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Ann Thorac Surg 2003;76:508-515
© 2003 The Society of Thoracic Surgeons

Original article: cardiovascular

Emboli capture using the Embol-X intraaortic filter in cardiac surgery: a multicentered randomized trial of 1,289 patients

Michael K. Banbury, MDa*, Nicholas T. Kouchoukos, MDb, Keith B. Allen, MDc, Mark S. Slaughter, MDd, Neil J. Weissman, MDe, Gerald J. Berry, MDf, Keith A. Horvath, MDg ICEM 2000 Investigators

a The Cleveland Clinic Foundation, Cleveland, Ohio, USA
b Missouri Baptist Medical Center, St. Louis, Missouri, USA
c St. Vincent Medical Center, Indianapolis, Indiana, USA
d Christ Hospital and Medical Center, Oak Lawn, Illinois, USA
e Washington Hospital Center, Washington, DC, USA
f Stanford University Medical Center, Stanford, California, USA
g Northwestern University Medical Center, Chicago, Illinois, USA

* Address reprint requests to Dr Banbury, The Cleveland Clinic Foundation, 9500 Euclid Ave, Desk F24, Cleveland, OH 44195, USA.
e-mail: banburm{at}ccf.org

Presented at the Thirty-ninth Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 31–Feb 2, 2003.


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 
BACKGROUND: Particulate emboli are thought to play a significant role in the development of cardiac surgical complications. Intraaortic filtration of particulate emboli may reduce the burden of this morbidity in cardiac patients.

METHODS: A multiinstitutional randomized trial was designed and enrolled 1,289 patients at 22 centers. Six hundred forty-five patients were assigned to the treatment arm and received the Embol-X intraaortic filter, whereas 644 patients were assigned to the control arm. The endpoints examined were mortality, stroke, transient ischemic attack, renal insufficiency/failure, myocardial infarction, gastrointestinal complications, and limb-threatening ischemia. All filters were examined for histologic evidence of particulate emboli.

RESULTS: Particulate emboli were identified in 598 (96.8%) of 618 filters successfully deployed. Composite event rates for the clinical endpoints were similar in both the filtered and nonfiltered arm (110/645 = 17% vs 122/644 = 19%, respectively). Individual event rates were also similar in both arms. A post hoc comparison of patients with moderate or greater preoperative risk scores demonstrated event reduction favoring the filtered group for renal complications (17/124 = 14% vs 28/117 = 24%, p = 0.04) and for the composite endpoint (30/124 = 24% vs 42/117 = 36%, p = 0.047). No clinically evident complications attributed to the use of the filter were identified.

CONCLUSIONS: The use of the Embol-X intraaortic filter is both safe and effective, as demonstrated by the emboli capture rate of 97%. In addition, post hoc analysis indicates a reduction in postoperative renal complications for patients with moderate or greater preoperative risk. Further study of high-risk patients is warranted.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 
A recent review of more than 1 million cardiac operations has demonstrated that the patients who are currently undergoing operation are at higher risk than they were a decade ago [1]. Despite this, the mortality rates over the same period of time have decreased significantly. In contrast, less significant reductions in morbidity have been observed in these "older" and "sicker" patients. One risk factor that has been demonstrated to play a significant role in postoperative complications is an atheromatous aorta. Manipulation of such aortas during cardiac surgery can lead to showers of emboli. The resultant end-organ damage can precipitate debilitating complications such as renal failure and stroke [2–4]. Attempts to manage this problem have ranged from minimizing aortic cross-clamping to replacement of the ascending aorta [5, 6].

The release of particulate emboli has been shown to correlate most frequently with the release of the aortic cross-clamp [7–9]. In an effort to reduce the embolic burden, a novel intraaortic filter device was developed for deployment before cross-clamp release. Previous nonrandomized investigations using this filter focused on feasibility and neurologic outcomes in patients [10–12]. The purpose of this study was to demonstrate the ability of this filter to capture particulate emboli and to assess its safety.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 Discussion
 Acknowledgments
 References
 
Intraaortic filter
The Embol-X intraaortic filtration system (Embol-X, Mountain View, CA) consists of a 24F metal-tipped intraaortic cannula that has been modified to allow the attachment of a collapsible filter that is inserted into the aorta through a side port of the cannula (Fig 1). The filter consists of a heparin-coated polyester mesh with pore size designed to capture particulate emboli with diameters of more than 120 µm. The flexible wire filter frame allows the filter to conform to the interior diameter of the aorta. The filter is available in five sizes to accommodate internal aortic diameters between 2.2 and 4.0 cm.



