Descriptive Analysis of Patients Receiving Outpatient eConsults for Neurological Disorders in the United States

Introduction: Interprofessional consultations ("eConsults"), which facilitate asynchronous specialist consultations, remain understudied in neurological disorders. We aimed to describe the patient population receiving eConsult services for neurological disorders nationwide and to conduct a comparative analysis between rural and urban patients within this eConsult cohort. Methods: We analyzed a dataset of U.S. outpatient claims from employer-sponsored commercial and Medicare plans. Using standardized mean differences, we compared clinical and sociodemographic patient characteristics between urban and rural patients within the eConsult group. Results: We identified 1,374 patients who had an eConsult order for a neurological disorder. Overall eConsult volume increased by 548.5% between 2019 and 2021. A majority of the cohort were aged 65 years or older (23.7%), had an eConsult order in 2021 (52.4%), and live in an urban area (90.4%). The primary diagnosis for our cohort was likely to be a sleep-wake disorder (21.9%), cerebrovascular disease (14.3%), neurological sign or symptom (14.2%), or headache (13.7%). In the secondary analysis, rural eConsult patients exhibited higher rates of primary diagnoses for traumatic brain injury, neuroophthalmic disorders, or neuropathy than their urban counterparts. Discussion: In this national sample of commercially insured patients, the utilization of eConsults for neurological conditions increased nationwide since 2019, especially for patients living in rural areas.

A retrospective cohort study of clinical factors, visit patterns, and demographic factors associated with use of remote communications in patients with headache

OBJECTIVE

To identify the characteristics associated with high utilization of remote communications (RCs) in patients with headache.

BACKGROUND

Patients with headache frequently communicate with their providers using secure portal messaging and telephone calls. However, clinical and demographic factors as well as visit patterns associated with RC utilization remain poorly characterized.

METHODS

We retrospectively analyzed data from patients with headache who were evaluated in the ambulatory neurology faculty practice at the Icahn School of Medicine at Mount Sinai in New York between January 1 and June 30, 2019. We extracted clinical and demographic characteristics, total office visits, secure MyChart portal messages, and telephone encounters from our institutional data warehouse. We defined high RC and MyChart utilization as the top tertile of RC and MyChart message volume, respectively, and assessed the relationship between patient characteristics and high RC (primary outcome), as well as high MyChart utilization (secondary outcome). We characterized the relationship between clinicodemographic characteristics and the ratio of MyChart messages to total RCs (secondary outcome).

RESULTS

We identified 1390 patients, of whom 477 (34.3%) were high RC utilizers and 321 (23.1%) were high MyChart utilizers. High RC utilizers generated 3306/3921 (84.3%) RCs. The presence of chronic headache (aOR 2.31, 95% CI 1.75-3.03, p < 0.0001), cluster headache (aOR 18.3, 95% CI 5.0-71.7, p = 0.001), and migraine (aOR 3.82, 95% CI 1.93-9.3, p = 0.011) was associated with high RC utilization. Patients ≥65 years of age were less likely to engage in MyChart messaging as a proportion of RC (191/680, 28.1%) compared with patients 18-30 years of age (243/620, 39.2%, p = 0.049) and 30-64 years of age (1172/2721, 43.1%, p < 0.0001).

CONCLUSIONS

A minority of patients with headache (477/1390; 34.3%) generated the majority (3306/3921; 84.3%) of RCs. Our findings should be validated in external patient cohorts with the objective of developing strategies to optimize RC utilization.

Usage Patterns of Web-Based Stroke Calculators in Clinical Decision Support: Retrospective Analysis

Background

Clinical scores are frequently used in the diagnosis and management of stroke. While medical calculators are increasingly important support tools for clinical decisions, the uptake and use of common medical calculators for stroke remain poorly characterized.

Objective

We aimed to describe use patterns in frequently used stroke-related medical calculators for clinical decisions from a web-based support system.

