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Advanced ML Algorithms: The Future of CT Perfusion?

Arooshi Kumar, MD

Bathla G, Liu Y, Zhang H, Sonka M, Derdeyn C. Computed Tomography Perfusion–Based Prediction of Core Infarct and Tissue at Risk: Can Artificial Intelligence Help Reduce Radiation Exposure? Stroke. 2021;52:e755–e759.

It is well accepted that advanced CT perfusion (CTP) technology can help select patients who could benefit from endovascular treatment (EVT).1 However, CTP imaging is arterial input dependent, requires higher radiation than CT angiography, and utilizes timely and costly post-processing software.2,3 Authors Bathla et al. in this study explored if a machine learning algorithm, a convolutional neural network, which establishes complex relationships between many layers of visual imagery, could estimate cerebral blood flow and area-at-risk similar to the standard arterial dependent prediction method (RAPID).

Retrospective CTP data from 57 patients was split into training/validation (60%/40%) sets. The authors devised and validated separate U-net models, allowing for imaging segmentation, to predict core infarct (CBF) and tissue at risk (Tmax). Once trained, the full sets of 28 input images were sequentially reduced to equitemporal 14, 10, and 7 time points (tp) to further investigate if suboptimal arterial capture could be overcome by this predictive algorithm. The averaged structural similarity index measure (SSIM), a measure of similarity between two images, between the model-derived images and true perfusion maps was compared. For reference, the higher the SSIM, the better the reconstruction technique.

By |January 12th, 2022|clinical|0 Comments

Chemical Thrombolysis Disparities in the United States

Kevin O’Connor, MD

Suolang D, Chen BJ, Wang NY, Gottesman RF, Faigle R. Geographic and Regional Variability in Racial and Ethnic Disparities in Stroke Thrombolysis in the United States. Stroke. 2021;52:e782–e787.

Disparities in the administration of IV thrombolysis (IVT) have previously been reported, but Suolang et al. report regional disparities in the administration of IVT based on race/ethnicity. They examined IVT administration in 47,031 (8.6%) of 545,509 patients diagnosed with acute ischemic stroke between 2012 and 2018 according to nine United States Census Bureau regions (see Figure 2B below). Race/ethnic groups comprised White, Black, Hispanic, Asian/Pacific Islander, as well as Native American and Other.

Figure 2. Regional variability in intravenous thrombolysis (IVT) disparities for all racial/ethnic minority groups.
Figure 2. Regional variability in intravenous thrombolysis (IVT) disparities for all racial/ethnic minority groups. B, Green areas indicate no disparity, that is, no IVT underutilization compared with White people (odds ratio [OR], ≥1); green-yellow checkered areas indicate no statistically significant disparity (OR, <1, but 95% CI including 1); yellow areas indicate a disparity (i.e., lower use) comparable to the national average (OR and 95% CI <1 but not significantly below the national average); and the red areas indicate a disparity below the national average (OR and 95% CI <1 and statistically significantly below the national average). NIS indicates National Inpatient Sample.
By |January 10th, 2022|clinical|0 Comments

Investigating Suspected Cardioembolic Strokes

Kevin O’Connor, MD

Bhat A, Mahajan V, Chen HHL, Gan GCH, Pontes-Neto OM, Tan TC. Embolic Stroke of Undetermined Source: Approaches in Risk Stratification for Cardioembolism. Stroke. 2021;52:e820-e836.

Embolic strokes of undetermined source (ESUS) account for about a fifth of all ischemic strokes and comprise pathologies including cardioembolic sources, undiagnosed malignancy, and arteriogenic emboli. There is no single strategy for investigating suspected cardioembolic strokes, and initiating empiric anticoagulation for these patients may result in more harm than benefit.

Cardiac monitoring — whether implanted or external — is an important part of a cardioembolic workup, but the ideal timeframe for monitoring is unclear. In the CRYSTAL AF trial, the median time for atrial fibrillation (AF) detection via implanted cardiac monitor (ICM) was 8.4 months. A meta-analysis of ICM use in patients monitored for AF reported detection rates of 5% for <6 months, 26% for 12-24 months, and 34% for >24 months of monitoring. Although prolonged monitoring appears beneficial, the utility may be limited by patient adherence, accurate interpretation of captured rhythms, and patient cost.

By |January 7th, 2022|clinical|0 Comments

Article Commentary: “Antithrombotic Therapy for Stroke Prevention in Patients With Ischemic Stroke With Aspirin Treatment Failure”

Meghana Srinivas, MD

Lusk JB, Xu H, Peterson ED, Bhatt DL, Fonarow GC, Smith EE, Matsouaka R, Schwamm LH, Xian Y. Antithrombotic Therapy for Stroke Prevention in Patients With Ischemic Stroke With Aspirin Treatment Failure. Stroke. 2021;52:e777–e781.

