ANNALS Vol. 184
OF SURGERY
July 1976
No. 1
Surgical Progress
Carotid Endarterectomy JESSE E. THOMPSON, M.D., C. M. TALKINGTON, M.D.
UNTIL RECENTLY the prevailing view held by physicians was that strokes were caused by intracranial vascular disease, in spite of the fact that occlusive lesions in the extracranial segments of the main arteries supplying the brain had been described in the mid-1800's and their association with cerebral ischemia noted.33'37 With the development of cerebral arteriography by Moniz in 1927,57 a practical method for precise diagnosis became available. More widespread use of arteriography led to increasing awareness of the extracranial location and segmental nature of atherosclerotic occlusive lesions. This was followed by the rapid development and employment of appropriate vascular surgical techniques for removing or bypassing the offending plaques. It is now estimated that 75% of patients with ischemic stroke syndromes have at least one obstructive lesion at a surgically accessible site,38 and that upwards of 40% have the principal occlusions confined to the extracranial vasculature. The first successful carotid reconstruction for stroke was performed by Carrea, Molins and Murphy in Buenos Aires in 1951,11 while the first successful carotid endarterectomy was done by DeBakey in 1953.17 The operation which gave greatest impetus to development of surgery for cerebral occlusive disease was that of Eastcott, Pickering and Rob, performed in 1954.23 The procedure most commonly employed at present is carotid endarterectomy. 1284
From the Department of General Surgery Baylor University Medical Center, Dallas, Texas
Although endarterectomy is therapeutic in its relief of symptoms, its most important role is prevention of strokes. As experience increases, indications for its use are becoming more precise. However, there has been disagreement in certain clinical categories because of the lack of adequate control data. In 1961, therefore, a nationwide Joint Study of Extracranial Arterial Occlusion was begun "to determine the efficacy of arterial reconstructive surgery in the treatment of cerebrovascular disease."30 The published reports of this randomized study contain a great deal of interesting and important data, although certain key clinical questions were not answered.8'31'38 It is the purpose of this article to review the recent literature on the management of cerebrovascular insufficiency, and present the current status of carotid endarterectomy. A completed frank stroke is a serious and incapacitating disorder with irqcalculable social and economic consequences to the patient and his family. Data from the Mayo Clinic reveal that 27% of patients suffering a thrombotic stroke died within 30 days of onset.91 It is therefore pertinent to consider methods for prevention of stroke based on the natural history of the disease. Symptoms of cerebrovascular insufficiency result from two basic mechanisms: 1) embolization into the brain of platelet aggregations or debris, or 2) reduction in cerebral blood flow. The various manifestations which may result during the development of an atherosclerotic
Submitted for publication February 5, 1976. Reprint requests: Jesse E. Thompson, M. D. Suite 505, 3600 Gaston Avenue, Dallas, Texas 75246. 1
THOMPSON AND TALKINGTON
Ann. Surg.
9
July 1976
Pathophysiology
;-...
...
,
.......
|
|
.
....
0
A
/
..
-.
.'
FIG. 1. Diagram showing the various manifestations which may result during the natural history of development of an atherosclerotic plaque at the common carotid bifurcation, from asymptomatic bruit to total occlusion with acute stroke.
The factors regulating cerebral circulatory responses in normal and pathologic states have been the subject of much recent review.2,25'63 94 The salient features related to surgical considerations will be discussed below. The concept of total cerebral blood flow (CBF) has important therapeutic implications. The functional capacity of the brain, when major vessels are obstructed, is largely dependent on the integrity of the compensatory mechanisms responsible for collateral circulation. The various pathways have been described in detail by Fields et al.29 and by Weibel and Fields.90 The concept of regional cerebral blood flow (rCBF) in addition to total cerebral blood flow is also important. The recent development of methods to measure rCBF using radioactive Xenon-133 isotope has made it possible to obtain much new and pertinent information about events in specific regions of the brain before and after carotid endarterectomy.9 Thus rCBF, total CBF, and pathways of collateral circulation must all be taken into consideration in assessing the influence of specific stenotic lesions on cerebral symptoms and their predicted relief by surgical therapy.