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  		Fig 1. The Embol-X intraaortic filtration system

 
Study design
The randomized clinical trial was developed and approved for Investigational Device Exemption (IDE) by the US Food and Drug Administration (FDA). From February 2000 to October 2001, 22 centers in North America enrolled 1,289 patients in this prospective randomized controlled trial. Each participating center obtained authorization from its Institutional Review Board, and written informed consent was obtained from each patient before randomization. The inclusion criteria were patients at least 60 years of age undergoing nonemergent, primary, isolated coronary artery bypass grafting (CABG), aortic valve replacement, or mitral valve repair/replacement surgery using cardiopulmonary bypass. Exclusion criteria included emergency operations, combined CABG and valve surgery, double valve surgery, and repair or replacement of the ascending aorta. Patients who were hemodynamically unstable or who had previous cardiac surgery or aneurysms of the ascending aorta were also excluded. Patients with fixed neurologic deficits or renal failure requiring dialysis were not enrolled.

After intraoperative assessment of the ascending aorta to confirm the absence of aneurysmal disease or extensive calcification that would preclude cross-clamping, patients were randomized in a 1:1 ratio to receive either the Embol-X cannula/filter or an identical metal tip cannula of the same diameter (Medtronic, Inc, Minneapolis, MN). Sizers were placed on the external surface of the aorta, just proximal to the site of cannulation, to determine the size of the filter to be inserted. After completion of the surgical procedure, and before removal of the aortic cross-clamp, the intraaortic filter was inserted through the sideport of the arterial cannula and deployed. The aortic clamp was then removed and the filter was left in place in the ascending aorta until the patient was weaned from cardiopulmonary bypass. The filter was then withdrawn into the side port of the cannula and the cannula was removed.

The filters, after removal from the aorta, were visually inspected for captured debris. The filters and debris were then fixed in formalin and submitted to a central histopathology core laboratory (Stanford University, Stanford, CA) for analysis. At less than 10x magnification, the quantity and size of captured particles were noted. Staining with hematoxylin and eosin, trichrome, and Elastica van Gieson was performed before histologic analysis.

The primary effectiveness objective of the study was to capture particulate emboli in at least 75% of the filtered patients. A composite endpoint was used to assess the safety of the device. Specifically, this composite included the occurrence of neurologic deficits, renal insufficiency, myocardial infarction, gastrointestinal complications, limb threatening peripheral embolism, or death due to any cause. These events were determined from the time of randomization up to the time of hospital discharge or 30 days, which ever occurred first. Neurologic evaluation was performed by trained examiners who were blinded to the randomization protocol and was conducted using the National Institutes of Health Stroke Scale [13]. Evaluation was performed preoperatively, on postoperative day 4 ± 1, postoperative day 7, and on postoperative day 30 if the patient was still hospitalized. Stroke (a central neurologic deficit persisting for longer than 24 hours), transient neurologic events (transient ischemic attack, delirium, or disorientation, and nonmetabolic coma were considered neurologic events. Renal insufficiency was defined as elevation of the serum creatinine above 2.0 mg/dL in patients with normal creatinine levels preoperatively, a >= 50% increase in creatinine above an abnormal baseline level, or the need for dialysis. Myocardial infarction was defined as the development of new pathologic Q waves in two or more contiguous leads on the postoperative electrocardiogram obtained within the first 24 hours postoperatively, or elevation of serum CK and CK-MB enzymes levels >= 5x normal for the institution in blood samples obtained in the operating room, upon arrival in the intensive care unit, and at 12 and 24 hours postoperatively. Gastrointestinal complications included gastrointestinal bleeding requiring transfusion, mesenteric ischemia requiring laparotomy, pancreatitis with abnormal amylase or lipase levels requiring nasogastric suction, or cholecystitis requiring cholecystectomy or drainage.

