Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Embolic Stroke”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1992

Aortogenic embolic stroke: a transesophageal echocardiographic approach.

BACKGROUND AND PURPOSE: We studied the frequency and grade of atherosclerotic changes in the thoracic aorta and their significance as embologenic lesions in patients with stroke. METHODS: Using transesophageal echocardiography, we evaluated complicated lesions in the thoracic aortas of 62 patients who met our clinical criteria for embolic stroke. A complicated lesion was defined as a raised lesion with an irregular surface or acoustic shadow based on a comparative study of echocardiographic and histopathologic findings. The results were compared with plain radiographic findings and in some cases with computed tomographic or aortographic findings. RESULTS: Twenty-six patients (42%) showed complicated aortic arch lesions on echocardiogram. Transesophageal echocardiography brought us more abundant information than other techniques. Aortic knob calcification by plain radiography correlated well with the presence of echocardiographically complicated lesions, suggesting its utility for rough screening of atherosclerotic changes. Fifty-two patients had other potential embolic sources in the heart or cervical arteries. Among the remaining 10 patients without extra-aortic embolic sources, three showed complicated lesions and were diagnosed as having aortogenic embolic stroke. CONCLUSIONS: Aortic atherosclerosis should be recognized as an embolic source of stroke and the advantage of transesophageal echocardiography recognized in its evaluation.

Adult↗
PubMed2000

Low incidence of embolic strokes with atrial septal aneurysms: A prospective, long-term study.

BACKGROUND: Previous retrospective studies have suggested that atrial septal aneurysms (ASA) are associated with embolic strokes. The purpose of this study was to evaluate prospectively the embolic potential of ASA. METHODS: Of 846 consecutive patients undergoing cardiac surgery from December 1990 to March 1993, we identified 42 patients who had ASA as an incidental finding on intraoperative transesophageal echocardiography. Patency was determined by color and/or contrast echocardiography. The majority of patients were given aspirin postoperatively. Patients were monitored by personal and/or telephone interviews, and their clinical conditions were confirmed by their personal physicians. Any patient with any question of a neurologic event had a detailed neurologic history, examination, and computed tomographic or magnetic resonance imaging scan. RESULTS: The incidence of ASA in our population was 4.9%; there were 22 men and 20 women with a mean age of 72 years. Oscillating ASA were present in 28 patients and fixed aneurysm in 10. The mean diameter of the ASA was 21 +/- 4 mm. Eighteen (56%) of 32 patients had a patent ASA. Patients were monitored for a mean period of 69.5 months (56 to 85 months). No patient had a cerebrovascular event or systemic embolization. CONCLUSION: The risk of cerebrovascular events or embolic strokes in our patient population with incidental ASA was low. If treatment is needed for this condition, aspirin appears to be effective therapy.

Aged↗
PubMed1994

A long-half-life and fibrin-specific form of tissue plasminogen activator in rabbit models of embolic stroke and peripheral bleeding.

BACKGROUND AND PURPOSE: We compared the activity of a new long-half-life, fibrin-specific tissue-type plasminogen activator (TPA) variant with that of wild-type TPA in rabbit models of embolic stroke and peripheral bleeding. METHODS: In the embolic stroke model. TPA-induced clot lysis is followed by continuous monitoring of a radiolabeled clot lodged in the middle cerebral artery. Twenty-four hours after embolization and treatment with either thrombolytic agent or excipient, the brains are removed, fixed, and evaluated for cerebral hemorrhage. In a parallel template bleeding time experiment, the effects of equipotent doses of the two TPA molecules were measured. RESULTS: Infusion of wild-type TPA or bolus administration of the TPA variant resulted in dose-dependent clot lysis. The TPA variant was found to be an order of magnitude more potent than wild-type TPA on a milligram-per-kilogram basis. Unlike wild-type TPA, the variant caused less systemic activation of plasminogen (P < .05) and fewer hemorrhagic transformations in this model (P < .05). The TPA variant did not extend template bleeding times. CONCLUSIONS: These findings show that by combining increased fibrin specificity with decreased plasma clearance, it is possible to produce a thrombolytic agent that is more convenient and more potent than wild-tpe TPA. At the same time the significant reduction in hemorrhagic conversions may be attributable to the conservation of systemic plasminogen seen with this molecule.

