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Andrei V Alexandrov

Publications and source records attributed to Andrei V Alexandrov.

At least 19 recordsLinked to original sources
PubMed2007

Role of transcranial Doppler ultrasonography in evaluation of patients with cerebrovascular disease.

Transcranial Doppler ultrasonography (TCD) is the only noninvasive examination method that enables the reliable evaluation of blood flow from the basal intracerebral vessels, adding physiologic information to the anatomic images. TCD is relatively inexpensive, can be performed at bedside, and allows monitoring in acute emergency settings and for prolonged periods with a high temporal resolution, making it ideal for studying dynamic cerebrovascular responses. In acute stroke, TCD is capable of providing rapid information about the hemodynamic status of the cerebral circulation and monitoring recanalization in real-time, with a potential for enhancing tissue plasminogen activator-induced thrombolysis. Extended applications such as emboli monitoring, right-to-left shunt detection, and vasomotor reactivity make TCD an important and valuable tool for evaluating stroke mechanisms, planning and monitoring treatment, and determining prognosis.

Cerebrovascular Disorders↗
PubMed2006

Writing good abstracts.

INTRODUCTION: Writing an abstract means to extract and summarize (AB - absolutely, STR - straightforward, ACT - actual data presentation and interpretation). Thousands of abstracts are submitted to stroke conferences each year. The following suggestions may improve the chances of your work being selected for presentation, and to communicate results in the most efficient and unambiguous way. TITLE AND STRUCTURE: Make the title dynamic and informative, rather than descriptive. Structure the abstract following the IMRaD (Introduction, Methods, Results and Discussion) principle for your future original paper where background would become Introduction and conclusions would enter Discussion. Select the appropriate category for submission carefully. This determines which experts grade the abstract and the session where your competitors represent their work. If selected appropriately, your abstract is more likely to be graded by peers with similar interests and familiarity with your work or field. Methods should describe the study design and tools of data acquisition shortly, not data. RESULTS: Provide data that answer the research question. Describe most important data with numbers and statistics. Make your point with data, not speculations and opinions. Abbreviations should be avoided and only be used after they have been spelled out or defined. Common mistakes include failure to state the hypothesis, rationale for the study, sample size and conclusions. Highlight the novelty of your work by carefully chosen straightforward wording. CONCLUSIONS: Conclusions have to be based on the present study findings. Make sure your abstract is clear, concise and follows all rules. Show your draft to colleagues for critique, and if you are not a native English speaker show it to a person who can improve/correct your text. Remember that accepted abstracts of completed original research should be followed by published original papers - if this is not intended or fails, it may indicate an impaired ability to succeed in scientific writing and an academic career.

Abbreviations as Topic↗
PubMed2006

Clinical deterioration after intravenous recombinant tissue plasminogen activator treatment: a multicenter transcranial Doppler study.

BACKGROUND AND PURPOSE: Patients may experience clinical deterioration (CD) after treatment with intravenous recombinant tissue plasminogen activator (rt-PA). We evaluated the ability of flow findings on transcranial Doppler to predict CD and outcomes on modified Rankin Scale. METHODS: Patients with acute stroke received intravenous rt-PA within 3 hours of symptom onset at four academic centers. CD was defined as an increase in the National Institutes of Health Stroke Scale (NIHSS) score by 4 points or more within 24 hours. Poor long-term outcome was defined by modified Rankin Scale > or =2 at 3 months. Transcranial Doppler findings were interpreted using the Thrombolysis in Brain Ischemia flow grading system as persistent arterial occlusion, reocclusion, or complete recanalization. Multiple regression analysis was used to identify transcranial Doppler flow as a predictor for CD after controlling for age, sex, baseline NIHSS, hypertension, and glucose. RESULTS: A total of 374 patients received intravenous rt-PA at 142+/-60 minutes (median pretreatment NIHSS score 16 points). At the end of intravenous rt-PA infusion, transcranial Doppler showed persistent arterial occlusion in 219 patients (59%), arterial reocclusion in 54 patients (14%), and complete recanalization in 101 patients (27%). CD occurred in 44 patients: 36 had persistent arterial occlusion or reocclusion (82%), 13 symptomatic intracerebral hemorrhage (29%), and both persistent occlusion/reocclusion and symptomatic intracerebral hemorrhage in 10 patients (23%). After adjustment, patient risk for CD with persistent occlusion was OR 1.7 (95% CI: 0.7 to 4) and with arterial reocclusion 4.9 (95% CI: 1.7 to 13) (P=0.002). Patient risk for poor long-term outcomes with persistent occlusion, partial recanalization, or reocclusion was OR 5.2 (95% CI: 2.7 to 9, P=0.001). CONCLUSIONS: Inability to achieve or sustain vessel patency at the end of rt-PA infusion correlates with the likelihood of clinical deterioration and poor long-term outcome. Early arterial reocclusion on transcranial Doppler is highly predictive of CD and poor outcome.

