Influence of antiplatelet therapy on cerebral micro-emboli after carotid endarterectomy using postoperative transcranial Doppler monitoring.

AIM: To study the effect of different antiplatelet regimens (APT) on the rate of postoperative TCD registered micro-embolic signals (MES) following carotid endarterectomy (CEA). DESIGN: Prospective, randomised, double-blinded, pilot study. METHODS: The study group of 102 CEA patients (76 men, mean age 66.8 years) was randomised to routine Asasantin (Dipyridamole 200mg/Aspirin 25mg) twice daily (group I; n=39), Asasantin plus 75 mg Clopidogrel once daily (group II; n=33), or Asasantin plus Rheomacrodex (Dextran 40) 100g/L iv; 500 ml (group III; n=30). TCD monitoring of the ipsilateral middle cerebral artery for the occurrence of MES was performed intra-operatively and during the second postoperative hour following CEA. Primary endpoints were the rate of postoperative emboli and the occurrence of cerebrovascular complications. Secondary endpoint was any adverse bleeding. RESULTS: There were no deaths or major strokes. We observed 2 intraoperative TIA's (group II and III) and 1 postoperative minor stroke (group I). In comparison with placebo, Clopidogrel or Rheomacrodex in addition to Asasantin produced no significant reduction in the number of postoperative MES. There was no significant difference between the number of postoperative MES and different antiplatelet regimens. The incidence of bleeding complications was not significantly different between the 3 APT groups. CONCLUSION: In the present study, we could not show a significant influence of different antiplatelet regimens on TCD detected postoperative embolization following CEA.     

The role of transcranial Doppler in carotid artery surgery.

In order to evaluate the usefulness of transcranial Doppler (TCD) in carotid artery surgery, 90 patients who underwent carotid endarterectomy were studied. Transcranial Doppler was performed preoperatively with digital compression of the carotid artery and intraoperatively at the time of cross-clamping, together with routine EEG monitoring. The percentage residual middle cerebral artery velocity (%MCAV) during carotid artery compression or cross-clamping was considered. The intraoperative %MCAV at cross-clamping was compared with the values obtained in the preoperative examination during the compression test and with the EEG data; the EEG records were blindly reviewed by a neurologist and divided into three groups: group A, normal; group B, moderate anomalies and group C, major anomalies. There were no significant differences between preoperative %MCAV (compression test) and intraoperative %MCAV (cross-clamping) by separate analysis of the data related to systolic, diastolic and mean velocity. The systolic, diastolic, mean %MCAV and the Gosling index after cross-clamping were then compared with the EEG data: no significant differences were seen between groups A and B; on the other hand, in all patients with major EEG anomalies (group C) the %MCAV at TCD was reduced to 0. In conclusion, preoperative TCD associated with carotid artery compression appears a safe and useful way of identifying patients at risk of cerebral ischaemia during carotid artery cross-clamping. Patients with no residual flow at intraoperative TCD need to be considered as presenting a very high risk of ischaemia and in this group the use of a shunt is mandatory.     

Middle cerebral artery circulation during carotid surgery. A transcranial Doppler study

OBJECTIVE: Perioperative carotid cross-clamping might induce low stump pressures as well as hypoperfusion of the middle cerebral artery. In this study blood flow velocities in the middle cerebral artery were compared with intraoperative measurements of the poststenotic carotid blood pressure. DESIGN: Forty-one patients with internal carotid artery stenosis were operated on without shunting, under general anesthesia. Poststenotic carotid pressures and middle cerebral artery flow velocities were measured before and during cross-clamping. The hemodynamic responses to preoperative carotid compressions and intraoperative cross-clamping were evaluated. RESULTS: In seven patients the poststenotic carotid blood pressure decreased on clamping despite unchanged or even increased middle cerebral artery blood flow velocities. In all other patients, pressure changes were significantly correlated to the decrease in middle cerebral artery blood flow velocities. Autoregulatory blood flow velocity responses after preoperative common carotid artery compression were not reproducible by cross-clamping. CONCLUSIONS: Stump blood pressure measurements may not reflect middle cerebral artery perfusion in about 20% of thrombendarterectomies performed under general anesthesia. A possible explanation might be dimished cerebral autoregulation and changes in collateral flow distributions.     

