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Biomedical subjects

Andrew R Xavier

Publications and source records attributed to Andrew R Xavier.

12 recordsLinked to original sources
PubMed2005

Catheter-based recanalization techniques for acute ischemic stroke.

Recent advances in endovascular interventional therapies have revolutionized the management of acute ischemic stroke. For patients who present with occluded circle of Willis vessels, timely and successful arterial recanalization is the best predictor of clinical improvement. Diagnostic neuroimaging has advanced noninvasive tools--namely, transcranial Doppler, CT angiography, and MR angiography--to screen individuals with acute neurologic syndromes rapidly for arterial occlusion, and hence to exclude from treatment those who are unlikely to benefit from or could be harmed by arterial recanalization strategies. Intra-arterial thrombolysis has been proven to be of benefit in large clinical trials. Moreover, the US Food and Drug Administration has recently approved the use of a mechanical clot retrieval device for acute embolic stroke, and a number of other similar strategies are under various stages of investigation. This article reviews the diagnostic and interventional approach to the management of large vessel embolic stroke.

Acute Disease↗
PubMed2005

What proportion of stroke is not explained by classic risk factors?

Ischemic stroke is a complex entity with multiple etiologies and variable clinical manifestations. The most frequent cause of stroke is atherosclerosis of cerebral vasculature followed by cardioembolism. Two thirds of strokes are explained by identifiable risk factors. Age, hypertension, and nonvalvular atrial fibrillation are by far the most frequent and well documented ones. Approximately 5% of strokes are caused by conditions other than atherosclerosis or heart disease, i.e., cervical arteries dissections, nonatherosclerotic vasculopathies, infectious or systemic vasculitis, and collagen vascular diseases. In spite of a thorough diagnostic evaluation, 30% of strokes remain cryptogenic, i.e., no specific cause is identified and the classic risk factors are not present. Identification of unknown environmental or genetic risk factors should be the subject of further research.

Age Distribution↗
PubMed2004

Computed tomographic angiography for diagnosis of brain death.

The authors report two patients with suspected brain death who required confirmatory tests other than clinical examination because of prolonged barbiturate administration for intracranial hypertension. Absence of intracranial blood flow was documented on CT angiography and confirmed by CT perfusion images. Cerebral angiography confirmed the findings consistent with brain death. CT angiography with CT perfusion may represent a rapid noninvasive method for diagnosis of brain death.

Adult↗
PubMed2004

Qureshi grading scheme for angiographic occlusions strongly correlates with the initial severity and in-hospital outcome of acute ischemic stroke.

BACKGROUND: The thrombolysis in myocardial infarction (TIMI) grading scheme and other classification systems have limitations in evaluating patients with ischemic stroke because they do not account for occlusion location or collateral circulation. The Qureshi grading scheme has been recently proposed to evaluate the severity of arterial occlusion in acute ischemic stroke because of limitations in existing grading systems. METHODS: The Qureshi grading scheme assigns a score from 0 to 5 on the basis of occlusion site and collateral supply. The authors determined the relationship between initial severity of stroke and outcome at discharge measured by the National Institutes of Health Stroke Scale (NIHSS) and the Qureshi grading scale assessed from initial angiography (by a neuroradiologist blinded to the clinical examination) in 57 patients who underwent intra-arterial therapy for acute ischemic stroke within 6 hours of symptom onset. RESULTS: A strong association was observed between the initial severity of neurological deficits and Qureshi scheme on angiography (F ratio = 2.6, P =.03). The initial NIHSS for grade 1 was 11 +/- 4 and progressively increased to 23 +/- 6 for grade 5. In the multivariate analysis, initial NIHSS was significantly associated with Qureshi scheme on angiography (R2 = 358, P =.03). The mean discharge NIHSS was 12 +/- 10 (range, 0-40). There was also a direct relationship between the Qureshi scheme and discharge NIHSS (F ratio = 2.8, P =.02). CONCLUSION: The Qureshi grading scheme can be effectively used to determine the severity of ischemic stroke (brain at risk) from the initial angiography.