Adult↗
PubMed2006

Does clinical-CT 'mismatch' predict early response to treatment with recombinant tissue plasminogen activator?

BACKGROUND: We hypothesized that patients with clinically severe strokes but less severe early ischemic changes on brain CT (i.e., clinical-CT mismatch) may respond better to intravenous recombinant tissue plasminogen activator (i.v. rt-PA) within 3 h of symptom onset. METHODS: In this secondary analysis of the CLOTBUST data, patients with middle cerebral artery occlusions on transcranial Doppler (TCD) were treated with i.v. rt-PA. Alberta Stroke Program Early CT Scores were obtained with raters blinded to the NIH Stroke Scale and TCD results. Two mismatch criteria and three criteria of response to therapy were explored. RESULTS: Of 126 patients, 67% had a mismatch type 1 and 74% had a mismatch type 2. The presence of clinical-CT mismatch by either definition did not correlate with any of the three criteria of response to rt-PA. Recanalization was a strong determinant of response, whether or not mismatch was present. CONCLUSIONS: Mismatch between severity of neurological deficit and CT findings is common but does not predict response to rt-PA therapy given within 3 h.

Brain Ischemia↗
PubMed2006

Nonpulsatile cerebral perfusion in patient with acute neurological deficits.

BACKGROUND AND PURPOSE: An extremely low pulsatile cerebral perfusion can result in a massive cerebral infarction and poor outcome. We report a patient who had complete recovery from initial neurological deficits in spite of nonpulsatile perfusion in the middle cerebral artery. METHODS: We used carotid duplex and transcranial Doppler to evaluate cerebral hemodynamics and the National Institutes of Health Stroke Scale (NIHSS) to score the neurological deficits. RESULTS: A 62-year-old man had a sudden chest pain and right hemispheric symptoms with NIHSS score of 18 on arrival. Carotid duplex showed no blood flow in the right common carotid artery. Transcranial Doppler showed a nonpulsatile waveform with slow antegrade flow in right middle cerebral artery. Chest CT angiography revealed type A aortic dissection. After surgical repair for the aortic dissection with brain retroperfusion, the patient had dramatic recovery from the initial neurological deficit, and normal pulsatile cerebral perfusion in the right carotid territory. CONCLUSIONS: Nonpulsatile cerebral perfusion points to a proximal source of arterial flow obstruction that may necessitate interventional treatment or surgery in order to restore brain perfusion and potentially reverse impending stroke.

Acute Disease↗
PubMed2006

Analysis of emboli during carotid stenting with distal protection device.

