Sequential morphological changes at the site of carotid endarterectomy

In-stent hypodense area at two weeks following carotid artery stenting predicts neointimal hyperplasia after two years

Introduction It has not been reported how long the follow-up study after carotid artery stenting (CAS) should be continued. The purpose of the present study is to clarify the dynamic change of the in-stent neointimal layer and residual arterial lumen by two years following CAS using three-dimensional computed tomography angiography (3D CTA) with volume rendering. Methods Thirty-six stented carotid arteries in 34 consecutive patients were examined by 3D CTA with volume rendering at two weeks and 3, 6, 12, 24 months of follow-up. Results An in-stent hypodense area could be detected in 10 of 36 (27.8%) carotid arteries at two weeks after CAS. In-stent hypodense areas gradually declined thereafter by three months. In the course of longer follow-up, the layer of the in-stent hypodense area (neointimal hyperplasia) continued to grow in size for up to 24 months. Patients with an in-stent hypodense area at two weeks have a thicker layer of neointimal hyperplasia at 24 months than patients without in-stent hypodense area at two weeks' follow-up. The predictive factors for growing neointimal hyperplasia at 24 months in multiple regression analysis are ulcer formation in pretreatment stenosis and the thickness of in-stent hypodense area at two weeks following CAS. Conclusion Our results suggest that follow-up study should be continued for a longer period even if in-stent restenosis could not be detected at one year following CAS. Especially in cases with ulcer formation in pretreatment stenosis and with a subacute in-stent hypodense area after CAS, longer follow-up is strongly recommended.

Long-Term Effect of the Type of Carotid Endarterectomy on Blood Pressure

BACKGROUND

The dissection of the carotid sinus nerve in eversion carotid endarterectomy (eCEA) has been hypothesized to cause an increase in postoperative blood pressure (BP). The objective of this study is to evaluate the effect of eCEA on BP and changes in BP medications over the course of year-long follow-up after eCEA compared with longitudinal incision carotid endarterectomy patch angioplasty (pCEA).

METHODS

A retrospective review of patients who underwent CEA between July 1, 2009 and June 30, 2014 in the Vascular Surgery Department at The University of Iowa Hospital and Clinics was conducted. Demographics, comorbidities, BP, and number, dosage, and type of antihypertensive medications were collected preoperatively, at 30 days, and at 12 months. The differences in BP and medications between pCEA and eCEA patients were compared. Demographic data and comorbidities were compared using t-tests and chi-squared analysis. Differences in BP and medication dosages were analyzed using multivariate analysis of variance.

RESULTS

In total, 363 CEA procedures were performed during the study period, of which 275 procedures were included in the final analysis. Thirty percent of the patients underwent eCEA. Fifty-four percent of the patients who underwent eCEA and 60% of the patients who underwent pCEA were symptomatic. Thirty-day mortality was 1.4% and 12-month mortality was 6.4% for the entire population. No postoperative neurologic deficits, including stroke, were observed. Analysis of BP did not yield a significant difference among preoperative, 30-day, and 12-month follow-up measurements (P = 0.893). There was no significant change to the number and total daily dose of BP medications preoperatively, at 30 days, or at 12 months.

CONCLUSIONS

There is no statistical difference in mortality, morbidity, and patency rates at 30 days and 12 months between pCEA and eCEA. eCEA is also not associated with long-term BP changes compared with pCEA.

Surgical Techniques from Intraoperative Angiographic and Velocimetric Controls in 43 Consecutive Carotid Bifurcation Endarterectomies

From January to November, 1985, 43 carotid bifurcation endarterectomies (CE) were performed with intraoperative functional (Doppler spectrum analy sis) and morphologic (angiography) controls.