Brain Ischemia↗
PubMed2004

Safety of high-dose intravenous eptifibatide as an adjunct to internal carotid artery angioplasty and stent placement: a prospective registry.

OBJECTIVE: Eptifibatide, a competitive platelet glycoprotein IIb-IIIa receptor inhibitor with high selectivity for platelet glycoprotein IIb-IIIa receptors and a short half-life, has been shown to reduce the risk of ischemic events associated with coronary interventions, particularly when used in high doses. However, its role in conjunction with neurointerventional procedures needs to be determined. We report the results of an open-label prospective registry to evaluate the safety (in terms of avoiding hemorrhagic complications) and effectiveness (in terms of preventing ischemic complications such as stroke) of administering high-dose eptifibatide during internal carotid artery angioplasty and stent placement (CAS) for extracranial carotid artery stenosis. METHODS: After femoral artery access was established and intravenous heparin (30 U/kg bolus) was administered, each patient was administered intravenous eptifibatide (two 180-microg/kg single-dose boluses before CAS, then a 2.0-microg/kg/min infusion for 20-24 hours thereafter). The primary end point was the 30-day composite occurrence of death, cerebral infarction, and unplanned or urgent endovascular or surgical intervention. The primary safety end point was bleeding, for which complications were classified according to the Thrombolysis in Myocardial Infarction scheme as major (hemoglobin decrease of more than 5 g/dl), minor (hemoglobin decrease of 3-5 g/dl), or insignificant. Platelet aggregation was measured in 13 consecutive patients with a rapid platelet-function analyzer. RESULTS: Twenty-six patients (mean age, 68.1 +/- 9.4 yr; 16 men) underwent treatment. The infusion and the CAS procedure were discontinued in one patient who developed angioneurotic edema after being administered intravenous heparin and the first bolus dose of eptifibatide. Among the 25 patients who underwent the procedure, no intracerebral hemorrhages and one minor ischemic stroke occurred during the 1-month follow-up period. The minor stroke was observed on postprocedure Day 7 in a patient for whom antiplatelet therapy was discontinued before a coronary artery bypass graft operation was performed. Another patient was discharged after an uncomplicated hospitalization but died as a result of urinary sepsis 12 days after CAS. One episode of major bleeding from the femoral insertion site required surgical repair and blood transfusions. Minor bleeding occurred in one patient. Platelet aggregation measurements obtained in 13 patients revealed a high degree (mean, 96%; range, 86-100%) of platelet inhibition after the administration of the second bolus dose of intravenous eptifibatide. CONCLUSION: High-dose eptifibatide administered as an adjunct to CAS seems to be safe. Further studies are required to analyze its effectiveness and role in neurointerventional procedures.

Adult↗
PubMed2004

Characteristics and predictors of aortic plaques in patients with transient ischemic attacks and strokes.

OBJECTIVE: To identify the prevalence and characteristics of aortic atherosclerotic plaque disease and its association with cerebrovascular risk factors in patients with cerebral ischemic events. BACKGROUND: Aortic atheroma is associated with ischemic stroke. Its characteristics, including morphology and distribution among different stroke subtypes, are not well described. METHOD: From July 2000 to August 2001, all patients evaluated by transesophageal echocardiography (TEE) with diagnoses of transient ischemic attacks (TIAs) and strokes were prospectively studied. Demographics, including age, gender, ethnicity, cerebrovascular risk factors, and stroke subtypes, were collected. RESULTS: Thoracic aortic atheromas (TAAs) were present in 141 of 237 patients (59%) (mean age = 59 +/- 14, 119 [50%] male). Mild plaque (< 2 mm) was present in 13 of 237 (5%), moderate plaque (2-4 mm) in 49 (21%), severe plaque (> or = 4 mm) in 79 (33%), and complex plaque in 64 (27%). Patients' ages (odds ratio [OR] = 1.05, confidence interval [CI] 1.03-1.08, P < .001), coronary artery disease (OR = 2.2, CI 1.02-4.8, P < .042), and patent foramen ovale (PFO) (OR = 0.39, CI 0.22-0.70, P < .002) were associated with the severity and complexity of aortic plaque. In multivariate analysis, age (OR = 1.06, CI 1.03-1.08, P < .001) and the presence of PFO (OR = 0.35, CI 0.18-0.65, P < .001) continued to be significant to the severity and complexity of aortic atheroma. Gender, history of stroke, hypertension, diabetes mellitus, hyperlipidemia, and history of smoking were not associated with TAA. CONCLUSION: One third of TAA plaques are severe and complex in nature and more frequently present in the descending aorta and the arch of the aorta than in the ascending aorta. TEE should be considered for the early detection and treatment of TAA in patients without identified causes of stroke.