Assessment of intracranial hemodynamics in carotid artery disease by transcranial Doppler ultrasound

Noninvasive transcranial Doppler recordings were correlated to the angiographic findings in 77 patients with carotid artery disease. Stenoses reducing the luminal area of the internal carotid artery by 75% or more also reduced the pulsatility transmission index (PTI) of the ipsilateral middle cerebral artery (MCA). The PTI is the pulsatility index of the artery under study expressed as a percent of the pulsatility index of another intracranial artery with presumed unimpeded inflow in the same individual. For stenoses in the 75% to 89% category. PTI reduction was significantly greater in patients with bilateral carotid stenosis, indicating an impaired potential for collateral flow in these patients. The PTI reduction probably reflects both the pressure drop across the stenosis and the cerebral autoregulatory response. Two criteria proved useful in demonstrating collateral MCA supply through the circle of Willis. On the recipient side, retrograde flow in the proximal anterior cerebral artery was demonstrated in 29 of the 31 patients when this flow pattern was disclosed angiographically. In 26 of these patients, the anterior cerebral artery on the supplying side also had clearly increased flow velocity. Increased flow velocities in the proximal posterior cerebral artery were present in 26 of the 30 vessels that were acting as a collateral channel to the ipsilateral MCA.     

Therapy for isolated,low and high grade symptomatic carotid artery stenosis

This study evaluates whether medical therapy alone can achieve satisfactory results in the treatment of low grade carotid stenosis or ulcerated plaques. Out of 525 patients presenting with transient or minor strokes, 64 were found with unilateral extracranial vascular disease as the sole potential source for their neurological symptoms. Utilizing arteriographic criteria, 35 patients with ulcerated plaques or carotid artery stenosis of less than 50% luminal artery diameter were treated conservatively with aspirin and dipyridamole (300 mg/day each). Twenty-nine patients with unilateral internal carotid artery stenosis of greater than 50% luminal artery diameter were treated by means of carotid endarterectomy. Follow-up in the two groups for a mean period of 24-26 months revealed no major strokes or neurological deaths in either group. Myocardial infarction was the major cause of death. Two patients developed subsequent transient ischemic attacks, and one a minor stroke with total recovery in the conservatively treated group. All became asymptomatic when warfarin replaced aspirin therapy. The findings in this study confirmed that "low grade" stenoses can be safely treated by medical measures alone.     

The role of intraoperative transcranial Doppler monitoring in carotid artery surgery

Of 135 carotid artery reconstructions performed under general anesthesia in 127 patients (mean age 68 years), 119 were performed with continuous intraoperative Doppler recording of the middle cerebral artery. This investigation was impossible in nine (6.7%) cases because of the absence of a visible temporal window, and results were deemed uninterpretable in six (4.5%) additional cases. The goals of this study were to test the feasibility and reliability of transcranial Doppler monitoring in the evaluation of intracranial perfusion and to determine the risk of cerebral ischemia during carotid artery clamping. The two outcome parameters measured were mean velocity and percentage of decreased flow in the middle cerebral artery during clamping. Patients were divided into four groups based on variations in these parameters. Groups I and IIA (low risk) represented 69.7% of cases, group IIB (significant risk) represented 21.9%, and group III (major risk) represented 8.4%. Transcranial Doppler monitoring appears to be a reliable means of observing middle cerebral artery flow during carotid surgery and in our opinion provides objective criteria for determining the need for an indwelling shunt. Accordingly, in this study no neurologic complications imputable to clamping were observed. Transcranial Doppler monitoring can also be used to ensure correct functioning of the shunt and to detect intraoperative embolic complications.We thank Marianne Iafisco and Florence Nouoilhit for their secretarial assistance, Joëlle Roggia for her help with the EEG recordings, and Mrs. M. Canova and C. Trontin for their statistical expertise.     

Haemodynamic classification of symptomatic obstructive carotid artery disease

Summary 63 subjects with symptomatic obstructive carotid artery disease were investigated with transcranial Doppler ultrasonography. Their blood velocities at rest (V) in the middle and posterior cerebral artery (MCA and PCA) and in the extracranial internal carotid artery were measured and the pulsatility index (PI) and U_hem index (V _mca ·PI _mca /V _pca ·PI _pca ) calculated. The vasomotor responses in both MCAs were also tested.The subjects were divided into groups based on the findings on physical examination and cerebral computed tomography. In the patient group with lacunar/territorial infarction we found in the stroke hemisphere: V _mca > V _pca , PI _mca = PI _pca and normal values for the U_hem index and total vasomotor reactivity. In the patient group with watershed infarction this hemisphere was characterized by: V _mca < V _pca , PI _mca < PI _pca and subnormal scores for the U_hem index and total vasomotor reactivity. Displaying features from both stroke groups, we obtained in the hemisphere of interest in patients with transient ischaemic attacks: V _mca = V _pca , PI _mca < PI _pca and normal values for the U_hem index and total vasomotor reactivity. Five patients with clinical evidence of stroke but with negative cerebral computed tomography findings had scores similar to those of the watershed group of patients.For the stroke patients, individual measurements of V, PI and total vasomotor reactivity failed to clearly identify to which stroke group a subject might belong. However, such an identification was achieved in all subjects when using the U_hem index. The U_hem index data in patients with transient ischaemic attacks suggest two subgroups with different pathogenesis underlying the ischaemic events.     

