Mandatory Versus Selective Preoperative Carotid Screening: A Retrospective Analysis

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1 Mandatory Versus Selective Preoperative Carotid Screening: A Retrospective Analysis Daniel J. Durand, BS, Bruce A. Perler, MD, Glen S. Roseborough, MD, Maura A. Grega, MSN, Louis M. Borowicz, Jr, MS, William A. Baumgartner, MD, and David D. Yuh, MD Department of Surgery, Division of Cardiac Surgery, Department of Surgery, Division of Vascular Surgery, Zanvyl Krieger Mind/ Brain Institute, The Johns Hopkins University, Baltimore, Maryland CARDIOVASCULAR Perioperative stroke remains a principal complication of coronary artery bypass surgery (CAB) with a reported incidence of 2.1% 5.2% [1, 2] and a related mortality of 0% 38% [3, 4]. Significant extracranial internal carotid artery stenosis (ie, 70% luminal narrowing) is a well-established risk factor for perioperative stroke in patients undergoing CAB [5]. To address this, carotid endarterectomy (CEA) has been performed in patients undergoing CAB in a staged or concomitant fashion resulting in more than 100 published studies on CEA/ CAB since the 1970s [6, 7]. Although the benefits of CEA/CAB are still unclear, some of these studies have noted stroke rate reductions prompting the notion that preoperative screening for carotid stenosis in all CAB patients might reduce perioperative and long-term stroke rates [8, 9]. Such nonselective carotid screening, Accepted for publication Feb 6, Presented at the Fiftieth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 13 15, Address reprint requests to Dr Yuh, Division of Cardiac Surgery, The Johns Hopkins Hospital, 600 N Wolfe St, Blalock 618, Baltimore, MD ; dyuh@csurg.jhmi.jhu.edu. Background. Extracranial internal carotid artery stenosis is a risk factor for perioperative stroke in coronary artery bypass (CAB) surgery. Although both selective and nonselective methods of preoperative carotid screening have been advocated, it is unclear which approach is most clinically efficacious. Methods. Hospital records for 1421 consecutive CAB patients from January 2000 through April 2002 were reviewed. Univariate and multivariate analyses were performed across selected parameters to identify risk factors for significant carotid stenosis (> 70%). Patients were retrospectively stratified into high- or low-risk groups based on risk factors common to carotid stenosis and perioperative stroke. The prevalence of carotid stenosis, surgical management, and perioperative stroke rates were determined for each group. Results. One-thousand one-hundred thirty-eight patients out of 1421 patients (80.1%) underwent preoperative carotid screening. The prevalence of significant carotid stenosis was 13.4%. Univariate risk factors for stenosis included an age of more than 65 years, peripheral vascular disease, prior cerebrovascular accident, history of cerebrovascular disease, left main coronary disease, carotid bruit, female gender, and hypertension. Carotid stenosis was a risk factor for stroke, neurologic injury, in-hospital mortality, and longer hospitalization. Prevalence of carotid stenosis was greater in high-risk patients (17.8%, N 708) versus low-risk patients (6.1%, N 426). Concomitant or staged carotid endarterectomy (CEA)/CAB was more commonly performed in the highrisk group (5.8% vs. 1%, p < 0.001). All nine patients with significant carotid stenosis who suffered perioperative strokes were in the high-risk group (9 out of 708 vs 0 out of 426, p 0.016). Conclusions. In our cohort, selectively screening only patients with either an age of more than 65, carotid bruit, or cerebrovascular disease would have reduced the screening load by nearly 40% with negligible impact on surgical management or neurologic outcomes. (Ann Thorac Surg 2004;78:159 66) 2004 by The Society of Thoracic Surgeons however, adds considerable time and expense to preoperative workups. Alternatively, some investigators have identified risk factors for carotid disease that could be used for more selective carotid screening. These risk factors include age [10, 11], carotid bruit [12, 13], prior neurologic event [12, 13], prior carotid surgery [12], peripheral vascular disease [12], hypertension, diabetes, and smoking [11]. Unfortunately, there are no consensus criteria for selective screening to provide guidance for centers seeking to systematically optimize their carotid screening practices. In this study, we reviewed our experience with routine, nonselective preoperative carotid screening of CAB patients over 28 consecutive months at a single center predicated upon testing our hypothesis that selective carotid screening can perform comparably with nonselective screening in detecting significant carotid stenosis and does not result in higher perioperative stroke rates. Toward this aim, we compared the efficacy of our nonselective approach versus a selective screening algorithm in identifying patients in this cohort with significant carotid stenosis. We also performed a post-hoc riskstratification analysis to determine if selective screening 2004 by The Society of Thoracic Surgeons /04/$30.00 Published by Elsevier Inc doi: /j.athoracsur

