Preoperative carotid artery screening in elderly patients undergoing cardiac surgery Eric S. Berens, M D , Nicholas T. Kouchoukos, M D , Sttzan F. M u r p h y , R N , and Thomas H. Wareing, M D , St. Louis, Mo. The role of preoperative screening for carotid artery disease in elderly patients undergoing cardiac surgical procedures is not dearly established. This prospective study was designed to determine the prevalence of carotid disease in this population and to identify preoperative risk factors for carotid artery stenosis. During a 54-month interval, 1087 patients of a consecutive series of 1184 patients 65 years of age and older who underwent cardiac surgical procedures (91% had coronary artery disease) were evaluated before operation with carotid duplex ultrasonography. The prevalence of disease was 17.0% for 50% or greater stenosis and 5.9% for 80% or greater stenosis. With use of a stepwise, logistic regression model of 12 preoperative variables, five variables were found by multivariate analysis to be significant (p -< 0.05) predictors of 80% or greater stenosis: female sex, peripheral vascular disease, history of transient ischemic attack or stroke, smoking history, and left main coronary artery disease. If all patients with at least one risk factor were screened, then this model predicts that 95% of patients with 80% or greater stenosis and 91% of patients with 50% or greater stenosis would be identified before operation. The probability of carotid disease in a given patient can also be estimated (range, 5% to 65%). Carotid endarterectomy combined with cardiac surgical procedures was performed on 46 patients who were either symptomatic (16) or had 80% or greater stenosis (30). The overall stroke rate for the 1087 patients was 2.0% (22 patients), and the 30-day mortality rate was 5.2% (56 patients). The stroke rate after carotid endarterectomy was 6.5% (3 of 46 patients; all 3 had severe bilateral disease). By use of the above risk factors, subgroups of elderly patients undergoing cardiac surgical procedures have been identified who should be screened for carotid artery disease before operation. (J VASC SURG 1992;15:313-23.)

Stroke is an important cause of death and morbidity after cardiac surgical procedures. Although several causes for stroke.exist in this setting, an association between high-grade carotid artery occlusive disease and stroke after cardiac operations has been observed. ~4 The appropriate treatment of patients with coexisting carotid and cardiac disease undergoing cardiac surgical procedures by means of cardiopuknonary bypass remains unclear.~-s The role of preoperative screening of patients undergoing cardiac surgery to detect significant carotid artery disease is also unclear. We conducted a prospective study to determine From the Divisions of Cardiothoracic and Vascular Surgery, Department of Surgery, Washington University School of Medicine and The Jewish Hospital of St. Louis. Presented at the Forty-fifthAnnual Meeting of the Societyfor Vascular Surgery, Boston,Mass., June 4-5, 1991. Reprint requests: NicholasT. Kouchoukos,MD, Departmentof Surgery, Jewish Hospital at Washington UniversityMedical Center, 216 S. Kingshighway,St. Louis, MO 63110. 24/6/33806

the presence of carotid artery disease in elderly patients undergoing cardiac surgical procedures and to identify preoperative variables that could define patients at high risk for carotid artery disease. The results of combined carotid endarterectomy ( t E A ) and cardiac surgery were also evaluated.

PATIENTS A N D METHODS Between January 1986 and June 1990, 1087 patients who were 65 years of age or older were examined by carotid duplex scanning before a cardiac surgical procedure. This represents 50% of the total number of cardiac surgical procedures performed during this interval. Ninety-seven elderly patients who underwent cardiac operation on an emergency basis were not scanned before operation. Nine hundred ninety-seven patients younger than 65 years of age were not entered into the study. The characteristics of the 1087 patients are summarized in Table I. There were 640 men (59%) and 447 women (41%). The mean age was 72 years (range, 65 to 89 313

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314 Berens et aL

Table I. Characteristics of the 1087 patients No. of patients

Gender Male Female Age (yr) 65-69 70-79 80-89 Hypertension Previous myocardial infarction Cigarette smoking Diabetes mellims Peripheral vascular disease Stroke Transient ischemic attack Renal disease Previous surgical procedure Cardiac operation Carotid endarterectomy Extent of coronary artery disease One vessel Two vessel Three vessel Left main *NYHA functional classification I II HI IV

%

64O 447

59 41

400 572 115 691 560 542 297 108 77 63 27

37 52 11 64 52 50 27 10 7.1 5.8 2.5

104 10

9.6 0.9

49 166 554 224

4.9 16.7 55.8 22.6

36 I48 223 680

3 14 20 63

*NYHA, New York Heart Association. years). A history of stroke or transient ischemic attack (TIA) was present in 7.1% and 5.8% of patients, respectively. One hundred four patients (9.6%) had a previous coronary artery bypass operation, and 10 patients (0.9%) had a previous CEA. Nine hundred ninety-three of the patients (91%) had significant coronary disease.