Hyperperfusion syndrome after carotid endarterectomy: a transcranial Doppler evaluation

Transcranial Doppler ultrasonography was used to evaluate 2 patients who developed hyperperfusion syndromes after carotid endarterectomy. During the initial postoperative period, each patient had symptoms that were associated with elevated flow velocities in the ipsilateral cerebral vasculature. In addition, vascular resistance of these vessels was found to be abnormally low, as reflected by the Gosling pulsatility index. As the patients' symptoms improved, flow velocities decreased to normal levels and pulsatilities were noted to increase proportionately.     

Role of transcranial Doppler in carotid surgery

Transcranial Doppler is a method for visualizing the intracranial circulation that has applications to the preoperative investigation of cerebrovascular disease. Estimations of the adequacy of collateral circulation around the circle of Willis may be made. In addition, the method may be used for intraoperative monitoring during carotid, cardiac, or neurosurgical procedures.     

Indications for treatment of symptomatic atherosclerotic carotid artery disease

Although the incidence of stroke and stroke mortality have declined during the past few decades, stroke still ranks third as a cause of death and a primary cause of long-term disability in most industrialized societies. Atherosclerotic disease at the carotid bifurcation accounts for approximately 20% to 30% of all ischemic strokes. In this article, the indications for treatment of symptomatic internal carotid artery stenosis are reviewed.     

Natural history of symptomatic and asymptomatic carotid artery occlusion contralateral to carotid endarterectomy: a prospective study

The natural history of carotid occlusion (CO) has generally been analyzed in the presence of a contralateral patent but diseased internal carotid artery (ICA). Few previous studies have focused on the fate of CO contralateral to the side of a prior carotid endarterectomy (CEA). The aim of this study was to analyze the mortality rate and the incidence of cerebrovascular events in the hemisphere ipsilateral to CO (HICO) in patients who had undergone contralateral CEA. The 30-day and long-term outcomes of 153 consecutive patients who had CEA for severe symptomatic and asymptomatic ICA lesions contralateral to a symptomatic or asymptomatic CO over a 15-year period were considered. The endpoints of the study were mortality and neurological events in the HICO. Overall, the 30-day mortality and stroke rates were 0.6% (1/153) and 1.9% (3/153), respectively; the only death was stroke-related and the stroke was ipsilateral to the operated side. The other 2 strokes were ipsilateral to a symptomatic CO. The follow-up was completed for all patients (mean, 7.7 years; range, 1-172 months). Overall, there were 4 late strokes (2.6%), one of them lacunar in a patient with a symptomatic CO, whereas the other 3 were atheroembolic and ipsilateral to the operated ICA. The risk of late stroke in the HICO at 5 and 12 years was 2%. Overall, there were 19 late deaths, none of them stroke-related. CO, with or without symptoms, contralateral to CEA could be considered a locally benign condition in the long term.     

Is transcranial Doppler useful in the detection of internal carotid artery cross-clamp intolerance?

The aim of this study was to test the hypothesis that a drop in the systolic blood flow velocity in the middle cerebral artery of 70% or more, measured by transcranial Doppler, is a better criteria in the detection of cross-clamp intolerance than electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring. After exclusion of patients with a recent stroke, urgent procedures and combined procedures, a transcranial Doppler with compression test was scheduled in 85 patients. In 13 patients the drop was 70% or more and in these patients a transcranial Doppler was also performed during the reconstruction of the internal carotid artery (the study group) under general anaesthesia. A shunt was used because of EEG and SSEP abnormality in one patient. No changes were observed in the remaining patients and no intraoperative strokes were seen. The transcranial Doppler monitoring was unreliable in three patients. During cross-clamp, the systolic blood flow velocity in the middle cerebral artery dropped less than 70% in four and 70% or more in six patients. It is concluded that using a drop of 70% or more of the systolic blood flow velocity in the middle cerebral artery during internal carotid artery cross-clamp, as an indicator of cross-clamp intolerance, will lead to unnecessary shunting.     