2 CARDIOVASCULAR 160 DURAND ET AL Ann Thorac Surg MANDATORY VS SELECTIVE CAROTID SCREENING 2004;78: Abbreviations and Acronyms ACAS Asymptomatic Carotid Atherosclerosis Study CAB coronary artery bypass CEA carotid endarterectomy CPB cardiopulmonary bypass CVA cerebral vascular accident CVD cerebrovascular disease DSA digital subtraction angiography LOS length of stay NASCET North American Symptomatic Carotid Endarterectomy Trial TIA transient ischemic attack would result in notable changes in surgical management or perioperative stroke rates. Material and Methods Patient Records Records were reviewed for 1421 consecutive patients undergoing isolated first-time (n 1348) or redo CAB (n 73) by six cardiothoracic surgeons at the Johns Hopkins Hospital from January 2000 through April Only patients undergoing CAB with no other concomitant cardiac operations (eg, valve replacement/repair, aneurysmectomy, atrial septal defect closure) were eligible. This retrospective data review was approved by the Johns Hopkins Joint Committee on Clinical Investigation on April 17, Data Collection Preoperative, intraoperative, and postoperative clinical data were obtained from the records of all patients reviewed. Preoperative patient data included history of previous stroke, hypertension, diabetes mellitus, age, carotid bruit, gender, left main coronary artery stenosis greater than 50%, peripheral vascular disease, cerebrovascular disease, and CEA done at the time of CAB. Screening for internal carotid stenosis was performed with duplex ultrasound and/or angiography. The degree of stenosis was expressed as the percentage of luminal narrowing estimated by ipsilateral internal common carotid artery flow velocity ratios (duplex ultrasound) and/or visual approximation (angiography). Patients were considered to have clinically significant carotid disease if their medical record contained a duplex ultrasound or other imaging study indicating stenosis greater than or equal to 70% in at least one internal carotid artery or if there was reference to uncorrected significant, severe, or critical carotid stenosis or occlusion in their medical record; at our institution, these terms are associated with 70%, 80%, 90%, and 100% carotid stenosis, respectively. Intraoperative data collection included cardiopulmonary bypass (CPB) time. Postoperative data was extracted from a neurologic assessment/outcome database initiated at our center to prospectively monitor the neurologic progress and clinical outcomes of all cardiac surgical patients. This data was collected on a daily basis by two individuals trained in neurocognitive assessment (MAG, LMB) and included postoperative length of stay, death, stroke, and neurologic injury. Operative Technique All patients underwent median sternotomy. Anesthetic technique was standardized and consisted of lowintermediate dose narcotics, inhalational agents, and paralytics. Cardiopulmonary bypass was carried out using a Sarns roller head pump, nonpulsatile flow, -stat ph blood gas management, moderate systemic hypothermia (28 32 C), and pump flow rates to achieve a mean arterial pressure of mm Hg. Myocardial protection was achieved with antegrade and/or retrograde cardioplegia and topical hypothermia. Cardiotomy suction was routinely returned to the CPB circuit. Both single and double clamp techniques were used for aortic cross clamping and were based on surgeon preference. Off-pump CAB was performed using the Medtronics Octopus Tissue Stabilization System (Medtronics Corp., Minneapolis, MN) under full or partial heparinization according to surgeon preference and with a cell-saving device. When performed concomitantly with CAB, CEAs were completed before sternotomy. Using uniform operative techniques, vascular surgeons from the Division of Vascular Surgery conducted each endarterectomy. Partial heparinization, common to internal carotid intraluminal shunting and, when indicated, patch carotid arteriotomy closure was used in each case. Definitions We defined significant stenosis as greater than or equal to 70% luminal narrowing of the affected internal carotid artery, which was determined by duplex ultrasonography and/or angiography in accordance with widely accepted clinical guidelines. At our institution, CEA is considered for carotid stenosis in excess of 70% and asymptomatic carotid stenosis is managed on a case-by-case basis. A cerebral vascular accident (CVA) or stroke was defined as an acute neurologic event resulting from circulatory impairment and lasting more than 24 hours. The outcome of postoperative stroke was defined as the clinical diagnosis of stroke made by a neurologist and confirmed by brain imaging (head computed tomography, magnetic resonance imaging, or both). A transient ischemic attack (TIA) was defined as a temporary neurologic deficit attributable to circulatory impairment and lasting less than 24 hours. Neurologic injury was defined as a dichotomous (ie, yes or no) outcome to include any of the following abnormal neurologic conditions recognized to have occurred postoperatively: confusion, delirium, combativeness, agitation, seizures, prolonged altered mental status, or coma. The stroke and neurologic injury outcomes were mutually exclusive. Cerebrovascular disease (CVD) connotes a history of CVA or TIA. Mortality was defined as any death occurring during the same hospital stay. Post-

