Risk Of Cerebral Embolism Research Articles

Effect of biologically active coating on biocompatibility of Nitinol devices designed for the closure of intra-atrial communications

Anti-thrombogenicity and rapid endothelialisation are prerequisites for the use of closure devices of intra-atrial communications in order to reduce the risk of cerebral embolism. The purpose of this study was therefore to assess the effect of bioactive coatings on biocompatibility of Nitinol coils designed for the closure of intra-atrial communications. Nitinol coils (n=10, each) and flat Nitinol bands (n=3, each) were treated by basic coating with poly(amino-p-xylylene-co-p-xylylene) and then coated with either heparin, r-hirudin or fibronectin. Anti-thrombogenicity was studied in vitro in a dynamic model with whole blood by partial thromboplastin time (PTT), platelet binding and thrombin generation, respectively, and cytotoxicity by hemolysis. Endothelialisation was studied on Nitinol bands with human umbilical venous endothelial cells (HUVEC) by 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium (MTT) assay and immnuofluorescence analysis of Ki67, vinculin, fibronectin and von Willebrand Factor. Uncoated or coated devices did not influence hemolysis and PTT. r-Hirudin (but not heparin) and fibronectin coating showed lower platelet binding than uncoated Nitinol (p<0.005, respectively). Heparin and r-hirudin coating reduced thrombin formation (p<0.05 versus Nitinol, respectively). HUVEC adhesion, proliferation, and matrix formation decreased in the order: fibronectin coating>uncoated Nitinol>r-hirudin coating>heparin coating>basic coating. MTT assay corroborated these findings. In conclusion, r-hirudin and fibronectin coating, by causing no acute cytotoxicity, decreasing thrombogenicity and increasing endothelialisation improve in vitro biocompatibility of Nitinol devices designed for the closure of intra-atrial communications.

The ICAROS registry of carotid artery stenting. Imaging in Carotid Angioplasties and Risk of Stroke.

ICAROS (Imaging in Carotid Angioplasties and Risk Of Stroke) is a multicenter international registry of carotid artery stenting designed to determine the criteria for identifying patients at higher or lower risk of periprocedural stroke and restenosis at 1 year. The aim of the registry is to improve patient selection and consequently reduce the risk of cerebral embolization during carotid stenting. The registry is open to all interventionists performing carotid stenting, and the participants are free to apply their own endovascular techniques and devices, including cerebral protection mechanisms. All cerebral ischemic events following the procedure will be reported. Follow-up surveillance to 1 year will include periodic duplex scanning and neurological examinations. Echographic plaque images will be standardized for comparison, processed for echodensity, and analyzed by computer at the Registry Center. Correlation will be investigated between the echographic index (gray-scale median) and the risk of embolism and outcome of carotid stenting.

Relation of fibrillatory wave amplitude with hemostatic abnormality and left atrial appendage dysfunction in patients with chronic nonrheumatic atrial fibrillation.

Large left atrium (LA) and LA appendage (LAA) dysfunction are known to relate to cardiogenic thromboembolism, so the present study investigated the relation of the atrial fibrillatory wave (F wave) amplitude to hemostatic markers and LAA function. Transthoracic and transesophageal echocardiographic studies were performed in 82 consecutive patients with chronic, nonrheumatic atrial fibrillation (AF). Patients were divided into 2 groups according to F wave amplitude in lead V1 on the 12-lead ECG: coarse AF (the greatest amplitude of F wave > or =1 mm, n=44) and fine AF (<1 mm, n=38). Plasma levels of thrombin-antithrombin III complex, D-dimer, platelet factor 4 and beta-thromboglobulin were determined. Compared with patients with coarse AF, those with fine AF had lower LAA peak flow velocity (p<0.05) and higher prevalence of embolic cerebral infarction (50% vs 27%, p<0.05). Platelet activity did not differ between the 2 groups; however, plasma levels of thrombin-antithrombin III complex and D-dimer were significantly higher in patients with fine AF than in those with coarse AF (p<0.05). Multiple logistic regression analysis showed that fine AF was independently associated with cerebral embolism. Therefore, the presence of fine F wave in V1 would be a useful marker of LAA dysfunction and hypercoagulability, and indicate a risk for cerebral embolism in patients with chronic, nonrheumatic AF.