BACKGROUND: The newly developed multi-frequency transcranial Doppler (TCD) is able to differentiate gaseous from solid emboli. Our goal was to apply this technology to initially characterize emboli detected during carotid stenting with distal protection. METHODS: Patients undergoing carotid angiography and stenting were monitored with 2-2.5 MHz TCD (Embo-Dop, DWL) over the middle cerebral artery unilateral to stent deployment. Sonographers insured optimal signal recordings during the procedures. Automated emboli detection and classification software (MultiXLab version 2.0) was applied for offline count and analysis. Monitoring using the Filter Wire EX (Boston Scientific) and ACCUNET system (Guidant Corporation) was performed. RESULTS: A total of 9,649 embolic signals were detected during 11 angiographic and 10 stenting procedures. An observer confirmed the signals using the International Consensus definition. Automated software classified these events into 5,900 gaseous and 3,749 solid emboli. During contrast injections without the protection device, 1,013 emboli were detected with 28% of these being solid. With deployment of the distal protection device, 8,636 emboli were found with 40% being solid (p < 0.001). During stenting and angioplasty with the protection device, 7,395 emboli with 42% solids were detected (p < 0.001). Finally injection of contrast after the procedure, with the protection device still deployed, yielded 1,241 emboli with 31% solids (NS). Only 1 patient developed transient hemiparesthesia during ballooning that reduced the flow velocity to zero for 14 s. Neither gaseous nor solid emboli resulted in a mean flow velocity decrease or clinical symptoms. CONCLUSIONS: Microembolization frequently occurs during stenting even with deployment of the distal protection device. More solid emboli are seen during manipulations associated with lesion crossing. Although novel TCD methods yield a high frequency of embolic signals, further validation of this technique to determine the true nature, size, and number of emboli is needed.

Aged↗
PubMed2006

Argatroban tPA stroke study: study design and results in the first treated cohort.

BACKGROUND: The benefit of intravenous recombinant tissue plasminogen activator (rtPA) in acute stroke is linked to clot lysis and artery recanalization. Argatroban is a direct thrombin inhibitor that safely augments the benefit of rtPA in animal stroke models. There are no human data on this combination. DESIGN: We report the first phase of the Argatroban tPA Stroke Study, an ongoing prospective, open-label, dose-escalation, safety and activity study of argatroban and rtPA in patients with ischemic stroke. The primary outcome was incidence of intracerebral hemorrhage; secondary outcome, complete recanalization at 2 hours. After standard-dose intravenous rtPA administration, a 100-mug/kg bolus of argatroban followed by infusion of 1 mug/kg per minute for 48 hours was adjusted to a target partial thromboplastin time of 1.75 times that of the control group. RESULTS: Fifteen patients (including 10 men) were enrolled, with a mean +/- SD age of 61 +/- 13 years. All patients had middle cerebral artery occlusions. Baseline median National Institute of Health Stroke Scale score was 14 (range, 4-25). The mean +/- SD time from symptom onset to argatroban bolus administration was 172 +/- 53 minutes. Symptomatic intracerebral hemorrhage occurred in 2 patients, including 1 with parenchymal hemorrhage type 2. Asymptomatic bleeding occurred in 1 patient and there was 1 death. Recanalization was complete in 6 patients and partial in another 4, and reocclusion occurred in 3 within 2 hours of rtPA bolus administration. CONCLUSION: The safety of low-dose argatroban combined with intravenous rtPA may be within acceptable limits, and its efficacy for producing fast and complete recanalization is promising, but a larger cohort of patients is required to confirm these preliminary observations.

Adolescent↗
PubMed2006

Derivation of power M-mode transcranial Doppler criteria for angiographic proven MCA occlusion.

BACKGROUND: Stringent transcranial Doppler (TCD) criteria for diagnosing occlusion are needed for more reliable TCD performance at bedside in the acute stroke setting. SUBJECTS AND METHODS: At three academic stroke centers, we performed TCD examination for patients with symptoms of cerebral ischemia who underwent digital subtraction angiography (DSA). We used a standard insonation protocol with power M-mode Doppler (PMD) TCD (TCD 100 M, Spencer Technologies Inc., Seattle, WA). We collected mean flow velocity (MFV), pulsatility indices (PI), and power M-mode resistance signature (absent, high, or low) in symptomatic middle (MCA), anterior (ACA), posterior (PCA), and in affected (a), ipsilateral (i), and contralateral (c-lat) cerebral arteries. Ratios of aMCA/c-lat MCA, aMCA/iACA, and aMCA/iPCA MFV were subsequently calculated. PMD-TCD flow findings were evaluated with a receiver-operating characteristic (ROC) analysis for angiographically proven MCA occlusion. RESULTS: We studied 120 patients with acute cerebral ischemia with PMD-TCD examinations prior to or immediately after DSA. Lower aMCA velocities pointed to higher probability of occlusion (P= .055). The aMCA/iPCA MFV ratio was superior to the aMCA/iACA ratio and strongly predictive of occlusion at a threshold ratio of 0.5 (RR 2.31 CI(95) 2.13-2.51). High resistance or absent M-mode flow signatures in the proximal MCA were present in 87% of M1 and M2 MCA occlusions (probability 87%). In the presence of a low-resistance PMD signature, obtaining the aMCA/iPCA MFV ratio <0.5 increases probability of occlusion to 87%. Normal MFV ratios and low-resistance M-mode signatures are highly predictive of a negative angiogram for MCA occlusion. CONCLUSION: In acute cerebral ischemia, reliable criteria for proximal MCA occlusion have been developed based on combination of MFV ratios and M-mode flow resistance signatures. Validation of these criteria will require multicenter studies.