Intraoperative assessment of the ascending aorta by transesophageal echocardiography (TEE) or epiaortic ultrasonographic imaging was performed at 18 of the 22 centers (70% of the patients for each group). These images were obtained according to a predetermined protocol to standardize the examination, and were recorded on tape before and after cardiopulmonary bypass. These studies were read at a core laboratory by two echocardiographers who were blinded to the randomization protocol (Washington Hospital Center, Washington, DC). The images were used to detect potential aortic injuries produced by cannulation, clamping, or by the intraaortic filter.

Data collection and management
All monitoring procedures were performed in accordance with applicable federal regulations and International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) good clinical practice guidelines [14]. On-site research coordinators collected the clinical data. Independent study monitors verified all of the case report forms. The data for all patients with endpoint or other adverse events were reviewed and adjudicated by an independent clinical events committee, whose members were blinded to the treatment assignment. A data and safety monitoring committee reviewed the blinded data regularly during the course of the trial, including the results of the interim analysis when 50% of the patients had been enrolled. The investigators had full access to the data at their respective sites.

Sample size
The sample size was based on a primary safety hypothesis. This hypothesis stated that the composite endpoint event rate in the Embol-X filter group would be five percentage points greater than that in the control group, and the alternative hypothesis was that it would be less than five percentage points greater. Based on this hypothesis, a total of 1,274 patients (637 per randomized group) would provide 80% power to reject the null hypothesis at the 0.0475 level of significance, assuming the composite endpoint event rates were 15% in each group. The calculations were based on methods described by Blackwelder [15]. Additionally, to allow for the interim analysis, an O’Brien-Fleming adjustment was performed [16]. To allow for a dropout rate of 1%, the sample size was increased to 1,286 patients.

Statistical analysis
The primary analyses were based on the intent-to-treat dataset, which included all patients in the treatment group to which they were randomized, regardless of which treatment they actually received. Analyses were performed to compare treatment groups on all baseline demographic, medical history, and operative variables. Categorical variables were compared using Pearson’s {chi}2 or Fisher’s exact test for variables with very low frequencies. Continuous variables were compared using two sample t tests. If any difference was found to be nominally significant at the 10% level, it was then included in subsequent analyses of the primary safety variable. All statistical analyses were performed using the SAS version 8.2 (SAS Institute, Carey, NC).


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 Discussion
 Acknowledgments
 References
 
Baseline patient characteristics were similar between the two groups and are outlined in Table 1. Of note, there were significantly more patients treated with the filter who had preoperative atrial fibrillation, valvular dysfunction, and carotid stenoses. The control group had a higher prevalence of aortic disease, as defined by a history of aortic pathology such as aneurysm, dissection, or pathology requiring aortic surgery. Multivariable analysis of these differences demonstrated no interaction with the study results. Twenty-four (3.7%) patients randomized to receive the filter did not have the filter deployed, and 5 (0.8%) patients randomized to the control group mistakenly received the filter. In addition, 3 patients in the filter group and 1 patient in the control group undergoing CABG were treated off-pump.


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  		Table 1. Patient Characteristics

 
There were no differences between the control group and the filter group with respect to the type of operation performed, the use of a partial aortic clamp, or the repositioning of the aortic cross-clamp during the operation (Table 2). Additionally, there were no significant differences in the other important operative variables, including the time on cardiopulmonary bypass and the duration of aortic cross-clamping. Filters were deployed for an average of 21 ± 12 minutes.


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  		Table 2. Operative Variables

 
Particulate emboli were captured in 598 of 618 (96.8%) successfully deployed filters. The average number of particles captured was 5.8, with a range of 0 to 38 particulates. The average surface area of the emboli retrieved, a more accurate representation of the embolic burden, was 4.0 mm2, with a range of 0 to 82.5 mm2 (Fig 2). The histologic characteristics of the captured emboli are described in Table 3. Of note, the majority of the emboli were of atheromatous origin. Calcific atheromata were more frequently seen in patients undergoing valve operations compared with those undergoing isolated CABG procedures (19% vs 1%). Scanning electron microscopic analysis was performed on 10% of filters to evaluate for thrombogenicity. Minimal platelet aggregation was noted.



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  		Fig 2. Captured particulate emboli. (A) Filter with captured particulate emboli. (B) Photomicrograph of captured fibrous atheroma (10 x, 3-mm grid). (C) Organized thrombus captured by the filter.