Carotid artery duplex scanning All patients were examined before operation according to a standard protocol for carotid duplex scanning. The common carotid, internal carotid, and external carotid arteries, and the carotid bulb were scanned bilaterally for the presence of occlusive atherosclerotic disease. In the long axis view, the flow velocity and Doppler frequency shift were estimated by use of a pulsed wave Doppler spectrum analyzer taken at a incident angle of 60 degrees (cos) with a 5.0 or 7.0 M H z transducer. During the first 2 years of the study, a Biosound N D 256 (Biosound Inc., Indianapolis, Ind.) was used to obtain systolic peak frequencies (4 to 6 kHz = 50% to 79% stenosis; > 6 kHz = 80% to 99% stenosis). During the last 21/2 years, all studies were performed with a color duplex

scanner, (Acuson 126; Acuson Inc., Mountain View, Califi), which estimates peak-systolic velocity. An angle adjusted peak-systolic velocity greater than 1.25 m/see indicated greater than 50% carotid artery stenosis. If the end-diastolic velocity was greater than 1.4 m/see, the artery was classified as having an 80% to 99% stenosis. 6-7 Patients classified as having a completely occluded artery had no flow detected by Doppler frequency shift within the lumen. All arteries were also examined by duplex imaging in the longitudinal and cross-sectional axes. If the findings by imaging did not correlate with the severity of stenosis determined by Doppler spectral analysis, then a carotid arteriogram was performed. This was necessary in 26 patients. However, for the purpose of this study, the degree of stenosis determined by Doppler spectral analysis was used in the analyses. Catheterization and operative procedures All patients underwent cardiac catheterization before operation. Coronary artery stenoses of greater than 50% to 60% of the luminal diameter were considered hemodynamically significant. Patients were classified as having one-vessel, two-vessel, three-vessel, or left main coronary artery disease. Coronary artery bypass grafting alone or in combination with other procedures was performed in 971 patients (89%) (Table II). Ninety-nine patients (9.1%) underwent valve replacement or repair with or without associated procedures, and 17 patients (1.6%) underwent other cardiac procedures. Carotid endarterectomy was performed in symptomatic patients with carotid disease in the appropriate anatomic distribution and in asymptomatic patients with unilateral or bilateral severe carotid artery disease ( > 75% to 80% stenosis). Carotid endarterectomy was combined with coronary artery bypass grafting in 45 patients and with valve replacement in one patient. The CEA was performed before cardiopulmonary bypass but during the same anesthetic in two patients, during cardiopulmonary bypass in 41 patients, and during a period of hypothermic circulatory arrest in three patients. The latter three patients had graft replacement of the ascending aorta and aortic arch or other complicated procedures that required the use of circulatory arrest. The mean age of the patients having the combined procedures was 72 years.

Neurologic evaluation Preoperative neurologic symptoms were classified either as a stroke or a TIA. Transient neurologic symptoms that had been evaluated by a physician

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were considered as TIAs. Permanent neurologic deficits were defined as strokes. All perioperative neurologic complications that occurred in the first 30 postoperative days were entered into the analyses. A permanent deficit was analyzed as a stroke. Reversible ischemic neurologic deficit (RIND) was diagnosed in patients who functionally returned to their baseline neurologic status within 3 weeks of onset of symptoms. Both global and hemispheric deficits were included. All patients demonstrating neurologic deficits were examined by a neurologist, and CT scanning of the head was performed. Data management and statistical analysis All data were compiled and stored in a computerized data bank with an IBM 3270 (IBM Corp., White Plains, N.Y.) system and were analyzed with the SAS s on the Washington University Division of Biostatistics Computing System. Twelve clinical variables were assessed for their ability to predict the presence of carotid artery disease, and a logistic regression model was fitted separately for each variable (PROC LOGISTIC). Thep value, risk ratio, and 95% confidence interval for each variable were computed. All of the variables were then entered into a stepwise regression model to select the best set of independent predictors of carotid artery diseasc. The following variables were analyzed: age, gender, diabetes mellitus, hypertension, left main coronary artery disease, previous cardiac surgery, preopcrative TIA or cerebral vascular accident, previous myocardial infarction, peripheral vascular disease, elevated cholesterol, smoking history, and NYHA functional class. Proportions were compared with Fisher's Exact Test (p < 0.05 was considered significant). All p values are two tailed. RESULTS Prevalence o f carotid artery disease Nine himdred one patients (83.0%) were found to have minimal or no atherosclerotic carotid disease ( < 50% stenosis). One hundred twenty-one patients (i1.1%) had either unilateral or bilateral moderate disease (50% to 79% stenosis). Forty-six patients (4.2%) had either unilateral or bilateral severe disease (80% to 99% stenosis). Nineteen patients (1.8%) had unilateral carotid artery occlusion with varying degrees of stenosis in the contralateral carotid artery (Table III). When divided into broad clinical subgroups, 186 patients (17.1%) had 50% or greater stenosis, and 65 patients (6%) had 80% or greater stenosis.