Methods

We conducted a retrospective study of calculators from MDCalc, a web-based and mobile app–based medical calculator platform based in the United States. We analyzed metadata tags from MDCalc’s calculator use data to identify all calculators related to stroke. Using relative page views as a measure of calculator use, we determined the 5 most frequently used stroke-related calculators between January 2016 and December 2018. For all 5 calculators, we determined cumulative and quarterly use, mode of access (eg, app or web browser), and both US and international distributions of use. We compared cumulative use in the 2016-2018 period with use from January 2011 to December 2015.

Results

Over the study period, we identified 454 MDCalc calculators, of which 48 (10.6%) were related to stroke. Of these, the 5 most frequently used calculators were the CHA₂DS₂-VASc score for atrial fibrillation stroke risk calculator (5.5% of total and 32% of stroke-related page views), the Mean Arterial Pressure calculator (2.4% of total and 14.0% of stroke-related page views), the HAS-BLED score for major bleeding risk (1.9% of total and 11.4% of stroke-related page views), the National Institutes of Health Stroke Scale (NIHSS) score calculator (1.7% of total and 10.1% of stroke-related page views), and the CHADS₂ score for atrial fibrillation stroke risk calculator (1.4% of total and 8.1% of stroke-related page views). Web browser was the most common mode of access, accounting for 82.7%-91.2% of individual stroke calculator page views. Access originated most frequently from the most populated regions within the United States. Internationally, use originated mostly from English-language countries. The NIHSS score calculator demonstrated the greatest increase in page views (238.1% increase) between the first and last quarters of the study period.

Conclusions

The most frequently used stroke calculators were the CHA₂DS₂-VASc, Mean Arterial Pressure, HAS-BLED, NIHSS, and CHADS₂. These were mainly accessed by web browser, from English-speaking countries, and from highly populated areas. Further studies should investigate barriers to stroke calculator adoption and the effect of calculator use on the application of best practices in cerebrovascular disease.

Calculated Decisions: Secondary intracerebral hemorrhage (sICH) score

The sICH score quantifies the likelihood of underlying vascular etiology in patients with intracerebral hemorrhage.

Calculated Decisions: Intracerebral hemorrhage (ICH) score

The ICH score grades intracerebral hemorrhage severity and subsequent 30-day mortality based on age and CT findings.

Safety and Feasibility of a Rapid Outpatient Management Strategy for Transient Ischemic Attack and Minor Stroke: The Rapid Access Vascular Evaluation-Neurology (RAVEN) Approach

STUDY OBJECTIVE

Although most transient ischemic attack and minor stroke patients in US emergency departments (EDs) are admitted, experience in other countries suggests that timely outpatient evaluation of transient ischemic attack and minor stroke can be safe. We assess the feasibility and safety of a rapid outpatient stroke clinic for transient ischemic attack and minor stroke: Rapid Access Vascular Evaluation-Neurology (RAVEN).

METHODS

Transient ischemic attack and minor stroke patients presenting to the ED with a National Institutes of Health Stroke Scale score of 5 or less and nondisabling deficit were assessed for potential discharge to RAVEN with a protocol incorporating social and medical criteria. Outpatient evaluation by a vascular neurologist, including vessel imaging, was performed within 24 hours at the RAVEN clinic. Participants were evaluated for compliance with clinic attendance and 90-day recurrent transient ischemic attack and minor stroke and hospitalization rates.

RESULTS

Between December 2016 and June 2018, 162 transient ischemic attack and minor stroke patients were discharged to RAVEN. One hundred fifty-four patients (95.1%) appeared as scheduled and 101 (66%) had a final diagnosis of transient ischemic attack and minor stroke. Two patients (1.3%) required hospitalization (one for worsening symptoms and another for intracranial arterial stenosis caused by zoster) at RAVEN evaluation. Among the 101 patients with confirmed transient ischemic attack and minor stroke, 18 (19.1%) had returned to an ED or been admitted at 90 days. Five were noted to have had recurrent neurologic symptoms diagnosed as transient ischemic attack (4.9%), whereas one had a recurrent stroke (0.9%). No individuals with transient ischemic attack and minor stroke died, and none received thrombolytics or thrombectomy, during the interval period. These 90-day outcomes were similar to historical published data on transient ischemic attack and minor stroke.

