Atheromatous disease of the aorta and perioperative stroke
2017; Elsevier BV; Volume: 155; Issue: 2 Linguagem: Inglês
10.1016/j.jtcvs.2017.08.132
ISSN1097-685X
AutoresNicholas D. Andersen, Stephen A. Hart, Ganesh Devendra, Esther S.H. Kim, Douglas R. Johnston, Jacob N. Schroder, Richard A. Krasuski,
Tópico(s)Aortic Disease and Treatment Approaches
ResumoCentral MessageIn this paper, we review the current understanding of atheromatous disease of the aorta and strategies for perioperative stroke prevention in patients undergoing cardiac surgery.PerspectiveAtheromatous disease of the aorta occurs frequently in patients undergoing cardiac surgery and poses a significant risk for perioperative stroke. The risk of stroke from aortic atheroma may be reduced with an increased understanding of atheroma characteristics and pathogenesis, risk factor modification, imaging identification, alterations in surgical technique, and use of embolic protection devices.See Editorial Commentaries pages 517 and 518.See Editorial page 507. In this paper, we review the current understanding of atheromatous disease of the aorta and strategies for perioperative stroke prevention in patients undergoing cardiac surgery. Atheromatous disease of the aorta occurs frequently in patients undergoing cardiac surgery and poses a significant risk for perioperative stroke. The risk of stroke from aortic atheroma may be reduced with an increased understanding of atheroma characteristics and pathogenesis, risk factor modification, imaging identification, alterations in surgical technique, and use of embolic protection devices. See Editorial Commentaries pages 517 and 518. See Editorial page 507. Despite continued improvements in patient outcomes after cardiac surgery, stroke remains one of the most feared and devastating complications of cardiac surgery and is estimated to occur in 1.2% to 1.6% of patients undergoing coronary artery bypass grafting (CABG).1Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting.Ann Thorac Surg. 2008; 85: 862-870Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 2Selnes O.A. Gottesman R.F. Grega M.A. Baumgartner W.A. Zeger S.L. McKhann G.M. Cognitive and neurologic outcomes after coronary-artery bypass surgery.N Engl J Med. 2012; 366: 250-257Crossref PubMed Scopus (246) Google Scholar, 3ElBardissi A.W. Aranki S.F. Sheng S. O'Brien S.M. Greenberg C.C. Gammie J.S. Trends in isolated coronary artery bypass grafting: an analysis of the Society of Thoracic Surgeons adult cardiac surgery database.J Thorac Cardiovasc Surg. 2012; 143: 273-281Abstract Full Text Full Text PDF PubMed Scopus (342) Google Scholar The incidence of stroke increases for other common cardiac surgical procedures, and contemporary studies from the Society of Thoracic Surgeons database have reported perioperative stroke rates of 1.4% for mitral valve repair,4O'Brien S.M. Shahian D.M. Filardo G. Ferraris V.A. Haan C.K. Rich J.B. et al.The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 2—isolated valve surgery.Ann Thorac Surg. 2009; 88: S23-S42Abstract Full Text Full Text PDF PubMed Scopus (973) Google Scholar 1.5% for aortic valve replacement,5Thourani V.H. Suri R.M. Gunter R.L. Sheng S. O'Brien S.M. Ailawadi G. et al.Contemporary real-world outcomes of surgical aortic valve replacement in 141,905 low-risk, intermediate-risk, and high-risk patients.Ann Thorac Surg. 2015; 99: 55-61Abstract Full Text Full Text PDF PubMed Scopus (224) Google Scholar 2.1% for mitral valve replacement,4O'Brien S.M. Shahian D.M. Filardo G. Ferraris V.A. Haan C.K. Rich J.B. et al.The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 2—isolated valve surgery.Ann Thorac Surg. 2009; 88: S23-S42Abstract Full Text Full Text PDF PubMed Scopus (973) Google Scholar and 6.6% for proximal aorta replacement.6Williams J.B. Peterson E.D. Zhao Y. O'Brien S.M. Andersen N.D. Miller D.C. et al.Contemporary results for proximal aortic replacement in North America.J Am Coll Cardiol. 2012; 60: 1156-1162Crossref PubMed Scopus (133) Google Scholar Stroke remains one of the most important contributors to postoperative morbidity and mortality and has been associated with 5-year survival rates of 60% or less.1Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting.Ann Thorac Surg. 2008; 85: 862-870Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 7Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, imaging analysis, and early and late outcomes of stroke after cardiac valve operation.Am J Cardiol. 