Thoracic and thoracoabdominal aneurysm repair under deep hypothermia using subclavian arterial perfusion

Background. Hypothermic circulatory arrest is a valuable adjunct for thoracic and thoracoabdominal aortic aneurysm repair. Retrograde aortic perfusion through the femoral artery, however, carries a risk of cerebral embolism or malperfusion. To avoid these complications we adopted antegrade aortic perfusion through a prosthetic graft attached to the left subclavian artery through a left thoracotomy. Methods. Ten patients had repair of descending thoracic and thoracoabdominal aortic aneurysm under deep hypothermia with antegrade aortic perfusion through the left subclavian artery. Hypothermic circulatory arrest was used because proximal aortic control was hazardous due to rupture or intraluminal disease, or for spinal cord protection. Results. There was no brain injury and one hospital death. The cause of death was massive bleeding from the gastrointestinal tract not related to deep hypothermia or the perfusion method. All 9 survivors were alive and well after a mean follow-up period of 9 months. Conclusions. Using the left subclavian artery as a site of aortic perfusion can avoid retrograde aortic perfusion, hence reducing the potential for brain injury due to embolic stroke or malperfusion through a dissected thoracoabdominal aorta.

High-intensity transient signals indicate a risk of cerebral embolism during left ventricular assist devices

Introduction. Cerebral embolism is still a serious complication during left ventricular assist devices (LVAD). We attempted to elucidate whether high-intensity transient signals (HITS) indicate a risk of cerebral embolism during LVAD in animal model. Methods. LVAD was established with XEMEX (Nippon ZEON) in 10 pigs. Animals were divided into two groups: heparin injection group and no heparin injection group. If HITS count exceeded 1 per 10 minutes, additional heparin was injected. HITS were detected by TC2020 with 2.0-MHz pulsed Doppler at the middle cerebral artery. Results. HITS were significantly reduced by additional heparin (8±3/h to 1±0.7/h, p<0.01). Middle cerebral artery occlusion occurred after rapidly increasing HITS. Issues. HITS can reflect thrombus formation in artificial devices. HITS can indicate a risk of cerebral embolism during LVAD. Monitoring of HITS is useful for preventing cerebral embolism during LVAD.

Rupture of Aortic Arch. A Report of 3 Cases.

A 75-year-old man had sudden congestive heart failure with continuous murmur due to ruptured aneurysm of ductus diverticulum into the pulmonary artery. Patch repair was successfully performed with deep hypothermic selective cerebral perfusion, and adjunctive lower body perfusion through the orifice of the aneurysm. A 71-year-old man with deep shock due to ruptured aneurysm of the aortic arch underwent total aortic arch replace-ment but died of severe brain infarction due to severe atherosclerosis on postoperative day 7. A 72-year-old man with deep shock due to spontaneous rupture of distal aortic arch was successfully operated after diagnosed with repeated computed tomography. Although rupture of the aortic arch is a lethal condition, patients may survive when an urgent operation is performed after appropriate diagnosis and adequate medical support during initial period. Deep hypothermic selective cerebral perfusion is helpful for these patients, but the risk of cerebral embolism due to severely atherosclerotic aorta should be reduced.

Unilateral Antegrade Cerebral Perfusion Through the Right Axillary Artery Provides Uniform Flow Distribution to Both Hemispheres of the Brain

Background —Bilateral antegrade cerebral perfusion (ACP) has decreased in popularity over the past decade because of its complexity and the risk of cerebral embolism. We used magnetic resonance (MR) perfusion imaging to assess flow distribution in both hemispheres of the brain during unilateral ACP through the right carotid artery via a cannula placed in the right axillary artery in conjunction with hypothermic circulatory arrest. Methods and Results —Twelve pigs were randomly exposed to 120 minutes of either bilateral ACP through both carotid arteries (n=6) or unilateral ACP through the right axillary artery (n=6) at pressures of 60 to 65 mm Hg at 15°C, followed by 60 minutes of cardiopulmonary bypass at 37°C. MR perfusion images were acquired every 30 minutes before, during, and after ACP. The brain was perfusion fixed for histopathology. During initial normothermic cardiopulmonary bypass, MR perfusion imaging showed a uniform distribution of flow in the brain. In both the bilateral and unilateral ACP groups, the same pattern was maintained, with an increase in regional cerebral blood volume during ACP and reperfusion. The changes in regional cerebral blood volume and mean transit time were similar in both hemispheres during and after unilateral ACP. No difference was observed between the 2 groups. Histopathology showed normal morphology in all regions of the brain in both groups. Conclusions —Both bilateral ACP and unilateral ACP provide uniform blood distribution to both hemispheres of the brain and preserve normal morphology of the neurons after prolonged hypothermic circulatory arrest.