 

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  		Table 3. Percent of Embol-X Filters Showing Particulate Emboli Grouped by Histological Characteristic

 
To gain familiarity with the cannula/filter, each participating surgeon was required to perform one nonrandomized filter case before enrolling patients in the trial. There was little difficulty with deployment and use of the filter. There were, however, five instances in which the surgeon noted intimal irregularities or endothelial disruptions at the time of intraoperative echocardiographic assessment. Three of these were repaired. At the time of repair, at least one intimal irregularity was thought to be due to scalpel perforation rather than filter related. There were no adverse clinical outcomes as a result of these repairs.

The individual adverse events noted during the trial are summarized in Table 4. This analysis demonstrated no significant difference between the filter and the control groups with regard to individual or composite adverse events.


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  		Table 4. Adverse Events

 
There were no intraoperative aortic dissections in the filter group and two in the control group. Endothelial disruptions were noted in 42 patients in the filtered group and 9 patients in the control group (p < 0.001). Thirty-three (78%) of these were not detected by the operating surgeon or the anesthesiologist on the postoperative epiaortic scan, and were only observed at the echocardiographic core laboratory. The majority of them were less than 5 mm in length. These disruptions were observed along the entire ascending aorta (ie, not always at the site of filter deployment). In an effort to determine whether these endothelial disruptions were associated with adverse clinical events, a comparison of patients with and without these disruptions was performed. The composite adverse event rate for patients with an endothelial disruption was 4.8%, and was 17.9% for patients without a disruption (p < 0.05). Control patients with an endothelial disruption also had a lower composite event rate (11% vs 18%) than those without a disruption (p < 0.05).

To further ensure that the endothelial disruptions did not lead to long-term adverse sequelae, 1-year mean follow-up was obtained for patients with endothelial disruptions and at four high enrolling centers, which did imaging for a total of 430 patients. Adverse outcomes of 6.1% were seen in both groups (n = 13 patients), and no aortic dissections were observed among the patients treated with the filter. There were 3 control patients who were found to have aortic aneurysms over the period of follow-up. None of the 3 had detectable endothelial disruptions during the study.

An odds ratio analysis was performed in which the preoperative variables and subsequent event rates were compared in the filter and control groups (Table 5). Patients with a low body mass index, low ejection fraction, and previous history of cerebral vascular disease fared significantly better when treated with the filter. Whereas not statistically significant, filtration was favorable for almost all baseline variables.


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  		Table 5. Odds Ratio Comparison of Baseline Variables and Composite Endpoint Adverse Event Rates

BMI = body mass index;

COPD = chronic obstructive pulmonary disease;

LVEF = left ventricular ejection fraction.

 
Using a validated risk stratification score [17], 241 (19%) of the patients in the study were found to be at moderate to high risk for postoperative morbidity or mortality. This post hoc analysis demonstrated a protective effect in the filter group for patients with moderate or greater preoperative risk (Table 6). Individual endpoint analysis shows that the protective effect was provided primarily by a reduction in renal complications (Table 7).


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  		Table 6. Composite Endpoint Events Stratified by Preoperative Risk

 

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  		Table 7. Individual Endpoint Events for Patients With Severity Score >= 5

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
Discussion
 Acknowledgments
 References
 
The fact that embolization occurs during cardiac surgery has been well established. The majority of the emboli result from necessary manipulation of the ascending aorta. Such manipulations are required during CABG whether or not cardiopulmonary bypass is used. It may in fact be the reason that there have been few demonstrated differences in stroke and neurologic dysfunction, regardless of an on-pump or off-pump strategy [18].

This large multiinstitutional randomized study was designed and powered to demonstrate the safety of the Embol-X intraaortic emboli filter as part of an FDA IDE submission. A low-risk and relatively homogeneous patient population was targeted for enrollment. The efficacy of intraaortic filtration was demonstrated by the high capture rate (96.8%) of particulate emboli. Both the treatment group and the control group had similar outcomes when either the composite endpoint or the individual endpoints were compared.