Preoperative carotid artery screening 315

Table II. Surgical procedures performed in the 1087 patients Procedure CABG CABG + valve replacement/repair CABG + other procedure* CABG + CEA Valve replacement/repair Valve replacement + other procedure* Valve replacement + CEA Other procedure* Total

No. of patients

%

754 109 63 45 96 2 I I7 1087

69.4 10.0 5.8 4.1 8.8 0.2 0.1 1.6 100

CABG, Coronary artery bypass grafting. *Graft replacement of aorta, ventricular aneurysmectomy, insertion of automatic internal cardioverter/defibrillator, repair of ventricular perforation.

The preoperative variables that predicted the presence of 50% or greater stenosis of one or both carotid arteries by univariate analysis were peripheral vascular disease, female sex, previous TIA or stroke, age, hypertension, left main coronary artery disease, and a smoking history (Table IV). In the multivariate analysis, peripheral vascular disease, female sex, previous TIA or stroke, and smoking history were significant predictors (p < 0.05) (Table IV). The logistic regression model predicts a 5% chance of 50% or greater carotid artery disease for a 65-yearold man who is a nonsmoker with no history of TIA or stroke and no peripheral vascular disease or left main coronary artery disease. In contrast, a 72-yearold woman with left main coronary artery disease, a history of TIA or stroke, the presence of peripheral vascular disease, and a positive smoking history has a 67% chance of having carotid artery disease (Fig. 1). The risk of carotid artery disease also increases with age (Fig. 2). The preoperative variables that predicted the presence of 80% or greater stenosis of one or both carotid arteries by univariate analysis included previous TIA or stroke, peripheral vascular disease, left main coronary artery disease, female sex, and NYHA class (Table V). Hypertension approached statistical significance (p = 0.053). In the multivariate analysis, previous TIA or stroke, peripheral vascular disease, left main coronary artery disease, female sex, and a positive smoking history were significant predictors (Table V). The stepwise logistic regression model is shown in Fig. 3. When the data were analyzed only for patients with coronary artery disease, the significant predictive variables for both clinical groups (>_ 50% or > 80% stenosis) did not change.

316

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Berens et al.

Table III. Prevalence of carotid artery disease in the 1087 patients No. ofpatients Severity of carotid artery stenosis

No. of patients

%

Pre~erative TIA or stroke

Carotid endarterectomy

< 5 0 % / < 50% 5 0 - 7 9 % / < 50% 50-79%/50-79% 8 0 - 9 9 % / < 50% 80-99%/50-79% 80-99%/80-99% 1 0 0 / < 50% 100/50-79% 100/80-99% Total

901 97 24 16 19 11 10 3 6 1087

82.9 8.9 2.2 1.5 1.7 1.0 0.9 0.3 0.6 100%

100 15 4 5 6 3 3 2 0 138

0 5 0 9 16 11 0 0 5 46

Table IV. Predictors of > 50% stenosis of one or both carotid arteries by univariate and multivariate analysis Variable Peripheral vascular disease Female sex T I A or stroke Age (per yr) Hypertension Left main disease Smoking history

Univariate p value

Risk ratio

0.0001 0.0004 0.0004 0.001 0.01 0.03 0.04

2.52 1.78 2.12 1.05 1.58 1.50 1.40

Characteristics of patients having carotid endarterectomy Forty-six CEAs were performed on 46 patients (Table III). Five of the 46 patients had unilateral 50% to 79% carotid artery stenosis. Four of the five patients had preoperative symptoms that corresponded to the carotid stenosis (Table VI). The remaining patient in this group had findings by duplex scanning suggestive of more severe disease. A carotid arteriogram showed a 90% unilateral stenosis. Thirty-six of the 46 patients had bilateral 80% to 99% stenosis or unilateral stenosis without occlusion of the contralateral carotid artery. Thirteen of these patients had preoperative neurologic symptoms (Table VI). Seven asymptomatic patients who had unilateral 80% to 99% stenosis and three asymptomatic patients with bilateral stenosis did not undergo CEA because of severe cardiac instability. One of these patients (10%) died of cardiogenic shock early after operation. No postoperative neurologic events occurred in the remaining nine patients. Five patients had occlusion of one carotid artery and 80% to 99% stenosis of the other. One asymptomatic patient with this pattern of carotid disease did not undergo CEA because of diffuse disease in a small internal carotid

95% confidence limits 1.62 1.30 1.40 1.02 1.11 1.04 1.02

- 3.92 - 2.45 - 3.21 - 1.08 - 2.23 - 2.16 - 1.93

Multivariate p value 0.0002 0.0001 0.0009

0.004

artery. He had a RIND in the postoperative period. In the postoperative period a stroke developed in three of the 46 patients (6.5%) who had CEA, and two patients (4.3%) sustained a RIND. All of these events occurred in patients with moderate or severe bilateral stenosis. Computerized tomography in the patients with stroke demonstrated multiple bilateral infarcts in two patients and a single hemispheric infarct in the third patient. The neurologic deficit in the two patients with RIND resolved completely within 72 hours. Five patients (10.9%) died of cardiac causes, and all had bilateral carotid stenosis (Table VI).