In the first 20 cases, after thromboendarterectomy and direct suture, Dop pler showed absence of or no significant variations of frequency in 17 cases, a frequency increase corresponding to a less than 45% diameter reduction steno sis at the apex of the suture in 2 cases, and no flow in the internal carotid artery (ICA) in 1 case. Angiography confirmed the thrombosis in the above mentioned case and showed 3 less than 50% stenoses at the distal end of the arteriotomy: 2 already recognized by Doppler in small-size ICAs and 1 in a medium-size ICA without significant changes of flow. The reason for thrombosis was a distal intimal flap, which was successfully removed; the 2 stenoses in which Doppler and angiography agreed were corrected by patch angioplasty. In the last 23 cases, patch angioplasty was performed routinely in small-size ICAs (6 cases); in 1 case, first treated by a direct suture, Doppler and angiography showed a medium-grade stenosis, immediately corrected; in 1 case both techniques showed a 50% stenosis in a common carotid artery, immediately corrected. The execution of intraoperative angiography in this group of patients al lowed the authors to define the indication for the use of patch angioplasty, never previously employed. Nevertheless, the authors state that, on account of loss of time, costs, and exposure to radiations, intraoperative angiography must be reserved for those cases selected by Doppler spectrum analysis. This method seems to be highly sensitive in recognizing significant technical defects that could lead to an immediate or late failure.

Color duplex sonography in the detection of internal carotid artery restenosis after carotid endarterectomy: comparison with computed tomographic angiography

OBJECTIVES

Internal carotid artery restenosis after carotid endarterectomy is a major postoperative event, but the clinically best suited means for diagnosis of restenosis are still debated. The objective of this study was to evaluate the sensitivity and specificity of color duplex sonography for detection of substantial internal carotid artery restenosis, verified by computed tomographic (CT) angiography.

METHODS

The study group consisted of 210 consecutive patients with internal carotid artery restenosis, defined as restenosis of 50% or greater, verified by color duplex sonography. The degree of restenosis was calculated according to the European Carotid Surgery Trial guidelines. All patients underwent CT angiography. The specificity, sensitivity, positive predictive value, and negative predictive value of color duplex sonography were calculated.

RESULTS

In 85 patients, internal carotid artery restenosis on color duplex sonography was 50% to 69%, whereas in 125 patients it was 70% or greater. When color duplex sonography was compared with CT angiography, only 2 patients in the group with restenosis of 50% to 69% were misclassified by color duplex sonography, in whom CT angiography showed stenosis of 70% or greater. No patient with stenosis of 70% or greater on color duplex sonography was shown to have a lesser degree of restenosis on CT angiography. When compared with CT angiography, color duplex sonography had specificity of 97.7%, sensitivity of 100%, a positive predictive value of 98.4%, and a negative predictive value of 100% for the detection of internal carotid artery restenosis.

CONCLUSIONS

Color duplex sonography can be effectively used as a primary diagnostic tool for evaluation of patients with suspected internal carotid artery restenosis after carotid endarterectomy.

Healing of carotid stents: a prospective duplex ultrasound study

PURPOSE

To study the dynamics of carotid stent healing over a 2-year period using duplex ultrasound imaging.

METHODS

One hundred twelve patients with 121 successfully stented carotid arteries were examined with color-coded duplex ultrasound the day after the stent procedure and at 1, 3, 6, 12, and 24 months in follow-up. The maximal thickness and echogenicity of the layer between the stent and the perfused lumen (SPL) were evaluated. Echogenicity was classified as echogenic if the SPL layer was clearly detected in B mode and echolucent if the SPL layer was barely visible in B mode, its border defined by assistance of color-coded flow.

RESULTS

At day 1, an echolucent SPL layer with a median thickness of 0.7 mm was interpreted as a thrombotic layer, which decreased at 1 month to practically zero (i.e., not detectable). In follow-up, increases in thickness (mainly up to 6 months) and echogenicity (up to 12 months) of the SPL layer were interpreted as neointimal ingrowth. At 3, 6, and 12 months, the median maximal thickness of the SPL layer was 0.5 mm, 0.9 mm, and 1.0 mm, respectively, whereas the percentage of patients with an echogenic SPL layer was 27% (32/119), 56% (66/117), and 95% (105/110), respectively, at the same time intervals. No further change was observed at the 24-month examination.