3 Ann Thorac Surg DURAND ET AL 2004;78: MANDATORY VS SELECTIVE CAROTID SCREENING 161 Fig 1. Selective preoperative carotid screening algorithm. Patients older than 65 years of age with a history of transient ischemic attack (TIA), stroke, or a carotid bruit are considered high risk and undergo preoperative carotid screening. Patients 65 years or younger with no history of TIA or stroke and no carotid bruit are considered low risk and do not undergo preoperative carotid screening. CARDIOVASCULAR operative length of stay (LOS) was the duration of postoperative hospitalization. Statistical Analysis In a univariate analysis, data were compared between patients with unilateral or bilateral carotid stenosis greater than or equal to 70% versus patients with less than 70% carotid stenosis bilaterally. Preoperative, intraoperative, and postoperative outcome data were reviewed. Continuous and dichotomous variables were compared using the Student t and 2 tests, respectively. The Mann Whitney U test was used when continuous data were not normally distributed. The Fisher exact test was used for comparisons in which at least one cell value was less than five. All probabilities were two-tailed with a p value less than 0.05 regarded as significant. Using the three most significant risk factors obtained from the univariate analysis (carotid bruit, peripheral vascular disease [PVD], prior CVA), multiple logistic regression analysis was used to construct a predictive formula for significant carotid stenosis. This formula was applied to each patient to calculate the probability that they had significant carotid stenosis and a receiver operator curve was determined based on the performance of the model in the screened cohort. All statistical computations were performed using the SPSS statistical software package (SPSS Inc., Chicago, IL). Risk-Stratification Algorithm In our cohort, we retrospectively stratified patients who underwent carotid screening (N 1138) according to an algorithm (Fig 1) based on three risk factors. Patients with either CVD or a carotid bruit or who were more than 65 years of age were designated as high-risk whereas those subjects aged less than or equal to 65 years with no bruit and no history of CVD were designated as low risk. All three of these risk factors have been identified by our group as common to both carotid stenosis (see results of univariate risk factor analysis) and perioperative stroke [1] in CAB patients. We determined the prevalence of significant carotid stenosis, the number of CEAs performed, and the number of perioperative strokes in the high-risk versus low-risk groups. Finally, we quantified the difference in perioperative stroke rates between high- and low-risk patients in the 283 patients who were not screened for carotid disease. Results Univariate and Multivariate Risk Factor Analyses Of 1421 consecutive CAB patients, 1138 (80.1%) underwent preoperative carotid screening either within the Johns Hopkins Hospital Health System or its referral centers. Off-pump CAB was performed in 129 patients (9.08%). In this cohort, 13.4% had significant unilateral carotid stenosis and 3.5% had significant bilateral stenosis. Univariate analysis identified an age of more than 65 years, peripheral vascular disease, prior CVA, a history of CVD, left main coronary disease of more than 50%, carotid bruit, female gender, and hypertension as risk factors for significant carotid stenosis (Table 1). Our multiple logistic regression analysis produced a predictive model for carotid stenosis with a receiver operator curve area of when applied to the screened cohort. Table 1. Results of Univariate Analysis of Risk Factors for Significant Carotid Stenosis ( 70% Luminal Narrowing) Risk Factors 70% Stenosis n 986 (86.7%) 70% Stenosis n 152 (13.4%) p Value Mean age (years SD) 64.7 ( 11) 67.7 ( 10) Age group 65 47% 34% 65 to 75 33% 41% % 25% Gender Male 73% 64% Female 27% 36% 0.02 History of PVD 3% 17% History of past CVA 6% 16% History of hypertension 71% 82% History of diabetes 32% 34% NS Carotid bruit heard 10% 39% Over 65 years 53% 66% Left main disease 50% 7% 13% 0.01 History of cerebrovascular 9% 24% disease (CVA or TIA) Mean CPB time (min SD) 94 ( 42) 86 ( 45) 0.03 CPB cardiopulmonary bypass; CVA cerebral vascular accident; PVD peripheral vascular disease; SD standard deviation; TIA transient ischemic attack.