Postoperative neurologic complications and deaths Within the study population of 1087 patients, 37 patients (3,4%) had a postoperative neurologic event. Twenty-two patients (2.0%) had a stroke, and 15 patients (1.4%) had a RIND. Seven (7.2%) of the 97 patients who were 65 years of age or older and who did not undergo preoperative carotid artery duplex scanning had a postoperative neurologic event (6 strokes, 1 RIND). Among the 997 patients who were younger than 65 years of age and who were not

Volume15 Number2 February1992

Preoperative carotid artery screening 317

70

Predicted

60 50

...........

g 40

~

¢o ¢1.

30 10

Observed /

J /

•% .

,..,

d

/\ "

!

! " % .~ I

',

'

,,,k

-,

P'--'

,,,/

/

";

PVD Female TIA/OVA

Smoker

Clinical Subgroups Fig. 1. Increased risk for 50% or greater carotid stenosis based on the four independent predictors. Closed squares (m) indicate the presence of the preoperative variable. One hundred fifty-two (82%) of the 185 patients with 50% or greater stenosis had one or two of the predictive variables on presentation. Only 16 patients (8.7%) with this degree of stenosis were not identified by the above risk factors. PVD, Peripheral vascular disease; CVA, cerebral vascular accident.

20

Percent

15

10

65-69

70-74

75-79

80+

Years Fig. 2. Prevalence of 50% or greater carotid artery stenosis according to age. entered into the study, the postoperative neurologic event rate was 1.7% (11 strokes, 6 R I N D ) . The total neurologic event rate for the entire population o f patients (2181) who underwent cardiac surgical procedures during the study interval was 2.8% (Table

VII). For elderly patients who underveent carotid artery duplex scanning the total neurologic event rate was 2.5% for less than 50% stenosis, 7.6% for a 50% or greater stenosis, 10.9% for 80% or greater stenosis, and 10.9% for unilateral occlusion.

Journal of VASCULAR SURGERY

318 Berens et al.

100 80

i

Predicted

|

Observed

1

4.-=

,- 60 ID

a.

40

20

0 TIA/CVA PVD LMD Female Smoker

Clinical Subgroups Fig. 3. Increased risk for 80% or greater carotid stenosis based on the five independent predictors. Closed squares (=) indicate the presence of the preoperative variable. Forty-three (67%) of the 64 patients with 80% or greater stenosis had one or two of the predictive variables on presentation. Only three patients (4.6%) with severe stenosis were not identified by the above risk factors. LMD, Left main coronary disease. Table V. Predictors of __80% stenosis of one or both carotid arteries by univariate and multivariate analysis Variable T I A or stroke Peripheral vascular disease Left main disease Female sex N Y H A class Hypertension Smo king history

Univariate p value

Risk ratio

0.0001 0.002 0.01 0.03 0.03 0.05 0.07

3.27 2.76 1.97 1.79 1.54 1.77 1.62

Fifty-six deaths (5.4%) occurred during the first 30 postoperative days (Table VII). Thirty-two of these patients (57%) had undergone previous cardiac surgical procedures. When compared with patients with less than 50% carotid stenosis (mortality rate, 4.4%), the mortality rate was significantly higher for patients with 50% or greater stenosis (8.7%; p = 0.003) and 80% or greater stenosis (11.1%; p = 0.015). Two patients died as the result of a stroke. Forty-one patients died of cardiac causes. Analysis o f stroke patients Twenty-two strokes occurred during the first 30 postoperative days. Three occurred in patients with severe carotid stenosis, five in patients with moderate stenosis, and 14 in patients with minimal or no

95% Confidence limits 1.85 1.47 1.15 1.08 1.05 0.99 0.97

-

5.78 5.19 3.40 2.97 2.24 3.17 2.71

Multivariate p value 0.0001 0.011 0.007 0.003

0.026

stenosis. Five of the 22 strokes were thought to result from embolization from or occlusion of a diseased carotid artery. All of these were apparent within the first 24 hours after operation. Three of these patients had severe bilateral disease and had undergone CEA on the side contralateral to the involved hemisphere. The other two patients had moderate unilateral stenosis ipsilateral to the involved hemisphere, were asymptomatic before operation, and had not undergone CEA. Two patients with moderate disease were thought to have sustained embolic strokes contralateral to the diseased carotid artery, and one patient had an intracranial hemorrhage. Among patients with minimal or no carotid stenosis, postoperative strokes as a result of embolism were thought to have developed in 11. Some of the

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Preoperative carotid artery screening 319

Table VL Characteristics of the 46 patients having combined surgical procedures and carotid endarterectomy Postoperative Severity of carotid artery stenosis 50% - 79%/< 50% 80% - 99%/< 50% 80% - 99%/50% - 79% 80% - 99%/80% - 99% 100%/80% - 99%

No. of patients

Preoperative TIA or stroke

Stroke

RIND

Death

4 4 6 3 0 17 (37%)

0 0 2 1 0 3 (6.5%)

0 0 1 1 0 2 (4.3%)

0 0 4 1 0 5 (10.9%)

5* 9 16 11 5 46

*One patiem: had a 90% stenosis on arteriography.