Significance of Stenotic Lesions A carotid lesion is significant if there is a reduction in the diameter of the internal carotid artery (ICA) depicted of 40-50%o or more as measured on the arteriogram.32
plaque at the common carotid bifurcation are in Fig. 1. The ischemic thrombotic stroke due to extracranial lesions begins as a plaque and its first physical manifestation may be an asymptomatic bruit. Frequently the plaque becomes ulcerated and necrotic with deposition of platelets and thrombi on the ulcerated areas which may embolize to cause transient ischemic attacks (TIA's) or frank strokes. As a plaque enlarges and lumen size diminishes, blood flow decreases. The final episode is thrombosis with complete occlusion. Hopefully the first symptom is a TIA, but it may be a hemiplegic stroke. The recognition of emboli as causative factors in producing symptoms has been a significant advance of the past 20 years.55 Likewise, a most important factor in our changing concepts has been the appreciation of the significance of TIA's as forerunners of actual strokes. Several series of untreated patients with TIA's have now been reported. On the average 30% of such patients developed strokes if followed three to five years or longer. 136' 88 Another advance has been the recognition ofamaurosis fugax and other eye symptoms as manifestations of carotid artery disease, from either emboli or reduction in blood flow. Amaurosis fugax is not a benign disease but results in unilateral total blindness in a significant number of cases if untreated.41'50'5'87'8
A 50% reduction in diameter results in a 75% reduction in cross-sectional area of the lumen, at which point significant pressure gradients begin to occur and blood flow begins to fall rather precipitously.16'20 Stenoses of lesser degree are of greater significance if the opposite carotid or vertebral arteries are also compromised, or if multiple stenotic lesions are present. A stenosis of any degree may be significant if its appearance suggests the deposition of platelet thrombi or an ulcerated plaque, sources of cerebral emboli.
Classification of Patients The clinical syndromes of cerebrovascular insufficiency vary from a few minor symptoms to catastrophic stroke with paralysis and coma. Manifestations may be related to the carotid system, vertebral-basilar system, or both. The most common extracranial occlusive lesions amenable to surgical therapy are found in the carotid system. It is important to classify patients into specific clinical categories based on the presenting neurologic status. Only in this way can proper therapy be selected and results of different methods of treatment within the same category be compared. Several classifications of cerebrovascular insufficiency
Vol. 184 . NO. I
CAROTID ENDARTERECTOMY
have previously been described. For purposes of surgical considerations related to carotid endarterectomy we have chosen the following four clinical groups.82 These are: 1) frank strokes -patients with neurologic deficits, including acute profound strokes, progressing strokes, recent and old completed strokes, fluctuating deficits, and mild neurologic deficits of more than 24 hours' duration; 2) transient cerebral ischemia -patients with focal attacks of neurologic dysfunction and transient symptoms of generalized cerebral ischemia lasting minutes or hours, but without residual neurologic deficit at 24 hours; 3) chronic cerebral ischemia -patients with obvious cerebrovascular insufficiency having loss of memory, impaired mentation, or overt motor or mental deterioration; and 4) asymptomatic carotid bruitspatients without neurologic symptoms but with cervical bruits arising from occlusive carotid plaques demonstrated by arteriography. Over the years this classification has proved satisfactory for assessing surgical indications and evaluating results of operation. In addition to a clinical classification, anatomic classification of occlusions by accurate arteriography is also necessary.