Axillary-to-carotid artery bypass grafting for symptomatic severe common carotid artery occlusive disease

PURPOSE: Revascularization of the internal or external carotid arteries is occasionally indicated for symptomatic atherosclerotic common carotid artery occlusion or long-segment high-grade stenosis beginning at its origin. I report the outcome of axillary artery-based bypass grafts to the distal common, internal, or external carotid arteries. METHODS: Between 1981 and 1997, 29 axillary-to-carotid bypass grafting procedures were performed on 28 patients, 15 men and 13 women, with a mean age of 68 years. Indications were transient ischemia in nine patients, amaurosis fugax in four patients, completed stroke in six patients, and nonlateralizing global ischemia in nine patients. Twenty-three common carotid arteries were totally occluded, and six had long-segment stenosis of 90% or greater beginning at the origin. Saphenous vein grafts were used in 25 procedures, and synthetic grafts were used in four. Grafts were placed to 13 internal, eight distal common, and eight external carotid arteries. RESULTS: There were no perioperative deaths; one stroke occurred (3.4%). No lymphatic or peripheral nerve complications occurred. In a 1- to 11-year follow-up period (mean, 4.5 years), there were no graft occlusions, one restenosis of 50% or greater, and two restenoses of 70% or greater. The 1-year stenosis-free rate for 50% or greater stenosis was 93%, and the 5- and 10-year rates were 87%. No late ipsilateral strokes occurred. The 5- and 10-year survival rates were 64% and 28%, respectively. Coronary artery disease was the major cause of late mortality. CONCLUSION: Axillary-to-carotid bypass grafting for severe symptomatic common carotid occlusive disease is safe, well tolerated, durable, and effective in stroke prevention. There is a high late mortality rate because of coronary artery disease in patients with severe proximal common carotid occlusive disease.     

Acute carotid artery stenting in symptomatic high-grade cervical carotid artery stenosis

The safety and efficacy of emergency carotid artery stenting (CAS) for patients with acute ischemic stroke resulting from internal carotid artery stenosis are not established. In this retrospective study, we evaluated outcomes for CAS performed within 2 weeks of acute ischemic stroke for 16 patients treated between December 2009 and February 2014. Cases of internal carotid artery occlusion, internal carotid dissection, or intracranial major arterial trunk occlusion were excluded. Five patients were treated with CAS during the hyperacute phase (within 24 h of stroke onset), three in the advanced phase (within 24 h of stroke-in-evolution after admission), and eight in the acute phase (24 h to 2 weeks after onset). We evaluated modified Rankin scale (mRS) scores 90 days after CAS. For patients treated during the hyperacute phase without intravenous tissue-type plasminogen activator (IV-tPA), two had mRS scores of 2 and one had a score of 3. Two patients treated in the hyperacute phase with IV-tPA had scores of 5: one with symptomatic intracerebral hemorrhage and the other with acute brain swelling. For patients treated in the advanced phase, mRS scores were 1, 3, and 5; the patient with 5 had contralateral cerebral infarction. All patients treated in the acute phase had scores of 2 or lower. Patients treated with IV-tPA in advanced or acute phases had no severe post-CAS complications. CAS was effective and safe for treating ischemic stroke within 2 weeks of onset. However, IV-tPA treatment may be a risk factor for CAS treatment during the hyperacute phase.     

Evaluating middle cerebral artery collateral blood flow reserve using acetazolamide transcranial Doppler ultrasound in patients with carotid occlusive disease

BACKGROUND: The objective of this study is to examine the utility of acetazolamide TCD ultrasound in the evaluation of MCA collateral blood flow reserve in patients with carotid occlusive disease. METHODS: Acetazolamide TCD and cerebral angiography were performed for 28 carotid territories in 14 patients with carotid occlusive disease. The percentage change in mean blood flow velocity and PI in the MCA was measured before and after 1 g of acetazolamide was administered. The carotid territories were divided into groups according their angiographic findings: (1) mild/moderate (<70%) vs severe (> or =70%) extracranial carotid artery stenosis, and (2) active collateral blood flow to the MCA territory vs no collateral blood flow to the MCA. RESULTS: After acetazolamide injection, the percentage increase in mean MCA velocity for mild/moderate vs severe carotid artery stenosis was 43% +/- 10% and 19% +/- 6%, respectively, indicating less collateral blood flow reserve in patients with severe stenosis (P = .04). The percentage decrease in the PI for MCA territories with vs without angiographic evidence of collateral blood flow was 4.6% +/- 4% and 16% +/- 3%, respectively (P = .04), indicating an exhausted vascular reserve in patients with evidence of active collateral blood flow on angiography. CONCLUSIONS: A decrease in the PI after acetazolamide administration represents a safe and noninvasive indicator of limited collateral blood flow reserve to the MCA territory ipsilateral to an extracranial carotid stenosis. Further study into the role acetazolamide TCD has in the preoperative evaluation of these patients, including threshold values, is warranted.     

