia treated with medication
• Smoking: present smoker or previous (stop-smoking within 1 year) smoker
• Obesity: body mass index >25 kg/m2
• Hyperuricemia: Uric acid >7.0 or a history of hyperuricemia treated with medication
• Stroke history: a history of symptomatic stroke, or obvious stroke detected by computed tomography or magnetic resonance imaging
• Peripheral vascular disease: ankle brachial index <0.7 or a history of peripheral vascular disease
• Carotid artery stenosis: >50% by carotid artery ultrasound imaging
• Preoperative atrial fibrillation: paroxysmal or permanent of preoperative atrial fibrillation
• Emergency operation: operation was performed within 24 hours after admission
• Unstable angina: including acute myocardial infraction
• Chronic hemodialysis: patients on chronic hemodialysis before operation
• Use of intraaortic balloon pump (IABP): Use of perioperative IABP including preoperative IABP
• Postoperative low output syndrome (LOS): Postoperative new use of IABP or percutaneous cardiopulmonary support system due to LOS


   Acknowledgments
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
References
 
We thank Dr Shigeyuki Saitou of Sapporo Medical University for his suggestions on statistical analysis and Dr Tomohiro Saitoh, Dr Hideo Satoh, and Dr Kazuma Kanetsuki of Teine Keijinkai Hospital for data collection. We also acknowledge editorial review from Dr Rita McGill and Dr Gregory Ruhnke as well as the assistance of Akemi Dohda in the preparation of the manuscript.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 

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Antonio Calafiore
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