4 CARDIOVASCULAR 162 DURAND ET AL Ann Thorac Surg MANDATORY VS SELECTIVE CAROTID SCREENING 2004;78: Table 2. Relationship Between Side of Stroke and Carotid Stenosis in 1138 Patients who Underwent Preoperative Carotid Screening Status of Carotids Number of Strokes (n 36) 70% stenosis bilaterally 27 (81%) Stenosis 70% on either side 9 (25%) Stenosis 70% on same side as stroke 7 (19%) a Table 3. Statistical Comparison of Surgical Outcomes in Patients With and Without Significant Carotid Stenosis ( 70% Luminal Narrowing) Outcomes 70% Stenosis 70% Stenosis p Value Stroke 2.7% 6.0% 0.03 Neurologic injury 5.7% 11.3% 0.01 Death 1.1% 7.2% Mean LOS (d SD) 7.4 ( 8) 10.1 ( 12) a Two strokes in this group were bilateral. SD standard deviation; LOS length of stay. Outcomes in Patients With Carotid Stenosis Of the 1138 patients who underwent carotid screening, 36 patients (3.2%) suffered perioperative strokes (Table 2). Of these patients, 9 had significant carotid stenosis with 7 suffering ipsilateral strokes. Significant carotid stenosis was also associated with higher rates of neurologic injury and in-hospital mortality as well as longer hospitalization (Table 3). Selective Screening Algorithm Applying a selective screening algorithm (Fig 1) to the 1138 screened patients, 708 were placed in the high-risk group and 426 were placed in the low-risk group (Fig 2). Four patients could not be categorized because their medical records were incomplete with regard to CVD, carotid bruit, or age. Among the high-risk patients, 126 (17.8%) had significant carotid stenosis. Nine (7%) of these high-risk patients, in whom screening detected significant carotid stenosis, suffered perioperative strokes. High-risk patients with significant carotid stenosis who underwent staged or combined CEA/CAB experienced a lower stroke rate than those who underwent CAB alone, although the difference was not statistically significant (1 out of 41 patients vs 8 out of 85 patients, p 0.27). Of the 426 low-risk patients, 26 (6.1%) were found to have significant carotid stenosis. None of these low-risk patients suffered perioperative strokes, therefore all patients with significant carotid stenosis who went on to suffer perioperative strokes were in the high-risk group (0 out of 426 patients vs 9 out of 708 patients, p 0.016). Among the low-risk patients, 5 (1%) underwent CEA/ CAB. Of these, 2 patients had greater than or equal to 80% ipsilateral carotid stenosis, 2 patients had greater than or equal to 80% bilateral stenosis, and 1 patient had unilateral occlusion and contralateral stenosis greater than or equal to 80%. When our selective screening algorithm was applied to the 283 patients who did not undergo carotid screening, 122 patients (43.1%) were categorized as high-risk and 160 patients (56.6%) were categorized as low risk (Fig 3). One patient could not be categorized because of an incomplete record. The perioperative stroke rate in unscreened high-risk patients was 7% compared with 0.6% in unscreened low-risk patients (p 0.003). Among the 1416 (screened and unscreened) patients who could be risk-stratified, high-risk patients experienced a significantly higher stroke rate compared with low-risk patients (4.2% vs 1.9%, p 0.012). Comment Unlike other complications associated with CAB including hemorrhage, infection, and myocardial infarction, stroke represents an often irreversible, lifelong, and debilitating complication that frequently negates the benefits of coronary revascularization. Because significant carotid stenosis is a well-recognized risk factor for stroke in CAB patients, our group has adopted routine, nonselective preoperative carotid screening over the past several years. Considering that such screening has little support in the literature in Fig 2. Outcome summary for the 1138 patients who underwent preoperative carotid screening. Outcomes for high- and low-risk patients grouped according to the presence or absence of carotid stenosis 70% and/or carotid endarterectomy (CEA) are shown. Note the low incidence of significant carotid stenosis ( 70%) and CEA/CAB (coronary artery bypass) procedures among low-risk patients. Four patients who were screened could not be categorized as high- or low-risk due to omissions in their respective medical records.

5 Ann Thorac Surg DURAND ET AL 2004;78: MANDATORY VS SELECTIVE CAROTID SCREENING 163 artery disease [18], and female gender [17]. Of these, the most statistically significant risk factors for carotid stenosis in our study were PVD, carotid bruit, and CVD. Carotid Stenosis as a Risk Factor For Stroke and Neurologic Injury In our study, significant carotid stenosis was associated with higher perioperative stroke and neurologic injury rates (Table 2) confirming this as a risk factor for these complications in CAB patients. Significant carotid stenosis was also associated with longer hospitalizations and higher in-hospital mortality rates. CARDIOVASCULAR Fig 3. Outcome summary when our selective preoperative carotid screening algorithm was retrospectively applied to the 283 patients who did not undergo screening. Outcomes for high- and low-risk patients are shown. One patient who was not screened could not be categorized as high- or low-risk due to omissions in his medical record. terms of clinical efficacy and cost-effectiveness, we wanted to critically evaluate this practice by testing the hypothesis that selective carotid screening can be comparable to nonselective screening in detecting significant carotid disease and does not result in higher perioperative stroke rates. Practicality of Routine Preoperative Carotid Screening Despite our current practice of routine carotid screening, we found that approximately 19.9% of the patients in our series had no record of carotid screening. This