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1.5 Value of the preoperative EEG during carotid endarterectomy
23rd World Congress of the LSCVS
1.3 Evaluation of Bleeding Characteristics and Neointimal Hyperplasia Following Carotid Angioplasty Using Polyester and Polytetrafluoroethylene (PTFE) Patch Materials D. WHITLEY, G. MOZES, S.S. MENAWAT and P. GLOVICZKZ, Rochester, Minnesota USA Purpose: Selective use of carotid patch angioplasty has been advocated. However, suture hole bleeding and healing in prosthetic patches remains a problem. We evaluated bleeding and healing characteristics of Polytetrafluxoethylene (PTFE) patch materials with different internodal distances and compared them to polyester patches. Methods: Bilateral carotid patch angioplasties were performed in adult dogs. New “experimental PTFE” (n = 12) was placed in one carotid artery of each dog and woven polyester (n = 5) or standard 0.4mm ePTFE (n = 7) were placed in the contralateral carotid artery. The surgeon alternated five suture throws on each patch until the anastomosis was complete. Flow was re-established bilaterally and blood loss recorded. Patches were harvested 4 and 6 months later. Segments of arteries were stained with hematoxylin and eosin and analyzed by computer assisted morphometry. Cross-sectional areas and thickness of neointima were determined. Results: There was no difference in blood loss between experimental PTFE and 0.4mm PTFE. Woven polyester patches demonstrated less bleeding than PTFE (P < 0.05). There was no difference in area and thickness of neointima over different patch materials when each animal was used as its own control. At 6 months, the cross-sectional area at the site of the patch was 3.6 times greater than at the artery proximal to the patch. The degree of arterial enlargement correlated with the cross-sectional area of the neointima over the patch (n = 12, P < 0.016). Conclusion: Modification of PTFE by alteration of nodal configuration and decreasing internodal distance did not decrease suture hole bleeding. Woven polyester patch had the least amount of bleeding. Neointima formed at similar rates on all materials tested. The cross-sectional area of the neointima, however, positively correlated with native arterial enlargement. This may be explained by vessel wall remodeling to maintain an arterial lumen which matches flow characteristics
1.4 Spiral CT Angiography Definitively Measures Carotid Artery Area Reduction M.E. CINAT, C.T. LANE, H. PHAM, A. LEE, T NGUYEN, S.E. WILSON and Z.L. GORDON, Orange, California, USA Catheter arteriography (ART) is the definitive study for carotid artery stenosis. However, its associated risks and cost have prompted the development of other imaging techniques. Spiral CT angiography (CTA) is a non-invasive test that allows visualization of the carotid arteries in both two- and three-dimensional planes. To determine the utility of CTA in carotid imaging, a three-way comparison of CTA, ART, and duplex was performed in 57 patients undergoing evaluation for carotid stenosis; mean age was 69.2 years. Images were
2
read by both radiologists and surgeons. CTA stenosis was determined by percent area reduction seen on axial images through the level of greatest narrowing. Data were analyzed using linear regression and paired Student’s t-tests. A significant correlation was found between CTA and ART (R = 0.78, P < 0.001; n = 48). Because CTA measures area reduction as opposed to diameter reduction, a higher degree of stenosis was measured by CTA, especially for lesions with an arteriographic diameter reduction of 50-75% (overall average: CTA 73.7%, ART 69.5%; P < 0.05 paired t-test). A significant correlation was found between CTA-duplex (R = 0.79, P < O.OOl;n = 77) and ART-duplex (R = 0.80, P < 0.001, 12 = 48). No significant difference was found in the overall average between duplex (66.2%) and CTA (68.7%). CTA accurately demonstrated plaque characteristics, such as ulceration and calcification when compared to operative findings. No complications or renal dysfunction were noted. However, CTA underestimated two cases of short segment stenoses due to volume averaging. Overall, CTA is a safe, non-invasive technique that accurately measures carotid artery area reduction and highly correlates to duplex scanning. Using these two complimentary diagnostic tests, conventional invasive arteriography may be safely avoided in the preoperative work-up of carotid artery disease.
