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Ann Thorac Surg 2003;75:472-478
© 2003 The Society of Thoracic Surgeons

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Original article: cardiovascular

Stroke after cardiac surgery: a risk factor analysis of 16,184 consecutive adult patients

^a Department of Cardiac Surgery, Heart Center, University of Leipzig, Leipzig, Germany

Accepted for publication August 27, 2002.

* Address reprint requests to Dr Bucerius, University of Leipzig, Heart Center, Department of Cardiac Surgery, Strümpellstr 39, 04289 Leipzig, Germany
e-mail: bucerj{at}medizin.uni-leipzig.de

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
BACKGROUND: Stroke remains a devastating complication after cardiac surgical procedures despite advances in perioperative monitoring and management. The purpose of this study was to determine the predictors of stroke in a large, contemporary cardiac surgery population.

METHODS: Prospective data on 16,184 consecutive patients undergoing cardiac surgery (coronary artery bypass grafting [CABG], n = 8,917; beating heart CABG, n = 1,842; aortic valve surgery, n = 1,830; mitral valve surgery, n = 708; double or triple valve surgery, n = 381; CABG and valve surgery, n = 2,506) between April 1996 and August 2001 were subjected to univariate and multivariate analysis. Stroke was defined as any new permanent (manifest stroke) or temporary neurologic deficit or deterioration (transient ischemic attack or prolonged reversible ischemic neurologic deficit) and was confirmed by computed tomography or magnetic resonance imaging whenever possible.

RESULTS: Overall incidence of stroke was 4.6% and varied between surgical procedures (CABG 3.8%; beating-heart CABG 1.9%; aortic valve surgery 4.8%; mitral valve surgery 8.8%; double or triple valve surgery 9.7%; CABG and valve surgery 7.4%). Of 63 patient-specific and treatment variables, 54 were found to have a significant univariate association with postoperative stroke. Multivariable analysis revealed 10 variables that were independent predictors of stroke: history of cerebrovascular disease, peripheral vascular disease, diabetes, hypertension, previous cardiac surgery, preoperative infection, urgent operation, CPB time more than 2 hours, need for intraoperative hemofiltration, and high transfusion requirement. Beating heart CABG was associated with a lower incidence of stroke in this multivariable analysis.

CONCLUSIONS: Identification of predictors for stroke is important for understanding the pathogenesis of this devastating complication as well as for developing preventative strategies. Although retrospective analyses can be subject to selection bias we believe beating heart CABG is associated with a lower incidence of stroke and may therefore improve patient outcomes.

	Introduction

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Stroke remains a devastating complication after cardiac surgical procedures with an incidence of as high as 6% [1–5]. Postoperative cognitive and neuropsychological dysfunction is even more common with an incidence that may exceed 60% [6]. Recent advances in cardiac surgical techniques, in particular the development of off-pump coronary artery bypass (OPCAB), may affect perioperative neurologic complications. While more patients are undergoing OPCAB surgery, patient risk profiles are also increasing owing to a higher proportion of advanced age and other comorbidities [7]. A contemporary risk factor analysis is therefore necessary to determine the predictors of stroke in the era of modern cardiac surgery.

Previous studies have attempted to identify predictors of stroke after coronary artery bypass grafting (CABG) as well as during other cardiac surgical procedures. Although these studies have yielded important data, most were derived from small study populations or were focused on a single surgical procedure. Only a few large-scale prospective studies are available on the incidence of stroke and its associated risk factors [8, 9, 10]. Furthermore, recent studies examining the impact of "minimally invasive" techniques including OPCAB surgery on stroke have yielded inconsistent and sometimes controversial results [11, 12].

The aim of the present study therefore was to investigate the incidence and predictors of perioperative stroke as well as its association with different cardiac surgical procedures in a large prospectively gathered database from a single institution.

	Material and methods

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Study population
A total of 16,184 consecutive adult patients undergoing cardiac surgery between April 1996 and August 2001 were included in this study. CABG with cardiopulmonary bypass (CPB) was performed in 8,917 patients and beating heart CABG through a median sternotomy(OPCAB, n = 765) or through a left lateral minithoracotomy (minimally invasive direct coronary artery bypass (MIDCAB, n = 1,077) was performed in 1,842 patients. A total of 1,830 patients had aortic valve repair or replacement with or without replacement of the ascending aorta. Mitral valve repair or replacement was performed in 708 patients. Double or triple valve surgery was performed in 381 patients. A total of 2,506 patients underwent CABG in combination with valve repair/replacement, ascending aortic surgery, or other procedures.

