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.     

Impact of cervical internal carotid clamping and radial artery graft bypass on cortical arterial perfusion pressure during craniotomy

Strategic cervical internal carotid occlusion is employed either temporarily or permanently in various neurosurgical procedures. The aim of the present study was to assess changes in cortical arterial pressure during cervical internal carotid cross-clamping before and after the placement of radial artery (RA) graft bypass in the treatment of complex carotid artery aneurysms. Perfusion pressure of the middle cerebral artery (MCA) was assessed in 22 patients with complex carotid aneurysm treated with RA graft bypass. Regional cerebral blood flow was assessed postoperatively using single-photon computed tomography. Mean cortical blood pressure (mcBP) was found to be 48.2?±?24.2 and 97.0?±?24.0 % of baseline after clamping the cervical internal carotid artery and opening the RA graft bypass, respectively. Cerebral perfusion pressure estimated by the mcBP failed to sustain a critical limit of greater than 70 mmHg under craniotomy in 16 out of 20 (80 %) patients. There was an inverse correlation in mcBP between the baseline and after the placement of the RA graft bypass (r?=?0.66, P?<?0.005). Postoperative regional cerebral blood flow in the MCA territory on the ipsilateral side of the aneurysm was 97?±?7 % of that of the contralateral side after internal carotid artery (ICA) ligation combined with RA graft bypass. Substantial pressure reductions in cerebral cortical arteries were observed during the cervical internal carotid cross-clamping. Perfusion pressure in peripheral cortical arteries after the placement of the RA graft bypass was comparable to the state before ICA clamping.     

Double-insurance bypass for internal carotid artery aneurysm surgery

OBJECTIVE: The aim of this article is to present the usefulness of a double-bypass method in the surgical treatment of complex internal carotid artery (ICA) aneurysms. For patients with clippable but complex aneurysms of the ICA having poor collateral circulation, bypass surgery is needed before temporary occlusion of the ICA. We propose a double bypass for safety. METHODS: The superficial temporal artery was anastomosed to the distal cortical branch of the middle cerebral artery (MCA), followed by anastomosis between the radial artery and the inferior trunk of the MCA. For patients with clippable ICA aneurysms, the radial artery was temporarily anastomosed to the inferior trunk of the MCA by raising the ipsilateral forearm to the head after the radial artery was harvested. After the aneurysm had been clipped, the anastomosed radial artery was cut close to the anastomosed site and repositioned back to the original arm. RESULTS: This double-bypass procedure was performed in two patients, and no ischemic complications related to revascularization were observed. Temporary occlusion times of the MCA for superficial temporal artery-to-MCA anastomosis and radial artery-to-MCA anastomosis were 30 and 46 minutes in one patient and 28 and 55 minutes in another. CONCLUSION: This surgical procedure, which we called "double-insurance bypass," can reduce the risk of ischemic complications associated with revascularization of the ICA.     

Management of internal carotid artery occlusion

Although attempts to restore patency of occluded internal carotid arteries are now rarely made, endarterectomy in the contralateral artery, external carotid endarterectomy and until recently EC/IC bypass have remained surgical options in the management of such patients. Over a four-year period at this institution 104 patients underwent carotid endarterectomy for stenosis. In this group the contralateral carotid was patent (Group A). Fifty-four patients with unilateral carotid artery occlusion underwent contralateral endarterectomy (Group B), 8 underwent ECA/ICA bypass (Group C) and 4 an ECA endarterectomy (Group D). No statistically significant difference was noted in perioperative stroke and death rates for Groups A and B were (1% and 1%) and (3.7% and 1.9%) respectively. One Group C patient died from perioperative stroke (12.5%). For late events the life table adjusted annual rates for stroke and mortality were similar, Group A (stroke 2.1% and death 5%), and Group B (stroke 1.6% and death 5%). In Group C stroke rate was 10% and death 3%. All four patients undergoing ECA endarterectomy were relieved of their symptoms. It is concluded that in patients with internal carotid artery occlusion TEA may be performed with perioperative morbidity and mortality rates comparable to those when the opposite carotid artery is patent. The late outcome for stroke compares favorably with the reported natural history of the disease and outcome for such patients treated medically in the Joint Study of Extracranial Occlusion and EC-IC Bypass Study. External carotid artery endarterectomy appears useful in the treatment of embolic events on the occluded side. ECA/ICA bypass does not appear to confer benefit.     