1.5 Value of the Preoperative EEG During Carotid Endarterectomy K.A. ILLZG,J.L. BURCHFZEL, K. OURIEL, P. RIGGS, ].A. DEWEESE and R.M. GREEN, Rochester, New York, USA Purpose: Although the cost of electroencephalographic (EEG) monitoring during carotid endarterectomy (CEA) (OR-EEG) is equivalent to that of a full hospital day, its utilization in many large centers is unquestioned despite the challenges of managed care. This study was designed to determine whether a single, inexpensive preanesthetic baseline EEG (BL-EEG) can be used as a substitute for OR-EEG to lower the total cost of CEA while maintaining optimal safety. Methods: Three hundred and three patients undergoing 331 CEAs by two surgeons with EEG monitoring from June 1991 to May 1995 had BL-EEG. BL- and OR-EEG were retrospectively analyzed and blindly graded without knowledge of clinical status or outcome of operation. One surgeon shunted only those patients with EEG changes after clamping (EEGA) while the second shunted all patients with prior CVA or any EEG abnormality prior to or after clamping. Results: The incidence of major neurological morbidity and mortality was 1.8%. BL-EEGs were abnormal in 105 patients (32%). While BL-EEG changes were highly predictive of EEG changes after anesthetic induction (P < O.OOOl), they were not predictive of EEG changes with clamping or of clinical outcome. Prior CVA predicted abnormal BL-EEGs (P c 0.0001) and postanesthetic (P c 0.0001) EEGs but did not predict changes with clamping or perioperative CVA. EEGAs with clamping occurred during 18% of operations; such changes were predicted only by contralateral occlusion (ICA-Occ; P < 0.0016) and EEGA during a prior contralateral CEA (P < 0.001). The only variable which predicted an adverse neurological outcome was the presence of a contralateral occlusion which
CARDIOVASCULAR SURGERY SEPTEMBER 1997
&~ebfovasculaf
increased the likelihood of a perioperative neurological event seven-fold (I’ = 0.0038). Clinical outcomes in the 57 of 105 patients with abnormal BL-EEGs and the 49 of 83 with prior CVA who were shunted were not different from those who were not. Conclusions: The policy of routine shunting for prior CVA should be re-examined. BL-EEG is not of value for the prediction of adverse events during CEA and can be eliminated. Because contralateral occlusion is highly predictive of changes with clamping and patients undergoing a second CEA will usually manifest EEGA changes identical to those at the first, OR-EEG monitoring can be eliminated from both these circumstances. The resultant cost savings from these findings, however, is debatable, since only a small percentage of patients would be affected. Justification for continued use of OR-EEG will require proof of its costeffectiveness.
1.6 Results of Conservative Management of Residual and Recurrent Lesions after Carotid Endarterectomy
KEN
]I RICOTTA and MS. O’BRIEN-IRR, tit&u York, USA
SURGERY
SEPTEMBER
1.7 Prior Stroke Does not Increase the Risk of Carotid Endarterectomy P.E. PARRINO, M. LOVELOCK, R.C. KING. K. SHOCKEY C.G. TRIBBLE and IL. KRON, Charlottesville, Virginia, USA Carotid endarterectomy has become a safe procedure with less than a 5% combined morbidity and mortality in most major centers. However, the timing of surgery following a stroke has been controversial. The anecdotal strategy has been to wait a minimum of 6 weeks prior to carotid endarterectomy. This delay, however, may result in additional neurological events. Our hypothesis was that in select patients, this high risk period can be shortened by performing elective carotid endarterectomy less than 6 weeks after a stroke. To analyze this question, we compared three groups of patients. Group I had surgery less than 6 weeks after a stroke (mean time = 16.5 days -c 2.76). These patients had small infarcts by CT scan and severe carotid stenoses. Group II had surgery more than 6 weeks following a stroke. Group III is a control group of carotid endarterectomies done between I January 1986 and 1 May 1994.