2008; 101: 1472-1478Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar In addition, stroke after cardiac surgery has been demonstrated to cause increased hospital mortality, increased duration of hospitalization, and may contribute up to 4 billion dollars in additional health care–related costs per year.1Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting.Ann Thorac Surg. 2008; 85: 862-870Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 7Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, imaging analysis, and early and late outcomes of stroke after cardiac valve operation.Am J Cardiol. 2008; 101: 1472-1478Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar, 8Roach G.W. Kanchuger M. Mangano C.M. Newman M. Nussmeier N. Wolman R. et al.Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators.N Engl J Med. 1996; 335: 1857-1863Crossref PubMed Scopus (1664) Google Scholar Aortic atherosclerosis is linked pathogenically with chronic inflammatory responses to injury of the arterial smooth muscle and endothelium and is morphologically characterized by the formation of intimal plaque and lipid deposition, fibrous proliferation, calcification, and necrosis.9Falk E. Pathogenesis of atherosclerosis.J Am Coll Cardiol. 2006; 47: C7-C12Crossref PubMed Scopus (834) Google Scholar The presence of aortic atheroma has been well established as an independent predictor of central nervous system (CNS) events in the general population and is as important as traditional contributors to embolism, such as left atrial thrombus, carotid lesions, and atrial fibrillation.10Amarenco P. Cohen A. Hommel M. Moulin T. Leys D. Bousser M.-G. French Study of Aortic Plaques in Stroke GroupAtherosclerotic disease of the aortic arch as a risk factor for recurrent ischemic stroke.N Engl J Med. 1996; 334: 1216-1221Crossref PubMed Scopus (585) Google Scholar Although surgery itself is a risk factor for stroke, the additional contribution of aortic atherosclerotic disease in patients undergoing cardiac surgical intervention cannot be understated. There are a number of intuitive mechanisms by which cardiac surgical operations may induce embolization: aortic manipulation, cannulation, crossclamping, and side clamping, among others. Accordingly, many studies have demonstrated a link between aortic atherosclerosis and postoperative CNS injury after cardiac surgery.1Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting.Ann Thorac Surg. 2008; 85: 862-870Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 7Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, imaging analysis, and early and late outcomes of stroke after cardiac valve operation.Am J Cardiol. 2008; 101: 1472-1478Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar, 8Roach G.W. Kanchuger M. Mangano C.M. Newman M. Nussmeier N. Wolman R. et al.Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators.N Engl J Med. 1996; 335: 1857-1863Crossref PubMed Scopus (1664) Google Scholar In 1996, The Multicenter Study of Perioperative Ischemia reported the results of a prospective multicenter analysis of 2108 patients undergoing elective CABG surgery and found that proximal aortic atheroma was the strongest independent predictor of stroke, with an odds ratio of 4.52.8Roach G.W. Kanchuger M. Mangano C.M. Newman M. Nussmeier N. Wolman R. et al.Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators.N Engl J Med. 1996; 335: 1857-1863Crossref PubMed Scopus (1664) Google Scholar Since then, multiple other studies have confirmed a 3- to 4-fold increased risk of perioperative stroke after cardiac surgery in patients with atheroma or calcification of the proximal aorta.1Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, topography, predictors and long-term survival after stroke in patients undergoing coronary artery bypass grafting.Ann Thorac Surg. 2008; 85: 862-870Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar, 7Filsoufi F. Rahmanian P.B. Castillo J.G. Bronster D. Adams D.H. Incidence, imaging analysis, and early and late outcomes of stroke after cardiac valve operation.Am J Cardiol. 