Unilateral antegrade cerebral perfusion through the right axillary artery provides uniform flow distribution to both hemispheres of the brain: A magnetic resonance and histopathological study in pigs.

Bilateral antegrade cerebral perfusion (ACP) has decreased in popularity over the past decade because of its complexity and the risk of cerebral embolism. We used magnetic resonance (MR) perfusion imaging to assess flow distribution in both hemispheres of the brain during unilateral ACP through the right carotid artery via a cannula placed in the right axillary artery in conjunction with hypothermic circulatory arrest. Twelve pigs were randomly exposed to 120 minutes of either bilateral ACP through both carotid arteries (n=6) or unilateral ACP through the right axillary artery (n=6) at pressures of 60 to 65 mm Hg at 15 degrees C, followed by 60 minutes of cardiopulmonary bypass at 37 degrees C. MR perfusion images were acquired every 30 minutes before, during, and after ACP. The brain was perfusion fixed for histopathology. During initial normothermic cardiopulmonary bypass, MR perfusion imaging showed a uniform distribution of flow in the brain. In both the bilateral and unilateral ACP groups, the same pattern was maintained, with an increase in regional cerebral blood volume during ACP and reperfusion. The changes in regional cerebral blood volume and mean transit time were similar in both hemispheres during and after unilateral ACP. No difference was observed between the 2 groups. Histopathology showed normal morphology in all regions of the brain in both groups. Both bilateral ACP and unilateral ACP provide uniform blood distribution to both hemispheres of the brain and preserve normal morphology of the neurons after prolonged hypothermic circulatory arrest.

Analysis of ultrasonic Doppler velocity data obtained in models of stenosed carotid bifurcations with irregular lesion surface

In this study properties are concerned of ultrasonic Doppler spectra recorded distal to an irregularity localised in the internal carotid artery of a true-to-scale elastic model of a severely stenosed carotid bifurcation. Four models differing in irregularity were obtained by melting graded holes in the original wax cast, about 5-7 mm distal to the bifurcation. Velocity data were collected using an HP Sonos 2500 ultrasonograph working in pulsed Doppler mode. The observed effect of the irregularity with respect to the smooth wall model consisted in: (1) presence of a reduced flow zone 15 mm distal to the severe irregularity situated at the outer wall of the model in the ICA branch; (2) presence of a recirculation zone 15 mm distal to the severe irregularity situated at the inner wall of this model; (3) negative values of the measure of symmetry of the Doppler spectrum and (4) decreased values of relative width of Doppler spectra obtained 25 mm distal to the bifurcation in models with severe irregularity. The alterations of flow distribution and Doppler spectra depend on the geometry of the model under investigation and this study provides an indication as to what phenomena can happen in a model of stenosed carotid bifurcation with irregular lesion surface and how these phenomena may affect the ultrasonic Doppler spectra. Such information could be used in the evaluation of the risk of cerebral embolism.

Visualization of Ventricular Fibroelastoma With a Video-Assisted Thoracoscope

Left ventricular papillary fibroelastomas are associated with a high risk of cerebral embolization. Two-dimensional echocardiography and intraoperative transesophageal echocardiography are helpful in diagnosing tumors, planning a surgical approach, and achieving adequate excision. A video-assisted thoracoscope via the left atrium was used to visualize a left ventricular papillary fibroelastoma. Thoracoscopic visualization facilitated excision of a mass within the chordae tendineae between the anterolateral papillary muscle and the left ventricular wall. Video-assisted thoracoscopy greatly facilitates exposure/excision of deeper intracavitary left ventricular masses. (Ann Thorac Surg 1997;63:221–3)

The effect of wall roughness on velocity distribution in a model of the carotid sinus bifurcation – analysis of laser and ultrasound doppler velocity data

The purpose of this work was to find out whether a rough surface in the sinus of a carotid model affects the flow velocity distribution and the properties of the corresponding ultrasonic Doppler spectrum, in view of potential application to the evaluation of risk of cerebral embolism. True-to-scale elastic models of carotid artery were used in the experiments. Experiments were performed in three models with varying severity of roughness and a normal (physiological healthy) model. The different degrees of roughness in the three models were created by melting graded holes in the wax cast used to make the model. Velocity data were collected using 4 Mhz pulsed ultrasonic and single component laser Doppler velocimeters. The roughness resulted in modified velocity distribution, affecting to various extent ultrasonic Doppler spectral parameters, in particular the measure of symmetry of spectral distribution.