Table VII. Postoperative neurologic complications and death > 65 years Scanned No. of patients Stroke RIND Total neurologic events 30-day mortality

22 15 37 56

1087 (2.0%) (1.4%) (3.4%) (5.2%)

neurologic deficits were noted in the immediate postoperative period, and others became apparent as late as the ninth postoperative day. Three strokes were attributed to postoperative hypotension. Characteristics o f patients with preoperative neurologic events One h~mdred thirty-eight patients had a preoperative history of one or more neurologic events (Table III). Thirty-eight patients (27.5%) were found to have 50% or greater stenosis, and 19 patients (13.8%) had 80% or greater stenosis. Four patients had postoperative strokes, and RINDs developed in three patients. Five of these seven patients had minimal carotid artery disease. Analysis o f asymptomatic patients Nine hundred fifty-one asymptomatic patients had preoperative duplex scanning. These patients were analyzed separately by multivariate analysis in the same manner as described above for the entire study population. One hundred forty-seven patients (15.4%) had 50% or greater stenosis. The significant independent predictors were peripheral vascular disease (p = 0.0003), female sex (p = 0.002), and age (p = 0.003). If all asymptomatic patients with one or more risk factors were screened, then the sensitivity

< 65 years Not scanned 6 1 7 25

97 (6.2%) (1.0%) (7.2%) (25.8%)

Not scanned 11 6 17 40

997 (1.1%) (0.6%) (1.7%) (4.0%)

Total 2181 39 (1.8%) 22 (1.0%) 61 (2.8%) 124 (5.7%)

for identifying 50% or greater stenosis would be 76%. Forty-five patients (4.7%) had 80% or greater stenosis. The significant independent predictors were peripheral vascular disease (2o = 0.007), previous myocardial infarction (p = 0.023), and left main coronary disease (20 = 0.049). The sensitivity for screening patients with one or more risk factors is 80%. DISCUSSION

The role of preoperative screening for carotid artery disease in patients undergoing cardiac surgery remains unclear.4-5,9-~4The potential benefits of such screening, when combined with CEA, include a reduced incidence of perioperative stroke and a reduced incidence of late postoperative stroke. 2,14In addition, screening may identify patients with carotid artery disease who should be carefully monitored for the development of late neurologic symptoms, s Faggioli et al) 4 recommended routine preoperative carotid duplex scanning for all patients over 60 years of age undergoing coronary artery bypass grafting. They observed a high stroke rate (14%) after cardiac surgical procedure in 28 tmtreated asymptomatic elderly patients with greater than 70% carotid stenosis and a zero stroke rate for 19 similar patients who had prophylactic CEA. Brener et al.4

320

Berens et al.

reported a 9.2% overall stroke rate in patients having coronary artery bypass grafting with 50% or greater carotid stenosis and a 20% stroke rate in patients with significant carotid stenosis contralateral to an internal carotid occlusion. Other investigators have also reported an increased risk ofperioperative stroke (9% to 17%) in patients with carotid artery disease. 24'11'1~-16 In addition, several studies have demonstrated an increased mortality rate (9% to 13%) in patients with significant carotid artery disease compared with patients without such disease (1% to 4%) .4,12 Without preoperative screening, many asymptomatic patients in our study with significant carotid artery disease would not have been detected. Of 64 patients with 80% or greater stenosis, only 18 (28%) were symptomatic. Furthermore, of 36 patients undergoing combined CEA and cardiac surgical procedures with severe unilateral or bilateral stenosis, only 13 patients were symptomatic. All five patients undergoing combined carotid and cardiac procedures with unilateral occlusion and severe contralateral stenosis were asymptomatic and would not have been identified before operation without carotid artery screening. The postoperative neurologic complication rate has been substantial (20% to 33%) for this latter group with or without CEA.~,4 The optimal treatment of patients with severe carotid artery stenosis who require cardiac surgical procedures has not been conclusively established. Some investigators have reported a low incidence of neurologic complications after combined carotid and cardiac procedures in selected patients, and have suggested that combined CEA and cardiac surgical procedures provide perioperative as well as late protection from stroke with the need for only a single anesthetic. 2-3 Nonoperative management of the carotid disease has been recommended by other authors who have found either a high postoperative stroke rate after combined procedures4 or no correlation between the presence of carotid stenosis (> 50%) and the frequency of perioperative neurologic events, m2 The latter studies, by failing to identify the highest risk subgroup of symptomatic and asymptomatic patients (i.e., those with > 70% stenosis), may have underestimated the important protective benefits of CEA. Our study was not specifically designed to determine the optimal management of combined carotid and cardiac disease. The stroke incidence of 6.5% after carotid and cardiac procedures in our study is similar to that reported from a