was generally due either to emergent clinical circumstances, inadequate insurance coverage for the test, or an incomplete medical record. Regardless of the cause, the fact that as many as 1 in 5 patients went unscreened at a major tertiary care center where routine carotid screening is performed indicates that, in practice, achieving a 100% screening rate is difficult. Prevalence of Significant Carotid Stenosis in CAB Patients Of the 1138 patients who underwent routine carotid screening, we found a 13.4% prevalence of significant carotid stenosis. This is consistent with previous studies which have reported a prevalence of 1.7% 22% in CAB patients [14, 15] depending on definitions of significant stenosis, methods of screening, and population demographics. Risk Factors for Carotid Stenosis Our univariate analysis of patients who underwent carotid screening confirmed risk factors associated with carotid stenosis in the literature (Table 1). These risk factors included age [10, 11, 16, 17], carotid bruit [13], neurovascular symptoms [13, 16, 17], peripheral vascular disease [13, 16], hypertension [11, 17], left main coronary Basis of Selective Carotid Screening Algorithm To develop a selective carotid screening algorithm to test our hypothesis, we initially performed a multiple logistic regression analysis based upon the most significant risk factors for carotid stenosis identified by our univariate analysis (ie, PVD, carotid bruit, and prior CVA). This produced a complex predictive model with a poor receiver operator curve indicating that selective screening according to this model would have offered low levels of specificity at high levels of sensitivity and vice-versa (data not shown). Alternatively, we adopted a much simpler screening algorithm (Fig 1) based upon three of the most prominent risk factors for carotid stenosis substantiated by our univariate analysis and the literature: history of CVD, carotid bruit, and an age of more than 65 years. There is clinically oriented reasoning behind the inclusion of each risk factor. First, patients with CVD are not only more likely to have greater than or equal to 70% carotid stenosis (Table 1), but those with carotid stenosis benefit more from CEA than their asymptomatic counterparts in terms of 5-year stroke reduction [19, 20]. Second, the finding of a carotid bruit raises the suspicion of turbulent flow secondary to carotid stenosis; in our cohort, 37% of CAB patients with a bruit also had greater than or equal to 70% carotid stenosis. Finally, advanced age has been reported to increase the association between carotid disease and perioperative stroke in CAB. Faggioli and associates found that CAB patients over age 60 with carotid stenosis more than 75% had a stroke rate of 15% [10]. In addition, our findings show that CAB patients over the age of 65 years are more likely to have carotid stenosis than their younger counterparts (Table 1). We did not incorporate additional risk factors into our algorithm for two reasons. First, other considerable risk factors for carotid stenosis we identified in our univariate analysis, such as hypertension and female gender, lacked specificity. Whereas peripheral vascular disease is quite specific for carotid stenosis, there was virtually complete patient overlap with the other risk factors we selected. Second, we limited our selected risk factors for simplicity s sake. In addition to being strongly associated with carotid stenosis in our univariate analysis, our selected risk factors are readily obtained from a routine preoperative workup and are inherently dichotomous.

6 CARDIOVASCULAR 164 DURAND ET AL Ann Thorac Surg MANDATORY VS SELECTIVE CAROTID SCREENING 2004;78: Selective Versus Routine Carotid Screening in Detecting Significant Carotid Stenosis We applied our screening algorithm retrospectively to our cohort of CAB patients who underwent routine carotid screening stratifying them into high-risk and low-risk groups (Fig 2). We then determined the prevalence of carotid stenosis in each group estimating the predictive value of a selective screening algorithm based upon these risk factors. We found that significant carotid stenosis was more prevalent in the high-risk group (17.8% vs 6.1%, p 0.001) and that selective screening was approximately 83% sensitive and 41% specific. From this, we can conclude that a selective approach toward screening only high-risk patients would have permitted only 2.3% of our screened patient cohort to proceed to CAB with undiagnosed significant, but clinically silent, carotid stenosis. This data supports the first component of our hypothesis: selective carotid screening can be comparable to nonselective screening in detecting significant carotid stenosis. Outcome Analysis of Selective Versus Routine Carotid Screening We performed a post-hoc analysis of the impact selective screening would have had on patient outcomes by retrospectively examining the surgical management and perioperative stroke rates of the high- versus low-risk groups among the 1138 patients who underwent carotid screening (Fig 2). In terms of overall stroke rates, 7% of high-risk patients with carotid stenosis suffered perioperative strokes compared with none among low-risk patients with carotid stenosis. CEA/CAB was performed in 5.8% of high-risk patients compared with just 1% of low-risk patients screened (41 out of 708 patients vs 5 out of 426 patients, p 0.001). From this, we can conclude that a selective approach toward screening solely highrisk patients would have resulted in only 10% fewer CEA/CAB procedures, all of which would have been performed on asymptomatic patients. Furthermore, our selective screening approach would have identified as high risk all 9 patients with carotid stenosis who ultimately suffered