Assessment of the ascending aorta was performed intraoperatively with digital palpation in all patients with the addition of transesophageal echocardiography in patients with suspected aortic disease. For coronary bypass patients (OPCAB and conventional CABG) in-situ arterial grafts were used whenever possible in patients less than 70 years of age and in patients with disease of the ascending aorta. Proximal anastomoses were performed with a partial occluding clamp in OPCAB patients and in conventional CABG patients before 1999. A single aortic cross-clamp technique was used in conventional CABG patients since 1999.

Patient characteristics are displayed in Table 1. Patients older than 70 years of age accounted for 32.5% and patients older than 80 years for 3.6% of the study population. The majority of patients were male (72.2%) and 3.6% had a history of cerebrovascular disease.

Data collection
Perioperative data were recorded prospectively using an online database system as previously described (Medwork database software; Lenz & Partner GmbH, Germany) [14]. All variables analyzed were entered in a prospective fashion by physicians involved in the daily care of patients, resulting in a complete data set for each patient. The quality of the data was routinely assessed when this information was used to generate text documents that became the patient’s chart while in hospital, thus resulting in a meticulous confirmation of the entered data. Perioperative risk factors analyzed by univariate and multivariate stepwise logistic regression are listed in the Appendix.

Statistical analysis
Continuous variables are expressed as mean ± SD throughout the manuscript, and categorical data as proportions. Comparisons of continuous variables for patients with and without perioperative stroke were made with Student’s unpaired t test and categorical variables were compared with the ² test. Groups of patients undergoing different surgical procedures were compared with one-way analysis of variance (ANOVA). Univariate analyses of risk factors were performed calculating odds ratios (OR) with 95% confidence intervals (CI). Variables with a p value less than 0.05 were consecutively subjected to a multivariate logistic regression model to assess the independent impact of each risk factor on stroke. A stepwise procedure (backward Wald) was used with a p value of less than 0.05 to enter and eliminate variables. All statistical analyses were performed using the SPSS statistical package 9.0 (SPSS, Birmingham, AL).

	Results

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The significant differences in preoperative patient characteristics for the different surgical procedures were as follows (Table 1): Patients in the CABG group were significantly older than the MIDCAB, aortic valve, mitral valve, and double or triple valve groups (p < 0.05). Within the beating heart CABG group, OPCAB patients were significantly older than MIDCAB patients (p < 0.001). Patients undergoing mitral valve surgery were significantly younger than all other groups (p < 0.05), and patients in the aortic valve group were significantly younger than the OPCAB (p < 0.001) and the multiple valve surgery groups (p = 0.002). Patients in the combined surgery group were significantly older than all other groups (p < 0.001).

Left ventricular ejection fraction (LVEF) in the coronary bypass groups (CABG, OPCAB, and MIDCAB) was significantly higher than all other surgical groups (p < 0.05), and LVEF in the aortic valve group was significantly higher compared with the combined group (p = 0.008).

The incidence of preoperative history of cerebrovascular disease was significantly (p < 0.01) higher in the mitral valve group than in the CABG, MIDCAB, and aortic valve groups.

The overall incidence of stroke was 4.6% for all patients but varied according to the different surgical procedures (Fig 1). The highest incidence of stroke was found in the double or triple valve group (9.7%) followed by the mitral valve (8.8%) and combined surgical groups (7.4%). The lowest incidence of stroke was found in the beating heart CABG groups (OPCAB 2.5% and MIDCAB 1.6%). The incidence of stroke was significantly (p < 0.05) lower in the MIDCAB group than in all other groups with the exception of patients undergoing OPCAB surgery. The OPCAB group had a significantly (p < 0.05) lower incidence than the mitral valve, double or triple valve, and combined groups. There was no statistically significant difference between the OPCAB and conventional CABG groups. The incidence of perioperative stroke in the CABG group was significantly lower than in the mitral valve, double or triple valve, and combined groups (all p < 0.001). Patients in the mitral valve and combined groups suffered significantly more often from stroke than patients in the aortic valve group (p < 0.001 for both).

View larger version (20K): [in this window] [in a new window]   Fig 1. Incidence of stroke in relation to different surgical procedures. See text for description of groups and significant p values. Grey bars: Total = whole study population; Beating Heart = all patients undergoing beating heart surgery (ie, OPCAB and MIDCAB together). Solid bars: discrete surgical interventions. (AV = aortic valve; CABG = coronary artery bypass grafting; COMB = combined procedures; DV = double and triple valve; MIDCAB = minimally invasive direct coronary artery bypass grafting; MV = mitral valve; OPCAB = off-pump coronary artery bypass grafting.)