2008; 101: 1472-1478Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar, 11van der Linden J. Bergman P. Hadjinikolaou L. The topography of aortic atherosclerosis enhances its precision as a predictor of stroke.Ann Thorac Surg. 2007; 83: 2087-2092Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar Atheromatous disease is a regional process explained in part by variations in hemodynamics (Figure 1),12Soulis J. Giannoglou G. Dimitrakopoulou M. Papaioannou V. Logothetides S. Mikhailidis D. Influence of oscillating flow on LDL transport and wall shear stress in the normal aortic arch.Open Cardiovasc Med J. 2009; 3: 128-142Crossref PubMed Scopus (17) Google Scholar and the risk of stroke after cardiac surgery may be altered by a plaque's location. In a meticulous analysis of stroke risk related to proximal aorta plaque location, van der Linden and colleagues11van der Linden J. Bergman P. Hadjinikolaou L. The topography of aortic atherosclerosis enhances its precision as a predictor of stroke.Ann Thorac Surg. 2007; 83: 2087-2092Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar demonstrated that the precise location of proximal aorta atheroma significantly altered the degree of stroke risk. The authors developed a topographic odds ratio map for late stroke based on disease located in 12 different segments of the ascending aorta. Although disease located in the proximal ascending aorta and along the anterior surface carried no increased risk, plaque located in the distal ascending aorta and the lesser curvature carried up to a 5-fold greater risk of late stroke. In multivariate analysis, they demonstrated that the extent of atheromatous disease was a strong predictor of late stroke but that plaque in key "high-risk" zones, including the distal ascending aorta and the lesser curvature, were far more predictive. Although it remains unknown why atheroma in these high-risk zones was more malignant than plaque in the proximal or anterior ascending aorta, the authors speculated that increased flow velocity in these regions may dislodge loose atherosclerotic material, which may have been slightly mobilized by earlier surgical maneuvers.11van der Linden J. Bergman P. Hadjinikolaou L. The topography of aortic atherosclerosis enhances its precision as a predictor of stroke.Ann Thorac Surg. 2007; 83: 2087-2092Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar It should be emphasized that these high-risk zones in the distal ascending aorta and lesser curvature are the most difficult to assess by manual palpation or transesophageal echocardiography (TEE). The authors estimated that patients with such high-risk anatomy comprised up to 10% of the cardiac surgical population. Careful research has resulted in improved characterization of pathologic plaques of the aorta. In addition to plaque location—plaque thickness, morphology, and mobility independently influence the likelihood of early and late stroke. The standard cut-off for "at-risk" plaque thickness has been established at 4 mm or greater, with plaques 4 mm or greater associated with a 4-fold increased likelihood of stroke and a linear increase in stroke seen with increasing plaque thickness.10Amarenco P. Cohen A. Hommel M. Moulin T. Leys D. Bousser M.-G. French Study of Aortic Plaques in Stroke GroupAtherosclerotic disease of the aortic arch as a risk factor for recurrent ischemic stroke.N Engl J Med. 1996; 334: 1216-1221Crossref PubMed Scopus (585) Google Scholar Similar to plaques in the coronary arteries, plaque instability is likely an even stronger risk factor for rupture and embolic stroke than plaque thickness. Vulnerable aortic plaques have been identified echocardiographically by the presence of increased hypoechoiety, calcification, and ulceration. Lastly, several studies have shown that mobile plaques (Figure 2) represent an extremely high-risk lesion and may increase the likelihood of stroke several-fold compared with nonmobile plaques.13Kronzon I. Tunick P.A. Aortic atherosclerotic disease and stroke.Circulation. 