Buffalo, Gr024p
Routine treatment of significant lesions after carotid endarterectomy (CEA) has been advocated, despite the lack of data on the natural history of such lesions. Objective: Our objective was to document long-term follow-up of patients with recurrent or residual lesions whose initial management has been non-operative. Methods: Patients with residual or recurrent stenoses, > 50% diameter, were identified from a carotid data base. Residual lesions were identified ~6 months after CEA while recurrent lesions occurred >6 months. The clinical course of patients with these lesions was compared to that of patients who had no residual lesions after CEA using life table analysis and the LEE-DESU statistics. Results: Duplex and clinical follow-up were available on 384 cases. Residual lesions were seen in 12 patients (3.1%) including four postoperative occlusions. Only one patient underwent re-operation for a residual lesion. Recurrent stenoses ~50% were seen in 24 patients (10 patients 50-79%, 12 patients 75-99%, two occlusions). The risk of restenosis was 8.6% at 3 years, 14% at 5 years and was associated with contralateral disease progression (I’ c 0.001). Although most of these lesions could be followed initially, (85% at 3 years, 79% at 5 years) 15/24 arteries eventually required re-operation: 12 for symptoms, three asymptomatic lesions with progressive proximal lesions or severe complex contralateral disease. The late stroke rate was increased in patients with residual or recurrent lesions (18% versus 6% at 5 years. P = 0.16 by LEE-DESU). Conclusions: Recurrent stenosis is more common in patients with progressive contralateral disease, emphasizing the importance of ongoing atherosclerosis. Although these lesions can be safely watched over the short-term, the late stroke rate is increased 3-fold in patients with recurrent or residual disease and many require late operation due to symptoms or progression of disease. Elective operation on patients with reasonable life expectancy is indicated.
CARDIOVASCULAR
I
1997
Group I Group II Group III 'P = NS (0.3621
Prior stroke does not increase the risk of carotid endarterectomy in either patient group. Early post-stroke surgery, if done for tight stenosis in patients with small infarcts, can be done with low morbidity and mortality. A more aggressive surgical approach may be warranted in neurulogically stable patients with limited strokes and tight stenoses to avoid new events or carotid occlusion while awaiting delayed surgery.
1.8 Is Preoperative Cardiac Testing Necessary Prior to Elective Carotid Endarterectomy? S. MELTSER, 0.W BROWN, I? BENDICK and J. GLOVER, Southfield, Michigan, USA The high incidence of coronary artery disease tn patrents with peripheral and cerebrovascular occlusive disease has been well established. While preoperative cardiac evaluation had been shown to be beneficial in patients undergoing elective aortic reconstruction, the role of preoperative cardiac testing in patients undergoing elective carotid endarterectomy had not been defined. In this study, the charts of 289 consecutive patients undergoing elective carotid endarterectomy between 1 January 199.5 and 31 December 1995 *were evaluated to determine the need for cardiac “clearance” prior to surgery. Ages ranged from 48 to 98, with a mean age of 70.4 years. The
3
1.3 Evaluation of Bleeding Characteristics and Neointimal Hyperplasia Following Carotid Angioplasty Using Polyester and Polytetrafluoroethylene (PTFE) Patch Materials D. WHITLEY, G. MOZES, S.S. MENAWAT and P. GLOVICZKZ, Rochester, Minnesota USA Purpose: Selective use of carotid patch angioplasty has been advocated. However, suture hole bleeding and healing in prosthetic patches remains a problem. We evaluated bleeding and healing characteristics of Polytetrafluxoethylene (PTFE) patch materials with different internodal distances and compared them to polyester patches. Methods: Bilateral carotid patch angioplasties were performed in adult dogs. New “experimental PTFE” (n = 12) was placed in one carotid artery of each dog and woven polyester (n = 5) or standard 0.4mm ePTFE (n = 7) were placed in the contralateral carotid artery. The surgeon alternated five suture throws on each patch until the anastomosis was complete. Flow was re-established bilaterally and blood loss recorded. Patches were harvested 4 and 6 months later. Segments of arteries were stained with hematoxylin and eosin and analyzed by computer assisted morphometry. Cross-sectional areas and thickness of neointima were determined. Results: There was no difference in blood loss between experimental PTFE and 0.4mm PTFE. Woven polyester patches demonstrated less bleeding than PTFE (P < 0.05). There was no difference in area and thickness of neointima over different patch materials when each animal was used as its own control. At 6 months, the cross-sectional area at the site of the patch was 3.6 times greater than at the artery proximal to the patch. The degree of arterial enlargement correlated with the cross-sectional area of the neointima over the patch (n = 12, P < 0.016). Conclusion: Modification of PTFE by alteration of nodal configuration and decreasing internodal distance did not decrease suture hole bleeding. Woven polyester patch had the least amount of bleeding. Neointima formed at similar rates on all materials tested. The cross-sectional area of the neointima, however, positively correlated with native arterial enlargement. This may be explained by vessel wall remodeling to maintain an arterial lumen which matches flow characteristics