Spontaneous intracranial internal carotid artery dissection treated by intra-arterial thrombolysis and superficial temporal artery-middle cerebral artery anastomosis in the acute stage--case report--

A 22-year-old man presented with sudden onset of right retro-orbital headache followed by left hemiparesis. Right carotid angiography demonstrated almost total occlusion of the intracranial internal carotid artery (ICA) and severe stenosis of the middle cerebral artery (MCA), presumably caused by arterial dissection. Local arterial injection of urokinase was performed 2 hours after onset. The ICA became patent, but the M2 portion of the MCA was still occluded, and the left hemiparesis did not improve. Superficial temporal artery-MCA anastomosis was immediately performed. The left hemiparesis disappeared completely 6 days after this procedure. Angiography 2 weeks after the onset revealed occlusion of the ICA, and maintenance of blood flow to the right cerebral hemisphere via the anastomosis. Magnetic resonance imaging showed small infarcts in the right cerebral cortex. Repeat angiography after 5 months showed recanalization of the right ICA and the right MCA. Combination of thrombolytic therapy and bypass surgery may be a useful treatment option for patients with sudden occlusion of the intracranial artery caused by dissection.     

The haemodynamic value of external carotid artery collateral blood supply in carotid artery disease

In the presence of severe obstruction of the internal carotid artery (ICA) blood supply to the ipsilateral hemisphere may be provided by collaterals. Whereas the circle of Willis in many cases makes a substantial contribution to cerebral perfusion, the value of collateral blood supply originating from the external carotid artery (ECA) is not clear. In thirty-five patients undergoing carotid endarterectomy (24 with proven external carotid artery collaterals) intra-arterial blood pressures were measured across the ICA stenosis, prior to endarterectomy. In order to evaluate the haemodynamic value of ECA collaterals, the distal ICA pressure was measured with and without the ECA clamped. In addition, volume blood flow in the common carotid artery was measured with and without the ECA clamped, before and after endarterectomy. No significant change in distal ICA pressure was observed when the ECA was clamped, whether or not external carotid artery collaterals had been demonstrated preoperatively. The greatest reduction in mean distal ICA pressure observed upon ECA clamping was 8 mmHg. However, this only occurred in three of 11 patients with a severe pressure reduction across the stenosis. ICA blood flow increased significantly following endarterectomy whereas ECA flow was reduced. This study indicates that ECA collaterals in most cases do not contribute substantially to cerebral perfusion. Endarterectomy of the ECA, in order to improve cerebral circulation, seems justified only in selected cases, where the distal ICA pressure has been shown to be severely reduced.     

Haemodynamic changes in the cerebral circulation of the cat during occlusion of the middle cerebral artery

Summary In a group of 21 cats, the middle cerebral artery pressure (MCAP) was recorded by means of a catheter introduced into the artery at its origin, just distal to the occlusion. The effects of hypertension, hypercapnia, and hypocapnia were studied.In a group of five cats, both middle cerebral arteries (MCA) were catheterized and the pressure was recorded simultaneously on both sides.In another group of five cats, O₂ tension measurements were made with the aid of oxygen electrodes in the brain tissue, the occluded MCA, and the common carotid artery.Some of the results obtained in this study are compared with the results of a previous study where monkeys were used as experimental animals.C. A. F. Tulleken is neurosurgeon at the Ursula Kliniek and staff member of the TNO-GO Workgroup in Clinical Neurophysiology, both at Wassenaar.     

