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Biomedical subjects

Michael D Hill

Publications and source records attributed to Michael D Hill.

16 recordsLinked to original sources
PubMed2003

Selection of acute ischemic stroke patients for intra-arterial thrombolysis with pro-urokinase by using ASPECTS.

BACKGROUND: Previous studies have suggested that baseline computed tomographic (CT) scans might be a useful tool for selecting particular ischemic stroke patients who would benefit from thrombolysis. The aim of the present study was to assess whether the baseline CT scan, assessed with the Alberta Stroke Program Early CT Score (ASPECTS), could identify ischemic stroke patients who might particularly benefit from intra-arterial thrombolysis of middle cerebral artery occlusion. METHODS: Baseline and 24-hour follow-up CT scans of patients randomized within 6 hours of symptoms to intra-arterial thrombolysis with recombinant pro-urokinase or control in the PROACT-II study were retrospectively scored by using ASPECTS. Patients were stratified into those with ASPECTS >7 or < or =7. Independent functional outcome at 90 days was compared between the 2 strata according to treatment assignment. RESULTS: The analysis included 154 patients with angiographically confirmed middle cerebral artery occlusion. The unadjusted risk ratio of an independent functional outcome, in favor of treatment, in the ASPECTS >7 group was 5.0 (95% confidence interval [CI], 1.3 to 19.2) compared with 1.0 (95% CI, 0.6 to 1.9) in the ASPECTS < or =7 group. After adjustment for baseline characteristics, the risk ratio in the ASPECTS score >7 was 3.2 (95% CI, 1.2 to 9.1). Similar favorable treatment effects were observed when secondary outcomes were used, but these did not reach statistical significance. CONCLUSIONS: Ischemic stroke patients with a baseline ASPECTS >7 were 3 times more likely to have an independent functional outcome with thrombolytic treatment compared with control. Patients with a baseline ASPECTS < or =7 were less likely to benefit from treatment. This observation suggests that ASPECTS can be both a useful clinical tool and an important method of baseline risk stratification in future clinical trials of acute stroke therapy.

Acute Disease↗
PubMed2003

Computed tomographic parameters predicting fatal outcome in large middle cerebral artery infarction.

BACKGROUND: Large middle cerebral artery (MCA) ischaemic stroke when associated with extensive mass effect can result in brain herniation and neurological death. As yet there are few guidelines to aid the selection of patients for aggressive interventional therapies, such as decompression hemicraniectomy and/or hypothermia. METHODS: We studied a cohort of patients from seven centres with large MCA infarction requiring neurocritical care. The purpose of this analysis was to assess the use of early radiological signs on follow-up computed tomographic (CT) signs performed within 48 h of stroke onset for predicting mortality at 30 days. The CT parameters assessed included horizontal displacement of the septum pellucidum, pineal shift, complete or partial infarction of the temporal lobe, involvement of additional vascular territories, and the presence of hydrocephalus. The primary outcome measure was in-hospital death within 30 days. RESULTS: One hundred and thirty-five patients who had follow-up CT scans within 48 h were identified from a total of 201 patients with large MCA infarction that received conventional medical therapy alone. The median age was 68 (range 29-99), 56% were female, and the median NIHSS category was 26-30 at 48 h. Among CT variables in univariable analysis, anteroseptal shift >/=5 mm, pineal shift >/=2 mm, complete temporal lobe infarction, involvement beyond the MCA territory, and moderate or severe hydrocephalus were equally predictive of death. Multivariable analysis adjusting for time to CT scan revealed the following predictors of fatal outcome: anteroseptal shift >/=5 mm (OR 10.9; 95% CI 3.2-37.6), NIHSS within 48 h >20 (OR 6.6; 95% CI 2.3-19.3), and infarction beyond the MCA territory (OR 4.9; 95% CI 1.6-15.0). CONCLUSIONS: We identified the role of early CT signs in predicting death following massive MCA infarction. The CT parameters anteroseptal shift (>5 versus </=5 mm), pineal shift >/=2 mm, hydrocephalus, temporal lobe infarction, and other vascular territory infarction if present were predictive of fatal outcome. These CT parameters require prospective validation before they should be considered reliable markers for decision-making.