When aspirin fails, what’s next? The use of aspirin for cardiovascular disease dates back to the 1950s to 1960s. It is only until very recently that studies have shown its lack of benefit in primary prevention of cardio and cerebrovascular diseases. In the United States, more than 40% of adults over the age of 70 years take aspirin for primary prevention of cardiovascular diseases, and more than 70% of patients of any age with a history of cardiovascular disease take daily aspirin. What’s next if patients who are taking aspirin for stroke prevention experience an ischemic stroke?

What can be tried? Increasing the dose of aspirin, adding a second drug, or switching to an alternate antiplatelet agent are often considered, but there is no evidence of superiority of one over the other. This study by Jay B. Lusk et al. used data from the American Heart Association Get with the Guidelines (GWTG) Stroke Registry to study the prevalence of aspirin failure in older patients who present with acute ischemic stroke and describe their discharge prescription pattern of antithrombotic therapy for secondary prevention of stroke.

By |January 5th, 2022|clinical|0 Comments

Delaying the Progression of AF: What is the Role of Catheter Ablation?

Wern Yew Ding, MBChB

Kuck KH, Lebedev DS, Mikhaylov EN, Romanov A, Gellér L, Kalējs O, Neumann T, Davtyan K, On YK, Popov S, et al. Catheter ablation or medical therapy to delay progression of atrial fibrillation: the randomized controlled atrial fibrillation progression trial (ATTEST). Europace. 2021;23:362-369.

Atrial fibrillation (AF) is closely linked to atrial cardiomyopathy and associated with structural and electrical remodelling that develops as the condition progresses. Currently, AF is classified based on a crude assessment of the estimated duration of each episode. Progression of AF is often signalled by an increase in AF burden, which is related to poorer outcomes, including excess thromboembolism. Therefore, halting (or even reversing) AF progression is of clinical importance.

In this study by Kuck and colleagues, the authors investigated whether catheter AF ablation could delay the progression of AF compared with drug therapy. To this end, they performed a study among patients aged equal or over 60 years old with symptomatic paroxysmal AF who were randomized to either radio frequency catheter ablation (RFCA) or anti-arrhythmic drug (AAD) therapy. The study was terminated prematurely due to slow enrolment; at the time of termination, 255 (79%) of the planned 322 patients were enrolled. Over a follow-up period of 3 years, the primary endpoint for the rate of persistent AF or atrial tachycardia was significantly lower with RFCA compared to AAD therapy (2.4% vs. 17.5%). The rate of any recurrent AF or atrial tachycardia was also significantly lower with RFCA over AAD therapy (49.2% vs. 84.8%). Serious adverse events occurred in 12 (11.8%) patients in the radiofrequency ablation arm.

By |January 3rd, 2022|clinical|0 Comments

Symptomatic Intracranial Thrombus Characteristics, Collateral Blood Flow and Recanalization Rates With/Without Intravenous Alteplase in Mild Ischemic Stroke Patients

Andrew Micieli, MMI MD

Lau HL, Gardener H, Coutts SB, Saini V, Field TS, Dowlatshahi D, Smith EE, Hill DM, Romano JG, Demchuk AM, et al. Radiographic Characteristics of Mild Ischemic Stroke Patients With Visible Intracranial Occlusion: The INTERRSeCT Study. Stroke. 2021.

Vascular imaging of the head and neck in the hyperacute stroke setting has important diagnostic and prognostic implications, especially in patients with mild stroke. The presence of an intracranial large vessel occlusion is a strong predictor of early neurological and radiographic deterioration in patients with mild stroke. Recanalization is associated with improved functional outcomes; however, the safety in mild stroke patients is less clear.

The authors sought to analyze thrombus characteristics, collateral blood flow and recanalization rates with or without intravenous alteplase in patients with mild ischemic stroke (NIHSS ≤5) and compare these with patients with moderate/severe symptoms (NIHSS >5) from the previously published INTERRSeCT study.

By |December 27th, 2021|clinical|0 Comments

Metabolic Consequences of Obesity, But Not Obesity Itself, Are Associated With Increased First Ischemic Stroke Risk

Dixon Yang, MD

Horn JW, Feng T, Mørkedal B, Strand LB, Horn J, Mukamal K, Janzsky I. Obesity and Risk for First Ischemic Stroke Depends on Metabolic Syndrome: The HUNT Study. Stroke. 2021;52:3555–3561.

Obesity is thought to be an important modifiable risk factor for ischemic stroke, especially given its high prevalence in certain European countries and the United States. However, obesity relationship to ischemic stroke may be more complex as there is still uncertainty on whether obesity itself or metabolic consequences of obesity are drivers of stroke risk. Horn et al. sought to assess the long-term association of weight, metabolic health, and ischemic stroke risk in the HUNT study (Trøndelag Health Study), a large prospective population-based cohort investigation based in Norway.