2006; 114: 63-75Crossref PubMed Scopus (219) Google Scholar Stroke in the perioperative setting is prevalent, but some events may be preventable.14Douglas Jr., J.M. Spaniol S.E. A multimodal approach to the prevention of postoperative stroke in patients undergoing coronary artery bypass surgery.Am J Surg. 2009; 197: 587-590Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar The risk of stroke is multifactorial and can be divided into modifiable and nonmodifiable risk factors. Nonmodifiable risk factors include age, sex, socioeconomic status, and genetics.15Hogue Jr., C.W. Barzilai B. Pieper K.S. Coombs L.P. DeLong E.R. Kouchoukos N.T. et al.Sex differences in neurological outcomes and mortality after cardiac surgery: a society of thoracic surgery national database report.Circulation. 2001; 103: 2133-2137Crossref PubMed Scopus (156) Google Scholar, 16Agabiti N. Cesaroni G. Picciotto S. Bisanti L. Caranci N. Costa G. et al.The association of socioeconomic disadvantage with postoperative complications after major elective cardiovascular surgery.J Epidemiol Community Health. 2008; 62: 882-889Crossref PubMed Scopus (57) Google Scholar Modifiable risk factors include comorbid disease, the type and technique of surgery, perioperative management, the experience of the surgical team, and the complexity of the surgical case. The first step in preventing perioperative stroke is to optimize comorbid diseases. After diet, exercise, and glucose control have been implemented, appropriate therapy with lipid-lowering medications can help reduce global atheroma burden. It has been shown that statins reduce the size of atherosclerotic plaques, and a retrospective matched-pairs analysis demonstrated that statin therapy resulted in a 17% reduction in the absolute risk of stroke among patients with severe atheromatous disease of the aorta.17Tunick P.A. Nayar A.C. Goodkin G.M. Mirchandani S. Francescone S. Rosenzweig B.P. et al.Effect of treatment on the incidence of stroke and other emboli in 519 patients with severe thoracic aortic plaque.Am J Cardiol. 2002; 90: 1320-1325Abstract Full Text Full Text PDF PubMed Scopus (210) Google Scholar However, randomized controlled trials have produced conflicting results on the ability of immediate preoperative statin therapy to reduce the risk of stroke after cardiac surgery.18Putzu A. Capelli B. Belletti A. Cassina T. Ferrari E. Gallo M. et al.Perioperative statin therapy in cardiac surgery: a meta-analysis of randomized controlled trials.Crit Care. 2016; 20: 395Crossref PubMed Scopus (35) Google Scholar The use of antiplatelet or anticoagulation medications is similarly controversial. Aspirin therapy administered within 48 hours of CABG surgery was shown to reduce the rate of stroke in a large, prospective study.19Mangano D.T. Multicenter Study of Perioperative Ischemia Research Group. Aspirin and mortality from coronary bypass surgery.N Engl J Med. 2002; 347: 1309-1317Crossref PubMed Scopus (563) Google Scholar A small number of retrospective studies also found benefit to oral anticoagulation with warfarin in patients with mobile aortic plaques,13Kronzon I. Tunick P.A. Aortic atherosclerotic disease and stroke.Circulation. 2006; 114: 63-75Crossref PubMed Scopus (219) Google Scholar although these findings have not been replicated or reproduced uniformly in patients undergoing heart surgery. The traditional gold standard for detecting aortic atheroma is epiaortic ultrasound (EAU), which is performed by positioning an ultrasound transducer directly on the aorta after sternotomy (Videos 1 and 2).20Glas K.E. Swaminathan M. Reeves S.T. Shanewise J.S. Rubenson D. Smith P.K. et al.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. 2008; 106: 1376-1384Crossref PubMed Scopus (44) Google Scholar Manual palpation and TEE (Figure 2) also have been used to detect aortic atheroma but have consistently underperformed when compared with EAU. Manual palpation of the aorta occurs in most cardiac surgeries requiring cardiopulmonary bypass, and TEE frequently is used to assess cardiac structure and function before and after a procedure, making these modalities very convenient. However, manual palpation may cause plaques to embolize, and adequate visualization of the highest-risk zones in the ascending aorta and aortic arch are limited with TEE because of tracheal shadow.20Glas K.E. Swaminathan M. Reeves S.T. Shanewise J.S. Rubenson D. Smith P.K. et al.