CONCLUSIONS

Three phases of carotid stent incorporation are defined: (1) an early unstable period soon after stent placement with an echolucent (thrombotic) SPL layer, (2) a moderately unstable phase with ingrowing neointima (1-12 months), and (3) a stable phase from the second year on. These data may indicate the need for different intensities of therapy and surveillance intervals.

Stroke from carotid endarterectomy: when and how to reduce perioperative stroke rate?

OBJECTIVES

To analyse four years of CEA with respect to the underlying mechanisms of perioperative stroke and the role of intraoperative monitoring in the prevention of stroke.

PATIENTS AND METHODS

From January 1996 through December 1999, 599 CEAs were performed in 404 men and 195 women (mean age: 65 years, range: 39-88). All operations were performed under general anaesthesia using computerised electroencephalography (EEG) and transcranial Doppler (TCD). Any new or any extension of an existing focal cerebral deficit, as well as stroke-related death were registered. Perioperative strokes were classified by time of onset (intraoperative or postoperative), outcome (minor or major stroke), and side (ipsilateral or contralateral). Stroke aetiology was assessed intraoperatively by means of EEG, TCD, completion arteriography or immediate re-exploration, and postoperatively by duplex sonography, computerised tomography (CT) or magnetic resonance imaging (MRI) of the head.

RESULTS

Perioperative stroke or death occurred in 20 (3.3%) patients. In four operations stroke was apparent immediately after surgery. Mechanisms of these strokes were ipsilateral carotid artery occlusion (1) and embolisation (3). In 16 patients stroke developed after a symptom-free interval (2-72 h, mean 18 h) due to occlusion of the internal carotid artery on the side of surgery (9). Other mechanisms were: contralateral occlusion of the internal carotid artery (1), postoperative hyperperfusion syndrome (1), intracerebral haemorrhage (1), and contralateral ischaemia due to prolonged clamping (1). In three procedures the cause was unknown.

CONCLUSIONS

In our experience most strokes from CEA developed after a symptom-free interval and mainly due to thromboembolism of the operated artery. We suggest the introduction of additional TCD monitoring during the immediate postoperative phase.

B-mode ultrasonographic investigations of morphological changes in endarterectomized carotid artery

BACKGROUND

The aim of this study was to assess morphological changes in the endarterectomized carotid region using B-mode ultrasonography (USG).

METHODS

USG examinations were performed on 54 Japanese patients who underwent carotid endarterectomy (CEA). The endarterectomized regions were periodically investigated and the intima-media thickness (IMT) was measured.

RESULTS

Postoperative USGs revealed an evident step formation (type I: 20.4%), a gentle slope (type II: 42.6%), or complete smoothness (type III: 37.0%) at the junction of the endarterectomized carotid region and the common carotid artery (CCA). The IMT of the CCA progressively increased from type I to type III. Patients were followed up for an average of 2.7 years. The new intima-media complex (IMC) was confirmed in all cases after 9 months; it was visualized as an isoechoic layer (7%) or a mixture of iso- and hypoechoic layers (93%). Changes in the IMT during the follow-up period were classified into three groups: no change (group I: 23.1%), decrease (group II: 15.4%), and increase (group III: 61.5%).

CONCLUSIONS

USG is useful to clarify the complicated healing processes of the endarterectomized carotid artery.

Combined use of aspirin and heparin inhibits in vivo acute carotid thrombosis

BACKGROUND AND PURPOSE

Carotid atherosclerotic thrombosis is an important cause of ischemic stroke in Western countries. The therapeutic efficacy of either aspirin or heparin alone in this setting is still controversial. Recently we developed a simple model, the "clamp" method, to induce acute carotid mural thrombosis in vivo in guinea pigs. In this study, we used this model to evaluate the antithrombotic effects of aspirin, heparin, and their combination.

METHODS

Sixty-four male guinea pigs were divided equally into control, aspirin, heparin, and combined groups. Physiological saline, aspirin (5 mg/kg body wt), heparin (200 units/kg body wt), or a combination of aspirin and heparin, respectively, was injected via the jugular vein before the use of the clamp method. Thirty minutes after the injection of saline or drug(s), Péan's forceps was used to clamp the carotid artery at a tangent angle for 3 minutes. One hour later, the carotid artery was resected and prepared for observation under a scanning electron microscope or light microscope to evaluate the degree of mural thrombosis.