Angiography, Digital Subtraction↗
PubMed2006

Flow diversion in transcranial Doppler ultrasound is associated with better improvement in patients with acute middle cerebral artery occlusion.

BACKGROUND: Flow diversion (FD) can occur with an acute middle cerebral artery (MCA) occlusion. FD is thought to represent the collateral blood flow to the occluded MCA territory, but it is unclear whether or not FD lessens the stroke severity or leads to improved outcome. METHODS: Patients with a proximal MCA occlusion were selected from the CLOTBUST trial data bank. FD to the anterior or posterior cerebral artery was determined using transcranial Doppler ultrasound. Stroke severity and clinical improvement were measured using the National Institutes of Health Stroke Scale (NIHSS) scores. RESULTS: We evaluated 47 patients with an isolated M1 MCA occlusion who received intravenous tissue-type plasminogen activator (t-PA) within 3 h of symptom onset. FD was present in 83% of the patients. Median baseline NIHSS scores were 15.5 in the FD- group and 18 in the FD+ group (n.s.). Complete recanalization rates were 25 and 25.6% (n.s.). In 35 patients with a persistent occlusion, the average NIHSS score reduction was 22% (FD+) and 0.52% (FD-) during 90 min after t-PA bolus (p=0.017), and 29 versus -25% during the first 24 h after the t-PA bolus, respectively (p=0.01). CONCLUSIONS: In patients with persistent MCA occlusions after thrombolytic treatment, arterial blood flow diversion is associated with earlier and better neurological improvement. FD has protective effects on the ischemic brain tissue with persistent MCA occlusion.

Aged↗
PubMed2006

Interaction of cardiovascular disease and neurodegeneration: transcranial Doppler ultrasonography and Alzheimer's disease.

OBJECTIVE: Recent post-mortem studies have reported that the severity of atheromatous deposits in the circle of Willis is significantly greater, relative to non-demented (ND) elderly persons, in subjects with neuropathologically diagnosed Alzheimer's disease (AD). Additionally, the severity of intracranial atherosclerosis correlates significantly with the densities of neuritic plaques and neurofibrillary tangles. In this study, we examine the arteries of the circle of Willis by transcranial Doppler (TCD) ultrasonography. METHODS: TCD was used to measure, in 25 AD patients and 30 ND elderly subjects, mean flow velocities and pulsatility indices in 16 different segments of the circle of Willis. The data were compared with and without adjustment for age, gender and systolic blood pressure. RESULTS: The AD patients had systematically higher pulsatility indices (p<0.005) than the ND group. Incremental increases of pulsatility indices in these segments had odds ratios ranging from 1.8 to 48 for the presence of AD when adjusted for age, gender and systolic blood pressure. The left internal carotid artery siphon and the left posterior cerebral artery were the two vessels that were strongly associated with AD diagnosis. Mean flow velocities were generally lower in patients with AD but the differences did not reach the significance level. DISCUSSION: The pulsatility indices of the arteries of AD patients were generally greater than those of similarly-aged ND subjects. This difference is most likely due to increased arterial wall rigidity imposed by atherosclerotic changes. Atherosclerotic disease of intracranial arteries may be a risk factor for AD.

Aged↗
PubMed2005

Telemedicine-guided carotid and transcranial ultrasound: a pilot feasibility study.