Animals↗
PubMed1998

Acute hypertension promotes hemorrhagic transformation in a rabbit embolic stroke model: effect of labetalol.

We examined the relationship between acute hypertension following cerebral embolization and subsequent hemorrhagic transformation (HT) in a rabbit embolic stroke model. We have shown previously that the likelihood and severity of hemorrhage were significantly correlated with the magnitude of an acute hypertensive response to embolization. It was not clear, however, whether hypertension actually caused hemorrhage or was merely a marker of more severe stroke. In the current studies, we attempted to clarify the relationship between acute hypertension and HT by either pharmacologically inducing or attenuating the brief hypertensive response to embolization in rabbits. Under halothane anesthesia, two catheters were implanted in the right carotid arteries of male New Zealand white rabbits, one oriented toward the heart and one toward the brain. The animals were allowed to awaken and were embolized using blood clot emboli injected into the middle cerebral artery. Blood pressure was monitored via the second carotid catheter. In the first experiment, hypertension was induced with angiotensin II, administered at the time of embolization or 1 h later. In the second experiment, we attempted to attenuate the hypertensive response using intravenous labetalol. The animals were sacrificed 18 h after embolization and the brains evaluated for hemorrhage. In the first experiment, administration of angiotensin II immediately after embolization did not increase the hypertensive response to embolization further than that spontaneously occurring, and no angiotensin II-related HT was observed. In contrast, an additional angiotensin-II-induced hypertensive episode 1 h after embolization significantly increased the number of 5-mm serial brain sections displaying HT, from 3.0 +/- .3 (mean +/- SE) in Controls to 5.4 +/- .8 in treated animals. In the second experiment, administration of labetalol (15 mg/kg) significantly reduced the number of brain sections with visible HT, from 3.2 +/- .5 in controls to 1.6 +/- .4 in treated animals. Acute hypertension during the first hour after cerebral embolization promotes HT in this rabbit embolic stroke model. Labetalol prevents blood pressure elevation and reduces the extent of HT in the same model.

Acute Disease↗
PubMed2002

Expression of recombinant adeno-associated virus in the brain of rats with a focal embolic stroke via carotid artery.

OBJECTIVE: To study whether recombinant adeno-associated virus (rAAV) mediated foreign gene, LacZ, could pass the blood brain barrier by intra-carotid artery delivery and express in vivo in ischemic brain of the focal embolic stroke rats to investigate a possibility of delivering foreign gene through carotid artery to treat acute ischemic stroke. METHODS: The carotid artery territory in 41 rats was embolized with or without arterial-like fibrin rich clots to make a model of focal embolic stroke rat. rAAV containing LacZ gene (rAAV-LacZ) was constructed in 293 cells by calcium phosphate cotransfection. The rats were assigned to one of the following treatments: 1 control (without embolism) groups, including PBS treated (n = 6), pLacZ treated (n = 6 ) and rAAV-LacZ treated (n = 6): 2 embolic groups, including embolism + PBS (n =7),embolism + pLacZ (n = 8) and embolism + rAAV-LacZ (n = 8). Brains were cryosectioned and kappa-Gal stain was performed at 2, 4, and 8 weeks, respectively, after transfection, and then infarct volume was measured and the percentage of LacZ staining-positive cells was calculated. RESULTS: In all the control groups and embolism + PBS treated animal, no kappa-Gal staining-positive cells were found, but in embolism + pLacZ (n = 8) and embolism+rAAV-LacZ groups a lot of kappa-Gal staining-positive cells were found. The expression cells were in the tissues around the infarction. The gene expression persisted only nearly four weeks in embolic group with pLacZ. In the embolic group with rAAV-LacZ the expression was very stable during the experiment course (eight weeks) and the percentage of the expressed cells was significantly higher than that of its contralateral areas at the same time points, respectively. CONCLUSIONS: The plasmid vector and rAAV could enter the brain through the ischemia-damaged blood barrier and foreign gene can be expressed in brain. The positive gene expression is mainly in the peripheral areas of the infarction. rAAV as a permanent expression vector may ultimately be used for gene therapy of human ischemia cerebravascular diseases.