RESULTS

The results showed that the combination of aspirin and heparin had an excellent effect in inhibiting in vivo acute carotid thrombosis (p < 0.001) and was significantly better than the effect of aspirin alone (p < 0.01) or heparin alone (p < 0.01).

CONCLUSIONS

Our study clearly demonstrated that the combined use of aspirin and heparin produced a much better antithrombotic effect than either agent alone at sites of carotid endothelial injury when given before the injury. This combined regimen may be useful clinically in acute carotid thrombosis secondary to carotid diseases or carotid endarterectomy.

Endothelial cell seeding after carotid endarterectomy in a canine model reduces platelet uptake

Post-endarterectomy platelet deposition may play an important role not only in vessel wall healing, but also in the development of progressive stenosis. Using a canine model, we investigated the effect of endothelial cell seeding on platelet deposition on endarterectomised arteries. Thirteen dogs underwent bilateral carotid intimectomy (5 cm long) and one side was seeded with an average of 2 x 10(6) viable freshly harvested endothelial cells. Blood flow was restored 20 min after seeding. On the contralateral side, a sham-seeding was performed. Deposition of 111indium-labelled autologous platelets was studied with sequential gamma camera images 3-5 h, 1, 2, 3, 4 days and 4 weeks after surgery. Platelet uptake was statistically reduced on the seeded side. Animals were killed at 4 weeks (nine dogs) and 5 weeks (four dogs) after surgery. Seven arteries for each group were found to be occluded. We conclude that endothelial cell seeding on endarterectomised arteries is feasible and reduces platelet uptake. Improvement in the efficiency of seeding and reduction of endothelial cell loss might permit clinical application of this technique.

Histological comparison of autogenous canine fascia lata, Gore-Tex, lyophilized human fascia lata, and autogenous canine vein for vascular patch graft material in a canine arteriotomy model

Autogenous fascia lata has found little clinical use as a vascular patch graft material. Previous experience, however, suggests that it possesses attributes that might make it useful in this regard. To assess its efficacy as a vascular patch graft, nine adult mongrel dogs each underwent four arteriotomies with placements of patch grafts. The four sites included both carotid arteries and both femoral arteries. In each animal, one of four patch graft materials (autogenous canine fascia lata, Gore-Tex, lyophilized human fascia lata, and autogenous canine vein) were placed as patch material at the arteriotomy site utilizing 7-0 running sutures and loop magnification. The site for placement of each graft material was rotated serially in the animals so that each site would have equal numbers of all four graft materials applied. The animals were killed at either 6 to 8 weeks or 11 to 12 weeks after angiography of all four vessels. The specimens were then evaluated histologically. No difference was observed among any of the patch graft materials with regard to myofibroblast plaque formation. Inflammatory responses were noted to be substantially less in the canine fascia lata group than in the other three groups. Granuloma formation, however, appeared to be most significant in the autogenous canine vein group. Only one vessel was occluded. Aneurysm or pseudoaneurysm formation was not noted in any specimen. It appears from the above results that autogenous fascia lata may be an appropriate alternative to currently utilized arterial patch graft materials and that it should be evaluated further for this purpose.

Doppler colour flow imaging after carotid endarterectomy

Sixty-six patients (72 carotid arteries) were examined after carotid endarterectomy (CEA) using Doppler colour flow imaging (DCFI). Examinations were performed 4-18 days (mean: 7 days) after surgery (32 patients, 34 arteries) or between 2 and 100 months (mean: 39 months) after CEA (34 patients, 38 arteries). Minor vessel wall abnormalities were found in 36% in the internal carotid artery (ICA) and in 55% in the common carotid artery (CCA) or bifurcation. One patient had a minor residual ICA stenosis after surgery; two low-grade stenoses and three ICA-occlusions were diagnosed at follow-up. Altered flow patterns occurred most in CCA (90%) and were predominantly located adjacent to the vessel wall and in dilated vascular segments of the CCA. Disturbed haemodynamics in the ICA were less marked (57%) and frequently found in the central vessel lumen or diffusely distributed. We conclude that surgically induced changes of the vessel geometry and residual or recurrent vascular wall abnormalities are often associated with distinct haemodynamic disturbances, which can reliably be detected by DCFI.