CONCLUSION

Rapid outpatient management appears a feasible and safe strategy for transient ischemic attack and minor stroke patients evaluated in the ED, with recurrent stroke and transient ischemic attack rates comparable to historical published data.

Abstract TP280: Triage and Outpatient Evaluation of Emergency Department Patients With TIA and Minor Stroke: Rapid Access Vascular Evaluation-Neurology (RAVEN)

Introduction: The timely evaluation of TIA and minor stroke (TIAMS) is important, but whether TIAMS patients with no debilitating deficits should be admitted or not remains unsettled. We piloted a clinical protocol to assess the feasibility and safety of discharging selected TIAMS patients without disabling deficits from the Emergency Department (ED) to a rapid outpatient stroke clinic: Rapid Access Vascular Evaluation-Neurology (RAVEN).

Methods: RAVEN was created as a specialized outpatient neurology clinic for TIAMS patients discharged within 24 hours from the ED at an urban quaternary academic medical center. Patients were first screened in the ED by a neurologist and selected using a decision tool identifying presumed low-risk TIAMS seen in the ED. Criteria included medical (e.g. National Institute of Health Stroke Scale of 5 or less, no disabling deficit, no fluctuating or recurrent symptoms over past month, no thrombolytic agent given, negative CT for hemorrhagic stroke, no new onset atrial fibrillation, blood pressure not over 180/110), as well as social criteria (e.g. patient ability to follow-up within 24 hours). Doppler ultrasound to exclude intracranial and extracranial stenosis, along with neurology re-evaluation was performed as part of RAVEN follow-up. Sample population was evaluated for rates of noncompliance with post-ED follow-up and need for hospitalization from clinic. Final diagnosis was also tabulated.

Results: Between December 2016 and June 2018, 162 TIAMS patients seen in the ED were recommended for RAVEN utilizing the decision tool. Of these patients, 153 (94.4%) were evaluated within 24 hours of ED discharge. Two patients (1.3%) who received outpatient evaluation required hospitalization; 101 (66%) of these patients had a final diagnosis of TIAMS. Other common diagnoses included peripheral neuropathy (15%), migraine (12.5%) and seizure/recrudescence (4%).

Conclusions: Our pilot data suggests that for a subset of TIAMS patients, rapid outpatient evaluation may be a feasible and safe strategy for TIAMS management. Future work exploring such strategies may improve TIAMS outcomes, reduce ED and inpatient crowding, and offer reductions in healthcare costs associated with TIAMS care.

Abstract TP277: A Hospital’s Perspective: Economic Evaluation of Hospitalization vs Rapid Outpatient Evaluation for TIA and Minor Strokes

Introduction: Patients presenting to emergency departments (ED) with TIA and minor strokes (TIAMS) are often admitted for expedited evaluation, though outpatient care models have been proposed. We piloted a rapid outpatient evaluation protocol for patients presenting with TIAMS within 24 hours of ED discharge. We hypothesized that this approach would reduce hospital costs and length of stay (LOS).

Methods: This analysis looked at patients presenting to our institution’s ED with TIAMS (NIHSS < 5) in calendar year 2017. We compared hospitalization LOS, costs and expected revenues between admitted patients and those referred for rapid outpatient evaluation. Patients eligible for outpatient evaluation were without disabling deficits, recurrent symptoms, new-onset atrial fibrillation, prior carotid imaging with >50% stenosis, and not receiving thrombolysis. Disabling deficits were defined as new gait impairments, significant motor weakness, hemianopia, dysphagia or severe aphasia. Cost data was obtained from our finance department and expected revenue was estimated using Medicare reimbursement data, assuming Medicare-Fee for Service as the primary payer for all patients.

Results: We identified 92 patients referred to our rapid outpatient clinic and 90 admitted patients (mean NIHSS 0.8 vs 1.8 respectively). In comparison to patients who were admitted, patients referred to outpatient evaluation had shorter hospital stays, lower total hospitalization costs, and decreased net-losses after accounting for expected revenue (Table). Only one patient in the outpatient cohort was readmitted for further management. Overall, the one-year pilot cohort averted approximately 138 bed-days and $950,000 in hospitalization costs.