Animals↗
PubMed2006

Tadalafil, a long-acting type 5 phosphodiesterase isoenzyme inhibitor, improves neurological functional recovery in a rat model of embolic stroke.

Sildenafil, a type 5 phosphodiesterase isoenzyme (PDE5) inhibitor with a short half-life, increases brain cyclic guanosine monophosphate (cGMP) levels and improves neurological functional recovery when administered after stroke. In the present study, we investigated the effects of tadalafil (Cialis), a long acting PDE5 inhibitor, on brain cGMP levels, neurogenesis, angiogenesis, and neurological function during stroke recovery in a rat model of embolic stroke. Male Wistar rats (n=28) were subjected to embolic middle cerebral artery (MCA) occlusion. Tadalafil was orally administered every 48 h at a dose of 2 mg/kg or 10 mg/kg for 6 consecutive days starting 24 h after stroke onset. Control animals received the equivalent volume of saline at the same time points. For mitotic labeling, bromodeoxyuridine (BrdU, 100 mg/kg) was administered twice a day at 5, 6, and 7 days after stroke. ELISA assays were performed to evaluate the specificity of the effect of tadalafil on cGMP. Treatment with tadalafil at a dose of 2 or 10 mg/kg significantly improved neurological functional recovery compared with saline-treated rats. In addition, tadalafil treatment increased cerebral vascular density and the percentage of BrdU-positive endothelial cells around the ischemic boundary compared with saline-treated rats. Moreover, tadalafil-treated rats showed greater ipsilateral SVZ cell proliferation than saline-treated rats. However, treatment with tadalafil did not reduce infarct volume when compared to the saline group. Tadalafil selectively increased cGMP but not cyclic adenosine monophosphate (cAMP) in brain. Our data demonstrate that treatment of ischemic stroke with tadalafil improved functional recovery, which was associated with increases of brain cGMP levels and enhancement of angiogenesis and neurogenesis.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

Embolic stroke following thrombolytic therapy for myocardial infarction in a patient with preexisting ventricular thrombi.

BACKGROUND: Dislodging of preexisting cardiac thrombi has been a reported but unconfirmed cause of embolic strokes after thrombolytic therapy for myocardial infarction. CASE DESCRIPTION: An 82-year-old woman was admitted with congestive heart failure. Initial echocardiogram demonstrated ventricular thrombi. Three days later she experienced an inferior wall myocardial infarction, and intravenous streptokinase was administered. Six hours later she abruptly developed a global aphasia with a dense right hemiparesis. Repeat echocardiogram did not show any thrombus. CONCLUSIONS: Thrombolytic therapy may have caused embolization of ventricular thrombi. Cardiac conditions that predispose to embolic strokes are not established contraindications to thrombolytic therapy. The potential for thrombolytic therapy to produce embolization in patients with preexisting cardiac mural thrombi should be evaluated.

Aged↗
PubMed2006

Effect of combined therapy with thrombolysis and citicoline in a rat model of embolic stroke.

An approach combining reperfusion mediated by thrombolytics with pharmacological neuroprotection aimed at inhibiting the physiopathological disorders responsible for ischemia-reperfusion damage, could provide an optimal treatment of ischemic stroke. We investigate, in a rat embolic stroke model, the combination of rtPA with citicoline as compared to either alone as monotherapy, and whether the neuroprotector should be provided before or after thrombolysis to achieve a greater reduction of ischemic brain damage. One hundred and nine rats have been studied: four were sham-operated and the rest embolized in the right internal carotid artery with an autologous clot and divided among 5 groups: 1) control; 2) iv rtPA 5 mg/kg 30 min post-embolization 3) citicoline 250 mg/kg ip x3 doses, 10 min, 24 h and 48 h post-embolization; 4) citicoline combined with rtPA following the same pattern; 5) rtPA combined with citicoline, with a first dose 10 min after thrombolysis. Mortality, neurological score, volume of ischemic lesion and neuronal death (TUNEL) after 72 h and plasma levels of IL-6 and TNF-alpha, were considered to assess ischemic brain damage. Compared with controls, the use of citicoline after thrombolysis produced the greatest reduction of mortality caused by the ischemic lesion (p<0.01), infarct volume (p=0.027), number of TUNEL positive cells in striatum (p=0.014) and plasma levels of TNF-alpha at 3 h (p=0.027) and 72 h (p=0.011). rtPA induced reperfusion provided a slight non-significant reduction of infarct volume and neuronal death, but it reduced mortality due to brain damage (p<0.01) although an increase in the risk of fatal bleeding was noted. CiT as monotherapy only produced a significant reduction of neuronal death in striatum (p=0.014). The combination of CiT before rtPA did not add any benefit to rtPA alone. The superiority of the combined treatment with rtPA followed by citicoline suggests that early reperfusion should be followed by effective neuroprotection to inhibit ischemia-reperfusion injury and better protect the tissue at risk.