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. 2008; 106: 1376-1384Crossref PubMed Scopus (44) Google Scholar Studies have estimated that the sensitivity of manual palpation for detecting atheroma may be as low as 25%.21Suvarna S. Smith A. Stygall J. Kolvecar S. Walesby R. Harrison M. et al.An intraoperative assessment of the ascending aorta: a comparison of digital palpation, transesophageal echocardiography, and epiaortic ultrasonography.J Cardiothorac Vasc Anesth. 2007; 21: 805-809Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar The sensitivity of TEE is, unfortunately, only marginally better.21Suvarna S. Smith A. Stygall J. Kolvecar S. Walesby R. Harrison M. et al.An intraoperative assessment of the ascending aorta: a comparison of digital palpation, transesophageal echocardiography, and epiaortic ultrasonography.J Cardiothorac Vasc Anesth. 2007; 21: 805-809Abstract Full Text Full Text PDF PubMed Scopus (47) Google Scholar Minor disadvantages of EAU are that it lengthens surgical time, requires expertise and training in its use, and it can only provide information intraoperatively after committing to an incision. For these reasons, EAU has not been adopted on a large scale. Recent guidelines set forth by the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists attempt to standardize intraoperative EAU examinations and provide rationale for its routine use in cardiovascular surgeries.20Glas K.E. Swaminathan M. Reeves S.T. Shanewise J.S. Rubenson D. Smith P.K. et al.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. 2008; 106: 1376-1384Crossref PubMed Scopus (44) Google ScholarVideo 2Case 1: long-axis view (best viewed on repeat with Windows Media Player). Video available at: http://www.jtcvsonline.org/article/S0022-5223(17)31908-6/fulltext.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Data supporting the use of EAU to identify at-risk patients have come largely from retrospective studies. The first study to explore the impact of EAU on postoperative stroke found that aortic scanning before CABG resulted in modification of the planned surgical procedure in 31% of patients (Videos 3 and 4). Those with the most severe disease suffered the greatest postoperative mortality but did not have increased incidence of stroke in the early postoperative period.22Hangler H.B. Nagele G. Danzmayr M. Mueller L. Ruttmann E. Laufer G. et al.Modification of surgical technique for ascending aortic atherosclerosis: impact on stroke reduction in coronary artery bypass grafting.J Thorac Cardiovasc Surg. 2003; 126: 391-400Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar The authors suggested that EAU appropriately identified patients at high risk for postoperative stroke and led to alterations in surgical strategy that may have prevented stroke in the greatest-risk patients. A more recent cohort series demonstrated that routine EAU led to altered surgical strategy in a much more modest number (4.1%) of patients.23Rosenberger P. Shernan S.K. Loffler M. Shekar P.S. Fox J.A. Tuli J.K. et al.The influence of epiaortic ultrasonography on intraoperative surgical management in 6051 cardiac surgical patients.Ann Thorac Surg. 2008; 85: 548-553Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar A careful study examining perioperative outcomes found that EAU led to a significantly increased number of modified surgical plans compared with manual palpation alone, but embolic load to the brain measured by transcranial Doppler and postoperative stroke scores remained unchanged.24Djaiani G. Ali M. Borger M.A. Woo A. Carroll J. Feindel C. et al.Epiaortic scanning modifies planned intraoperative surgical management but not cerebral embolic load during coronary artery bypass surgery.Anesth Analg. 