In the post hoc analysis of patients with moderate or greater preoperative risk scores, differences in renal outcomes emerged and were the principal reason for the difference in the composite endpoint event rate. The sensitivity of the kidneys to particulate emboli is well known [4]. In addition, the serum creatinine is a sensitive and measurable marker for renal function and injury. Postoperative renal injury has been associated with increased length of stay and higher mortality rates in cardiac surgery patients [19].

Other endpoints such as stroke and transient ischemic attack are not expected to show a difference because their overall event rate is low among populations of patients similar to those in this study, and currently there is no sensitive biological or biochemical marker to detect subclinical injury. Neurocognitive dysfunction may occur with greater frequency than transient ischemic attack or stroke, but its detection requires sophisticated testing, which was not included in the protocol of our study. The National Institutes of Health stroke scale is easy to perform and requires little time from the patients. However, it is not designed to detect subtle neurocognitive deficits, which may be the result of smaller particulate emboli.

One of the early concerns about intraaortic filtration was the potential for iatrogenic injury to the inside of the aorta. Aortic dissection is an uncommon but catastrophic complication of cardiac surgery. Transesophageal echocardiography and epiaortic imaging were utilized in a majority of the study patients. No aortic dissections were detected in the filter group, but two were seen in the control group. However, endothelial disruptions were found in both filter and control patients, but more often in the filter group. No clinically evident sequelae were observed among the patients with disruptions. Whereas the mechanism for these disruptions appears to be shear forces created either by the filter, cross-clamp, or the blood flow from the aortic cannula, the clinical significance of the disruptions appears to be negligible. Ura and colleagues noted similar findings in 5.3% of cardiac surgery patients who were carefully studied with epiaortic imaging both before cannulation and after decannulation [20]. Taken together, these results indicate that endothelial disruption is most likely a byproduct of aortic manipulation, one of which is insertion of an intraaortic filter.

Limitations
This trial was designed to show the safety of intraaortic filtration. It was not designed nor powered to detect clinical superiority, and thus capture of emboli was used as the endpoint to assess effectiveness. Although clinical effectiveness may be a more compelling endpoint, removal of emboli from the blood stream is a suitable and intuitively compelling surrogate.

The use of post hoc analysis to detect clinical benefits in the moderate- to high-risk group is a less compelling argument for a claim of superiority than detected benefits defined a priori in the study design.

Conclusions
The use of the Embol-X intraaortic filter is both safe and effective, as demonstrated by the emboli capture rate of 97%. In addition, post hoc analysis indicates a reduction in postoperative morbidity, specifically renal complications, for patients with moderate or greater preoperative risk. Further study of high-risk patients is warranted. (Appendix)


   Discussion
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Discussion
Acknowledgments
 References
 
DR SARA J. SHUMWAY (Minneapolis, MN): I would like to congratulate Dr Banbury and colleagues for a very well–thought out and carefully executed clinical trial. This obviously took a lot of time and effort. The Society of Thoracic Surgeons is the ideal setting for such a presentation. Just a few questions.

Is there any correlation between elevated serum cholesterol and/or other lipids and the finding of particulate fibrous atheroma? Are you sure the higher prevalence of aortic disease in the control group did not contribute to renal insufficiency in the control group afterward? Is there any correlation with duration of time that the filter is in the aorta, or filter dwell time, as you call it, and the number of endothelial disruptions? Is the vasculopath your targeted population, or because this device is safe and effective, does every patient need it? Finally, does it reduce morbidity/mortality enough that the cost/benefit ratio is there? I would guess the cost/benefit ratio would be present in patients with bad aortas and renal insufficiency.

Thank you for an excellent presentation.

DR BANBURY: Doctor Shumway, thank you for your kind comments and kind questions.

In order that you asked: Is there a correlation between cholesterol levels or lipid levels and debris captured? Since the capture of debris was so large, it would be difficult to show that, although we did not look specifically at serum lipid levels and serum cholesterol levels, and that is a provocative question that we will address in follow-up.

Is there a correlation between aortic disease in the control group and the subsequent finding of higher renal complications in the higher risk patients? We did a multivariable and stepwise logistic regression analysis to look for confounding factors, and that did not fall out in the analysis and we do not feel that that had an effect.