3
TABLE 1. Indications for Carotid Endarterectomy in Cerebrovascular Insufficiency
A. Indications 1. Transient cerebral ischemia 2. Stable strokes-selected 3. Asymptomatic bruits-selected 4. Chronic cerebral ischemia-selected B. Contraindications 1. Acute profound strokes 2. Progressing strokes 3. Severe intracranial disease 4. Other severe generalized disorders (e.g., cancer)
the blood-brain barrier as a guide in timing of surgical revascularization.3 Most surgeons have applied clinical criteria to determine operability, using the brain scan as an adjunct. The phonoangiogram has been adapted for study of cervical bruits.22'48 It takes on added significance when used in conjunction with oculoplethysmography.48 Doppler imagery mapping of the carotid artery has been accomplished but is still in the developmental stage.6'80 With perfection of the technology this method promises to be extremely valuable. At present writing the most helpful non-invasive tests derive from an older method of study, ophthalmodynamometry (ODM), which measures and compares the ophthalmic artery pressures of the eyes. It has not enjoyed widespread use, however, because of inaccuracies based on technical difficulties.13 Oculopneumoplethysmography (OP G- Gee), reported most recently by Gee et al.,3 measures ophthalmic artery pressure,72 and when accompanied by carotid compression gives an estimate of ICA stump pressure, and thereby assesses collateral blood flow to the ipsilateral cerebral hemisphere. In Gee's hands the results have been quite accurate. Carotid compression tonography (CCT), as reported by Cohen et al.,13 records volume adjustments within the vascular space of each eye in association with carotid compression, and provides data relative to the contribution each carotid artery makes to blood flow in the respective ophthalmic artery. The test has given a 92% correct correlation with arteriography. Carotid compression does carry slight hazards of cerebral embolization and reflex effects of carotid sinus stimulation. Oculoplethysmography (OPG), as reported by Kartchner et al.,48 compares the ocular pulse waveforms in the two eyes to assess the presence and significance of ICA lesions. Carotid compression is not used. Compared with arteriograms, OPG-Kartchner gave 87%
Diagnostic Studies Arteriography remains the definitive diagnostic maneuver. Four-vessel studies should be considered in every case but need not be routinely carried out unless indicated. Bilateral carotid arteriograms should be done routinely with serial films of the head and neck showing intracranial and extracranial vessels in both anteroposterior and lateral planes. If clinical findings are suggestive of vertebral-basilar as well as carotid insufficiency, one must perform vertebral studies. Many satisfactory techniques for arteriography are now available.38 Direct carotid puncture in the neck may be used together with a percutaneous retrograde brachial technique to visualize both carotid and vertebral-basilar systems. The retrograde catheter approach through the femoral, brachial or axillary arteries is being employed with increasing frequency, visualizing the aortic arch vessels as well as the carotids and vertebrals. Although cerebral arteriography has become progressively safer, it still poses certain hazards.83'88 Therefore non-invasive methods of study have been sought in attempts to avoid unnecessary arteriograms in puzzling diagnostic situations. This field is expanding rapidly as numerous non-invasive techniques are being devised and evaluated at the present time. Cutaneous carotid photoplethysmography34 and directional Doppler studies of supraorbital blood flow49'51'92 are reported to be helpful in predicting total ICA occlusions. Radionuclide angiography has been a correct interpretations. The electronically-based instruments for these latter useful adjunct in the hands of some investigators.10'77'92 Brain scans have been employed in attempts to define three tests are available commercially. Each has its
THOMPSON AND TALKINGTON TABLE 2. Timing of Carotid Endarterectomy for Cerebrovascular Insufficiency
A. Elective operation 1. Stable stroke, recent or old 2. Transient cerebral ischemia 3. Asymptomatic bruit 4. Chronic cerebral ischemia (rare) B. Delayed operation (days to weeks) 1. Mild stroke 2. Fluctuating stroke C. Emergency operation (rarely necessary) 1. Frank stroke a. Disappearance of bruit b. Slowly worsening c. Fluctuating 2. Transient cerebral ischemia a. Severe stenosis, especially if bilateral b. Disappearance of bruit 3. Carotid thrombosis immediately following arteriography or endarterectomy
advantages and limitations. Our own experience has been with the OPG-Kartchner,48 with which we have performed more than 900 examinations. It has proved useful and is singularly free of complications. Further experience and continued innovations in technology will undoubtedly result in refining indications for arteriography and increasing the accuracy of preoperative assessment of cerebral collateral circulation. Indications for and Timing of Operation Indications for carotid endarterectomy are listed in Table 1. The principal indication is transient cerebral ischemia. Patients with recent mild stable strokes or those with old strokes who develop new symptoms may also be candidates. Mild intracranial disease is not a contraindication if severe proximal cervical stenosis is present. Age in itself is not necessarily a contraindication if the patient's general condition otherwise does not pose any undue hazard.