Conclusions: For patients who presented to our ED with TIAMS without disabling deficits, rapid outpatient evaluation reduced hospital LOS and total costs. Further research is needed to incorporate costs to payers and patients.

Angiographic Blush after Mechanical Thrombectomy is Associated with Hemorrhagic Transformation of Ischemic Stroke

BACKGROUND AND PURPOSE

Risk factors for hemorrhagic transformation of ischemic stroke after mechanical thrombectomy (MT) are not well established. We conducted a study to determine if prominent angiographic cerebral vascularity following recanalization with thrombectomy (angiographic blush) is associated with hemorrhagic transformation.

METHODS

Using the Cornell AcutE Stroke Academic Registry, we identified stroke patients who had thrombectomy and achieved recanalization of anterior circulation large-vessel occlusion between 2012 and 2015. The exposure variable was presence of angiographic blush after recanalization, defined as capillary blush with or without early venous drainage. The primary outcome was volume of hemorrhagic transformation on brain imaging after thrombectomy, as determined by semiautomated volumetric analysis on computed tomography or magnetic resonance imaging among those adjudicated to have hemorrhagic conversion by neuroradiology investigators blinded to angiography results. Using a doubly robust estimator with propensity scores and outcome regression adjusting for demographics and known risk factors for hemorrhagic transformation, we evaluated whether angiographic blush after recanalization is associated with an increased volume of hemorrhagic transformation.

RESULTS

Among 48 eligible patients, 31 (64.6%) had angiographic blush and 26 (54.2%) had radiographic hemorrhagic transformation (mean volume, 7.6 ml). Patients with angiographic blush averaged lower thrombolysis in cerebral infarction scores and more often received intravenous thrombolysis. In adjusted analysis, angiographic blush was associated with an increased volume of hemorrhagic transformation: mean volume, 10.3ml (95% CI, 3.7-16.9 ml) with blush versus 1.8ml (95% Confidence Interval (CII = Confidence Interval), 0.1-3.4 ml) without (P = .01).

CONCLUSIONS

Presence of angiographic blush after MT was independently associated with the volume of hemorrhagic transformation.

Can I Send This Patient with Stroke Home? Strategies Managing Transient Ischemic Attack and Minor Stroke in the Emergency Department

BACKGROUND

While transient ischemic attack and minor stroke (TIAMS) are common conditions evaluated in the emergency department (ED), there is controversy regarding the most effective and efficient strategies for managing them in the ED. Some patients are discharged after evaluation in the ED and cared for in the outpatient setting, while others remain in an observation unit without being admitted or discharged, and others experience prolonged and potentially costly inpatient admissions.

OBJECTIVE OF THE REVIEW

The goal of this clinical review was to summarize and present recommendations regarding the disposition of TIAMS patients in the ED (e.g., admission vs. discharge).

DISCUSSION

An estimated 250,000 to 300,000 TIA events occur each year in the United States, with an estimated near-term risk of subsequent stroke ranging from 3.5% to 10% at 2 days, rising to 17% by 90 days. While popular and easy to use, reliance solely on risk-stratification tools, such as the ABCD2, should not be used to determine whether TIAMS patients can be discharged safely. Additional vascular imaging and advanced brain imaging may improve prediction of short-term neurologic risk. We also review various disposition strategies (e.g., inpatient vs. outpatient/ED observation units) with regard to their association with neurologic outcomes, such as 30-day or 90-day stroke recurrence or new stroke, in addition to other outcomes, such as hospital length of stay and health care costs.

CONCLUSIONS

Discharge from the ED for rapid outpatient follow-up may be a safe and effective strategy for some forms of minor stroke without disabling deficit and TIA patients after careful evaluation and initial ED workup. Future research on such strategies has the potential to improve neurologic and overall patient outcomes and reduce hospital costs and ED length of stay.

Population-Based Assessment of the Long-Term Risk of Seizures in Survivors of Stroke

BACKGROUND AND PURPOSE

We sought to determine the long-term risk of seizures after stroke according to age, sex, race, and stroke subtype.