The effect of acetylsalicylic acid on the outcome after lower limb arterial surgery with special reference to cigarette smoking

A prospective controlled study of 144 patients with peripheral obstructive arterial disease was undertaken to evaluate the efficacy of acetylsalicylic acid (ASA) treatment (250 mg daily) on the outcome after lower limb arterial surgery which mainly involved endarterectomy. By random enrollment, 2 groups of 72 patients were formed after the surgery. Patients with ASA treatment for 3 months, starting from the seventh postoperative day, were compared with patients who were not treated with ASA. The patients in both groups had similar characteristics as to sex ratio, age, concomitant diseases, preoperative arm-ankle systolic blood pressure index, and type and primary success of the reconstruction. Forty-seven of the ASA-treated and 48 of the untreated patients reported to continue cigarette smoking. Postoperative ASA-treatment protected against local adverse events which occurred in 15 patients (21%) of the ASA-treated group compared with 31 patients (43%) of the untreated group (p less than 0.01). Among heavy smokers (greater than 15 cigarettes/day) the efficacy of antiplatelet treatment was not detectable. These results imply that, in patients with peripheral arterial disease, ASA prevents platelet interaction to endarterectomized and atherosclerotic lower limb arteries thereby affecting the subsequent risk of occlusion; however, heavy cigarette smoking, which is very common among patients with peripheral arterial disease, counteracts the local antithrombotic potency of ASA.

Indobufen versus placebo in the prevention of restenosis after carotid endarterectomy: a double-blind pilot study

A randomized clinical trial was undertaken to assess the efficacy of indobufen in inhibiting platelet adhesiveness in carotid thromboendarterectomy. The patients were treated under double-blind conditions with indobufen and with placebo, and were then assessed by means of scintigraphy with labelled platelets, ultrasonic tomography and angiography for a minimum follow-up period of 6 months. Haematological and clinical assessments were also performed. The results of the study suggest that platelet accumulation in carotid endarterectomy may be an early sign of restenosis; anti-aggregant treatment with indobufen carried out at an early stage prior to surgery inhibited platelet accumulation. The final result showed that anti-aggregant treatment had a positive influence on the short- and medium-term outcome of carotid endarterectomy.

Reoperative carotid surgery

Fourteen patients underwent carotid reoperation for symptomatic recurrent carotid stenosis after previous ipsilateral carotid endarterectomy. Eight of these patients presented with focal transient ischemic attacks, two with strokes, and four with vertebrobasilar insufficiency. Recurrent symptoms in eight patients were similar to those prompting the initial carotid endarterectomy. Symptoms recurred early after previous carotid endarterectomy in 2 patients and late in 12 patients. Eleven patients underwent repeat endarterectomy and carotid patch angioplasty, two patients underwent patch angioplasty alone, and one patient underwent carotid artery replacement with a vein graft. Persistent or recurrent focal symptoms referable to the reoperated carotid artery were not present during follow-up (mean 27.4 months, range 4 to 79 months). Vertebrobasilar symptoms were relieved by carotid reoperation in each patient. Although the natural history of asymptomatic postoperative carotid restenosis is unknown, reluctance to reoperate on symptomatic patients is unwarranted, since carotid reoperation can be performed safely with the expectation that recurrent focal and nonfocal vertebrobasilar symptoms will be relieved.

Long-term effect of carotid endarterectomy on carotid sinus baroreceptor function and blood pressure control

In order to assess whether carotid endarterectomy had any long-term hypotensive effect, by altering the function of the carotid sinus baroreceptors, blood pressure and carotid sinus baroreceptor function were recorded in 25 patients undergoing carotid endarterectomy. No overall change in blood pressure was recorded 6 months after surgery. Sinus function was shown to decrease in 2 (8 per cent), to remain unchanged in 15 (60 per cent) and to increase in 8 (32 per cent) patients 6 months postoperatively. There was no relationship between changes in sinus function and changes in blood pressure over the 6 months period. Thus, carotid endarterectomy has no long-term hypotensive effect.