perioperative strokes. These data suggest that patients classified as low risk, comprising 37.4% of all patients screened, derived negligible benefit from routine carotid screening in terms of affecting surgical management or neurologic outcomes. Furthermore, the fact that routine carotid screening of all low-risk patients over 28 months on a busy clinical cardiac surgical service revealed only 26 patients with significant carotid stenosis suggests that this practice is relatively inefficient. There was a trend toward lower perioperative stroke rates in high-risk patients who underwent CAB/CEA (1 out of 41 patients, 2%) versus those who did not (8 out of 85 patients, 9%). Although our study lacks the statistical power to prove conclusively that CEA/CAB lowers perioperative stroke rates among high-risk patients with carotid stenosis, the 7% risk reduction associated with CEA in the high-risk group is noteworthy. When we retrospectively applied our selective screening algorithm to the 283 unscreened patients in our cohort (Fig 3), we noted that high-risk patients displayed a higher risk of perioperative stroke (7%) than their low-risk counterparts (0.6%). Likewise, across all stratified patients (screened and unscreened), high-risk patients had a considerably higher stroke rate (4.2% vs 1.9%, p 0.012). These findings are consistent with previous reports by our group identifying all three risk factors employed in our algorithm as independent predictors of perioperative stroke in CAB patients [1]. In summary, patients under 65 years of age without a history of CVD and no carotid bruit have both a lower risk of having significant carotid stenosis and suffering perioperative stroke with CAB. We found no reliable evidence to suggest that CEA/CAB lowers perioperative stroke rates in these patients. We observed no strokes in low-risk patients attributable to significant carotid stenosis over the 2 years encompassed by our study. Taken together, these results support the second component of our hypothesis, that is, selective carotid screening does not result in higher perioperative stroke rates. Study Limitations An inherent limitation of our retrospective analysis is the heterogeneous nature of our dataset. Whereas the overwhelming majority of our patients were screened by duplex ultrasonography, several underwent contrast angiography instead. This is somewhat problematic because each method determines the degree of stenosis in a different fashion. With angiography, percentage stenosis is defined as one-hundred times the quotient of the carotid luminal diameter at the point of stenosis divided by the luminal diameter distal to the stenosis. Duplex ultrasonographic measurements are obtained from peak blood flow velocities measured across the proximal internal carotid artery which are correlated to percentage stenoses derived from digital subtraction angiography. Another limitation arises from the fact that most perioperative strokes in CAB patients are unrelated to carotid stenosis [5]. In this study, only 9 of the 36 patients who suffered a perioperative stroke (25%) had significant carotid stenosis (Table 2). In 2 of these patients, the carotid stenosis was contralateral to the side of brain injury inferring that carotid stenosis was an incidental finding. Therefore, only 7 of the 36 strokes (19%) suffered by the 1138 patients screened can be plausibly attributed to significant carotid stenosis, though the use of CEA/ CAB in this population may have lowered these numbers. Certainly, this is consistent with the multifactorial nature of perioperative stroke in CAB patients (eg, atheromatous/gaseous emboli, diffuse intracranial cerebrovascular disease) and we recognize that, although significant carotid stenosis plays an important role in the etiology of perioperative stroke, the combined effect of other factors is substantial. It is plausible that carotid stenosis may serve as a marker for diffuse cerebrovascular disease and ascending aortic arteriosclerosis. We also recognize that our selective carotid screening algorithm may not work as well at other centers, as part of its appeal is based on statistical associations observed

7 Ann Thorac Surg DURAND ET AL 2004;78: MANDATORY VS SELECTIVE CAROTID SCREENING within our own patient population. However, as noted above, each of these statistical associations has been reported elsewhere. A similar screening algorithm was proposed by Archbold and associates for use in patients undergoing urgent cardiac procedures [9]. Despite several investigations of the clinical efficacy of CEA, the role of endarterectomy in CAB patients remains controversial. Although the North American Symptomatic Carotid Endarterectomy Trial (NASCET) convincingly concluded that CEA reduces the 5-year stroke risk by 16.5% in symptomatic patients with carotid stenosis greater than or equal to 70% [19], the effect of combined CEA/CAB on perioperative stroke is unclear. Although several studies have noted stroke rate reductions with CEA/CAB in patients with symptomatic and asymptomatic carotid disease, these studies are generally handicapped by their small patient cohorts. Our analysis uses perioperative stroke rates rather than 5-year stroke rates as an endpoint. Therefore, this selective screening approach is only intended for preoperative workups in CAB patients. Low-risk patients with ischemic heart disease and their physicians should still be cognizant that coronary artery disease is itself a risk factor for carotid stenosis [21] and that carotid studies may be warranted. Conclusion The results of this retrospective review support our hypothesis that selective carotid screening can be comparable with nonselective screening in detecting significant carotid disease and does not lead to higher perioperative