	Comment

Top Abstract Introduction Material and methods Results Comment References

 
Neurologic complications after cardiac surgical procedures remain a relatively common problem despite improvements in anesthetic and surgical techniques as well as in perioperative monitoring and management. Several previous studies have demonstrated that permanent neurologic deficits occur in as many as 6% of patients undergoing cardiac surgery [1–5]. In the current prospective large-scale series the incidence of stroke was 4.6% with significant variation among different surgical procedures. For the purpose of this study we included temporary neurologic deficits (ie, TIA and PRIND) in our definition of stroke in contrast to previous studies that have generally focused on permanent deficits. Our definition of stroke may have therefore led to a slight overestimation of its incidence despite the fact that the vast majority of neurologic deficits recorded were permanent in nature.

Previous studies in the literature have speculated that the cause of stroke after cardiac surgery is multifactorial. Age greater than 70 years, one of the most commonly reported independent predictors of stroke [15, 16, 17, 18], was present in approximately one third of our patient population. However our analysis did not reveal age as an independent predictor of stroke. Advanced age is not thought to be a cause of stroke per se but rather a marker of increased atherosclerotic burden [16]. The explanation of why advanced age did not arise as an independent predictor of stroke in our study may have therefore been because of the inclusion of other markers of arteriosclerosis in our model: peripheral vascular disease, cerebrovascular disease, diabetes, and hypertension (discussed in more detail below).

Our analysis revealed that history of cerebrovascular disease (ie, TIA, PRIND, or stroke) was the strongest preoperative predictor of stroke with an odds ratio (OR) of 3.55. History of cerebrovascular disease denotes the existence of pathologic conditions within the cerebrovascular system or an underlying stenosis of one or both carotid arteries. Other investigators have demonstrated a 7% to 13% incidence of postoperative stroke for patients with a history of previous neurologic events [19, 20]. Patients with cerebrovascular disease had a 16.8% incidence of stroke in our study, demonstrating the high risk associated with this variable. We suggest intensive preoperative screening including duplex scanning of the carotid arteries and transesophageal assessment of the ascending aorta in such patients in order to identify lesions that may alter intraoperative management.

We found that patients with hypertension were at increased risk for stroke (OR: 1.27), similar to other studies [8, 9, 18]. Cautious management of blood pressure in severely hypertensive patients is important because of the risk of precipitating ischemic stroke during aggressive blood pressure reduction [21].

Diabetes and peripheral vascular disease were two more independent predictors of stroke in our analysis (OR = 1.31 and 1.39, respectively) and have been reported by several other investigators. Both of these risk factors place patients at increased risk of atherosclerotic embolization as well as impaired autoregulation of cerebral blood flow [3, 10, 16, 22].

Previous cardiac surgery was also identified as a risk factor for stroke (OR: 1.33), probably due to extended duration of CPB and elevated risk of particulate embolization. Preparation of the mediastinum after previous surgery is difficult and manipulation of the aorta with subsequent embolization may occur more frequently. In addition such patients are at elevated risk of laceration of the heart or great vessels during surgical dissection resulting in severe hemorrhage and prolonged hypotension.

Urgent operation secondary to unstable cardiac conditions was also an independent predictor of stroke in our analysis (OR: 1.47). Urgent surgery was mainly performed for unstable angina pectoris in patients with coronary artery disease and endocarditis in patients with valvular disease. Patients with unstable angina are more likely to suffer from peripheral vascular disease and increased atherosclerotic burden. These patients are also at increased risk for perioperative hemodynamic instability and impaired blood thrombogenicity [23]. Patients with endocarditis are at increased risk of particulate embolization from valvular vegetations [24]. We also included such patients under the variable "preoperative infection," another strong predictor of perioperative stroke in our analysis (OR: 2.39). Preoperative infection including endocarditis has been previously reported as a risk factor for stroke [9, 24, 25].

Our analysis revealed that CPB time longer than 2 hours was a predictor of stroke (OR: 1.42). Prolonged CPB times often denote technical difficulties in executing the planned operation due to unfavorable anatomy or intraoperative complications. The association between prolonged CPB time and perioperative stroke has been demonstrated by other investigators [4, 5, 15, 26].