2008; 106: 1611-1618Crossref PubMed Scopus (55) Google Scholar In a much larger cohort study, Yamaguchi and colleagues25Yamaguchi A. Adachi H. Tanaka M. Ino T. Efficacy of intraoperative epiaortic ultrasound scanning for preventing stroke after coronary artery bypass surgery.Ann Thorac Cardiovasc Surg. 2009; 15: 98-104PubMed Google Scholar demonstrated that EAU resulted in 0 postoperative strokes among 909 consecutive patients undergoing CABG. If ascending aortic atheroma at least 3 mm thick was detected, the surgical strategy was altered to allow for a "no-touch" approach.Video 4Case 2: long-axis view (best viewed on repeat with Windows Media Player). Video available at: http://www.jtcvsonline.org/article/S0022-5223(17)31908-6/fulltext.View Large Image Figure ViewerDownload Hi-res image Download (PPT) It should be noted that newer imaging technologies, such as A-view TEE, magnetic resonance imaging (MRI), and computed tomography (CT; Figure 3) demonstrate growing potential as screening modalities but currently lack the evidence base of EAU. A-view TEE uses a fluid-filled balloon catheter placed in the trachea to image the "blind spot" of the aorta that normally is concealed by the tracheal shadow. Although this technique has shown promise in small studies, widespread adoption has not occurred, possibly due to the need for additional training, the cost of the A-view catheter (Cordatec Inc, Zoersel, Belgium), and concerns with tracheal instrumentation.26Nierich A.P. van Zaane B. Buhre W.F. Coddens J. Spanjersberg A.J. Moons K.G. Visualization of the distal ascending aorta with A-Mode transesophageal echocardiography.J Cardiothorac Vasc Anesth. 2008; 22: 766-773Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar The advantage of CT or MRI modalities is that surgical decision making may take place far in advance of surgery, allowing for a change in surgical plan or procedure before incision, as well as reduced operative time. Disadvantages include cost and radiation exposure. Although one study found that CT was inferior to EAU in detecting aortic atheroma,27Bergman P. van der Linden J. Forsberg K. Ohman M. Preoperative computed tomography or intraoperative epiaortic ultrasound for the diagnosis of atherosclerosis of the ascending aorta?.Heart Surg Forum. 2004; 7 (discussion E249): E245-E249Crossref PubMed Google Scholar a more recent meta-analysis found that preoperative CT imaging significantly reduced the rate of stroke in patients undergoing primary and reoperative heart surgery,28den Harder A.M. de Heer L.M. Meijer R.C. Das M. Krestin G.P. Maessen J.G. et al.Effect of computed tomography before cardiac surgery on surgical strategy, mortality and stroke.Eur J Radiol. 2016; 85: 744-750Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar and additional randomized controlled trials of preoperative CT imaging are currently underway.29den Harder A.M. de Heer L.M. Maurovich-Horvat P. Merkely B. de Jong P.A. Das M. et al.Ultra low-dose chest ct with iterative reconstructions as an alternative to conventional chest x-ray prior to heart surgery (CRICKET study): rationale and design of a multicenter randomized trial.J Cardiovasc Comput Tomogr. 2016; 10: 242-245Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Although these studies do not prove superiority of CT imaging over EAU, it is likely that preoperative CT imaging will become the preferred screening modality for many practitioners as these techniques are optimized and accumulate evidence. Whether these preoperative imaging studies should be applied to all patients or only select high-risk patients with risk factors for atherosclerosis also warrants additional study. In addition to improvements in screening methods, research also has focused on variations in surgical techniques designed to prevent stroke in patients with atheromatous disease of the aorta. Aortic atherectomy was first reported by Culliford and colleagues,30Culliford A.T. Colvin S.B. Rohrer K. Baumann F.G. Spencer F.C. The atherosclerotic ascending aorta and transverse arch: a new technique to prevent cerebral injury during bypass: experience with 13 patients.Ann Thorac Surg. 1986; 41: 27-35Abstract Full Text PDF PubMed Scopus (101) Google Scholar and this technique has been used successfully in patients with extensive disease but has not been widely used for patients with mild or moderate disease. Graft reconstruction of the ascending aorta and aortic arch also has been studied as a stroke prevention technique and has been shown to be efficacious in patients undergoing cardiac surgery, especially aortic valve surgery.31Zingone