Platelet deposition at carotid endarterectomy sites in humans

Following carotid endarterectomy, early postoperative thrombosis or late restenosis occurs in up to 20% of vessels. Both complications may be related to platelet mechanisms. To assess platelet deposition at endarterectomy sites, we injected indium-111 labelled platelets in 24 men less than 30 minutes after carotid endarterectomy, with subsequent imaging 24-96 hours later. To determine if deposition decreased over time, 12 patients had follow-up studies 0.5-24 months later. For comparison, 2 control groups were studied: 1) patients with noncarotid surgery (n = 6) and 2) normal young subjects without endarterectomy and without evidence of carotid disease (n = 12). Quantitative analysis was performed performed using a deposition index that compared activity in operated with unoperated sites in surgical patients or activity in the right with left carotid arteries in normal subjects. Patients with recent endarterectomy had a mean deposition index of 1.7 +/- 0.5 (range 1.2-3.5) compared with a similarly determined ratio of 1.1 +/- 0.1 in normal subjects and 1.2 +/- 0.1 in the surgical controls (both p less than or equal to 0.05 vs. acute endarterectomy). At follow-up after endarterectomy, the mean deposition index decreased to 1.0 +/- 0.1, documenting reduced platelet deposition over time. We conclude that the arterial injury of carotid endarterectomy results in early platelet deposition, which is no longer present in most patients who are studied late. These findings suggest a reduction in platelet thrombus formation with time and are compatible with reendothelialization of the endarterectomized surface. This model may be useful for the in vivo assessment of therapies designed to reduce platelet accumulation following endothelial injury in humans.

Effect of perioperative platelet inhibition on postcarotid endarterectomy mural thrombus formation. Results of a prospective randomized controlled trial using aspirin and dipyridamole in humans

A prospective randomized double-blind trial was conducted to study the effect of platelet-inhibiting drugs on mural thrombus formation after carotid endarterectomy. Twenty-two patients undergoing carotid endarterectomy were randomly assigned to perioperative administration of an aspirin/dipyridamole combination or a placebo, and the postoperative results were compared. Autologous indium-111-labeled platelets were injected postoperatively, and platelet deposition was measured at the endarterectomy site. It was found that the treated group had a significant reduction in platelet accumulation compared with the placebo group. The results suggest that the perioperative use of aspirin/dipyridamole may reduce the risk of operative stroke and the long-term risk of repeat carotid stenosis.

Quantitative effects of antiplatelet therapy on healing of the endarterectomized canine aorta

This study was designed to quantitatively evaluate the effects of an antiplatelet agent, ibuprofen, on mural thrombus formation and pseudointimal development in the endarterectomized canine aorta. A 3 cm segment of abdominal aorta was endarterectomized in 18 dogs. Nine dogs served as controls and nine dogs were treated with ibuprofen (12.5 mg/kg) given intravenously 1 hour preoperatively and orally (7.5 mg/kg) three times a day in the postoperative period. Three dogs were killed from each group at 7, 14, and 21 days. Healing of the endarterectomized aortic segment was assessed by means of computer-assisted surface morphometry, light microscopy, and both scanning and transmission electron microscopy. One week postoperatively, the thrombus-free surface in the treated dogs was 75 percent, compared with 20 percent in control animals; at 2 weeks 97 percent, compared with 38 percent and at 3 weeks 98 percent, compared with 38 percent (p less than 0.01 for each group). The thickness of the pseudointima was 9 percent of the aortic wall thickness in treated dogs compared with 60 percent in control animals 1 week postoperatively (p less than 0.001); at 2 weeks 24 percent in treated animals and 64 percent in control animals (p less than 0.001); and at 3 weeks 31 percent in treated animals and 55 percent in control animals (p less than 0.05). Partial reendothelialization was observed 1 week postoperatively and complete reendothelialization at 3 weeks in both the control and treated animals. These data suggest that administration of preoperative and maintenance therapy with ibuprofen significantly reduces mural thrombus formation and pseudointimal thickness in the endarterectomized canine aorta.