Aorta, Thoracic↗
PubMed2004

Reocclusion of recanalized arteries during intra-arterial thrombolysis for acute ischemic stroke.

BACKGROUND AND PURPOSE: Early reocclusion of recanalized arteries has been observed after thrombolysis for acute coronary occlusion and has been attributed to platelet activation after exposure to thrombolytic agents. We conducted a retrospective study to determine the rate of reocclusion during intra-arterial thrombolysis for acute ischemic stroke and the effect of reocclusion on functional outcome. METHODS: Patients treated for acute ischemic stroke at our center between September 2000 and May 2002 received a maximum total dose of 4 U of reteplase intra-arterially in 1-U increments via superselective catheterization. Pharmacologic thrombolysis was supplemented by mechanical thrombolysis with balloon angioplasty or snare manipulation at the occlusion site. Angiography was performed after each unit of reteplase or mechanical maneuver, and the images were interpreted by a blinded reviewer. Reocclusion was defined as partial or complete initial recanalization with occlusion recurring at the same site as documented by angiography during the endovascular treatment. Reocclusions were treated by further pharmacologic and/or mechanical thrombolysis according to the discretion of the treating physician. Clinical evaluations were performed before and 24 hr, 7 to 10 days, and 1 to 3 months after treatment. RESULTS: Forty-six consecutive patients underwent intra-arterial thrombolysis. Reocclusion was observed in eight (17%). Among these patients, initial sites of occlusion were in the following arteries: intracranial internal carotid artery (n = 2), M1 segment of the middle cerebral artery (n = 3), M1 and M2 segments of the middle cerebral artery (n = 2), and basilar artery (n = 1). The mean initial National Institutes of Health Scale score for these eight patients was 23.3 +/- 6.2; mean time from symptom onset to treatment was 4.4 +/- 1.2 hr. The reocclusions were treated by using additional doses of reteplase alone (n = 1), reteplase with snare maneuver and/or angioplasty (n = 5), reteplase with angioplasty or snare and then stent placement (n = 1), and angioplasty with stent placement (n = 1). The reocclusions resolved in six of eight patients after further treatment. Six patients died and two survived but were severely disabled at 1 month (modified Rankin Scale scores of 4 and 5, respectively). Independent functional outcome scores (modified Rankin Scale scores of 0-2) were significantly lower among patients with angiographically shown reocclusion than in those without (0 of 8 versus 17 of 38, P =.02). CONCLUSION: Reocclusion occurs relatively frequently during intra-arterial thrombolysis for ischemic stroke and seems to be associated with poor clinical outcomes.

Acute Disease↗
PubMed2003

Management of carotid artery stenosis: comparing endarterectomy and stenting.

Stroke ranks as the third leading cause of death, behind diseases of the heart and cancer. It is also the most important cause of disability. Approximately 750,000 people experience a stroke annually, costing an estimated $40 billion in direct and indirect costs. Approximately 25% of these ischemic events are related to occlusive disease of the cervical internal carotid artery. Carotid atherovascular stenosis increases the risk of ischemic stroke by acting as an embolic source, and causing hypoperfusion of the ipsilateral cerebral hemisphere. With some limitations, the North American Symptomatic Carotid Endarterectomy Trial (NASCET), European Carotid Surgery Trialists' Collaborative Group (ECST), and Asymptomatic Carotid Atherosclerosis Study (ACAS) have shown that carotid endarterectomy (CEA) substantially reduces the risk of stroke associated with certain grades of carotid stenosis. During the past few years, carotid angioplasty and stenting (CAS) has evolved as an alternative to CEA, particularly in patients who are known to have a higher complication rate with CEA.