B. Rauber E. Gatti G. Pappalardo A. Benussi B. Forti G. et al.Diagnosis and management of severe atherosclerosis of the ascending aorta and aortic arch during cardiac surgery: focus on aortic replacement.Eur J Cardiothorac Surg. 2007; 31: 990-997Crossref PubMed Scopus (30) Google Scholar Instead of removing diseased segments from the aorta, many investigators have tried to avoid atherosclerotic plaques altogether. Techniques such as off-pump coronary artery bypass grafting (OPCABG), alternate cannulation sites, use of single aortic crossclamp techniques, and use of fibrillatory arrest have proliferated in an effort to reduce perioperative stroke. Some groups have found that use of a single crossclamp reduces perioperative stroke, but a recent meta-analysis did not confirm these findings.32Hammon J.W. Stump D.A. Butterworth J.F. Moody D.M. Rorie K. Deal D.D. et al.Single crossclamp improves 6-month cognitive outcome in high-risk coronary bypass patients: the effect of reduced aortic manipulation.J Thorac Cardiovasc Surg. 2006; 131: 114-121Abstract Full Text Full Text PDF PubMed Scopus (95) Google Scholar, 33Raja S.G. Navaratnarajah M. Fida N. Kitchlu C.S. For patients undergoing coronary artery bypass grafting at higher risk of stroke is the single cross-clamp technique of benefit in reducing the incidence of stroke?.Interact Cardiovasc Thorac Surg. 2008; 7: 500-503Crossref PubMed Scopus (4) Google Scholar Alternate bypass cannulation sites also have been shown to reduce stroke, especially when used in concert with EAU to identify disease-free regions of the aorta (Videos 5 and 6).34Kokotsakit J. Lazopoulos G. Milonakis M. Athanasiadis G. Romana K. Skouteli E. et al.Right axillary artery cannulation for surgical management of the hostile ascending aorta.Tex Heart Inst J. 2005; 32 (discussion 5): 189-193PubMed Google Scholar, 35Smith P.K. Predicting and preventing adverse neurologic outcomes with cardiac surgery.J Card Surg. 2006; 21: S15-S19Crossref PubMed Scopus (11) Google Scholar Many studies have demonstrated considerable benefit to OPCABG, and this technique also has been shown to be safe and further prevent stroke in the greatest-risk patients.36Sharony R. Bizekis C.S. Kanchuger M. Galloway A.C. Saunders P.C. Applebaum R. et al.Off-pump coronary artery bypass grafting reduces mortality and stroke in patients with atheromatous aortas: a case control study.Circulation. 2003; 108: II15-II20PubMed Google Scholar Meta-analyses have confirmed the benefits of OPCABG in the short term, but long-term outcomes have been less conclusive.37Kuss O. von Salviati B. Borgermann J. Off-pump versus on-pump coronary artery bypass grafting: a systematic review and meta-analysis of propensity score analyses.J Thorac Cardiovasc Surg. 2010; 140 (835.e1-13): 829-835Abstract Full Text Full Text PDF PubMed Scopus (142) Google Scholar, 38Feng Z.Z. Shi J. Zhao X.W. Xu Z.F. Meta-analysis of on-pump and off-pump coronary arterial revascularization.Ann Thorac Surg. 2009; 87: 757-765Abstract Full Text Full Text PDF PubMed Scopus (60) Google ScholarVideo 6Case 3: long-axis view (best viewed on repeat with Windows Media Player). Video available at: http://www.jtcvsonline.org/article/S0022-5223(17)31908-6/fulltext.View Large Image Figure ViewerDownload Hi-res image Download (PPT) To date, 2 devices intended to reduce cerebral emboli during cardiac surgery have received approval from the Food and Drug Administration and remain the focus of on-going comparative effectiveness studies. Both devices represent modified aortic cannulas with technology for protecting the brain from showered emboli. The Embol-X intra-aortic filtration system (Edwards Lifesciences, Irvine, Calif; Figure 4, A) is an aortic cannula with a collapsible filter that is deployed in the ascending aorta before crossclamp removal and captures embolic material released from the aorta or heart during reperfusion. In a large, multicenter, randomized controlled trial of 1289 patients undergoing isolated CABG, aortic valve replacement (AVR), or mitral valve replacement, particulate emboli were captured successfully in 97% of patients who underwent surgery with the Embol-X device. There were no differences in adverse events, including