Intraoperative hemofiltration was another predictor of stroke (OR: 1.25) in our study, possibly due to preoperative renal insufficiency secondary to renal artery arteriosclerosis. Arteriosclerosis has been well documented to be a systemic disease affecting multiple parts of the systemic circulation. Anderson and associates [27] found renal failure as a predisposing factor for adverse outcomes including neurologic deficits in patients undergoing coronary bypass surgery.

High transfusion requirement was a strong risk factor (OR: 6.04) for stroke in our analysis. However, this variable did not distinguish between intraoperative and postoperative transfusions and therefore may have simply been a marker for postoperative complications. The interpretation of this risk factor is therefore difficult.

Beating heart CABG consisting of OPCAB and MIDCAB procedures was the only variable associated with a significantly lower incidence of perioperative stroke in our risk-adjusted analysis (OR: 0.53). Beating heart techniques presumably lower the risk of stroke by mininimizing emboli production, particularly those caused by disruption of atheromatous plaques during cannulation, crossclamping, and manipulation of the ascending aorta [12, 28]. Patients undergoing MIDCAB surgery should have a very low incidence of stroke given that the ascending aorta is never exposed or manipulated and indeed this is what we found. However, it is interesting to note that stroke still occurred in 17 MIDCAB patients, or 1.6% of our total MIDCAB population. This finding suggests that there are other causative mechanisms of stroke in addition to atheroembolization from the ascending aorta in patients undergoing CABG.

Unfortunately our database did not enable us to distinguish between proximal anastomoses performed directly to the aorta and those performed to other bypass conduits using a T- or Y-graft technique. In general, however, we tended to anastomose saphenous venous and radial artery grafts directly to the ascending aorta in patients undergoing OPCAB and conventional CABG surgery. Since 1999 it has been our policy during conventional CABG to perform proximal anastomoses under a single cross-clamp technique thereby avoiding repeated aortic manipulation with the partial occluding clamp. This may have contributed to the relatively low risk of stroke (3.8%) in these patients.

The incidence of stroke in the OPCAB group was nonsignificantly higher than the MIDCAB group (2.5% vs 1.6%) although manipulation of the aorta is obviously more common during OPCAB surgery. Patients in the conventional CABG group suffered more often from perioperative stroke when compared with both beating heart groups although the difference between the CABG and OPCAB groups did not reach statistical significance. This finding could be due to increased manipulation of the aorta, as well as to potential hypoperfusion during mechanical stabilization and lifting of the heart, during OPCAB surgery when compared with the MIDCAB technique. We believe the lower incidence of perioperative stroke within the beating heart CABG group can be explained by the avoidance of aortic cannulation and subsequent decreased risk of embolization. In addition avoiding CPB eliminates the risks of gaseous embolization and potential "sandblasting" of the aorta [29].

Patients with stroke had a prolonged intensive care stay when compared with patients without stroke, probably related to the increased incidence of respiratory insufficiency and reintubation as well as to delayed mobilization. Furthermore, stroke patients had a markedly higher mortality rate. These findings have been previously reported by several other investigators [8–10, 16, 24].

In summary stroke is a devastating complication of cardiac surgery and continues to affect approximately 5% of patients. The incidence of stroke varies with different surgical procedures with the lowest risk observed for patient undergoing beating heart CABG. Using our large prospectively gathered, single-institution database we were able to identify several independent risk factors for perioperative stroke. Identification of these predictors is important for understanding the pathogenesis of stroke and for developing possible preventative strategies, with the caveat that retrospective analyses are always subject to possible selection bias. The increased use of beating heart CABG may be one such preventative strategy given its association with a significantly lower risk of stroke.

	Appendix

 