Carotid angioplasty with internal carotid artery flow reversal is well tolerated in the awake patient

OBJECTIVE: The purpose of this study was to evaluate the neurologic tolerance and changes in ipsilateral hemispheric oxygen saturation during transcervical carotid artery stenting with internal carotid artery (ICA) flow reversal for embolic protection. PATIENTS AND METHODS: This was a prospective study of 10 patients (mean age 68 years) undergoing transcervical carotid angioplasty and stenting. All ICA stenoses were greater that 70%. Seven patients had an ipsilateral hemispheric stroke (3) or transient ischemic attack (4), two patients had a contralateral stroke, and one patient was asymptomatic. Nine procedures were done under local anesthesia. Cerebral protection was established through a cervical common carotid (CCA) cutdown to create an external fistula between the ICA and the internal jugular vein with temporally CCA occlusion. Venous oxygen saturation (SVO(2)) was continuously monitored through a catheter placed in the distal internal jugular vein. Mental status and motor-sensory changes were categorized and assessed throughout and after the procedure. RESULTS: All procedures were technically successful without significant residual stenosis. Mean ICA flow reversal time was 22 minutes (range, 15 to 32). Common carotid artery (CCA) occlusion produced a slight (SVO(2) = 72.6%+/-9.4) but significant decrease (P =.012) in SVO(2), compared with baseline (SVO(2) = 77% +/-10.5). During ICA flow reversal (SVO(2) = 72.4% +/-10.1) cerebral oxygen saturation did not change compared with CCA occlusion alone (P =.85). Transient balloon occlusion during angioplasty of the ICA (SVO(2) = 64.6%+/-12.9) produced a significant decrease in cerebral SVO(2) compared with CCA occlusion (P =.015) and compared with CCA occlusion with ICA flow reversal (P =.018). No mental status changes or ipsilateral hemispheric focal symptoms occurred during CCA occlusion with ICA flow reversal. One patient with contralateral ICA occlusion sustained brief upper extremity weakness related to the contralateral hemisphere. Five patients sustained a vasovagal response during balloon dilatation, four did not require treatment, and one had asystole requiring atropine injection. Mean SVO(2) saturation was not different in these five patients compared with the five who did not sustain a vasovagal response. No deaths or neurologic deficits occurred within 30 days after the procedure. CONCLUSIONS: Our data suggest that transcervical carotid angioplasty and stenting with ICA flow reversal is well tolerated in the awake patient, even in the presence of symptomatic carotid artery disease. Cerebral oxygenation during ICA flow reversal is comparable to that during CCA occlusion. ICA angioplasty balloon inflation produces a decrease in cerebral SVO(2) significantly greater than that occurring during ICA flow reversal.     

Superficial temporal artery to proximal middle cerebral artery anastomosis: clinical and angiographic long term results

Anastomosis of the superficial temporal artery (STA) with a proximal segment of the middle cerebral artery (MCA) has been proposed as a new cerebral revascularization technique alternative to the conventional bypass on the cortical surface. We introduced this procedure in our surgical practice in 1982 for patients with internal carotid artery (ICA) aneurysms not suitable for direct repair in whom occlusion of the ICA is considered necessary. One patient died because a conventional STA-MCA bypass did not prevent a major stroke caused by a therapeutic ICA occlusion. We are reporting our surgical technique and the immediate and long term clinical and angiographic results in five cases operated on during the period June 19, 1982, through January 19, 1983. The early and late patency rates were good. No neurological complications were observed after the bypass procedure or during a 3-year follow-up period. In our opinion, the use of proximal segments of the MCA as recipient arteries for supratentorial revascularization is a good alternative to the use of cortical surface arteries and, in selected cases, could be the first choice technique.     