Ann. Surg. * July 1976
The appropriate timing of operation is summarized in Table 2. Although delayed operation is an important principle, emergency operation is not often indicated. There is considerable difference of opinion regarding operation for acute carotid thrombosis following arteriography or endarterectomy. If operation can be performed immediately (one to two hours), it is our opinion that this is a justifiable and worthwhile procedure. Patients with significant bilateral lesions should have bilateral endarterectomies, but in separate stages, at least one to two weeks apart. A number of strokes have occurred in patients with previous unilateral operations whose unoperated lesions were being followed.82 Bilateral operation in a single stage is inadvisable because of the complications which may ensue, including respiratory difficulties, postoperative hypertension, and aggravation of neurologic deficits. Occasionally one finds patients in whom occlusive lesions are located in the ipsilateral or paradoxical carotid artery relative to the neurologic picture. Removal of these "inappropriate" lesions results in a clinical response to be expected had they been located on the appropriate side. Fields has recently published an enumeration of principles for selection of patients for carotid surgery which is in line with the foregoing discussion.32 Indication for operation is also based on a critical evaluation of operative risk," since a high proportion of these patients have hypertension and generalized atherosclerosis, especially coronary disease. Sundt78 has devised a system of five grades of risk employing a combination of medical, neurologic and angiographic factors. Javid et al.46 have applied risk factors specifically to patients with asymptomatic bruits and believe endarterectomy is inadvisable in hypertensive patients over the age of 65 with a history of myocardial infarction.
aS
OF SURGERY
July 1976
No. 1
Surgical Progress
Carotid Endarterectomy JESSE E. THOMPSON, M.D., C. M. TALKINGTON, M.D.
UNTIL RECENTLY the prevailing view held by physicians was that strokes were caused by intracranial vascular disease, in spite of the fact that occlusive lesions in the extracranial segments of the main arteries supplying the brain had been described in the mid-1800's and their association with cerebral ischemia noted.33'37 With the development of cerebral arteriography by Moniz in 1927,57 a practical method for precise diagnosis became available. More widespread use of arteriography led to increasing awareness of the extracranial location and segmental nature of atherosclerotic occlusive lesions. This was followed by the rapid development and employment of appropriate vascular surgical techniques for removing or bypassing the offending plaques. It is now estimated that 75% of patients with ischemic stroke syndromes have at least one obstructive lesion at a surgically accessible site,38 and that upwards of 40% have the principal occlusions confined to the extracranial vasculature. The first successful carotid reconstruction for stroke was performed by Carrea, Molins and Murphy in Buenos Aires in 1951,11 while the first successful carotid endarterectomy was done by DeBakey in 1953.17 The operation which gave greatest impetus to development of surgery for cerebral occlusive disease was that of Eastcott, Pickering and Rob, performed in 1954.23 The procedure most commonly employed at present is carotid endarterectomy. 1284
From the Department of General Surgery Baylor University Medical Center, Dallas, Texas
Although endarterectomy is therapeutic in its relief of symptoms, its most important role is prevention of strokes. As experience increases, indications for its use are becoming more precise. However, there has been disagreement in certain clinical categories because of the lack of adequate control data. In 1961, therefore, a nationwide Joint Study of Extracranial Arterial Occlusion was begun "to determine the efficacy of arterial reconstructive surgery in the treatment of cerebrovascular disease."30 The published reports of this randomized study contain a great deal of interesting and important data, although certain key clinical questions were not answered.8'31'38 It is the purpose of this article to review the recent literature on the management of cerebrovascular insufficiency, and present the current status of carotid endarterectomy. A completed frank stroke is a serious and incapacitating disorder with irqcalculable social and economic consequences to the patient and his family. Data from the Mayo Clinic reveal that 27% of patients suffering a thrombotic stroke died within 30 days of onset.91 It is therefore pertinent to consider methods for prevention of stroke based on the natural history of the disease. Symptoms of cerebrovascular insufficiency result from two basic mechanisms: 1) embolization into the brain of platelet aggregations or debris, or 2) reduction in cerebral blood flow. The various manifestations which may result during the development of an atherosclerotic
Submitted for publication February 5, 1976. Reprint requests: Jesse E. Thompson, M. D. Suite 505, 3600 Gaston Avenue, Dallas, Texas 75246. 1
THOMPSON AND TALKINGTON
Ann. Surg.