Early versus delayed heparin reversal after carotid endarterectomy in the dog. A scanning electron microscopy study

The present study investigates the hematological reaction to arterial injury during the first 10 minutes after endarterectomy in dogs to determine if heparin reversal during this early period predisposes to thrombus formation. Known platelet physiology would predict that heparinization during this early period would be useful to allow a fibrin-free platelet monolayer to form. After systemic heparinization (145 mu/kg) of the experimental animals, 42 endarterectomies were performed. Blood flow was then resumed for specific periods of time, and the vessels were prepared for scanning electron microscopy. Group 1 vessels (from the unheparinized control group) revealed mural thrombus formation after 10 minutes of blood flow. Group 2 vessels revealed the progressive formation of a fibrin-free platelet monolayer after 2, 5, or 10 minutes of blood flow resumption under systemic heparinization. Group 3 arteries, harvested at 10 minutes, underwent immediate (within 1 to 2 minutes after resumption of flow) heparin reversal with protamine sulfate, and demonstrated numerous patches of fibrin covering the platelet monolayer. Group 4 arteries, studied after 3 hours of blood flow, also underwent immediate heparin reversal. Two of these seven specimens had clumps of fibrin overlying the platelet monolayer. The Group 5 vessels had heparin reversal at 10 minutes, and demonstrated no fibrin overlying the platelet monolayer after 3 hours of blood flow. This study demonstrates the formation of a fibrin-free platelet monolayer over the endarterectomized vessel wall within 10 minutes of resumption of flow under systemic heparinization. These findings suggest that heparin may safely be reversed following a carotid endarterectomy if one awaits the initial critical 10 minutes of blood flow.

The effect of heparin reversal after carotid endarterectomy in the dog. A scanning electron microscopy study

The purpose of this study was to determine reversal of heparin, immediately after carotid endarterectomy would have an adverse effect on the thrombogenicity of the endarterectomized vessel wall. After systemic heparinization, unilateral common carotid endarterectomies were performed under the operating microscope on 14 dogs. Half of the animals were given protamine sulfate to reverse the heparin. Three hours after resumption of blood flow, these arteries, as well as contralateral vessels used as controls for fixation technique, were perfused with glutaraldehyde and prepared for scanning electron microscopy (SEM). Thrombin clotting times were measured throughout the experiments. Sections of the endarterectomized portions viewed by SEM showed nearly total coverage of the exposed collagen of the media with flattened platelets. There were scattered leukocytes, but few erythrocytes, little fibrin, and no true thrombus. There were no difference between the animals that received heparin reversal and those that did not. A group of five additional arteries underwent the same procedure except that no heparin was given. As expected, large amount of thrombus had formed within the lumina of these control vessels by 3 hours. Since previous studies suggest that arterial thrombosis usually occurs within 3 hours of endothelial injury, the authors conclude that total reversal of heparin does not increase thrombogenicity of the endarterectomized vessel. This suggests that heparin may be safely reversed in patients to help maintain postoperative hemostasis.

Re-endothelialization of microvascular carotid end-to-side anastomosis in the rat

A carotid end-to-side anastomosis was performed on 25 male and female Wistar rats (mean weight 197.8 gm). The animals were sacrificed at time intervals varying from 0 to 21 days after the operation. The anastomosis was exposed, the aorta cannulated, and the animals perfused with a 2.5% buffered glutaraldehyde solution at a constant pressure of 80 mm Hg. The anastomoses were removed for scanning electron microscopic (SEM) and light microscopic studies. The SEM results indicate that after the acute platelet-fibrin reaction in the first 48 hours, the suture line itself becomes re-endothelialized after 4 days. On the stitches, however, a cellular population consisting of leukocytes transforming into flattened cells was seen after 2 days. The morphology of these cells and their role in the regeneration of endothelium is discussed. This study presents evidence supporting a blood-borne genesis of endothelial cells in vivo.