Dwell time in the aorta appeared to have no effect on EDS or endothelial disruption. Early in the series, if the cannula is moved back and forth vigorously, it could potentially have an abrasive effect, and we felt that one of those small disruptions may have been caused by the shearing forces, and we have instructed people who use it not to rock it back and forth when trying to position the aortic cannula.

Who is the target population for this filter and does it reduce morbidity and mortality enough to justify a cost/benefit analysis? Clearly, I think that higher risk patients benefit from this particular filtration device. I think that all patients could potentially benefit. And I have used the analogy of the seat belt in the car: you do not need your seat belt unless you wreck your car. And even low-risk patients do not need the intraaortic filter unless one of those thrombi that I showed on the slides comes loose for whatever reason, and the day that saves a life is the day that that filter is worthwhile, and we just do not know when that comes.

I think that we have done very well in cardiac surgery and we have to decide what is good enough. Is the current level of morbidity and mortality enough or do we use incremental improvements such as intraaortic filtration of debris to try to make more improvements towards a better operation, similar to reducing the mortality that Dr Mack talked about? We need to continue to improve to provide the best care for patients so that issues like percutaneous intervention do not threaten our specialty in helping the patients that we do so well with.

Thank you for your attention.


   Acknowledgments
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Discussion
 Acknowledgments
References
 
This study was funded by Embol-X, Inc, Mountain View, CA, under a US FDA Investigational Device Exemption. The seven principal authors served as consultants to the company during the FDA review process.

The following principal investigators and sites participated in the ICEM 2000 study: Dr M. Zenati, University of Pittsburgh Medical Center; Dr M. Platt, Dallas Presbyterian Hospital; Dr M. Banbury, Cleveland Clinic; Dr K. Allen, Schumacker Isch; Dr J. Murkin, London Health Sciences Center; Dr M. Moon, Barnes Jewish Hospital; Dr R. Matheny, Atlanta Cardiology; Dr. K. Horvath, Northwestern University; Dr N. Kouchoukos, Missouri Baptist Hospital; Dr J. Horneffer, St. Joseph’s Hospital (MD); Dr M. Slaughter, Christ Hospital; Dr S. Aranki, Brigham and Women’s Hospital; Dr M. Pompili, Kaiser Permanente, SF; Dr J. M. Duncan, Texas Heart Institute; Dr J. Bassett, William Beaumont Hospital; Dr R. Robbins, Stanford University Hospital; Dr S. Szentpetery, Sentara Norfolk General Hospital; Dr H. Garrett, Baptist Memorial Hospital; Dr H. Rashid, Charleston Area Medical Center; Dr R. Engelman, Baystate Medical Center; Dr S. Boyce, Washington Hospital Center; Dr A. Chavez, Elyria Memorial Hospital.


   Appendix
 
In addition to the authors and the investigational sites in this study, the following institutions and individuals participated in the ICEM 2000 study:

Clinical Events Committee: Dr J. St. Louis (Chairman), Dr J. Breall, Dr. P. Blake.

Data and Safety Monitoring Committee: Dr R. Shemin (Chairman), Dr R. Wityk, Dr. R. Heuser, Dr C. Redmond (Statistician).

Statistical analysis: Eugene R. Heyman, PhD
ECG Core Laboratory (Harvard Clinical Research Institute, Boston MA): G. Foley, Dr P. Zimetbaum.

Histology Core Laboratory (Stanford University): Dr G. Berry

Imaging Core Laboratory (Washington Hospital Center, WA DC): K Horton, Dr N. Weissman.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 Discussion
 Acknowledgments
 References
 