9
July 1976
Pathophysiology
;-...
...
,
.......
|
|
.
....
0
A
/
..
-.
.'
FIG. 1. Diagram showing the various manifestations which may result during the natural history of development of an atherosclerotic plaque at the common carotid bifurcation, from asymptomatic bruit to total occlusion with acute stroke.
The factors regulating cerebral circulatory responses in normal and pathologic states have been the subject of much recent review.2,25'63 94 The salient features related to surgical considerations will be discussed below. The concept of total cerebral blood flow (CBF) has important therapeutic implications. The functional capacity of the brain, when major vessels are obstructed, is largely dependent on the integrity of the compensatory mechanisms responsible for collateral circulation. The various pathways have been described in detail by Fields et al.29 and by Weibel and Fields.90 The concept of regional cerebral blood flow (rCBF) in addition to total cerebral blood flow is also important. The recent development of methods to measure rCBF using radioactive Xenon-133 isotope has made it possible to obtain much new and pertinent information about events in specific regions of the brain before and after carotid endarterectomy.9 Thus rCBF, total CBF, and pathways of collateral circulation must all be taken into consideration in assessing the influence of specific stenotic lesions on cerebral symptoms and their predicted relief by surgical therapy.
Significance of Stenotic Lesions A carotid lesion is significant if there is a reduction in the diameter of the internal carotid artery (ICA) depicted of 40-50%o or more as measured on the arteriogram.32
plaque at the common carotid bifurcation are in Fig. 1. The ischemic thrombotic stroke due to extracranial lesions begins as a plaque and its first physical manifestation may be an asymptomatic bruit. Frequently the plaque becomes ulcerated and necrotic with deposition of platelets and thrombi on the ulcerated areas which may embolize to cause transient ischemic attacks (TIA's) or frank strokes. As a plaque enlarges and lumen size diminishes, blood flow decreases. The final episode is thrombosis with complete occlusion. Hopefully the first symptom is a TIA, but it may be a hemiplegic stroke. The recognition of emboli as causative factors in producing symptoms has been a significant advance of the past 20 years.55 Likewise, a most important factor in our changing concepts has been the appreciation of the significance of TIA's as forerunners of actual strokes. Several series of untreated patients with TIA's have now been reported. On the average 30% of such patients developed strokes if followed three to five years or longer. 136' 88 Another advance has been the recognition ofamaurosis fugax and other eye symptoms as manifestations of carotid artery disease, from either emboli or reduction in blood flow. Amaurosis fugax is not a benign disease but results in unilateral total blindness in a significant number of cases if untreated.41'50'5'87'8
A 50% reduction in diameter results in a 75% reduction in cross-sectional area of the lumen, at which point significant pressure gradients begin to occur and blood flow begins to fall rather precipitously.16'20 Stenoses of lesser degree are of greater significance if the opposite carotid or vertebral arteries are also compromised, or if multiple stenotic lesions are present. A stenosis of any degree may be significant if its appearance suggests the deposition of platelet thrombi or an ulcerated plaque, sources of cerebral emboli.