Effects of varied cardioplegic perfusion pressure on myocardial preservation with critical coronary stenosis

Inadequate delivery of cardioplegic solution distal to coronary artery stenosis may result in increased injury during ischemic arrest. This study was performed to determine the effects of cardioplegic perfusion pressure on cardioplegia delivery and myocardial preservation in hearts with critical coronary artery stenosis. Twenty dogs underwent 90 minutes of cold potassium cardioplegic arrest with partial occlusion of the circumflex coronary artery. Group 1 received cardioplegia at 50 mm Hg pressure, Group 2 at 90 mm Hg pressure, and Group 3 at 130 mm Hg pressure. It was found that cooling rates were 5.4 degrees, 9.1 degrees, and 18.2 degrees C per minute in the nonischemic area (p = 0.004) and 2.0 degrees, 4.5 degrees, and 7.9 degrees C in the ischemic area (p = 0.008) in Groups 1, 2, and 3, respectively. Total of cardioplegic solution flows were 86, 188, and 262 ml per minute per 100 gm in Groups 1, 2, and 3, respectively (p = 0.001). However, flow did not differ significantly between groups in the ischemic area. Rate of rise of left ventricular (LV) pressure decreased significantly in Groups 1 and 2 but not in Group 3 (p = 0.002). Other measured variables did not differ significantly between groups, although LV function curves showed less deterioration in the high-pressure groups. It is concluded that higher cardioplegic perfusion pressure resulted in more rapid cooling in normal and ischemic areas and slightly better preservation of ventricular function as measured by some indexes. However, preservation was generally good for each of the pressures for up to 90 minutes of ischemia when the septum was consistently cooled to 10 degrees C.     

Protection of anastomotic pathways to the vertebral artery during stenting of external carotid artery stenosis

A 61-year-old man presented with a severe external carotid artery (ECA) stenosis with concomitant ipsilateral internal carotid artery (ICA) occlusion manifesting as amaurosis fugax. The left ophthalmic artery was supplied from the left ECA. The left intracranial ICA was supplied by the collateral flow from the contralateral ICA and ipsilateral ECA through the ophthalmic artery. The left vertebral artery also participated in the latter collateral pathway through the left occipital artery and ascending pharyngeal artery. Percutaneous revascularization of the ECA was performed using a nitinol self-expanding stent. To prevent embolic complications through the ophthalmic or vertebral arteries, distal protection was performed using a balloon. During a 22-month follow-up period, the patient was completely free from any ocular or neurological symptoms. The present case of severe ECA stenosis with ipsilateral ICA occlusion showed that percutaneous balloon angioplasty with stenting is feasible and effective. This intervention requires cautious evaluation of the anastomotic pathways connecting the ECA to the cerebral circulation to avoid embolic complications.     

Percutaneous transluminal angioplasty for multiple brachiocephalic artery stenosis: case report

We encountered a patient with multiple stenotic lesions. He was treated by percutaneous transluminal angioplasty (PTA). The patient, a 59 year-old male, complained of right motor weakness. CT scan showed a multiple low density area (LDA) in the distribution of the right middle cerebral artery (MCA), but did not reveal LDA in the distribution of the left MCA on the affected side. After hospitalization, right motor weakness gradually worsened and aphasia became apparent. A repeat CT scan, 8 days after the stroke, disclosed a new LDA in the left watershed zone and the basal ganglia. Angiographical findings revealed a right ICA occlusion, left ICA stenosis, right VA anaplasia and left subclavian artery stenosis, which proved inadequate for anatomical collateral supply. We treated both the left ICA stenosis and the left subclavian artery stenosis by Dotter balloon dilatation catheter, and successfully obtained sufficient dilatation of the vessels concerned. No complication occurred. PTA is a useful method to use in patients with multiple stenotic lesions which might result in ischemic injury if surgical procedures were used. It would also be of value in cases where surgery using general anesthesia might be highly risky.     

Superficial temporal artery to middle cerebral artery anastomosis. Intraoperative evaluation by fluorescein angiography and xenon-133 clearance.