Adult↗
PubMed2003

Successful endovascular therapy for acute basilar thrombosis in an adolescent.

Pediatric stroke is an underrecognized, potentially treatable cause of childhood neurologic disease. Acute basilar artery thrombosis is a devastating disease rarely encountered in children. Acute interventions with both chemical and mechanical thrombolysis techniques can improve outcomes in adults with arterial thrombosis of the posterior cerebral circulation. We report a case of intervention with both intra-arterial alteplase (tissue plasminogen activator) and cerebral balloon angioplasty to treat a prolonged basilar artery occlusion secondary to idiopathic thrombosis in an adolescent. Despite the patient being clinically locked-in and intervention being delayed at least 20 hours from symptom onset, he obtained complete neurologic recovery. Issues of pediatric stroke, late therapeutic intervention, chemical thrombolysis, and cerebral angioplasty are discussed. This case highlights the underrecognition and subsequent delay in diagnosis of pediatric stroke and how acute intervention may cure otherwise catastrophic strokes in children.

Adolescent↗
PubMed2003

Regional comparisons of inpatient and outpatient patterns of cerebrovascular disease diagnosis in the province of Alberta.

The diagnosis of cerebrovascular disease (CBVD) from administrative data has been critically examined by epidemiologists in recent years. Much of the existing literature suggests that hospital discharge diagnoses based on ICD-9-CM codes are an unreliable source of information for determining a diagnosis of stroke, particularly when four- and five-digit codes are used. We examined how diagnoses for CBVD in hospital inpatient and outpatient facilities vary between rural and urban areas and among the 16 administrative health regions. Our analysis revealed differences in diagnostic patterns between the two sources of data, differences between rural and urban areas, and variation across most of the regions. Geographic variation in health service utilization, diagnostic practices, specialty of the physician making the diagnosis, and disease burden may explain our findings. Our results suggest that the diagnosis of patients attending rural facilities are either coded differently (and less precisely) than those of urban residents or are coded more precisely only after the patients attend urban facilities. Regional differences in coding practices show that any CBVD surveillance system based on administrative data requires a large-scale (in this case, province-wide) and person-oriented approach.

Alberta↗
PubMed2002

Neurological outcome and quality of life after stroke due to vertebral artery dissection.

BACKGROUND: Vertebral artery dissection is a well-recognized cause of posterior circulation stroke for which there is relatively little information on long-term outcomes. Quality of life (QOL) is an important patient-centred outcome measure. METHODS: Stroke due to vertebral artery dissection was conservatively defined by neuroimaging documentation. Thirty sequential cases were identified based on a retrospective database and chart review with prospective follow-up. Surviving patients completed the Short Form-36 (SF-36) and the Stroke-Specific Quality of Life (SSQOL) scales and were subsequently examined neurologically and scored on the National Institutes of Health Stroke Scale (NIHSS). Comparisons were made between outcome on the stroke scale and QOL scales and between outcome on the SF-36 and the Canadian population. RESULTS: There was discordance between outcomes recorded on a standard stroke scale and QOL measures with more patients scoring poorly on QOL measures. QOL was low in one third of the survivors. Overall QOL was significantly lower than the general population. CONCLUSIONS: Stroke due to vertebral artery dissection results in poorer outcomes on patient-centred QOL measures than on a standard stroke scale.

Adult↗
PubMed2002

Acute intravenous--intra-arterial revascularization therapy for severe ischemic stroke.