Perioperative Variables Analyzed as Univariate Predictors of Stroke Patients With Stroke (n = 743) Patients Without Stroke (n = 15,441) p Value Preoperative variables Prevalence % (n) Age <50 years 8.5% (63) 8.8% (1,366) 0.791 70–80 yearsa 39.2% (291) 32.2% (4,967) <0.0001 >80 years 4.6% (34) 3.6% (556) 0.161 Sex (male)a 67.3% (500) 71.4% (11,022) 0.018 History of syncopea 12.5% (93) 9.8% (1,518) 0.017 History of embolisma 6.7% (50) 3.0% (469) <0.0001 History of cardiogenic shocka 25.7% (191) 11.1% (1,716) <0.0001 Diabetes mellitusa (glucose intolerance treated with diet, oral hypoglycemics or insulin) 40.9% (304) 32.9% (5,089) <0.0001 Hyperlipidemiaa 41.2% (306) 46.5% (7,180) 0.019 Hypertensiona (patient taking antihypertensive medication preoperatively) 71.5% (531) 67.6% (10,443) 0.024 History of renal diseasea (history of renal failure or pathologically elevated serum creatinine treated medically without hemofiltration and dialysis) 11.0% (82) 4.0% (623) <0.0001 Dialysis-dependent renal insufficiencya 1.9% (14) 0.6% (99) 0.001 Preoperative infectiona (infectious disease including endocarditis) 8.6% (64) 1.8% (275) <0.0001 History of cerebrovascular diseasea (including stroke, TIA, and PRIND) 13.3% (99) 3.2% (490) <0.0001 Duration of surgery 3 hoursa 32.4% (241) 21.0% (3,250) <0.0001 CPB time 2 hoursa 30.7% (228) 12.6% (1,944) <0.0001 Aortic crossclamp time 1 houra 35.1% (261) 21.5% (3,313) <0.0001 Intraoperative hemofiltrationa 22.9% (170) 9.5% (1,468) <0.0001 Intraoperative hypothermia <32°Ca 52.2% (388) 36.6% (5,652) <0.0001 Intraoperative RBC transfusion 1,000 mLa 9.9% (74) 2.5% (386) <0.0001 Intraoperative low cardiac outputa 6.2% (46) 2.0% (314) <0.0001 Intraoperative IABPa 6.3% (47) 1.8% (274) <0.0001 Intraoperative assist devicea (including ECMO, Berlin Heart, TCI) 3.6% (27) 0.6% (89) <0.0001 Intraoperative need for pacemaker stimulationa 31.5% (234) 20.3% (3,130) <0.0001 Use of fibrillatory cardiac arresta 4.3% (32) 1.2% (190) <0.0001 Use of cardioplegia 76.7% (570) 77.5% (11,968) 0.621 Beating heart surgery 4.8% (36) 11.7% (1,806) <0.0001 OPCABa 2.6% (19) 4.8% (746) 0.005 MIDCABa 2.3% (17) 6.9% (1,060) <0.0001 CABGa 51.0% (379) 67.2% (10,380) <0.0001 Two or more coronary bypass graftsa 51.9% (386) 61.8% (9,540) <0.0001 Valve surgerya 50.1% (372) 32.7% (5,053) <0.0001 Combined surgerya (CABG and valvular surgery, ascending aortic surgery, and / or other procedures) 24.9% (185) 15.0% (2,321) <0.0001 Double or triple valve surgery 4.8% (36) 2.2% (345) 0.107 OPCAB conversion to CPB 0% (0) 0.2% (31) 0.401 Aortic valve and ascending aortic surgery 10.1% (75) 11.4% (1,755) 0.313 Mitral valve surgery 5.7% (42) 4.3% (666) 0.097 Intraoperative blood loss 500 mL 0.1% (8) 0.6% (94) 0.145 NYHA heart failure class 3a 81.7% (607) 77.5% (11,964) 0.007 LVEF 30%a (assessed by angiography or echocardiography) 14.5% (108) 8.9% (1,383) <0.0001 History of peripheral vascular diseasea 30.7% (228) 19.4% (3,001) <0.0001 Atrial fibrillationa (history of preoperative artrial fibrillation) 14.5% (108) 8.8% (1,365) <0.0001 Urgent operationa 47.6% (354) 22.5% (3,478) <0.0001 History of pulmonary diseasea (chronic pathologic pulmonary function tests) 8.9% (66) 6.8% (1,053) 0.031 Prior myocardial infarction 42.5% (316) 39.3% (6,065) 0.939 Emergency surgerya (emergent surgery due to complications during coronary angiography or PTCA) 1.3% (10) 0.6% (91) 0.026 CCS angina class 3a 36.5% (271) 32.7% (5,056) 0.038 Prior cardiac surgerya 10.5% (78) 5.1% (791) <0.0001 Prior CABGa 5.5% (41) 3.2% (493) 0.001 Prior surgery for aortic aneurysma 0.8% (6) 0.3% (46) 0.031 Prior aortic valve surgerya 2.4% (18) 0.9% (144) <0.0001 Prior mitral valve surgerya 2.4% (18) 0.9% (146) 0.001 Prior pacemaker implantationa 6.1% (45) 3.0% (464) <0.0001 Intraoperative variables Perioperative variables Total blood loss 500 mLa 79.7% (592) 67.6% (10,438) <0.0001 Total RBC transfusion 1,000 mLa 48.7% (362) 8.4% (1,303) <0.0001 Total RBC transfusion 2,000 mLa 21.5% (160) 7.2% (1,116) <0.0001