Animals↗
PubMed2006

Acute embolic stroke after electroconvulsive therapy.

This is the case report of a 44-year-old woman presented with an acute stroke immediately after electroconvulsive therapy (ECT). The patient had no significant medical history other than chronic depression. She was taking sertraline, and she had had multiple previous ECT treatments without any complications. While being monitored in the recovery room within 10 minutes after the last ECT session, she was found to have sudden onset of left-sided flaccid hemiplegia and numbness along with slurred speech. On arrival to our hospital, she was found to have flaccid hemiplegia on the left side involving the face, arm, and leg (face and arm more than the leg involvement), severe dysarthria, and mild neglect syndrome (National Health Institute Stroke Scale of 14). Noncontrast computed tomography (CT) of the head showed no signs of early ischemia, and iodine contrast CT angiography revealed right middle cerebral artery (MCA) (distal M1 segment) clot. Patient received intravenous recombinant tissue plasminogen (rt-PA) at 2.5 hours after the onset of symptoms, and then a total of 3.0 mg of intra-arterial (IA) rt-PA. Angiography at the end of the procedure showed successful recanalization of the M1 segment and normal vessel caliber with adequate distal flow. After the procedure, the patient made rapid improvements in all of her initial symptoms during the first 24 hours. An extensive stroke workup failed to reveal any cause of the stroke, including usual stroke and hypercoagulable risk factors. This was an acute embolic stroke immediately following an ECT, and without the aggressive thrombolytic therapy, the patient's outcome would have been poor because there was an M1 segment clot with a major MCA syndrome with relatively high National Institute of Health Stroke Scale. The neurological side effect profile of ECT is reported to be minimal with most common symptoms being headache, disorientation, and memory complaints. There is no clear cause-and-effect relationship in this case, and the stroke after ECT is extremely rare. In such rare event of stroke while receiving ECT, there is an effective treatment available using both intravenous and IA thrombolysis as reported in this case.

Acute Disease↗
PubMed2006

Angiogenesis and improved cerebral blood flow in the ischemic boundary area detected by MRI after administration of sildenafil to rats with embolic stroke.

To dynamically investigate the long-term response of an ischemic lesion in rat brain to the administration of sildenafil, male Wistar rats subjected to embolic stroke were treated with sildenafil (n=11) or saline (n=10) at a dose of 10 mg/kg administered subcutaneously 24-h after stroke and daily for an additional 6 days. Magnetic resonance images were acquired and functional performance was measured in all animals at 1 day, 2 days and weekly for 6 weeks post-stroke. All rats were sacrificed 6 weeks after stroke and endothelial barrier antigen immunostaining was employed for morphological analysis and quantification of cerebral vessels. Map-ISODATA was computed from T(1), T(2) and T(1sat) maps. ISODATA derived tissue signatures characterize the degree of ischemic injury. Based on the map-ISODATA calculated at 6 weeks, the ischemic lesion for each animal was divided into two specific regions, the ischemic boundary and ischemic core. The temporal profiles of cerebral blood flow (CBF) and tissue signature were retrospectively tracked in these two regions and were compared with histological evaluation and functional outcome. After 1 week of sildenafil treatment, the ischemic lesion exhibited two significantly different regions, with higher CBF level and correspondingly, lower tissue signature value in the boundary region than in the core region. Sildenafil treatment did not significantly reduce the lesion size, but did enhance angiogenesis. Functional performance was significantly increased after sildenafil treatment compared with the control group. Administration of sildenafil to rats with embolic stroke enhances angiogenesis and selectively increases the CBF level in the ischemic boundary, and improves neurological functional recovery compared to saline-treated rats.