death, stroke, or renal failure, between treated and control patients. However, a subgroup analysis of patients at moderate-to-high risk for postoperative morbidity or mortality demonstrated a reduced risk of renal failure with the Embol-X device.39Banbury M.K. Kouchoukos N.T. Allen K.B. Slaughter M.S. Weissman N.J. Berry G.J. et al.Emboli capture using the Embol-X intraaortic filter in cardiac surgery: a multicentered randomized trial of 1,289 patients.Ann Thorac Surg. 2003; 76 (discussion 515): 508-515Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar The CardioGard Embolic Protection cannula (CardioGard Medical, Or Yehuda, Israel; Figure 4, B) is a modified aortic cannula with a suction orifice at the tip intended to extract solid and gaseous emboli from the ascending aorta during all phases of cardiopulmonary bypass. In a small, multicenter, randomized, controlled trial in which authors compared the CardioGard cannula (n = 27) with control patients (n = 24) undergoing AVR with or without CABG, results showed a reduced volume of new brain lesions detected by diffusion-weighted MRI in treated versus control patients, as well as a lower proportion of patients (41% vs 66%) with any new brain lesion detected by diffusion-weighted MRI. However, there were no differences in clinical end-points between groups, including stroke, death, major adverse events, or Mini-Mental State Examination scores.40Bolotin G. Huber C.H. Shani L. Mohr F.W. Carrel T.P. Borger M.A. et al.Novel emboli protection system during cardiac surgery: a multi-center, randomized, clinical trial.Ann Thorac Surg. 2014; 98 (discussion 1633-34): 1627-1633Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar Based on these data, a National Heart Lung and Blood Institute-sponsored Cardiothoracic Surgical Trials Network clinical trial (#NCT02389894) randomized 383 participants undergoing AVR with or without CABG to surgery using the Embol-X, CardioGard, or control cannula in a 1:1:1 ratio.41CTSN Network. Neuroprotection in Patients Undergoing Aortic Valve Replacement. Available at: http://www.ctsurgerynet.org/NPAbstract.html. Accessed January 30, 2017.Google Scholar The primary end-point was freedom from clinical or radiographic CNS infarction at 7 ± 3 days after the procedure. Results demonstrated that neither embolic protection device led to improvements in freedom from clinical or radiographic CNS infarction, clinical stroke, the overall volume of CNS infarcts by MRI, or neurocognitive outcomes assessed at 90 days. However, both devices successfully captured embolic debris in most patients and led to reductions in postoperative delirium and large volume infarcts. Despite not meeting the primary end-point of reduced perioperative stroke, further study aims to determine whether there are long-term neurocognitive benefits from embolic capture.42Cerebral Embolic Protection in Patients Undergoing Surgical Aortic Valve Replacement (SAVR). Available at: http://clinicaltrialresults.org/Slides/ACC2017/Cerebralembolicprotection_Mack.pdf. Accessed May 17, 2017.Google Scholar Atheromatous disease of the aorta occurs frequently in patients undergoing cardiac surgery and poses a significant risk for perioperative stroke. Certain atheroma characteristics such as location, thickness, mobility, and ulceration have been shown to pose the greatest risk of stroke. Preoperative or intraoperative identification of aortic atheroma may reduce the risk of stroke by allowing for alterations to the surgical plan. The gold-standard for detecting aortic atheroma intraoperatively is EAU, and its use has been shown to decrease the incidence of stroke in the perioperative setting, especially among the greatest-risk patients. Preoperative CT imaging is gaining in popularity and can successfully identify atheromatous disease and allow for alteration of the surgical plan before the operating theater. Novel embolic protection devices successfully captured embolic debris in the majority of patients but failed to reduce the rate of perioperative stroke in a recent randomized clinical trial. These devices remain the focus of ongoing study and may benefit from further technologic optimization.
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