The present analysis included 35105 participants from HUNT who were free of stroke at baseline and had complete information on demographics, metabolic risk factors, and relevant covariates. Body weight categories were determined by standard body-mass index (BMI) thresholds (normal weight: 18.5 to <25 kg/m2, overweight: 25 to 29.9 kg/m2, obese: ≥30 kg/m2). The authors used a modified definition of metabolic syndrome from the International Diabetes Federation. Metabolically unhealthy was defined as the presence of increased waist circumference (WC) (≥102 cm in men, ≥88 cm in women) and 2 or more of the following: increased non-fasting triglycerides (≥1.7 mmol/L), decreased high-density lipoprotein (<1.03 mmol/L in men, <1.29 mmol/L in women), increased blood pressure (≥130/85 mmHg) or use of blood pressure medication, increased non-fasting glucose (≥11.1 mmol/L), or diabetes diagnosis. Outcomes were stroke diagnosis based on ICD codes in administrative hospital system data.

By |December 22nd, 2021|clinical|0 Comments

Patent Foramen Ovale Closure Reduces Clinical but Not Silent Brain Infarcts

Mona Al Banna, MB BCh, Msc(Res)

Messé SR, Erus G, Bilello M, Davatzikos C, Andersen G, Iversen HK, Roine RO, Sjöstrand C, Rhodes JF, Søndergaard L, Kasner SE, and on behalf of the Gore REDUCE Study Investigators. Patent Foramen Ovale Closure Decreases the Incidence but Not the Size of New Brain Infarction on Magnetic Resonance Imaging: An Analysis of the REDUCE Trial. Stroke. 2021;52:3419–3426.

Patent foramen ovale (PFO) is found in one quarter of the population. However, in cryptogenic strokes, PFOs have been found in approximately one half of patients. (1) The association is even stronger in younger patients with a stroke, as a four-fold greater incidence of PFO has been detected compared to a stroke-free age- and sex-matched control group. (2) The pathophysiology of PFO-related stroke involves the paradoxical embolism of a clot from the venous circulation to the arterial circulation through a right-to-left shunt. Therefore, PFO closure to eradicate the right-to-left shunt has been proposed as an intervention to reduce PFO-related stroke. Percutaneous PFO closure devices have been in use for many years. However, up until recently, clinical trials did not show significantly lower rates of recurrent stroke with PFO closure compared to standard medical therapy alone. (3-5) A sub-group analysis of the RESPECT (Randomized Evaluation of Recurrent Stroke Comparing PFO Closure to Established Current Standard of Care Treatment) trial showed significant reduction of stroke recurrence in patients with larger sized PFOs and atrial septal aneurysm. (6) The latest randomized controlled trials investigating the benefit of PFO closure utilized stricter inclusion criteria, in which patients were only eligible for closure if they had PFOs with an associated large interatrial shunt or atrial septal aneurysm, cortical stroke, and were <60 years old. (7-9) These trials concluded that the rate of recurrent stroke was significantly lower with closure, with one stroke avoided at 2 years for every 24 treated patients. (7)However, due to feasibility, these trials used an open label design where the patients and the treating clinicals were aware of the treatment assignment, increasing the risk of bias.

Real-World Experience of Mechanical Thrombectomy in Patients With Pre-Stroke Disability

Ammad Mahmood, MBChB

Millán M, Ramos-Pachón A, Dorado L, Bustamante A, Hernández-Pérez M, Rodríg uez-Esparragoza L, Gomis M, Remollo S, Castaño C, Werner M, et al., and on behalf of the Cat-SCR Consortium. Predictors of Functional Outcome After Thrombectomy in Patients With Prestroke Disability in Clinical Practice. Stroke. 2021.

Major clinical trials generally exclude patients with pre-stroke disability, generally defined as pre-stroke modified Rankin scale (mRS) of ≥2 or 3. Accordingly, thrombectomy guidelines [1, 2] state the benefit of mechanical thrombectomy (MT) for patients with pre-stroke disability is less clear, particularly for those aged >80. Patients with pre-stroke disability are routinely considered for MT particularly when other clinical and radiological factors are favorable, such as early presentation or good ASPECTS score. In this registry-based study, patients with mRS of 2 or 3 who underwent MT in the Catalonia stroke network were examined to assess any association between pre-stroke disability and outcomes, as well as aiming to identify factors predictive of favorable outcome for patients with pre-stroke disability. A favorable outcome in this context was defined as a return to baseline mRS at 90 days.

The Relationship Between Cerebrovascular Disease Profiles and Neurodegenerative Disease

Mona Al Banna, MB BCh, Msc(Res)

Lamar M, Leurgans S, Kapasi A, Barnes LL, Boyle PA, Bennett DA, Arfanakis K, Schneider JA. Complex Profiles of Cerebrovascular Disease Pathologies in the Aging Brain and Their Relationship With Cognitive Decline. Stroke. 2021.

Neurodegenerative disease with concurrent cerebrovascular disease (CVD) is associated with poorer long-term outcomes and increased functional dependency. Studies suggest that the co-existence of neurodegenerative pathologies and cerebrovascular pathologies ranges from 33-75%. However, little is known about the most common frequencies of cerebrovascular disease pathology types and the combinations of cerebrovascular pathologies that are encountered with dementia. The authors of this study set out to identify CVD frequencies and combinations in neurodegenerative disease and their association with cognitive domains affected.

By |December 15th, 2021|clinical|0 Comments