METHODS

We performed a retrospective cohort study using administrative claims from 2 complementary patient data sets. First, we analyzed data from all emergency department visits and hospitalizations in California, Florida, and New York from 2005 to 2013. Second, we evaluated inpatient and outpatient claims from a nationally representative 5% random sample of Medicare beneficiaries. Our cohort consisted of all adults at the time of acute stroke hospitalization without a prior history of seizures. Our outcome was seizure occurring after hospital discharge for stroke. Poisson regression and demographic data were used to calculate age-, sex-, and race-standardized incidence rate ratios (IRR).

RESULTS

Among 777 276 patients in the multistate cohort, the annual incidence of seizures was 1.68% (95% confidence interval [CI], 1.67%-1.70%) after stroke versus 0.15% (95% CI, 0.15%-0.15%) among the general population (IRR, 7.3; 95% CI, 7.3-7.4). By 8 years, the cumulative rate of any emergency department visit or hospitalization for seizure was 9.27% (95% CI, 9.16%-9.38%) after stroke versus 1.21% (95% CI, 1.21%-1.22%) in the general population. Stroke was more strongly associated with a subsequent seizure among patients <65 years of age (IRR, 12.0; 95% CI, 11.9-12.2) than in patients ≥65 years of age (IRR, 5.5; 95% CI, 5.4-5.5) and in the multistate analysis, the association between stroke and seizure was stronger among nonwhite patients (IRR, 11.0; 95% CI, 10.8-11.2) than among white patients (IRR, 7.3; 95% CI, 7.2-7.4). Risks were especially elevated after intracerebral hemorrhage (IRR, 13.3; 95% CI, 13.0-13.6) and subarachnoid hemorrhage (IRR, 13.2; 95% CI, 12.8-13.7). Our study of Medicare beneficiaries confirmed these findings.

CONCLUSIONS

Almost 10% of patients with stroke will develop seizures within a decade. Hemorrhagic stroke, nonwhite race, and younger age seem to confer the greatest risk of developing seizures.

Abstract WP24: Angiographic Blush After Mechanical Thrombectomy is Associated With Hemorrhagic Conversion of Ischemic Stroke

Introduction: Risk factors for hemorrhagic transformation of ischemic stroke after mechanical thrombectomy are not well established.

Hypothesis: Prominent cerebral tissue vascularity on angiography after recanalization with thrombectomy (angiographic blush) is associated with hemorrhagic transformation.

Methods: Among patients in the Cornell AcutE Stroke Academic Registry (CAESAR), we identified those who underwent stent-retriever-based thrombectomy for anterior circulation occlusion between 2012 and 2015. The presence of hemorrhagic transformation and angiographic blush were determined by neuroradiologists and neurointerventionalists. We identified angiographic blush as hypervascularity with or without early venous drainage. Hemorrhagic transformation was defined using CT or MRI studies performed within 7 days of thrombectomy. Our primary outcome was the volume of hemorrhagic transformation, determined using 3D-Slicer software. Our secondary outcome was the presence of any hemorrhagic transformation. Using a doubly robust estimator, we analyzed whether the presence of angiographic blush after recanalization was associated with an increased volume of hemorrhagic transformation after adjustment for demographics and previously published risk factors for hemorrhagic transformation.

Results: Among 48 eligible patients (median age, 68 years; median NIHSS score, 18), 31 (64.6%) had angiographic blush and 26 (54.2%) had hemorrhagic transformation (mean volume, 7.6 cc). Patients with angiographic blush had lower TICI scores and had more often received alteplase. After adjustment for demographics and risk factors for hemorrhagic transformation, the presence of angiographic blush was significantly associated with an increased volume of hemorrhagic transformation: mean volume, 10.3 (95% CI, 3.7-16.9) cc with any blush versus 1.8 (95% CI, 0.1-3.4) cc without any blush (p=0.01). Angiographic blush was nonsignificantly associated with the presence of any hemorrhagic transformation (odds ratio, 1.5; 95% CI, 0.9-2.5).