CABG = coronary artery bypass grafting; CCS = Canadian Cardiovascular Society; CPB = cardiopulmonary bypass; ECMO = extracorporeal membrane oxygenation; IABP = intraaortic balloon pump; LVEF = left ventricular ejection fraction; MIDCAB = minimally invasive direct coronary artery bypass grafting; NYHA = New York Heart Association; OPCAB = off pump coronary artery bypass grafting; PRIND = prolonged reversible ischemic neurologic deficit; PTCA = percutaneous transluminal coronary angioplasty; RBC = red blood cell; TIA = transient ischemic attack.

^a Variables that had a statistically significant association with stroke.

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				K. E. Glas, M. Swaminathan, S. T. Reeves, J. S. Shanewise, D. Rubenson, P. K. Smith, J. P. Mathew, S. K. Shernan, and Council for Intraoperative Echocardiography of the Guidelines for the Performance of a Comprehensive Intraoperative Epiaortic Ultrasonographic Examination: Recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; Endorsed by the Society of Thoracic Surgeons Anesth. Analg., May 1, 2008; 106(5): 1376 - 1384. [Full Text] [PDF]

				A. Russo, F. Grigioni, J.-F. Avierinos, W. K. Freeman, R. Suri, H. Michelena, R. Brown, T. M. Sundt, and M. Enriquez-Sarano Thromboembolic Complications After Surgical Correction of Mitral Regurgitation: Incidence, Predictors, and Clinical Implications J. Am. Coll. Cardiol., March 25, 2008; 51(12): 1203 - 1211. [Abstract] [Full Text] [PDF]

				N. Echahidi, P. Pibarot, G. O'Hara, and P. Mathieu Mechanisms, Prevention, and Treatment of Atrial Fibrillation After Cardiac Surgery J. Am. Coll. Cardiol., February 26, 2008; 51(8): 793 - 801. [Abstract] [Full Text] [PDF]

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				G. Y. Gandhi, G. A. Nuttall, and M. D. Abel Intensive Intraoperative Insulin Therapy versus Conventional Glucose Management during Cardiac Surgery Ann Intern Med, October 2, 2007; 147(7): 522 - 522. [Full Text] [PDF]

				L. D.C. Sauren, M. la Meir, M. Palmen, E. Severdija, F. H. van der Veen, W. H. Mess, and J. G. Maessen New ultrasonic radiation reduces cerebral emboli during extracorporeal circulation Eur. J. Cardiothorac. Surg., August 1, 2007; 32(2): 274 - 280. [Abstract] [Full Text] [PDF]

				M. Appelblad and K. G. Engstrom Fat content in pericardial suction blood and the efficacy of spontaneous density separation and surface adsorption in a prototype system for fat reduction J. Thorac. Cardiovasc. Surg., August 1, 2007; 134(2): 366 - 372. [Abstract] [Full Text] [PDF]

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				E. Sisillo, M. R. Marino, G. Juliano, C. Beverini, L. Salvi, and F. Alamanni Comparison of on pump and off pump coronary surgery: risk factors for neurological outcome Eur. J. Cardiothorac. Surg., June 1, 2007; 31(6): 1076 - 1080. [Abstract] [Full Text] [PDF]

				M. Selim Perioperative Stroke N. Engl. J. Med., February 15, 2007; 356(7): 706 - 713. [Full Text] [PDF]

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				G. N. Djaiani Aortic arch atheroma: stroke reduction in cardiac surgical patients. Seminars in Cardiothoracic and Vascular Anesthesia, June 1, 2006; 10(2): 143 - 157. [Abstract] [PDF]

				T. F. Floyd, P. N. Shah, C. C. Price, F. Harris, S. J. Ratcliffe, M. A. Acker, J. E. Bavaria, H. Rahmouni, B. Kuersten, S. Wiegers, et al. Clinically Silent Cerebral Ischemic Events After Cardiac Surgery: Their Incidence, Regional Vascular Occurrence, and Procedural Dependence Ann. Thorac. Surg., June 1, 2006; 81(6): 2160 - 2166. [Abstract] [Full Text] [PDF]

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				G. M. McKhann, M. A. Grega, L. M. Borowicz Jr, W. A. Baumgartner, and O. A. Selnes Stroke and Encephalopathy After Cardiac Surgery: An Update Stroke, February 1, 2006; 37(2): 562 - 571. [Abstract] [Full Text] [PDF]

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