  1. Ferguson T.B., Hammill B.G., Peterson E.D., DeLong E.R., Grover F.L. A decade of change: risk profiles and outcomes for isolated coronary artery bypass grafting procedures, 1990–1999: a report from the STS National Database Committee and the Duke Clinical Research Institute. Ann Thorac Surg 2002;73:480-490.[Abstract/Free Full Text]
  2. Katz E.S., Tunick P.A., Rusinek H., RibaKove G., Spenser F.C., Kronzon I. Protruding aortic atheromas predict stroke in elderly patients undergoing cardiopulmonary bypass: experience with intraoperative transesophageal echocardiography. J Am Coll Cardiol 1992;20:70-77.[Abstract]
  3. Calafiore A.M., Di Mauro M., Teodori G., et al. Impact of aortic manipulation on incidence of cerebrovascular accidents after surgical myocardial revascularization. Ann Thorac Surg 2002;73:1387-1393.[Abstract/Free Full Text]
  4. Davila-Roman V., Kouchoukos N., Schechtman K., Barzilai B. Atherosclerosis of the ascending aorta is a predictor of renal dysfunction after cardiac operations. J Thorac Cardiovasc Surg 1999;117:111-116.[Abstract/Free Full Text]
  5. Aranki S.F., Rizzo R.J., Adams D.H., et al. Single-clamp technique: an important adjunct to myocardial and cerebral protection in coronary operations. Ann Thorac Surg 1994;58:296-303.[Abstract]
  6. Wareing T.H., Davila-Roman V.G., Barzilai B., Murphy S.F., Kouchoukos N.T. Management of the severely atherosclerotic ascending aorta during cardiac operations. J Thorac Cardiovasc Surg 1992;103:453-462.[Abstract]
  7. Stump D.A., Newman S.P. Emboli detection during cardiopulmonary bypass. In: Tegler C.H., Babikian V.L., Gomez C.R., eds. Neurosonology. St. Louis: Mosby, 1996:252-255.
  8. Topol E.J., Yadav J.S. Recognition of the importance of embolization in atherosclerotic vascular disease. Circulation 2000;101:570-580.[Free Full Text]
  9. Barbut D., Hinton R.B., Szatrowski T.P., et al. Cerebral emboli detected during bypass surgery are associated with clamp removal. Stroke 1994;25:2398-2402.[Abstract]
  10. Reichenspurner H., Navia J.A., Berry G., et al. Particulate emboli capture by an intra-aortic filter device during cardiac surgery. J Thorac Cardiovasc Surg 2000;119:233-241.[Abstract/Free Full Text]
  11. Harringer W. Capture of particulate emboli during cardiac procedures in which aortic cross-clamp is used. Ann Thorac Surg 2000;70:1119-1123.[Abstract/Free Full Text]
  12. Schmitz C., Blackstone E. International Council of Emboli Management (ICEM) Study Group Results: risk adjusted outcomes in intra-aortic filtration. Eur J Cardiothorac Surg 2001;20:986-991.[Abstract/Free Full Text]
  13. Lyden P, Brott T, Tilley B, et al. Improved reliability of the NIH Stroke Scale using video training: Stroke 1994;25:2220–6
  14. Federal Register. May 9, 1997 (62 FR 25692)
  15. Blackwelder W. Proving the null hypothesis in clinical trials. Controlled Clinical Trials 1982;3:345-353.[Medline]
  16. O’Brien P., Fleming T. A multiple testing procedure for clinical trials. Biometrics 1979;35:549-556.[Medline]
  17. Higgins T.L., Estafanous F.G., Loop F.D., Beck G.J., Blum J.M., Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients: a clinical severity score. JAMA 1992;267:2344-2348.[Abstract/Free Full Text]
  18. Van Dijk D., Jansen E.W., Hijman R., et al. Cognitive outcome after off-pump and on-pump coronary artery bypass graft surgery a randomized trial. JAMA 2002;287:1405-1412.[Abstract/Free Full Text]
  19. Ryan T.A., Rady M.Y., Bashour C.A., Leventhal M., Lyle B., Starr N.J. Predictors of outcome in cardiac surgical patients with prolonged intensive care stay. Chest 1997;112:1035-1042.[Abstract/Free Full Text]
  20. Ura M., Sakata R., Nakayama Y., Miyamoto T., Goto T. Extracorporeal circulation before and after ultrasonographic evaluation of the ascending aorta. Ann Thorac Surg 1999;67:478-483.[Abstract/Free Full Text]



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R. Lee, N. Matsutani, A. C. Polimenakos, L. C. Levers, M. Lee, and R. G. Johnson
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J. Bonatti, W. J. van Boven, G. Nagele, G. Shahin, T. Schachner, G. Laufer, P. Bergman, J. van der Linden, and The AORTIC Study Group (Assessment Of the Risk of
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Intraluminal aortic manipulation by means of intra-aortic filter, cannulation, and external clamp maneuvers evaluated versus dislodged embolic material
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