Reconstitution of "totally" occluded internal carotid arteries: angiographic and technical considerations

The authors describe their experiences with five patients with delayed transient ischemic symptoms homolateral to internal carotid artery (ICA) occlusions. In each instance, initial arteriograms were interpreted as showing irreversible occlusions of these arteries in the neck and microvascular bypass procedures were contemplated. However, after repeat arteriographic evaluations with a modified injection technique, certain angiographic features were identified that suggested the mechanism of the symptoms in these patients and that their ICA's could be reconstituted in the neck. This was successfully accomplished in each patient with complete relief of ischemic symptoms. The angiographic technique employed and the arterial flow patterns identified in these patients are discussed. The details of the operative technique are described. It is concluded that routine arteriographic techniques may be inadequate to identify the reversible carotid occlusion. This may account for some of the confusion which surrounds the surgery of these vessels as well as the failure of extracranial-intracranial bypass to relieve recurrent ischemic symptoms in these individuals.

Carotid endarterectomy. Temporal profile of the healing process and effects of anticoagulation therapy

The healing of the canine carotid endarterectomy was defined at intervals from 30 minutes to 3 months after surgery by means of angiography, light microscopy, and scanning electron microscopy. Immediately after flow was established, a fibrinplatelet carpet formed on the endarterectomized surface. A typical thrombus formed on this initial layer resulting in vessel occlusion in 52% of non-heparinized animals. By 48 hours after surgery, there was little evidence of active thrombus formation, and reendothelialization from existing endothelial cells was noted. One week later, most of the mural thrombus had disappeared and re-endothelialization was well underway; by 3 months after surgery, re-endothelialization was complete. Intraoperative heparinization resulted in a striking reduction in mural thrombus formation and 100% patency rate. Vessel closure with vein-patch grafts resulted in no improvement of vessel patency. However, the results of this aspect of the study cannot be totally extrapolated to human carotid endarterectomy for the reasons discussed. The survival of the vein-patch grafts was investigated.

Recurrent stenosis at site of carotid endarterectomy

Five patients studied by the authors and 28 mentioned in the literature indicate that recurrent stenosis occurs in no less than 0.6% of patients after carotid endarterectomy. The pathology of the recurrent stenosis was stated in only 10 cases indicating atherosclerotic disease in various stages of development in 7 and a fibrous intimal hyperplasia in 3. Correlation between risk factors for the development of atherosclerosis and the pathology of the recurrent disease was poor. Six patients developed recurrent disease despite postoperative prophylactic oral anticoagulation. Surgical technique appeared to have contributed to re-stenosis in 8 patients (1) by failure to remove the distal tongue of plaque or (2) narrowing of the lumen by the arteriotomy suture or (3) damage by a vascular clamp. In 18 symptomatic patients, 44% had symptoms by 3 years, 67% by 5 years, and 83% by 7 years after operation. The 8 patients with possible errors in surgical technique did not develop symptoms earlier than the other patients. Seventeen symptomatic patients had surgical correction of the re-stenosis (endarterectomy 9, vein patch 6, arterial homograft 1, not detailed 1). The incidence of recurrent stenosis after carotid endarterectomy is low and usually the operation provides a patent artery for life.

Effect of anticoagulants and inhibitors of platelet aggregation on thrombotic occlusion of endarterectomized cat carotid arteries

Cat carotid arteries measuring 1.8 to 2 mm in diameter were endarterectomized under the operating microscope over a 1-cm segment and the arteriotomy was closed with a 9-0 monofilament nylon suture. Vessels exhibiting significant narrowing of the lumen due to faulty closure of the arteriotomy were excluded from the study. The vessels were divided into six groups according to the method of treatment of the animals: control, aspirin, Coumadin, Coumadin plus aspirin, heparin for less than four hours, and heparin for four to eight hours. All vessels in the untreated group subjected to simple arteriotomy and closure remained patent. Only heparin demonstrated an apparent beneficial effect after endarterectomy with 100% of the vessels treated more than four hours and 30% of those treated less than four hours remaining patent. This is contrasted to a 0% patency in other endarterectomized vessels.