Animals↗
PubMed2005

Investigation of neural progenitor cell induced angiogenesis after embolic stroke in rat using MRI.

Using MRI, we investigated dynamic changes of brain angiogenesis after neural progenitor cell transplantation in the living adult rat subjected to embolic stroke. Neural progenitor cells isolated from the subventricular zone (SVZ) of the adult rat were labeled by superparamagnetic particles and intracisternally transplanted into the adult rat 48 h after stroke (n = 8). Before and after the transplantation, an array of MRI parameters were measured, including high resolution 3D MRI and quantitative T1, T1sat (T1 in the presence of an off-resonance irradiation of the macromolecules of brain), T2, the inverse of the apparent forward transfer rate for magnetization transfer (kinv), cerebral blood flow (CBF), cerebral blood volume (CBV), and blood-to-brain transfer constant (Ki) of Gd-DTPA. The von Willerbrand factor (vWF) immunoreactive images of coronal sections obtained at 6 weeks after cell transplantation were used to analyze vWF immunoreactive vessels. MRI measurements revealed that grafted neural progenitor cells selectively migrated towards the ischemic boundary regions. In the ischemic boundary regions, angiogenesis confirmed by an increase in vascular density and the appearance of large thin wall mother vessels was coincident with increases of CBF and CBV (CBF, P < 0.01; CBV, P < 0.01) at 6 weeks after treatment, and coincident with transient increases of K(i) with a peak at 2 to 3 weeks after cell therapy. Relative T1, T1sat, T2, and kinv decreased in the ischemic boundary regions with angiogenesis compared to that in the non-angiogenic ischemic region (T1, P < 0.01 at 6 weeks; T1sat, P < 0.05 at 2 to 6 weeks; T2, P < 0.05 at 3 to 6 weeks; kinvP < 0.05 at 6 weeks). Of these methods, Ki appear to be the most useful MR measurements which identify and predict the location and area of angiogenesis. CBF, CBV, T1sat, T1, T2, and kinv provide complementary information to characterize ischemic tissue with and without angiogenesis. Our data suggest that select MRI parameters can identify the cerebral tissue destined to undergo angiogenesis after treatment of embolic stroke with cell therapy.

Algorithms↗
PubMed2000

Low molecular-weight heparin versus aspirin in patients with acute ischaemic stroke and atrial fibrillation: a double-blind randomised study. HAEST Study Group. Heparin in Acute Embolic Stroke Trial.

BACKGROUND: Patients with acute ischaemic stroke and atrial fibrillation have an increased risk of early stroke recurrence, and anticoagulant treatment with heparins has been widely advocated, despite missing data on the balance of risk and benefit. METHODS: Heparin in Acute Embolic Stroke Trial (HAEST) was a multicentre, randomised, double-blind, and double-dummy trial on the effect of low-molecular-weight heparin (LMWH, dalteparin 100 IU/kg subcutaneously twice a day) or aspirin (160 mg every day) for the treatment of 449 patients with acute ischaemic stroke and atrial fibrillation. The primary aim was to test whether treatment with LMWH, started within 30 h of stroke onset, is superior to aspirin for the prevention of recurrent stroke during the first 14 days. FINDINGS: The frequency of recurrent ischaemic stroke during the first 14 days was 19/244 (8.5%) in dalteparin-allocated patients versus 17/225 (7.5%) in aspirin-allocated patients (odds ratio=1.13, 95% CI 0.57-2.24). The secondary events during the first 14 days also revealed no benefit of dalteparin compared with aspirin: symptomatic cerebral haemorrhage 6/224 versus 4/225; symptomatic and asymptomatic cerebral haemorrhage 26/224 versus 32/225; progression of symptoms within the first 48 hours 24/224 versus 17/225; and death 21/224 versus 16/225. There were no significant differences in functional outcome or death at 14 days or 3 months. INTERPRETATION: The present data do not provide any evidence that LMWH is superior to aspirin for the treatment of acute ischaemic stroke in patients with atrial fibrillation. However, the study could not exclude the possibility of smaller, but still worthwhile, effects of either of the trial drugs.