1.4 Spiral CT Angiography Definitively Measures Carotid Artery Area Reduction M.E. CINAT, C.T. LANE, H. PHAM, A. LEE, T NGUYEN, S.E. WILSON and Z.L. GORDON, Orange, California, USA Catheter arteriography (ART) is the definitive study for carotid artery stenosis. However, its associated risks and cost have prompted the development of other imaging techniques. Spiral CT angiography (CTA) is a non-invasive test that allows visualization of the carotid arteries in both two- and three-dimensional planes. To determine the utility of CTA in carotid imaging, a three-way comparison of CTA, ART, and duplex was performed in 57 patients undergoing evaluation for carotid stenosis; mean age was 69.2 years. Images were
2
read by both radiologists and surgeons. CTA stenosis was determined by percent area reduction seen on axial images through the level of greatest narrowing. Data were analyzed using linear regression and paired Student’s t-tests. A significant correlation was found between CTA and ART (R = 0.78, P < 0.001; n = 48). Because CTA measures area reduction as opposed to diameter reduction, a higher degree of stenosis was measured by CTA, especially for lesions with an arteriographic diameter reduction of 50-75% (overall average: CTA 73.7%, ART 69.5%; P < 0.05 paired t-test). A significant correlation was found between CTA-duplex (R = 0.79, P < O.OOl;n = 77) and ART-duplex (R = 0.80, P < 0.001, 12 = 48). No significant difference was found in the overall average between duplex (66.2%) and CTA (68.7%). CTA accurately demonstrated plaque characteristics, such as ulceration and calcification when compared to operative findings. No complications or renal dysfunction were noted. However, CTA underestimated two cases of short segment stenoses due to volume averaging. Overall, CTA is a safe, non-invasive technique that accurately measures carotid artery area reduction and highly correlates to duplex scanning. Using these two complimentary diagnostic tests, conventional invasive arteriography may be safely avoided in the preoperative work-up of carotid artery disease.
1.5 Value of the Preoperative EEG During Carotid Endarterectomy K.A. ILLZG,J.L. BURCHFZEL, K. OURIEL, P. RIGGS, ].A. DEWEESE and R.M. GREEN, Rochester, New York, USA Purpose: Although the cost of electroencephalographic (EEG) monitoring during carotid endarterectomy (CEA) (OR-EEG) is equivalent to that of a full hospital day, its utilization in many large centers is unquestioned despite the challenges of managed care. This study was designed to determine whether a single, inexpensive preanesthetic baseline EEG (BL-EEG) can be used as a substitute for OR-EEG to lower the total cost of CEA while maintaining optimal safety. Methods: Three hundred and three patients undergoing 331 CEAs by two surgeons with EEG monitoring from June 1991 to May 1995 had BL-EEG. BL- and OR-EEG were retrospectively analyzed and blindly graded without knowledge of clinical status or outcome of operation. One surgeon shunted only those patients with EEG changes after clamping (EEGA) while the second shunted all patients with prior CVA or any EEG abnormality prior to or after clamping. Results: The incidence of major neurological morbidity and mortality was 1.8%. BL-EEGs were abnormal in 105 patients (32%). While BL-EEG changes were highly predictive of EEG changes after anesthetic induction (P < O.OOOl), they were not predictive of EEG changes with clamping or of clinical outcome. Prior CVA predicted abnormal BL-EEGs (P c 0.0001) and postanesthetic (P c 0.0001) EEGs but did not predict changes with clamping or perioperative CVA. EEGAs with clamping occurred during 18% of operations; such changes were predicted only by contralateral occlusion (ICA-Occ; P < 0.0016) and EEGA during a prior contralateral CEA (P < 0.001). The only variable which predicted an adverse neurological outcome was the presence of a contralateral occlusion which
CARDIOVASCULAR SURGERY SEPTEMBER 1997
&~ebfovasculaf
increased the likelihood of a perioperative neurological event seven-fold (I’ = 0.0038). Clinical outcomes in the 57 of 105 patients with abnormal BL-EEGs and the 49 of 83 with prior CVA who were shunted were not different from those who were not. Conclusions: The policy of routine shunting for prior CVA should be re-examined. BL-EEG is not of value for the prediction of adverse events during CEA and can be eliminated. Because contralateral occlusion is highly predictive of changes with clamping and patients undergoing a second CEA will usually manifest EEGA changes identical to those at the first, OR-EEG monitoring can be eliminated from both these circumstances. The resultant cost savings from these findings, however, is debatable, since only a small percentage of patients would be affected. Justification for continued use of OR-EEG will require proof of its costeffectiveness.