Preventing Systemic Embolization in Patients with Atrial Fibrillation

Patients with atrial fibrillation have an annual risk of stroke of 4.5%. Randomized clinical trials have reliably demonstrated that for every 1000 atrial fibrillation patients treated with warfarin, there is a reduction of 31 strokes per year at a cost of 3 major bleeds per year (including cerebral hemorrhage). Aspirin therapy is also effective for the reduction of stroke, although less so than warfarin; the bleeding risk is less with aspirin. It is possible to select patients at particularly high risk of cerebral embolism based upon simple clinical and echocardiographic parameters. Ongoing clinical trials are evaluating regimens of warfarin versus aspirin, combinations of warfarin and aspirin, and low-dose warfarin.

Central Nervous System Complications After Cardiac Surgery

Central nervous system (CNS) complications (disturbance of consciousness, focal motor deficits, and seizures) after coronary artery bypass grafting (CABG) and cardiac valve surgery were studied retrospectively. The incidence of CNS complications was significantly more frequent in CABG (11%, 71/638) than in valve surgery (7%, 24/345). Major contributory factors of CNS complications were preexisting cerebrovascular disease and cardiopulmonary bypass time. In comparison to previous reports, older age, hypertension, diabetes mellitus, and cerebrovascular disease were more common in the patients undergoing CABG. The preexisting cerebrovascular disease and prolonged cardiopulmonary bypass time probably increase the risk of cerebral embolism and/or cerebral hypoperfusion. We conclude that patients undergoing CABG surgery are at greater risk for neurological damage in comparison to those undergoing valve surgery.

Stroke prevention in nonvalvular atrial fibrillation: A review of prospective randomized trials

Patients with atrial fibrillation are at risk for cerebral embolism; however, the roles of chronic anticoagulation or antiplatelet therapy for stroke prevention in patients with nonvalvular atrial fibrillation have been controversial. Recently, the results of three large prospective randomized trials that examined the risks and benefits of warfarin or aspirin for stroke prophylaxis in patients with nonvalvular atrial fibrillation were reported. All three studies revealed a reduction in the stroke rate for patients treated with warfarin and a small incidence of major bleeding. One of the studies also reported a reduced stroke rate in aspirin-treated patients. The reduction of thromboembolic events associated with chronic warfarin therapy appears to outweigh the risks of significant bleeding for most patients with nonvalvular atrial fibrillation. Aspirin may offer an alternative for subgroups of patients who are at low risk for stroke or those who are not good candidates for anticoagulation.

Identifying High-Risk Patients for Percutaneous Transluminal Angioplasty of Subclavian and Innominate Arteries

We have performed percutaneous transluminal angioplasty for 7 subclavian (4 stenoses, 3 occlusions) and 2 innominate (both stenoses) artery obstructions in 7 patients by percutaneous femoral approach in all, and ipsilateral percutaneous brachial puncture in 2, patients. Initial success was obtained in 4 of the 6 stenoses (2 subclavian and both innominate) but in none of the 3 occlusions. Three of the 4 subclavian stenoses were located proximal to the vertebral artery origin and antegrade vertebral flow without subclavian steal was present in 2 of these lesions. Three patients had complications during the procedure. Two of them developed symptoms and signs of cerebral embolization. Both had shown antegrade vertebral flow and no evidence of subclavian steal in the initial angiogram. The third patient developed angina pectoris. The follow-up period ranged from 4 to 18 months (mean 10.8 months) and no re-stenosis was detected. Angioplasty appears suitable for management of a selected group of patients with nonocclusive lesions in whom subclavian steal phenomenon is evident in the initial diagnostic angiogram. The patients with antegrade vertebral flow are at a high risk of cerebral embolization during angioplasty.

An experimental model to assess the value of laser angioplasty in the management of atheromatous disease of the carotid bifurcation

Laser angioplasty is used to vaporize atheroma in limb arteries. The present investigation was undertaken to determine the nature, size and quantity of particulate matter generated, and the appearance of the intima of a carotid artery model after laser treatment. Particulate matter was not significantly increased following treatment of 39 autopsy carotid bifurcations, but superficial plaques were vaporized and the surface of fibrous lesions glazed. It is anticipated that atheromatous carotid vessels would be rendered less thrombogenic and the risk of cerebral embolism reduced later angioplasty.