Fluorescein angiography and xenon-133 (133Xe) clearance studies were performed during surgery on 15 patients who were undergoing superficial temporal artery (STA) to middle cerebral artery (MCA) anastomosis. Fourteen patients had occlusive disease of the internal carotid artery (ICA), and one patient had severe stenosis of the MCA. Before anastomosis, fluorescein angiography showed slow filling of the MCA branches through collateral channels. Focal areas of impaired microcirculatory filling and washout were seen in the territory of severely sclerotic cortical arteries. The findings of preanastomotic 133Xe clearance studies were variable and a uniform pattern of regional cerebral blood flow (rCBF) changes was not defined. In 55% of the patients, rCBF was reduced to 25 ml/100 gm/min or less at one or more detector sites. Fluorescein angiography provided an immediate assessment of anastomotic patency and clearly displayed the distribution of blood entering the epicerebral circulation through the STA. In 67% of patients, multiple MCA cortical branches filled with fluorescein, whereas in 33% filling was restricted to the receptor artery territory. An immediate, substantial (greater than or equal to 15 ml/100 gm/min) increase in rCBF was demonstrated in 73% of patients after anastomosis. The rCBF changes were consistently better in patients with donor and receptor arteries greater than 1 mm in diameter. Redistribution of collateral input acted to increase rCBF in areas distant from the anastomotic site. Some improvement in fluorescein circulation and rCBF also was seen in cortex supplied by sclerotic MCA branches.     

The risk of stroke with occlusion of the internal carotid artery

Reports of all cervicocephalic arteriograms (n = 1836) performed at one institution during a 10-year period were reviewed and the patients were classified into three groups according to the indication for arteriography. Group I included all patients with symptoms or findings compatible with occlusive disease of the carotid or vertebral artery (n = 806). Group II included patients with cerebrovascular symptoms unrelated to carotid or vertebral disease (e.g., patients with subarachnoid hemorrhage) (n = 367). Group III consisted of patients with no evidence of cerebrovascular disease (e.g., patients with primary and metastatic brain tumors) (n = 663). One hundred ten atherosclerotic occlusions of the internal carotid artery (ICA) were found in 106 patients in group I. Fifty-one percent of these patients had a history of stroke before arteriography, 24% had transient ischemic attacks (TIAs) or amaurosis fugax (AF), and 12% had nonhemispheric symptoms. Only 13% (1.7% of group I patients) were without symptoms. Ninety-one percent of the strokes and 75% of the TIAs or AF were ipsilateral to the ICA occlusion. Seventy-six percent of patients with stroke and 80% with ipsilateral TIAs or AF vs only 29% of patients without symptoms had contralateral stenosis of 60% diameter reduction or greater (p less than 0.003). No occlusions of the ICA occurred in groups II or III. Three hundred forty-six patients in groups II and III were more than 60 years of age. Assuming either Poisson or binomial distributions, the incidence of silent ICA occlusion in the population at large older than 60 years was estimated at less than 1% (p less than 0.03).     

The use of esmolol and magnesium to prevent haemodynamic responses to extubation after coronary artery grafting

BACKGROUND AND OBJECTIVE: The haemodynamic responses during extubation can cause complications after open-heart surgery. In this study, we aimed to examine the effect of esmolol and magnesium before extubation on these haemodynamic responses. METHODS: Following the approval of local Ethics Committee, 120 patients having coronary artery bypass grafting with extubation in the intensive care unit were included in the study. Patients were allocated to receive esmolol 1 mg kg-1 (group I, n = 40), magnesium 30 mg kg-1 (Group II, n = 40) or normal saline (Group III, n = 40). Study medication was administered as a 20-min infusion in a volume of 20 mL. Patients were extubated just after termination of the infusion. Heart rate, blood pressure and central venous pressure were recorded prior to drug administration, before extubation, during extubation and 1 min after extubation. RESULTS: Heart rate was lower in Group I than in Groups II (P < 0.05) and III (P < 0.001) and lower in Group II than in Group III (P < 0.05) during extubation. It was also lower in Group I than in Group III (P < 0.05) after extubation. Systolic blood pressure was lower in Group I than in Groups II and III (P < 0.001) during extubation. Diastolic blood pressure was higher in Group III than in Groups I and II during extubation (P < 0.001) and after extubation (P < 0.05). Mean arterial pressure was lower in Group I than in Groups II and III (P < 0.001) during extubation, lower in Group II than in Group III (P < 0.05) during extubation and lower in Group I than in Group III (P < 0.05) after extubation. CONCLUSION: We found that using esmolol before extubation following coronary artery bypass graft surgery prevents undesirable haemodynamic responses while magnesium reduces undesirable haemodynamic responses but does not prevent them.     