•ournal of VASCULAR SURGERY

previous study of combined operations in elderly patients (7.4%). 16 It is less than the stroke rate reported for elderly patients undergoing cardiac surgical procedures with severe carotid disease who did not have CEA (14%)}4 In addition, although an increased incidence of stroke in patients 65 years of age and older could be expected based on previous studies, ~,14,17the stroke rate of 2.0% in our study for all elderly patients who were screened before operation, including patients in whom CEA was performed, was not significantly different from the stroke rate for patients less than 65 years of age who were not screened (1.1%) (p = 0.11). The results of our study confirm those from previous reports that have demonstrated a 12% to 20% prevalence of 50% or greater carotid stenosis, 4''4 and a 9% prevalence of 80% or greater stenosis in patients undergoing coronary artery bypass grafting. 14It is likely that carotid duplex scanning, because of its accuracy in identifying carotid artery disease, will supplant other techniques that have been used in e a r l i e r s t u d i e s . 4.s'9'n-13,18 Several centers, including our own, have performed CEA based only on the results of the duplex scan (20 of 46 CEA patients in this study)} 923 This approach has been particularly useful in patients with unstable cardiac conditions who require urgent cardiac surgery}9 With the exception of the studies of Brener et al.,4.~3 previous reports examining the prevalence of carotid artery disease in patients undergoing cardiac surgery have evaluated patients who were asymptomatic with respect to the carotid artery disease. Our objective was to define the prevalence of carotid artery disease in the entire population of elderly patients undergoing cardiac surgery, and symptomatic patients were included. If only asymptomatic patients are considered, then the model we used would still be applicable. For carotid stenosis 50% or greater elderly women with peripheral vascular disease are at greatest risk. For stenosis 80% or greater the presence of atherosclerotic disease (peripheral vascular disease, history of previous myocardial infarction, left main coronary artery disease) is the most important predictor. If all patients with at least one risk factor would undergo preoperative duplex scanning, then screening would have a 91% sensitivity (20% specificity) for a 50% or greater stenosis and a 95% sensitivity (15% specificity) for 80% or greater stenosis. With use of the presence of one risk factor, approximately 80% of the patients 65 or more years of age would

Volume 15 Number 2 February 1992

require screening. Consequently, a major deterrent to r e c o m m e n d i n g routine preoperative screening, even in the elderly population, is the cost o f the procedure (approximately $500). O u r study confirms the findings f r o m previous reports that patients with severe bilateral carotid artery disease are at increased risk for stroke during a cardiac surgical procedure. 1'2'4 A l t h o u g h some studies suggest that C E A in such patients m a y reduce the frequency o f postoperative stroke, 2,3 the results are n o t conclusive. Because o f the low overall prevalence o f stroke, a study o f a large n u m b e r o f patients treated with or w i t h o u t C E A w o u l d be necessary to confirm this hypothesis. Until the results o f such studies b e c o m e available, we believe that C E A should be p e r f o r m e d in asymptomatic and s y m p t o m a t i c patients with 80% or greater stenosis o f one or b o t h carotid arteries u n d e r g o i n g cardiac surgical procedures and in symptomatic patients with lesser degrees ofstenosis. W e recognize that other strategies m a y be equally or possibly even m o r e effective in preventing or reducing the frequency o f stroke in patients with high-grade occlusive disease. This underscores the need to identify patients before operation with severe carotid occlusive disease w h o are to u n d e r g o cardiac surgical procedures so that alternative strategies can be evaluated. W e believe that all elderly patients with at least one o f the risk factors defined above, should u n d e r g o routine preoperative carotid duplex scanning before cardiac surgery. We acknowledge the assistance of Brad Wilson, MA, of the Division of Biostatistics, Washington University School of Medicine, with the statistical analyses and that of Pam Pigg and Grace Ceriotti with the preparation of the manuscript. We also acknowledge the vascular technologists, Barbara Beck, RN, and Pat Reinecke, SVT, for their assistance. REFERENCES 1. Hertzer NR, Loop FD, Taylor PC, et al. Combined myocardial revascularization and carotid endarterectomy. Operative and late results in 331 patients. I Thorac Cardiovasc Surg 1983;85:577-89. 2. Hertzer NR, Loop FD, Beven EG, et al. Surgical staging for simultaneous coronary and carotid disease: a study including prospective randomization. J VASe SURG 1989;9:455-63. 3. Cambria RP, Ivarsson BL, Akins CW, et al. Simultaneous carotid and coronary disease: safety of the combined approach. J VASe SURG 1989;9:56-64. 4. Brener BI, Brief DK, Alpert J, et al. The risk of stroke in patients with asymptomatic carotid stenosis undergoing cardiac surgery: a follow-up study. J VASeSURG1987;5:269-