Classification of Patients The clinical syndromes of cerebrovascular insufficiency vary from a few minor symptoms to catastrophic stroke with paralysis and coma. Manifestations may be related to the carotid system, vertebral-basilar system, or both. The most common extracranial occlusive lesions amenable to surgical therapy are found in the carotid system. It is important to classify patients into specific clinical categories based on the presenting neurologic status. Only in this way can proper therapy be selected and results of different methods of treatment within the same category be compared. Several classifications of cerebrovascular insufficiency
Vol. 184 . NO. I
CAROTID ENDARTERECTOMY
have previously been described. For purposes of surgical considerations related to carotid endarterectomy we have chosen the following four clinical groups.82 These are: 1) frank strokes -patients with neurologic deficits, including acute profound strokes, progressing strokes, recent and old completed strokes, fluctuating deficits, and mild neurologic deficits of more than 24 hours' duration; 2) transient cerebral ischemia -patients with focal attacks of neurologic dysfunction and transient symptoms of generalized cerebral ischemia lasting minutes or hours, but without residual neurologic deficit at 24 hours; 3) chronic cerebral ischemia -patients with obvious cerebrovascular insufficiency having loss of memory, impaired mentation, or overt motor or mental deterioration; and 4) asymptomatic carotid bruitspatients without neurologic symptoms but with cervical bruits arising from occlusive carotid plaques demonstrated by arteriography. Over the years this classification has proved satisfactory for assessing surgical indications and evaluating results of operation. In addition to a clinical classification, anatomic classification of occlusions by accurate arteriography is also necessary.
3
TABLE 1. Indications for Carotid Endarterectomy in Cerebrovascular Insufficiency
A. Indications 1. Transient cerebral ischemia 2. Stable strokes-selected 3. Asymptomatic bruits-selected 4. Chronic cerebral ischemia-selected B. Contraindications 1. Acute profound strokes 2. Progressing strokes 3. Severe intracranial disease 4. Other severe generalized disorders (e.g., cancer)
the blood-brain barrier as a guide in timing of surgical revascularization.3 Most surgeons have applied clinical criteria to determine operability, using the brain scan as an adjunct. The phonoangiogram has been adapted for study of cervical bruits.22'48 It takes on added significance when used in conjunction with oculoplethysmography.48 Doppler imagery mapping of the carotid artery has been accomplished but is still in the developmental stage.6'80 With perfection of the technology this method promises to be extremely valuable. At present writing the most helpful non-invasive tests derive from an older method of study, ophthalmodynamometry (ODM), which measures and compares the ophthalmic artery pressures of the eyes. It has not enjoyed widespread use, however, because of inaccuracies based on technical difficulties.13 Oculopneumoplethysmography (OP G- Gee), reported most recently by Gee et al.,3 measures ophthalmic artery pressure,72 and when accompanied by carotid compression gives an estimate of ICA stump pressure, and thereby assesses collateral blood flow to the ipsilateral cerebral hemisphere. In Gee's hands the results have been quite accurate. Carotid compression tonography (CCT), as reported by Cohen et al.,13 records volume adjustments within the vascular space of each eye in association with carotid compression, and provides data relative to the contribution each carotid artery makes to blood flow in the respective ophthalmic artery. The test has given a 92% correct correlation with arteriography. Carotid compression does carry slight hazards of cerebral embolization and reflex effects of carotid sinus stimulation. Oculoplethysmography (OPG), as reported by Kartchner et al.,48 compares the ocular pulse waveforms in the two eyes to assess the presence and significance of ICA lesions. Carotid compression is not used. Compared with arteriograms, OPG-Kartchner gave 87%