Percutaneous Transluminal Angioplasty for Experimental Carotid Artery Stenosis

Percutaneous transluminal angioplasty (PTA) is not commonly applied to the carotid artery because of the risk of cerebral embolization and the uncertainty concerning the long-term results. To test its effectiveness and safety, the author performed PTA in dogs with experimentally induced carotid artery stenosis. Under general anesthesia, one carotid artery was exposed by midline incision. Two vascular tourniquets were applied to the artery, 2 to 5 cm apart, and the blood between them was replaced with pentobarbital sodium for 5 minutes. The drug was then removed and the tourniquets released. Angiography revealed the formation of stenotic lesions within 1 to 6 weeks. Histological examination showed the source of stenosis to be thrombi adhering to the vessel wall. PTA was performed 1 week or 3 to 6 weeks after induction of stenosis using either Grüntzig or Dotter catheters. Immediately after PTA, considerable enlargement of stenotic areas was angiographically observed, and no emboli were detected in distal arteries. Histological findings included depressions in the intima, thrombi, and stretching of the internal elastic membrane and tunica media. Angiograms obtained 3 and 6 months after PTA disclosed persistence of dilatation of the carotid lumen and diminution of the inner surface irregularities. Six months after PTA, the histological features included intimal proliferation and rarefaction of the tunica media. On the other hand, stenotic arteries not subjected to PTA were totally occluded by thrombi and intimal proliferation 6 months after induction of stenosis. It is apparent that PTA was effective not only in bringing about dilatation of the carotid artery but also in arresting the progression of stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

A Valveless Counterpulsation Left Ventricular Assist Pump in the Descending Aorta: Hemodynamic Benefit with a Reduced Risk of Cerebral Emboli

Because of valve malfunction and cerebral embolism reported with use of the total artificial heart, the descending aorta was reexamined as a site for a valveless counterpulsation left ventricular assist pump. The pump was introduced into the thoracic aorta at the level of the eighth thoracic vertebra in 11 canine right-heart bypass preparations. Heart rate (110 beats per minute), stroke volume (20 ml), and mean arterial pressure (80 or 100 mm Hg) were precisely controlled. The pump ejection volume was adjusted to equal 1 time or 2 times the stroke volume of the dog. A 20-ml ejection led to an 11% reduction in left atrial pressure, an 11% reduction in peak left ventricular pressure, and a 20% reduction in tension time index (all, p < .05 at a mean arterial pressure of 80 mm Hg). Systolic shortening (ultrasonic crystals) increased by 5% ( p < .05 at a mean arterial pressure of 80 mm Hg). A 40-ml pump ejection led to an 11% reduction in mean left atrial pressure, a 17% reduction in peak left ventricular pressure, and a 21% reduction in tension time index (all, p < .05 at a mean arterial pressure of 80 mm Hg). The systolic shortening increased by 15% ( p < .05). To assess the relative risk of cerebral embolism, albumin spheres (40 to 60 μg) labeled with technetium-99 were injected into the pump chamber in 5 dogs (40-ml ejection, 2.1 ± 0.1 times the dog's stroke volume). Simultaneous sampling from the descending aorta and brachiocephalic artery revealed that 90 ± 4% of the total counts were from the descending aorta and 10 ± 4% were from the brachiocephalic artery. Exposure of the cerebral circulation to blood that had passed through the pump was approximately one-tenth that of the lower body. This valveless counterpulsation left ventricular assist pump, positioned in the descending aorta, significantly improved cardiac function with a greatly reduced risk of cerebral embolism.

Studies in artificial peripheral embolism in the rabbit.

In a study for possible means of diminishing the risk of cerebral embolization following mitral valvulotomy, radio-opaque emboli were injected into the left ventricle of the rabbit's heart and the subsequent distribution of the emboli assessed roentgenographically.The observations may be summarized as follows:1) ligation of the left carotid artery does not increase the risk of cerebral embolization on the other side;2) maintenance of the head in a raised position or manual compression of the carotid arteries diminishes the risk of cerebral embolization;3) combination of the last 2 methods diminishes the risk of cerebral embolization to 2 per cent in comparison with 27 per cent in the control group. No cerebral embolus was found in 4 of 7 animals in this group.