Tandem middle cerebral artery-internal carotid artery occlusions: reduced occlusion-to-revascularization time using a trans-anterior communicating artery approach with a penumbra device

Rapid revascularization of tandem extracranial and intracranial acute thromboembolic occlusions can be challenging and can delay restoration of blood flow to the cerebral circulation. Taking advantage of collateral pathways in the circle of Willis for thrombectomy can reduce the occlusion-to-revascularization time significantly, thereby protecting brain tissue from ischemic injury. The authors report using the trans-anterior communicating artery (ACoA) approach by using the Penumbra microcatheter to rapidly restore blood flow to the middle cerebral artery (MCA) territory prior to treating the ipsilateral internal carotid artery (ICA) occlusion. Two patients with acute onset of tandem ipsilateral ICA and MCA occlusions and a competent ACoA underwent rapid revascularization of the MCA using a trans-ACoA approach for pharmaceutical and mechanical thrombolysis with the 0.026-in Penumbra microcatheter. Subsequently, once blood flow was reestablished in the MCA territory via cross-filling from the contralateral ICA, the proximally occluded ICA dissection was revascularized with a stent. Both patients had rapid revascularization of the MCA territory (both Thrombolysis in Myocardial Infarction Grade 3) with the trans-ACoA approach (19 and 36 minutes) followed by treatment of the ipsilateral proximal ICA occlusion. This prevented prolonged MCA ischemia time (72 and 47 minutes for ICA revascularization time saved) that would have otherwise occurred if the dissections were treated prior to revascularization of the MCA. Both patients had improved NIH Stroke Scale scores after the procedure. No adverse events from crossing the ACoA with the Penumbra microcatheter were encountered during the revascularization procedure. The trans-ACoA approach with the Penumbra microcatheter for rapid revascularization of an acutely thrombosed MCA in the setting of a simultaneous ipsilateral proximal ICA occlusion is feasible in patients with a competent ACoA. This technique can significantly minimize ischemic injury by reducing the occlusion-to-revascularization time and allow for MCA perfusion via collateral circulation while treating a proximal occlusion. To the best of the authors' knowledge, this is the first reported trans-ACoA approach with the Penumbra microcatheter and the first to report the utilization of the collateral intracranial circulation to reduce occlusion-to-revascularization time.     

Middle cerebral artery thrombolysis through the contralateral internal carotid artery--case report

A 63-year-old male presented with sudden onset of right hemiplegia and global aphasia. On admission he was stuporous. Computed tomography (CT) revealed no abnormalities except for right intraventricular meningioma found incidentally. Emergency angiography confirmed complete occlusion of the left internal carotid artery (ICA) and left M1 trunk whereas the left ICA bifurcation remained patent. The ipsilateral ICA was permanently occluded with two detachable balloons to prevent thrombus migration into the distal ICA and middle cerebral artery (MCA), followed by thrombolysis of the clot in the ipsilateral M1 through the contralateral ICA with urokinase (total dose 420,000 U) under systemic heparinization. Partial recanalization of the ipsilateral MCA was accomplished. The time interval from onset to recanalization was about 3 hours. Postoperative CT showed no hemorrhagic transformation. Slight right paresis and mild motor aphasia persisted 2 months later and he was transferred to a rehabilitation facility. Thrombolysis of the MCA embolism can be performed through the contralateral ICA in the presence of ipsilateral ICA occlusion.     