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) and carotid duplex (CD) provide rapid and safe screening for stroke patients but are highly operator dependent. We explored the feasibility of telemedicine (TM)-guided TCD/CD administered by a health care provider inexperienced with ultrasound. METHODS: Dual video screens transmitted real-time TCD/CD images and sound to a neurosonographer. TM TCD/CD characteristics were compared with an in-person (IP) examination independently obtained on the same patient. We compared carotid stenosis, thrombolysis in brain ischemia (TIBI) flow grades, and the time spent on testing. RESULTS: We examined 8 subjects with a median age of 51 (31 to 63 range). IP and TM successfully examined 100% of internal carotid and middle cerebral arteries, 50% versus 44% of anterior cerebral artery, and 100% versus 88% of the basilar arteries, respectively. The median time in minutes IP versus TM was 15 (range 10 to 35) and 30 (15 to 50) for CD (P=0.07) and 18 (15 to 30) and 45 (30 to 55) for TCD (P=0.002), respectively. TM correctly identified all normal CD/TCD examinations in 7 subjects. In 1 patient, TM identified carotid occlusion but misread TIBI flow grades in both middle cerebral arteries. CONCLUSIONS: Our pilot study showed the feasibility of TCD/CD by an inexperienced health professional guided by a sonographer via TM. Tests were completed within times comparable to outpatient setting in a vascular laboratory.

Adult↗
PubMed2005

Intravenous TPA for very old stroke patients.

BACKGROUND: Although thrombolysis in patients with advanced age is considered more risky, some may benefit from TPA treatment. We studied safety and recanalization/recovery in patients older than 80 years treated with TPA and compared them with younger stroke patients. METHODS: We studied patients treated with intravenous TPA and divided them into younger (<80 years) and older (> or =80 years) groups for comparison. Diagnostic transcranial Doppler was completed before bolus, and patients were consequently monitored for up to 2 h when feasible. Clinical data included NIH Stroke Scale score, symptomatic intracranial hemorrhage (ICH) and discharge disposition. RESULTS: We studied 127 younger (mean 63 years, range 31-79) and 56 older patients (mean 84 years, range 80-93). Median baseline NIH Stroke Scale score was higher in the older group (18 vs. 14 points, NS). Occlusion locations, onset to needle time (median 130 vs. 120 min) as well as improvement at 24 h (median 5 vs. 4 points) were similar in both groups. Transcranial Doppler monitoring showed similar partial or complete recanalization rates (66 vs. 66%), onset to recanalization time (median 160 vs. 158 min) and reocclusion rates (26 vs. 25%). Symptomatic and fatal ICH was not higher in the older group (7.1 and 3.5% vs. 6.3 and 3.9%, NS). There was higher mortality among older patients (20 vs. 11%, NS). At discharge, 23% of older patients went home, 41% underwent rehabilitation and 16% were transferred to skilled nursing facilities, compared with 31, 43 and 15% respectively, in the younger group. CONCLUSION: After intravenous TPA treatment, patients over 80 years of age have similar recanalization, short-term improvement and symptomatic ICH rates compared with younger patients. However, older patients tend to have higher in-hospital mortality.

Adult↗
PubMed2005

Houston paramedic and emergency stroke treatment and outcomes study (HoPSTO).