Administration, Oral↗
PubMed1998

Efficacy of intra-arterial and intravenous prourokinase in an embolic stroke model evaluated by diffusion-perfusion magnetic resonance imaging.

OBJECTIVE: To explore the utility of intravenous (i.v.) prourokinase treatment, we compared intra-arterial (i.a.) and i.v. delivery in a rat embolic stroke model, using diffusion (DWI) and perfusion (PI) magnetic resonance imaging to assess in vivo effects on ischemic lesion evolution and reperfusion. BACKGROUND: Thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA) for acute ischemic stroke is useful during the initial hours after onset. Prourokinase is a novel thrombolytic agent with potential safety advantages in comparison to rt-PA. METHODS: Twenty-four male Sprague-Dawley rats were embolized with autologous blood clots into the middle cerebral artery territory and then randomly assigned at 30 minutes after embolization to a 2-hour bolus infusion with i.a. prourokinase, i.v. prourokinase, or vehicle. DWI and PI were performed before treatment and repeated during and at the end of the treatment. RESULTS: PI demonstrated that both i.a. and i.v. significantly improved the percentage of the ischemic hemisphere that was normally perfused when the 20-minute, pretreatment, and 145-minute after embolization time points were compared; in the control group, the hypoperfused volume increased over time. DWI disclosed that the ischemic lesion evolution slightly decreased in the i.a. group, remained stable in the i.v. group, and increased over time in the control group. Infarct volume by triphenyltetrazolium chloride (TTC) staining was significantly smaller in both treatment groups than controls. CONCLUSIONS: These results demonstrate that i.a. and i.v. therapy with prourokinase are equally effective in promoting reperfusion and inhibiting the development of focal ischemic injury in this rat embolic stroke model.

Animals↗
PubMed1994

Thrombolytic therapy in experimental embolic stroke.

The effect of thrombolytic therapy is well-documented in acute myocardial infarction. In acute cerebral infarction, thrombolytic therapy has been evaluated in small series of patients. The point of thrombolytic therapy is to avoid or reduce ischemic damage of neuronal tissue by rapid arterial recanalization. In thrombolytic therapy of cerebral vascular occlusion, the pathophysiology of reperfusion needs further investigation and documentation. This review describes studies of thrombolysis in embolic stroke using animals embolized by intracarotid injections of blood clots. Vascular occlusion was demonstrated by angiography and measurement of cerebral blood flow. Thrombolytic therapy with recombinant tissue-type plasminogen activator was initiated after varying periods of time. Reperfusion, cellular function, and brain damage were examined by angiography and by clinical and pathoanatomical examination. Based mainly on results from our own investigations, the following theses concerning ischemic stroke were made: (a) Cerebral infarction caused by arterial occlusion is due to delayed, incomplete, or no reperfusion. Spasms, or hemodynamic mechanisms, seem to be of only minor importance. (b) Early thrombolytic therapy in animal models increases the degree of reperfusion and reduces brain damage, clinical deficits, and mortality. (c) Early arterial reperfusion reduces cerebral infarction and related edema. With early reperfusion, the extent of brain damage correlates to the length of the delay from onset of ischemia. (d) Cerebral stunning is caused by arterial occlusion followed by very early spontaneous or induced reperfusion, as neurons temporarily lose their functional capabilities without dying. (e) Multiple embolic microclots in experimental stroke result in more brain damage than a single macroclot, and with clots the extent of brain damage is dependent on the structural composition and volume of emboli. (f) The ability to recanalization in experimental embolic stroke is related to the amount of red cells in the emboli and inversely related to the volume of emboli and to the fibrin content and density of the clots. (g) Infarct-limiting effects in experimental stroke can be obtained by ischemic neuroprotectants or by hypothermia, either alone or with thrombolytic therapy, which then reduces brain damage further.