BACKGROUND: Intravenous alteplase for acute ischemic stroke is least efficacious for patients with proximal large-artery occlusions and clinically severe strokes. Intra-arterial therapy has the theoretical advantage of establishing a neurovascular diagnosis and high symptomatic artery patency rate but the disadvantage of requiring extra time and technical expertise. A combination of these two approaches may provide the best chance of improving outcome in severe acute ischemic stroke. We sought to assess the safety and feasibility of this approach. METHODS: This was a prospective, open-label study. Sequential patients arriving to our center within 3 hours of stroke onset who were treated with intravenous alteplase were screened for possible additional intra-arterial therapy using noninvasive neuroimaging. Clinical measures and outcomes were recorded prospectively. RESULTS: A total of 861 patients with ischemic stroke were admitted to Calgary hospitals during the study period. Eight patients over 21 months underwent a combined intravenous-intra-arterial approach. Six received intra-arterial alteplase and 1 underwent intracranial angioplasty; in a final patient, technical aspects prevented intra-arterial therapy. Early neurovascular and/or neurometabolic imaging identified the location of occlusion and tissue-at-risk (DWI-PWI mismatch) in all 8 patients. Two patients had a poor outcome, 1 patient suffered a significant groin hematoma, and there were no instances of symptomatic intracerebral hemorrhage. CONCLUSIONS: Intravenous followed by intra-arterial therapy is a promising approach to the treatment of severe acute ischemic stroke. Early noninvasive neurovascular and neurometabolic imaging is very helpful in choosing candidates for this type of therapy. On-going monitoring of alteplase-treated patients may allow the opportunity to perform rescue intra-arterial therapy.

Acute Disease↗
PubMed2002

Comparison of pre- and postcontrast 3D time-of-flight MR angiography for the evaluation of distal intracranial branch occlusions in acute ischemic stroke.

BACKGROUND AND PURPOSE: Three-dimensional time-of-flight (TOF) MR angiography is used routinely in stroke workup to detect arterial occlusions, but a major drawback is its inadequate depiction of vessels with slow or in-plane flow. We hypothesized that the use of contrast-enhanced MR angiography improves delineation of vessels with diminished or absent flow on precontrast MR angiograms. METHODS: Pre- and postcontrast 3D TOF MR angiograms were acquired in 55 consecutive patients with acute stroke. Patency of 480 intracranial vessels was assessed on both the pre- and postcontrast angiograms. Diffusion-weighted (DW) and perfusion-weighted (PW) imaging data were also obtained and results correlated with those of pre- and postcontrast MR angiography. RESULTS: For 50 abnormal vessel segments seen on precontrast MR angiograms, postcontrast MR angiograms resulted in change in the vascular signal intensity in 70% (35 vessel segments); 94% of these changes showed a greater extent of vessel patency. Venous and soft-tissue contrast enhancement had no effect on assessment in 95% of all 480 vessels examined. Interobserver reliability was moderate, with postcontrast interpretation (kappa = 0.48) showing a slight improvement over precontrast interpretation (kappa = 0.41). Good agreement was found between the TOF results and the pooled DW and PW imaging results. CONCLUSIONS: Compared with precontrast 3D TOF MR angiograms, postcontrast 3D TOF angiograms improve assessment of intracranial vessel patency in acutely ischemic vascular territories. In some patients, an improved understanding of acute ischemic stroke was obtained by viewing the pre- and postcontrast images. Postcontrast MR angiography should be included in the MR evaluation of acute stroke.

Acute Disease↗
PubMed2002

Weather, Chinook, and stroke occurrence.

BACKGROUND: Changes in weather and season have been linked to stroke occurrence. However, the association has been inconsistent across stroke types. Calgary is a city in the Chinook belt and is subject to high variability in weather conditions. METHODS: We obtained hourly weather data over a 5-year period from 1996 to 2000; Chinook events were identified according to the accepted definition. We reviewed administrative data to determine stroke occurrence and defined stroke types to maximize specificity of diagnosis. To examine the hypothesis that weather affected the number of strokes occurring in a given day, we compared average daily stroke occurrence on Chinook days and non-Chinook days; we compared mean daily temperature, relative humidity, barometric pressure, and wind speed by the number of strokes occurring on any given day. RESULTS: Annual variation in stroke frequency was observed. No seasonal, monthly, or weekly variation in overall stroke occurrence or occurrence by type was evident. No relationship with changes in weather parameters was observed. CONCLUSIONS: We found no association between weather changes and stroke occurrence. A cause-and-effect relationship between weather and stroke occurrence is dubious because of a lack of consistency across studies.

Alberta↗