1.6 Results of Conservative Management of Residual and Recurrent Lesions after Carotid Endarterectomy
KEN
]I RICOTTA and MS. O’BRIEN-IRR, tit&u York, USA
SURGERY
SEPTEMBER
1.7 Prior Stroke Does not Increase the Risk of Carotid Endarterectomy P.E. PARRINO, M. LOVELOCK, R.C. KING. K. SHOCKEY C.G. TRIBBLE and IL. KRON, Charlottesville, Virginia, USA Carotid endarterectomy has become a safe procedure with less than a 5% combined morbidity and mortality in most major centers. However, the timing of surgery following a stroke has been controversial. The anecdotal strategy has been to wait a minimum of 6 weeks prior to carotid endarterectomy. This delay, however, may result in additional neurological events. Our hypothesis was that in select patients, this high risk period can be shortened by performing elective carotid endarterectomy less than 6 weeks after a stroke. To analyze this question, we compared three groups of patients. Group I had surgery less than 6 weeks after a stroke (mean time = 16.5 days -c 2.76). These patients had small infarcts by CT scan and severe carotid stenoses. Group II had surgery more than 6 weeks following a stroke. Group III is a control group of carotid endarterectomies done between I January 1986 and 1 May 1994.
Buffalo, Gr024p
Routine treatment of significant lesions after carotid endarterectomy (CEA) has been advocated, despite the lack of data on the natural history of such lesions. Objective: Our objective was to document long-term follow-up of patients with recurrent or residual lesions whose initial management has been non-operative. Methods: Patients with residual or recurrent stenoses, > 50% diameter, were identified from a carotid data base. Residual lesions were identified ~6 months after CEA while recurrent lesions occurred >6 months. The clinical course of patients with these lesions was compared to that of patients who had no residual lesions after CEA using life table analysis and the LEE-DESU statistics. Results: Duplex and clinical follow-up were available on 384 cases. Residual lesions were seen in 12 patients (3.1%) including four postoperative occlusions. Only one patient underwent re-operation for a residual lesion. Recurrent stenoses ~50% were seen in 24 patients (10 patients 50-79%, 12 patients 75-99%, two occlusions). The risk of restenosis was 8.6% at 3 years, 14% at 5 years and was associated with contralateral disease progression (I’ c 0.001). Although most of these lesions could be followed initially, (85% at 3 years, 79% at 5 years) 15/24 arteries eventually required re-operation: 12 for symptoms, three asymptomatic lesions with progressive proximal lesions or severe complex contralateral disease. The late stroke rate was increased in patients with residual or recurrent lesions (18% versus 6% at 5 years. P = 0.16 by LEE-DESU). Conclusions: Recurrent stenosis is more common in patients with progressive contralateral disease, emphasizing the importance of ongoing atherosclerosis. Although these lesions can be safely watched over the short-term, the late stroke rate is increased 3-fold in patients with recurrent or residual disease and many require late operation due to symptoms or progression of disease. Elective operation on patients with reasonable life expectancy is indicated.
CARDIOVASCULAR
I
1997
Group I Group II Group III 'P = NS (0.3621
Prior stroke does not increase the risk of carotid endarterectomy in either patient group. Early post-stroke surgery, if done for tight stenosis in patients with small infarcts, can be done with low morbidity and mortality. A more aggressive surgical approach may be warranted in neurulogically stable patients with limited strokes and tight stenoses to avoid new events or carotid occlusion while awaiting delayed surgery.
1.8 Is Preoperative Cardiac Testing Necessary Prior to Elective Carotid Endarterectomy? S. MELTSER, 0.W BROWN, I? BENDICK and J. GLOVER, Southfield, Michigan, USA The high incidence of coronary artery disease tn patrents with peripheral and cerebrovascular occlusive disease has been well established. While preoperative cardiac evaluation had been shown to be beneficial in patients undergoing elective aortic reconstruction, the role of preoperative cardiac testing in patients undergoing elective carotid endarterectomy had not been defined. In this study, the charts of 289 consecutive patients undergoing elective carotid endarterectomy between 1 January 199.5 and 31 December 1995 *were evaluated to determine the need for cardiac “clearance” prior to surgery. Ages ranged from 48 to 98, with a mean age of 70.4 years. The
3