Conclusions: In a single-center study, we found that the presence of angiographic blush after mechanical thrombectomy was independently associated with an increased volume of hemorrhagic transformation.

Abstract TMP112: Left Atrial Enlargement is Associated With Anticoagulation Failure in Patients With Acute Ischemic Stroke and Atrial Fibrillation

Background: Biomarkers to predict anticoagulation failure in patients with atrial fibrillation (AF) may help identify high-risk AF patients for further study. We hypothesize that left atrial enlargement (LAE) is more prevalent in AF patients admitted with ischemic stroke who are therapeutic, as opposed to non-therapeutic (NT), on anticoagulation.

Methods: We included consecutive patients with AF admitted with a diagnosis of ischemic stroke between April 1 st , 2015 and December 31 st , 2016. Patients were divided into two groups based on whether they were therapeutic (warfarin with international normalized ratio ≥ 2.0 or non-vitamin K oral anticoagulant with uninterrupted use in the prior 2 weeks) vs. non-therapeutic on anticoagulation. We compared clinical and imaging characteristics, cardiac data (left atrial diameter on transthoracic echocardiogram), and outcomes (discharge modified Rankin Scale, discharge disposition, and symptomatic intracranial hemorrhage [sICH]) between the two groups. Multivariable logistic regression was used to estimate associations between therapeutic anticoagulation and variables, including CHADS 2 score and LAE (none/mild vs. moderate/severe).

Results: We identified 225 patients; 52 (23.1%) were therapeutic on anticoagulation. The baseline demographics and risk factors were similar between the two groups. Patients therapeutic on anticoagulation were more likely to have a larger left atrial diameter (45.6 ± 9.2 vs. 42.3 ± 8.6 mm, p = 0.032), a higher CHADS2 score (2.9 ± 1.1 vs. 2.4 ± 1.1, p = 0.03), and sICH (13.5% vs. 3.5%, p = 0.013). After adjusting for the CHADS 2 score, patients who had stroke despite therapeutic anticoagulation were more likely to have moderate to severe LAE (odds ratio 2.05, 95% confidence interval 1.01-4.16). Results were unchanged when the CHA 2 DS 2 -VASc score was used.

Conclusion: LAE is associated with anticoagulation failure in AF patients admitted with an ischemic stroke. This provides indirect evidence that LAE may portend failure of anticoagulation therapy in patients with AF; further studies are needed to delineate the significance of this association and improve stroke prevention strategies.

Abstract WP232: Biomarkers of Atrial Cardiopathy and Atrial Fibrillation Detection on Mobile Continuous Outpatient Telemetry After Cryptogenic Stroke

Background: In population-based studies, biomarkers of atrial dysfunction or “cardiopathy” have been shown to be associated with embolic stroke risk. However, it is unclear if this risk is mediated by undiagnosed paroxysmal atrial fibrillation or flutter (AF). We aim to determine whether atrial cardiopathy biomarkers predict atrial fibrillation on continuous heart-rhythm monitoring after embolic stroke of undetermined source (ESUS).

Methods: This was a single-center retrospective study including all patients who met consensus criteria for ESUS and who underwent 30 days of ambulatory heart-rhythm monitoring looking for AF between Jan 1 st , 2013 and Dec 31 st , 2015. We reviewed medical records for clinical, radiographic, and cardiac variables. The primary outcome was new diagnosis of AF detected during heart-rhythm monitoring. The primary predictors were atrial biomarkers: left atrial diameter on echocardiography, P-wave terminal force in ECG lead V1 , and PR interval on ECG. Multiple logistic regression was used to assess the relationship between atrial biomarkers and AF detection.

Results: Among 196 eligible patients, 23 (11.7%) were diagnosed with AF. In unadjusted analyses, patients with AF were older (72.4 vs. 61.4 years, p < 0.001) and had larger left atrial diameter (39.2 vs. 35.7 mm, p = 0.03). In a multivariable model including variables significant on univariate analyses, the only predictor of AF was age ≥ 60 years (odds ratio, 3.0; 95% CI, 1.06-8.5; p = 0.04). Atrial biomarkers were not associated with AF detection.