stroke rates. In retrospect, screening only those patients with either a history of CVD, carotid bruit, or age of more than 65 years would have reduced our screening load by nearly 40% with negligible impact on surgical management (ie, CEA/CAB) and neurologic outcomes. This data supports the conduct of future prospective studies to validate such selective screening practices. We wish to acknowledge Maryanne Bailey, Sarah Moeller, and Catherine Cristinzio for their assistance in this data collection. In addition, we thank the nursing staff in the Cardiac Surgical Intensive Care Unit and the Advanced Practice Nurses at Johns Hopkins Hospital for their assistance with postoperative outcome data collection. References 1. McKhann GM, Goldsborough MA, Borowicz LM Jr, et al. Predictors of stroke risk in coronary artery bypass patients. Ann Thorac Surg 1997;63: D Ancona G, Saez de Ibarra JI, Baillot R, et al. Determinants of stroke after coronary artery bypass grafting. Eur J Cardiothorac Surg 2003;24: McKhann GM, Grega MA, Borowicz LM Jr, et al. Encephalopathy and stroke after coronary artery bypass grafting: 165 incidence, consequences, and prediction. Arch Neurol 2002; 59: Salazar JD, Wityk RJ, Grega MA, et al. Stroke after cardiac surgery: short- and long-term outcomes. Ann Thorac Surg 2001;72: ; discussion Naylor AR, Mehta Z, Rothwell PM, Bell PR. Carotid artery disease and stroke during coronary artery bypass: a critical review of the literature. Eur J Vasc Endovasc Surg 2002;23: Bernhard VM, Johnson WD, Peterson JJ. Carotid artery stenosis: association with surgery for coronary artery disease. Arch Surg 1972;105: Naylor AR, Cuffe RL, Rothwell PM, Bell PR. A systematic review of outcomes following staged and synchronous carotid endarterectomy and coronary artery bypass. Eur J Vasc Endovasc Surg 2003;25: Fukuda I, Gomi S, Watanabe K, Seita J. Carotid and aortic screening for coronary artery bypass grafting. Ann Thorac Surg 2000;70: Archbold RA, Barakat K, Magee P, Curzen N. Screening for carotid artery disease before cardiac surgery: is current clinical practice evidence based? Clin Cardiol 2001;24: Faggioli GL, Curl GR, Ricotta JJ. The role of carotid screening before coronary artery bypass. J Vasc Surg 1990;12: Ascher E, Hingorani A, Yorkovich W, Ramsey PJ, Salles- Cunha S. Routine preoperative carotid duplex scanning in patients undergoing open heart surgery: is it worthwhile? Ann Vasc Surg 2001;15: Walker WA, Harvey WR, Gaschen JR, Appling NA, Pate JW, Weiman DS. Is carotid screening for coronary surgery needed? Am Surg 1996;62: Hill AB, Obrand D, Steinmetz OK. The utility of selective screening for carotid stenosis in cardiac surgery patients. J Cardiovasc Surg (Torino) 1999;40: Cosgrove DM, Hertzer NR, Loop FD. Surgical management of synchronous carotid and coronary artery disease. J Vasc Surg 1986;4: Schwartz LB, Bridgman AH, Kieffer RW, et al. Asymptomatic carotid artery stenosis and stroke in patients undergoing cardiopulmonary bypass. J Vasc Surg 1995;21: Salasidis GC, Latter DA, Steinmetz OK, Blair JF, Graham AM. Carotid artery duplex scanning in preoperative assessment for coronary artery revascularization: the association between peripheral vascular disease, carotid artery stenosis and stroke. J Vasc Surg 1995;21: Birincioglu L, Arda K, Bardakci H, et al. Carotid disease in patients scheduled for coronary artery bypass: analysis of 678 patients. Angiology 1999;50: D Agostino RS, Svensson LG, Neumann DJ, Balkhy HH, Williamson WA, Shahian DM. Screening carotid ultrasonography and risk factors for stroke in coronary artery surgery patients. Ann Thorac Surg 1996;62: North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade stenosis. N Engl J Med 1991;325: Asymptomatic Carotid Atherosclerosis Study Group. Carotid endarterectomy for patients with asymptomatic internal carotid artery stenosis. JAMA 1995;273: Qureshi AI, Janardhan V, Bennett SE, Luft AR, Hopkins LN, Guterman LR. Who should be screened for asymptomatic carotid artery stenosis? Experience from the Western New York Stroke Screening Program. J Neuroimaging 2001;11: CARDIOVASCULAR DISCUSSION DR CURT TRIBBLE (Charlottesville, VA): That was very well presented, Mr Durand. Thanks for asking me to look over your paper and discuss it. The question of the relationship between carotid stenosis and stroke has been thought about long and hard by a lot of people, including a lot of people in this room. We ought to take one step back, I guess, and ask where most strokes

8 CARDIOVASCULAR 166 DURAND ET AL Ann Thorac Surg MANDATORY VS SELECTIVE CAROTID SCREENING 2004;78: that occur during cardiopulmonary bypass actually come from. The truth is that they come from the ascending aorta; they come from diffuse vascular disease; they come from intracranial disease; they come from fat; they come from air; they may come from the cardiopulmonary bypass circuit itself; and, in a few cases, they may come from carotid disease. We certainly need to study each and every one of those things. You have chosen to tackle carotid disease, and to ask who should be screened. This is certainly an important issue. I think your study gives me some reasonable guidelines on this issue. Although your study was of a very heterogeneous group of people, I know you worked very hard to see if you could make some recommendations, and I like the fact that you boil it down to a fairly simple set. These are that we should screen people who have had neurological symptoms (that makes sense), people with a bruit (that makes sense), and people over 65 (and that makes some sense as well). If none of these characteristics are present, you are telling us that we probably don t need screening. That advice is certainly helpful because it is hard to screen everyone undergoing heart