Ultrasound carotid artery plaque morphology and perioperative stroke risk in patients undergoing coronary artery bypass grafting

OBJECTIVE: To determine the influence of carotid artery plaque (CAP) morphology on perioperative stroke in coronary artery bypass grafting (CABG). PATIENTS AND METHODS: Ninety-three patient undergoing CABG were studied. CAPs and other lesions including intima-media thickness (IMT) and stenosis were examined by using ultrasound imaging. CAPs were morphologically classified as either homogeneous (HmP) or heterogeneous (HtP). RESULTS: Mean and max IMT were 1.26 +/- 0.15 and 2.44 +/- 0.76 mm. Mean total plaque score was 15.75 +/- 6.82. HmP and HtP were seen in 80 (86.0%) and 54 (58.1%) patients. Stenosis greater than 50% was found in 22 (23.7%) patients. HtP was significantly associated with age (p<0.05), diabetes and severity of coronary artery disease (p<0.01) and stenosis was associated with diabetes and history of cerebrovascular events (p <0.05). Late postoperative stroke occurred in 3 (3.2%) patients during hospitalization. One of them had 90% stenosis in the carotid artery. The others had no carotid stenosis. In all of the 3, the predominant plaques were heterogeneous. CONCLUSION : CAP morphology in patients undergoing CABG was detailed. As well as stenotic lesion, plaque heterogeneity may be a risk factor for perioperative stroke. Diabetes is associated with severity of both plaque heterogeneity and stenosis.     

Cerebral hemodynamics immediately following carotid occlusion

During carotid endarterectomy, we routinely monitor internal carotid artery pressure (P(ICA)) and middle cerebral artery flow velocity (V(MCA)). P(ICA) has been previously shown to accurately reflect pressure at the origin of the middle cerebral artery, even during times of rapidly changing pressure such as occurs with sudden occlusion of the common carotid artery. We retrospectively analyzed pressure recordings around the time of carotid cross clamping in 29 consecutive carotid endarterectomy operations. Suitable transcranial Doppler recordings of V(MCA) were available from eight of the operations. Comparing the cardiac cycle prior to cross clamping with the first complete cardiac cycle after cross clamping, the mean P(ICA) fell from 93 mm Hg to 62 mm Hg and the mean V(MCA) fell from 41 cm x sec-1 to 25 cm x sec-1. Over the subsequent 10 seconds, there was a further decrease in P(ICA) to 51 mm Hg (P <.0001), while V(MCA) changed in the opposite direction, increasing to 32 cm x sec-1 (P <.01). The patients with the greatest decrease in P(ICA) immediately on cross clamping also had the greatest additional decrease over the following 10 seconds (r = 0.74). The increase in V(MCA) during the first 10 seconds after carotid occlusion is well recognized and is presumed to be due to autoregulatory vasodilatation. The simultaneous decrease that we observed in P(ICA) indicates an increase in the pressure gradient along the collateral vessels, which is to be expected during a period of increasing flow along those vessels.     

Prevention of spinal cord injury after cross-clamping of the thoracic aorta

Paraplegia has been a devastating and unpredictable complication following cross-clamping of the thoracic aorta. In this study, the effect of the pressure gradient between the aortic pressure distal to occlusion and cerebrospinal fluid pressure (CSFP), defined as relative spinal cord perfusion pressure (RSPP), on the development of spinal cord injury was investigated. In 32 mongrel dogs, the thoracic aorta just distal to the left subclavian artery was cross-clamped. After a complete loss of somatosensory evoked potentials (SEP) had been confirmed, the dogs were divided into six groups by an additional cross-clamp interval and RSPP as follows: Group I (n = 6): 0 mmHg for 10 minutes; Group II (n = 8): 0 mmHg for 20 minutes; Group III (n = 3): 7.5 mmHg for 20 minutes; Group IV (n = 3): 7.5 mmHg for 40 minutes; Group V (n = 6): 15 mmHg for 40 minutes and Group VI (n = 6): 15 mmHg for 60 minutes. RSPP was adjusted by either withdrawal of cerebrospinal fluid or injection of normal saline solution into the subarachnoid space. SEP were generated by the stimulation of bilateral peroneal nerves. The incidence of postoperative paraplegia was 0% in Groups I and V, 33% in Group III, 50% in Group VI and 100% in Groups II and IV. This study showed that RSPP plays an important role in the development of spinal cord injury during cross-clamping of the thoracic aorta. Therefore, RSPP should be maintained at as high a level as possible in order to prevent spinal cord injury even if SEP disappear during aortic occlusion.