Transcranial Doppler ultrasound in internal carotid artery and middle cerebral artery disease

Using noninvasive transcranial Doppler sonography, we studied cerebral collateral patterns in 30 patients with stenosis and/or occlusion of the extracranial internal carotid artery (ICA). All patients with unilateral ICA stenosis ⩽ 80% had normal transcranial Doppler findings. 80% of patients with unilateral and 50% of patients with bilateral ICA stenosis of more than 80% including those with occlusion showed a collateralization via the ipsilateral anterior and/or posterior cerebral artery. 20% of patients with unilateral and 50% of patients with bilateral ICA stenoses of more than 80% (including occlusion) had two or three collateral pathways, including the ophthalmic artery. Another ten patients with stenosis or spasm of the middle cerebral artery (MCA) showed increased flow velocities with turbulence in the narrow segment. In four patients with severe MCA disease with a systolic peak velocity of more than 200 cm/s, the Doppler waveform distal to the lesion was damped. Decreased regional cerebral blood flow (rCBF) measured by^99mTc-HMPAO-SPECT was found in two patients with severe MCA stenosis. Another patient with moderate MCA stenosis with a systolic peak velocity of 140 cm/s showed a normal cerebral perfusion pattern.     

Flow redistribution in the major cerebral arteries after carotid endarterectomy: a study with transcranial Doppler scan

PURPOSE: This open single-center prospective study aimed to determine the redistribution of blood flow within the circle of Willis and through collateral pathways after carotid endarterectomy. Blood flow velocity and flow direction in the major cerebral arteries were determined, both at rest and during CO(2) inhalation. METHODS: Carotid endarterectomy was performed in 148 patients with a 70% or greater diameter stenosis of the internal carotid artery while patients were under general anesthesia. Arteriotomy closure was done with a venous patch. Selective shunting was performed with an electroencephalogram. Baseline blood flow velocity of the basal cerebral arteries was measured by means of transcranial Doppler sonography preoperatively (within 1 week before surgery) and 3 months postoperatively. At the same times, cerebrovascular reactivity was calculated during CO(2) inhalation insonating both middle cerebral arteries. RESULTS: Baseline blood flow velocity in the ipsilateral middle cerebral artery hardly changed 3 months postoperatively, but there was a considerable redistribution of flow in the circle of Willis. This was characterized by a decrease in contribution from the contralateral hemisphere through the anterior communicating artery, reduced cerebropetal flow rates in the ophthalmic artery, and smaller contribution of the posterior collateral sources. The CO(2) reactivity on the side of surgery increased in all patients. In patients with a contralateral occlusion, CO(2) reactivity increased on both sides. The redistribution of flow was most pronounced in patients who needed intraoperative shunting and in patients with a contralateral internal carotid artery occlusion. CONCLUSION: After carotid endarterectomy, flow redistribution, as expressed by changes in blood flow velocity values, occurs in the circle of Willis. The contribution of collateral sources is diminished, and the CO(2) reactivity increases, both of which reflect improvement of the hemodynamic condition. The most improvement occurs in patients with contralateral occlusion.     

Patterns of failure of aspirin treatment in symptomatic atherosclerotic carotid artery disease

Over a 24-month period, 291 patients were consecutively admitted to the West Haven Veterans Administration Medical Center with new ischemic neurological symptoms. Of these, 90 patients (31%) developed ischemic neurological symptoms while taking aspirin (aspirin treatment failure). Of those in whom aspirin treatment failed, 66 patients had ischemic symptoms in the distribution of the carotid artery. Aspirin treatment failed in 21 patients with severe carotid stenosis (greater than 75% stenosis). Eleven of these 21 patients had cerebral infarctions while taking aspirin, and 7 of these 11 infarcts occurred without the prior warning of transient ischemic attacks. Aspirin treatment failed in 45 patients with lesser degrees of carotid stenosis. Transient ischemic attack without permanent ischemia was the most common manifestation of failure in these patients. Infarction occurred in only 12 of these 45 patients and in only 4 patients did infarction occur without warning. We conclude that patients with symptomatic high-grade carotid stenosis (greater than 75%) in whom aspirin treatment failed are likely to suffer an infarct without warning as the first sign of treatment failure (P less than 0.033). We suggest that this subgroup of patients should be considered for alternative forms of therapy.