BACKGROUND AND PURPOSE: Establishment of stroke centers, combined with accurate paramedic diagnosis and rapid transport, is essential to deliver acute stroke therapy. We wanted to measure and improve paramedic and hospital performance through implementation of the Brain Attack Coalition and American Stroke Association guidelines. METHODS: Pre-intervention and active-intervention phases with parallel data measurement points were used. The study involved six hospitals comprising the majority of acute-stroke admissions in Houston, Tex. Hospital, paramedic, and patient data were collected prospectively pre-intervention and during the active-intervention phase on all suspected acute-stroke patients admitted by Houston Fire Department-Emergency Medical Services. A multilevel educational intervention included paramedic, hospital, and community education. Paramedic diagnostic accuracy, hospital-performance efficiency, and thrombolytic treatment rates were the main outcome measures of the study. RESULTS: Four hundred forty-six patients (74 per month) were transported in the pre-intervention phase to participating hospitals (59.8% of all suspected stroke patients transported city wide by Houston Fire Department-Emergency Medical Services), compared with 1072 patients (89 per month, or 68.7%) transported in the active-intervention phase (P<0.001). Accuracy of paramedic diagnosis of stroke increased from 61% to 79%. Admission within 2 hours of symptom onset increased from 58% to 62% (P=0.002). Thrombolysis rates increased in 4 of 6 centers, with 1 post- tissue plasminogen activator hemorrhage (3.7%) reported. CONCLUSIONS: A multilevel educational program improves rapid hospitalization and paramedic diagnostic accuracy and increases the number of patients presenting for evaluation within the 3-hour tissue plasminogen activator window. Stroke center development supports safe thrombolytic practice in community settings.

Aged↗
PubMed2005

Heads down: flat positioning improves blood flow velocity in acute ischemic stroke.

BACKGROUND: Acute stroke patients are routinely positioned with the head of the bed (HOB) elevated at 30 degrees despite lack of evidence for increased intracranial pressure. OBJECTIVES: To determine the effect of HOB positions in real time on residual blood flow velocity in acutely occluded arteries causing stroke and whether resistance to residual flow increased with lower HOB positions. METHODS: In a repeated-measures quasi-experiment, the effect of 30, 15, and 0 degrees HOB on middle cerebral artery (MCA) mean flow velocity (MFV) in patients with acute (<24 hours) ischemic stroke was measured with transcranial Doppler using MFV and pulsatility index (PI) of the residual flow signals at the site of persisting acute occlusion. RESULTS: Twenty patients were evaluated (mean age 60 +/- 15 years; median NIH Stroke Scale [NIHSS] score 14 points). MCA MFV increased in all patients with lowering head position (maximum absolute MFV value increase 27 cm/s, range 5 to 96% from baseline values at 30 degrees). On average, MCA MFV increased 20% (12% from 30 to 15 degrees and 8% from 15 to 0 degrees; p < or = 0.025). Mean arterial pressure and heart rate were unchanged throughout the intervention. PI remained unchanged (mean values 0.89 at 30 degrees elevation, 0.91 at 15 degrees elevation, and 0.83 at 0 degrees elevation) at each HOB position, indicating no increase in resistance to blood flow. Immediate neurologic improvement (average 3 NIHSS motor points) occurred in three patients (15%) after lowering head position. CONCLUSION: Acute ischemic stroke patients may benefit from lower head-of-the-bed positions to promote residual blood flow to ischemic brain tissue.

Acute Disease↗
PubMed2005

Early recanalization rates and clinical outcomes in patients with tandem internal carotid artery/middle cerebral artery occlusion and isolated middle cerebral artery occlusion.

BACKGROUND: Patients with isolated middle cerebral artery (MCA) and tandem MCA/internal carotid artery (ICA) obstruction have similar presenting symptoms and stroke severity. We aimed to investigate early recanalization of MCA and clinical outcomes in patients with tandem ICA/MCA obstructions and isolated MCA occlusion. METHODS: Patients with MCA occlusion on pretreatment transcranial Doppler were treated with intravenous tissue plasminogen activator. ICA lesions were detected with carotid duplex. Early neurological improvement (ENI) was defined by reduction of National Institutes of Health Stroke Scale (NIHSS) > or =10 points or total NIHSS < or =3 points. Good outcome at 3 months was a modified Rankin score of < or =2. RESULTS: Among 104 patients, 31% had tandem lesions and 69% had isolated MCA occlusions. Complete recanalization rate was 39% in isolated MCA occlusion group and 9% in tandem group (P=0.002). ENI at 24 hours occurred in 46% of the isolated MCA occlusion group and in 25% of the tandem group (P=0.045). Good outcome was achieved by 30% and 39% respective patients (NS). CONCLUSIONS: The tandem lesion group showed lower early recanalization rate and ENI rate than the isolated MCA occlusion group. Despite this, good outcomes were similar in both groups.

Aged↗