Diagnostic Studies Arteriography remains the definitive diagnostic maneuver. Four-vessel studies should be considered in every case but need not be routinely carried out unless indicated. Bilateral carotid arteriograms should be done routinely with serial films of the head and neck showing intracranial and extracranial vessels in both anteroposterior and lateral planes. If clinical findings are suggestive of vertebral-basilar as well as carotid insufficiency, one must perform vertebral studies. Many satisfactory techniques for arteriography are now available.38 Direct carotid puncture in the neck may be used together with a percutaneous retrograde brachial technique to visualize both carotid and vertebral-basilar systems. The retrograde catheter approach through the femoral, brachial or axillary arteries is being employed with increasing frequency, visualizing the aortic arch vessels as well as the carotids and vertebrals. Although cerebral arteriography has become progressively safer, it still poses certain hazards.83'88 Therefore non-invasive methods of study have been sought in attempts to avoid unnecessary arteriograms in puzzling diagnostic situations. This field is expanding rapidly as numerous non-invasive techniques are being devised and evaluated at the present time. Cutaneous carotid photoplethysmography34 and directional Doppler studies of supraorbital blood flow49'51'92 are reported to be helpful in predicting total ICA occlusions. Radionuclide angiography has been a correct interpretations. The electronically-based instruments for these latter useful adjunct in the hands of some investigators.10'77'92 Brain scans have been employed in attempts to define three tests are available commercially. Each has its
THOMPSON AND TALKINGTON TABLE 2. Timing of Carotid Endarterectomy for Cerebrovascular Insufficiency
A. Elective operation 1. Stable stroke, recent or old 2. Transient cerebral ischemia 3. Asymptomatic bruit 4. Chronic cerebral ischemia (rare) B. Delayed operation (days to weeks) 1. Mild stroke 2. Fluctuating stroke C. Emergency operation (rarely necessary) 1. Frank stroke a. Disappearance of bruit b. Slowly worsening c. Fluctuating 2. Transient cerebral ischemia a. Severe stenosis, especially if bilateral b. Disappearance of bruit 3. Carotid thrombosis immediately following arteriography or endarterectomy
advantages and limitations. Our own experience has been with the OPG-Kartchner,48 with which we have performed more than 900 examinations. It has proved useful and is singularly free of complications. Further experience and continued innovations in technology will undoubtedly result in refining indications for arteriography and increasing the accuracy of preoperative assessment of cerebral collateral circulation. Indications for and Timing of Operation Indications for carotid endarterectomy are listed in Table 1. The principal indication is transient cerebral ischemia. Patients with recent mild stable strokes or those with old strokes who develop new symptoms may also be candidates. Mild intracranial disease is not a contraindication if severe proximal cervical stenosis is present. Age in itself is not necessarily a contraindication if the patient's general condition otherwise does not pose any undue hazard.
Ann. Surg. * July 1976
The appropriate timing of operation is summarized in Table 2. Although delayed operation is an important principle, emergency operation is not often indicated. There is considerable difference of opinion regarding operation for acute carotid thrombosis following arteriography or endarterectomy. If operation can be performed immediately (one to two hours), it is our opinion that this is a justifiable and worthwhile procedure. Patients with significant bilateral lesions should have bilateral endarterectomies, but in separate stages, at least one to two weeks apart. A number of strokes have occurred in patients with previous unilateral operations whose unoperated lesions were being followed.82 Bilateral operation in a single stage is inadvisable because of the complications which may ensue, including respiratory difficulties, postoperative hypertension, and aggravation of neurologic deficits. Occasionally one finds patients in whom occlusive lesions are located in the ipsilateral or paradoxical carotid artery relative to the neurologic picture. Removal of these "inappropriate" lesions results in a clinical response to be expected had they been located on the appropriate side. Fields has recently published an enumeration of principles for selection of patients for carotid surgery which is in line with the foregoing discussion.32 Indication for operation is also based on a critical evaluation of operative risk," since a high proportion of these patients have hypertension and generalized atherosclerosis, especially coronary disease. Sundt78 has devised a system of five grades of risk employing a combination of medical, neurologic and angiographic factors. Javid et al.46 have applied risk factors specifically to patients with asymptomatic bruits and believe endarterectomy is inadvisable in hypertensive patients over the age of 65 with a history of myocardial infarction.
aS