Blood Vessel Prosthesis Implantation↗
PubMed2003

Neuroimaging of stroke: a review.

Advances in neuroimaging technology during the past 30 years have resulted in a virtual explosion in the amount of pathologic information that can be obtained in the clinical stroke setting. This neuroimaging revolution has led to a much better understanding of cerebrovascular and tissue pathology, creating a wide array of opportunities for acute treatment and secondary prevention. Advances include early and accurate detection of ischemic and infarcted tissue and the ability to reveal hypoperfused tissue at risk. Clinicians are increasingly able to noninvasively detect embolic and atherothrombotic intravascular lesions. Vascular lesions associated with stroke can be characterized through endovascular neuroimaging techniques and repaired by various means. In this article, we provide an overview and update on the various techniques used in the neuroimaging of stroke and intracranial hemorrhage, including computed tomography, magnetic resonance imaging, ultrasound, and catheter angiography. We outline the specific role of each modality in clinical practice.

Acute Disease↗
PubMed2003

Clinical potential of intra-arterial thrombolytic therapy in patients with acute ischaemic stroke.

Acute ischaemic stroke is a leading cause of mortality and morbidity around the world. An arterial occlusive lesion is found in the majority of patients with acute ischaemic stroke, and recanalisation has been shown to result in a better clinical outcome. The only widely approved recanalisation strategy is the use of intravenous alteplase (recombinant tissue-type plasminogen activator; tPA) within 3 hours of stroke onset. However, this therapy has limitations, and alternative or supplemental recanalisation strategies need to be considered in a large number of patients with acute ischaemic stroke. One such promising strategy is intra-arterial thrombolysis. This article reviews the pharmacology of the various drugs used for intra-arterial thrombolysis in the setting of acute ischaemic stroke and the results of the clinical trials that have studied their benefit. Three generations of thrombolytic agents have been available for clinical use so far. The first-generation agents such as streptokinase and urokinase were the first to be studied in acute stroke, and a number of positive case reports and series of their intra-arterial use have been reported from around the world. Second-generation products include alteplase and pro-urokinase. The clinical benefits of intra-arterial pro-urokinase were recently proven in a randomised, placebo-controlled study. Third-generation agents, such as reteplase, lanoteplase and tenecteplase, offer superior recanalisation rates with limited systemic adverse effects and might prove to be the agents of choice for intra-arterial acute stroke thrombolysis in the future. The exact administration regimens as well as the identification of patient sub-populations most likely to benefit from intra-arterial thrombolysis are subjects of current investigations, and hopefully firmer guidelines will be established in the next few years, once the results of the clinical trials are available.

Combined Modality Therapy↗
PubMed2002

Outcome following intracerebral hemorrhage and subarachnoid hemorrhage.

Intracerebral hemorrhage and subarachnoid hemorrhage account for almost 20% of all stroke cases. Both forms of stroke are associated with a high morbidity and mortality rate. The incidence of intracerebral hemorrhage increases with the age and certain ethnical groups are more affected. Subarachnoid hemorrhage tends to occur in a much younger population than other types of strokes. Outcome predictors for intracerebral and subarachnoid hemorrhage have been extensively discussed in the literature. Based on the current literature, we review the morbidity and mortality rates and predictors of outcome for these two life-threatening diseases. Initial Glasgow Coma Scale (GCS) score, hematoma volume, and presence of ventricular blood are the most prominent predictors of outcome following intracerebral hemorrhage. Age and initial severity of neurologic deficits on presentation, measured by GCS, Hunt and Hess Scale or the World Federation of Neurological Surgeons Scale, are the most important predictors of outcome following subarachnoid hemorrhage.

Cerebral Hemorrhage↗