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5. Barnes RW, Nix ML, Sansonetti D, et al. Late outcome of untreated asymptomatic carotid disease following cardiovascular operations. J VAse SURG 1985;2:843-9. 6. BlackshearWM, Lamb SL, Kotlipara VS, et al. Correlation of hemodynamically significant internal carotid stenosis with pulsed Doppler frequency analysis. Am1 Surg 1984;199:47581. 7. Roederer GO, Lang/ois YE, Jager ICA,et al. A simple spectral parameter for accurate classification of severe carotid disease. Bmit 1984;8:174-8. 8. SAS/STATUsers guide, release 6.03 edition. Cary, NC: SAS Institute, Inc. 1988. 9. Turnipseed WD, Berkoff HA, Belzer FO. Postoperative stroke in cardiac and peripheral vascular disease. Ann Surg i980;I92:365-8. 10. Breslau PJ, Fell G, Ivey TD, et al. Carotid arterial disease in patients undergoing coronary artery bypass operations. J Thorac Cardiovasc Surg 1981;82:765-7. 11. Kartchner MM, McRae LP. Carotid occlusivedisease as a risk factor in major cardiovascular surgery. Arch Surg 1982;117: I086-8. 12. Barnes RW, Liebman PR, Marszalek PB, et al. The natural history of asymptomatic carotid disease in patients undergoing cardiovascular surgery. Surgery 1981;90:1075-83. 13. Brener BJ, Brief DK, Alpert J, et al. A four-year experience with preoperative noninvasive carotid evaluation of two thousand twenty-six patients undergoing cardiac surgery. 1 VAsc SURG 1984;1:326-38. 14. Faggioli GL, Curl GR, Ricotta 11. The role of carotid screening before coronary artery bypass. J VASC SURG 1990;12:724-3i. I5. Reed GL, Singer DE, Picard EH, et al. Stroke following coronary-artery bypass surgery. A case-control estimate of the risk from carotid bruits. N Engl J Med 1988;319:i246-50. 16. Perler BA, Burdick IF, Minken SL, et al. Should we perform carotid endarterectomy synchronously with cardiac surgical procedures? J Vase SURG1988;8:402-9. 17. Gardner TI, Horneffer PI, Manofio TA, et al. Stroke following coronary artery bypass grafting: a ten-year study. Ann Thorac Surg 1985;40:574-8I. 18. Balderman SC, Gutierrez IZ, Makula P, et al. Noninvasive screening for asymptomatic carotid artery disease prior to cardiac operation. Experience with 500 patients. J Thorac Cardiovasc Surg 1983;85:427-33. I9. Marshall WG, Kouchoukos NT, Murphy SF, et al. Carotid endarterectomy based on duplex scanning without preoperative arteriography. Circulation 1988;78(suppl I):I-1-5. 20. O'Donnell TF, Callow AD, Willet C, et al. The impact of coronary artery disease on carotid endarterectomy. Ann Surg I983;198:705-I2. 21. Moore WS, Ziomek S, Quinones-Baldrich WJ, et al. Can clinical evaluation and non-invasive testing substitute for arteriography in the evaluation of carotid artery disease? Ann Surg 1988;208:91-4. 22. Gelabert HA, Moore WS. Carotid endarterectomy without angiography. Surg Clin North Am 1990;70:213-24. 23. Goodson SF, Flanigan DP, Bishara RA, et al. Can carotid duplex scanning supplant arteriography in patients with focal carotid territory symptoms? J VASCSURG 1987;5:551-7. Submitted June 10, 1991; accepted Sept, 17, 1991.