surgery. Unfortunately, the heterogeneity of the patients you were looking at and the difficulty of doing this type of study leaves a lot of questions. We don t know how tight the carotids were. Surely, there is a difference in outcome between a person who has a carotid that is 90% stenotic when compared with someone who has a 70% stenosis. I think John Gott and his group at Emory looked at that question and taught us that, at the very least, we do need to find and treat very tight lesions before heart surgery. You also weren t able to tell from your data, I know, the difference between the on-pump and off-pump patients, nor the difference between the people who had one clamp and two clamps, nor whether these strokes occurred intraoperatively or in the early postoperative period, which I will bet has a very different epidemiology. Nor did you know, whether the patients had postoperative arrhythmias or not, which certainly can contribute to some perioperative strokes. I have two questions for you. One is, can you tell us a little bit about what your group s standard anticoagulation protocol is perioperatively? Specifically, most but not all surgeons would use aspirin in these patients pre- and postoperatively. Was that done very assiduously? Was everyone on aspirin pre- and postoperatively? How about Plavix? Is that being used? Is it being used postoperatively in off-pump patients, for instance? There has been a good bit of talk lately about using even subcutaneous heparin in some patients, especially after offpump cases, and I wondered if you had any data on that. Secondly, could you comment on the amount of disease that was noted in the aorta at the time of the operations? I still would say that surely most perioperative cerebrovascular problems come from aortic disease and diffuse arch vessel disease, and any information you could give us about that might be of help in trying to sort through what we should be doing. Thank you again for allowing me to review your manuscript and for asking me to comment on your presentation. MR DURAND: Thank you for your questions, Dr Tribble. In terms of anticoagulation, the standard at our institution is aspirin pre- and postoperatively. We do not use subcutaneous heparin in place of aspirin, though we have been using Plavix postoperatively since some early data suggest improved graft patency rates with this. I would defer any more specific clinical questions to the surgical faculty. We recognize that ascending aortic atherosclerotic disease is a major risk factor for stroke; however, this was not universally recorded in our database. This study was focused upon providing guidelines for preoperative screening for carotid disease, which comprises another risk factor for perioperative stroke in coronary artery bypass patients. DR ALAA Y. AFIFI (Albany, NY): I really enjoyed your presentation very much. I echo Dr Tribble s concerns that the source of the majority of these ministrokes occurs from the ascending aorta. This leads to two questions. Can you clarify your approach to the patient who has critical disease involving the carotid artery as well as severe coronary artery disease. Do you do a staged or simultaneous procedure? We have been performing simultaneous carotid endarterectomies with concomitant surgical coronary revascularization for a period of time, then recently changed our approach to performing an awake carotid endarterectomy followed by coronary bypass surgery, typically within 24 hours. This leads to my next question. How do you handle the high-risk patient, ie, one with severe/mobile atheroma of the ascending aorta? We have approached these patients with transesophageal, and many times, epiaortic echocardiograms. What are your thoughts on these modalities? Thank you. MR DURAND: I would like to answer the first question and I will probably hand you off to Dr Yuh, the principal investigator on this effort, for the second. In terms of staged versus combined procedures, we had 21 of the one and 26 of the other, and there was no significant difference in terms of perioperative stroke. Of course, there was only one stroke in the carotid endarterectomy/coronary artery bypass group, and that fell in a staged procedure, but that is certainly not significant with only one incident. So we had about half and half, and we didn t find any difference. There was recently a large meta-analysis published by Naylor and colleagues who also authored the other meta-analysis data I cited earlier in the European Journal of Vascular and Endovascular Surgery (Eur J Vasc Endovasc Surg 2003;25(5):380 9), and they looked at that and didn t seem to find a difference over all the previously reported cases in the literature. DR DAVID D. YUH (Baltimore, MD): I would like to thank the discussants for some very insightful questions, and I certainly want to address a couple of them. First of all, we do recognize that this retrospective study is quite limited with respect to the conclusions we could derive from it. Indeed, we look at carotid disease as more of a marker of more extensive cerebrovascular and aortic disease and a predisposition to stroke as opposed to a direct cause. Certainly for the high-risk patients, for those with Grade III and Grade IV ascending aortic disease, we do make every effort to obtain a transesophageal echocardiogram intraoperatively to modify the conduct of the operation (eg, no clamp, off-pump techniques). This study was borne out of our heretofore unsubstantiated practice to screen all of our patients for carotid disease. We wanted to retrospectively see if this was indeed valid and indeed supported by the data, and clearly we found that it is not and that there are selective criteria that we can use to more efficiently screen for carotid disease. Thank you very much.