Animals↗
PubMed2001

Delayed rt-PA treatment in a rat embolic stroke model: diagnosis and prognosis of ischemic injury and hemorrhagic transformation with magnetic resonance imaging.

The authors characterized effects of late recombinant tissue plasminogen activator (rt-PA) administration in a rat embolic stroke model with magnetic resonance imaging (MRI), to assess potential MRI correlates, or predictors, or both, of rt-PA-induced hemorrhage. Diffusion-, perfusion-, and postcontrast T1-weighted MRI were performed between 4 and 9 hours and at 24 hours after embolic stroke in spontaneously hypertensive rats. Treatment with either rt-PA or saline was started 6 hours after stroke. A spectrophotometric hemoglobin assay quantified hemorrhage severity. Before treatment, relative cerebral blood flow index (rCBFi) and apparent diffusion coefficient (ADC) in the ischemic territory were 30% +/- 23% and 60% +/- 5% (of contralateral), respectively, which increased to 45% +/- 39% and 68% +/- 4% 2 hours after rt-PA. After 24 hours, rCBFi and ADC were 27% +/- 27% and 59 +/- 5%. Hemorrhage volume after 24 hours was significantly greater in rt-PA-treated animals than in controls (8.7 +/- 3.7 microL vs. 5.1 +/- 2.4 microL, P < 0.05). Before rt-PA administration, clear postcontrast T1-weighted signal intensity enhancement was evident in areas of subsequent bleeding. These areas had lower rCBFi levels than regions without hemorrhage (23% +/- 22% vs. 36% +/- 29%, P < 0.05). In conclusion, late thrombolytic therapy does not necessarily lead to successful reperfusion. Hemorrhage emerged in areas with relatively low perfusion levels and early blood-brain barrier damage. Magnetic resonance imaging may be useful for quantifying effects of thrombolytic therapy and predicting risks of hemorrhagic transformation.

Animals↗
PubMed2003

Embolic cerebral ischemia in carotid surgery: a model for human embolic stroke?

BACKGROUND: If carotid endarterectomy (CEA) is a clinical model of embolic stroke, then it should be possible to determine the relevance of embolus size and of the total quantity of embolic material (embolus load) for ischemic stroke. MATERIAL/METHODS: Thirty-one patients underwent a total of 33 CEAs. Diffusion weighted imaging (DWI) was performed on the day before and after CEA. A new hyperintense signal on the postoperative DWI was considered a new ischemic lesion. Intraoperatively detected microembolic signals (MES) were quantified (in cm) by multiplying embolus velocity by the embolus presence within the Doppler sample volume. With this relative index, emboli were classified into small (<0.56 cm), medium-sized (0.56-1.12 cm) and large (1.12-1.70 cm). RESULTS: For each category of embolus size, embolus load (in cm/minute) was expressed as the sum of all quantified emboli divided by minutes of CEA duration. By logistic regression analysis, the occurrence of a new ischemic lesion was related to an embolus load with medium-sized emboli (without lesion, 0.029 cm/minute; with lesion, 0.157 cm/minute; p=0.018), and with large emboli (without lesion, 0.015; with lesion, 0.055; p=0.038), but not to an embolus load with small emboli or the largest embolus per CEA. CONCLUSIONS: The leading reason for cerebral ischemia in CEA is multiple embolism with emboli of medium and large size. This conceptual model may also apply to carotid artery disease.

Brain Ischemia↗
PubMed1988

Tissue plasminogen activator. Reduction of neurologic damage after experimental embolic stroke.

Tissue plasminogen activator (tPA) has become available for pharmacologic use, and it appears to produce relatively fewer hemorrhagic complications than the previously available, less specific thrombolytic agents. We tested the effects of tPA in several models of embolic stroke and found that neurologic damage was reduced when the drug was administered as late as 45 minutes after cerebral embolic occlusion. The mechanism of therapeutic efficacy of tPA was probably thrombolysis. Drug-induced hemorrhages did not occur when therapy was started within four hours after the onset of vascular occlusion. These results suggest that tPA may be useful for thrombolytic therapy of embolic stroke if the drug is administered rapidly after the onset of vascular occlusion.

Animals↗