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DISCUSSION Dr. Robert Barnes (Little Rock, Ark.). This paper differs from many previous reports because it is the largest series of patients undergoing cardiac surgery screened with carotid duplex scanning, the patients were 65 years of age or older, and patients with both asymptomatic and symptomatic carotid disease were included in the study. These factors, thus, make it difficult to compare the results of this study with previous reports. Nevertheless, I believe the authors have shown that the prevalence of severe carotid stenosis is greater in this older population of patients undergoing cardiac surgery; second, that risk factors for the presence of carotid disease can be identified in this patient population; and third, the risk of perioperative stroke after concomitant carotid and cardiac surgery remains high, namely 10.8% in this study if one combines patients suffering stroke and RIND. I would like to point out that in past years many of us reported perioperative deficits of strokes and TIAs, and now it has become popular to exclude TIAs and to report strokes and RINDs. I consider RINDs to be strokes with recovery, and we should report these as such. I believe this study has not established the value of risk factors in identifying subsets of patients appropriate for noninvasive carotid screening inasmuch as 80% to 85% of patients must be scanned to identify 90% to 95% of carotid stenoses. And second, I do not believe, as you have indicated, that there is a value of concomitant CEA and cardiac surgery in reducing the incidence of perioperative stroke. Your overall stroke rate was 3.4% in all of your elective cardiac procedures in patients over 65 years of age and 2.8% of all cardiac operations. These are figures similar to those in many published series. Your stroke rate in 46 patients undergoing combined carotid and cardiac procedures was approximately 11%, whereas 10 patients with severe carotid stenosis who did not undergo carotid surgery because of cardiac instability had no perioperative neurologic deficits. I have one question for Dr. Berens. What was the difference in the incidence of perioperative stroke or R I N D in patients with symptomatic versus asymptomatic carotid stenosis who underwent combined carotid and cardiac operations? Dr. Eric Berens. Thank you for your comments, Dr. Barnes. We are accumulating late follow up data on this study population for further analysis. Because the precise duration of a temporary neurologic deficit is often difficult to assess in the early postoperative period, we have used the " R I N D " designation to include all reversible neurologic deficits, including those that lasted less than 24 hours. This has simplified our data analysis while allowing us to distinguish strokes from less severe neu-

Journal of VASCULAR SURGERY

rologic deficits. The data were also analyzed for the subgroup of asymptomatic patients. We identified significant prognostic risk factors in this group as well. Among the five neurologic deficits in the patients who had undergone combined operation, four of those occurred in asymptomatic patients. Your questions relating to reduction of perioperative and long-term stroke in asymptomatic patients should be addressed by future studies. However, in view of today's presentation of preliminary results from randomized carotid endarterectomy trials, identification of patients with asymptomatic carotid stenosis may be important in reducing stroke risk. Dr. Richard Cambria (Boston, Mass.). The authors have presented valuable information on markers of carotid disease in elderly patients undergoing cardiac surgery. The incidence of significant carotid disease they have reported is somewhat higher than in prior screening studies, but this is likely accounted for by the fact that they have studied older patients only. Similar to previous reports, they have noted that both stroke morbidity and operative mortality rates after cardiac surgery are significantly increased in the presence of severe carotid disease. Furthermore, risk of both postoperative stroke and death is stratified according to the severity of the carotid disease. Finally, cardiac and not neurologic events account for most postoperative deaths. The authors have reached several of the same conclusions we did a few years ago, namely, that although stroke risk during cardiopulmonary bypass is increased by the presence of severe carotid disease, it remains unclear if that risk can be decreased by the performance of simultaneous CEA. And second, and perhaps most important, we believe the combined operation can be done safely. Therefore, if each lesion requires treatment on its own merit, we continue to perform a combined operation in selected patients. My questions for the authors are the following. I noted that they selected their patients for combined operations largely on the basis of noninvasive testing only. In asymptomatic patients, we have felt strongly that only critical stenoses as defined by arteriography should be treated. Would you comment? Second, would you comment further on your technique for the combined operation? I noted from your manuscript that many of the carotid procedures were performed after the induction of cardiopulmonary bypass. In our own unit, the strategy is to do the carotid operation first, expeditiously, while vein harvest proceeds in the leg. Dr. Berens. Thank you, Dr. Cambria, for your questions. Twenty-six patients underwent carotid angiogram after duplex scanning before combined carotid

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endarterectomy and cardiac procedures. Severe carotid stenosis predicted by duplex scanning was confirmed by angiography in 25 of 26 patients. In one case, the angiogram demonstrated a more severe stenosis than the duplex scan. Overall, reliable duplex scan results have allowed us to perform carotid endarterectomy in patients

at high risk who have required more urgent operation. We performed 43 of the 45 procedures under cardiopulmonary bypass for the theoretic advantages provided by systemic heparinization, control of blood pressure, and mild hypothermia.

CORRECTION In the article, "Lower extremity calf thrombosis: to treat or not to treat?" by Joann Lohr, MD, Thomas Kerr, MD, Kenneth Lutter, MD, Robert Cranley, MD, Katherine Spirtoff, BS, and John Cranley, MD (1991;14:618-23), an incorrect copy of Fig. 1 was inadvertently printed. The correct figure and legend follow:

Fig. 1. In an average-sized adult, one zone equals a length of approximately 10 cm on the extremity. Zone 1 is defined as the intersection of the femoral vessels with the inguinal ligament. Zone 5 is an imaginary line passing from midpatella to the popliteal crease. Zone 8 corresponds to a line from midmedial malleolus to the midlateral malleolus. Zone 9 corresponds to the tips of the toes. With use of the above landmarks, the thigh and calf are subdivided into four and three equal zones, respectively.