Conclusion: Atrial biomarkers were not associated with AF after ESUS. This suggests that previously reported associations between these markers and stroke may reflect independent cardiac pathways leading to stroke. Prospective studies are needed to investigate these mechanisms and study anticoagulation versus antiplatelet treatment for secondary stroke prevention in patients with ESUS and atrial cardiopathy.

Abstract WP312: Identifying Acute Ischemic Stroke by Analyzing Icd-10 Claims Data Using Machine Learning Models

Introduction: Retrospective identification of patients hospitalized with new diagnosis of acute ischemic stroke is important for administrative quality assurance, post-discharge clinical management, and stroke research. The benefit of using administrative claims data is its widespread availability, but the disadvantage is in the inability to accurately and consistently identify the clinical diagnosis of interest.

Hypothesis: We hypothesized that decision tree and logistic regression models could be applied to administrative claims data coded using International Classification of Diseases, version 10 (ICD-10) to create algorithms that could accurately identify patients with acute ischemic stroke.

Methods: We used hospital records from our institution to develop a gold standard list of 243 patients, continuously hospitalized with a new diagnosis of stroke from 10/1/2015 to 3/31/2016. We used 1,393 neurological patients without a diagnosis of stroke as negative controls. This list was used to train and test two machine learning methods of diagnosis and procedure codes analysis, for the purpose of ischemic stroke identification: one using classification and regression tree (CART) and another using regularized logistic regression. We trained the models using 75% of the data and performed the evaluation using the remaining 25%.

Results: The CART model had a κ=0.78, sensitivity of 96%, specificity of 90%, and a positive predictive value of 99%. The regularized logistic regression model had a κ=0.73, sensitivity of 97%, specificity of 81%, and a positive predictive value of 98%.

Conclusion: Both the decision tree and logistic regression machine based learning models showed very high accuracy in identifying patients with a new diagnosis of ischemic stroke, using ICD-10 code claims data, when compared to our gold standard. Applying these machine learning models to identify patients with ischemic stroke has widespread applications, especially in this period where national billing data has transitioned from ICD-9 to ICD-10 codes.

Abstract WP331: Identifying Stroke Subtypes with High Accuracy Using Machine Learning and Icd-9 Claims Data

Introduction: Stroke research using widely available institutional, state-wide and national retrospective data is dependent on accurate identification of stroke subtypes using claims data. Despite the abundance of such data and the advances in clinical informatics, there is limited published data on the application of machine learning models to improve previously reported administrative stroke identification algorithms.

Hypothesis: We hypothesized that machine learning models can be applied to claims data coded using the International Classification of Disease, version 9 (ICD-9), to accuracy identify patients with ischemic stroke (IS), intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH), and these models would outperform previously published algorithms in our patient cohort.

Methods: We developed a gold standard list of 427 stroke patients continuously admitted to our institution from 1/1/2015 to 9/30/2015 using an internal stroke database and applied 75% of it to train and 25% to test two machine learning models: one using classification and regression tree (CART) and another using regularized logistic regression. There were 2,241 negative controls. We further applied a previously reported stroke detection algorithm, by Tirschwell and Longstreth, to our cohort for comparison.

Results: The CART model had a κ of 0.72, 0.82, 0.59; sensitivity of 95%, 99%, 99%; and a specificity of 88%, 78%, 75%; for IS, ICH and SAH respectively. The regularized logistic regression model had a κ of 0.73, 0.80, 0.59; sensitivity of 95%, 99%, 99%, and a specificity of 89%, 78%, 75%; for IS, ICH and SAH respectively. The previously reported algorithm by Tirschwell et al, had a κ of 0.71,0.56, 0.64; sensitivity of 98%, 99%, 99%; and a specificity of 64%, 52%, 50%; for IS, ICH and SAH.

Conclusion: Compared with the previously reported ICD 9 based detection algorithm, the machine learning models had a higher κ for diagnosis of IS and ICH, similar sensitivity for all subtypes, and higher specificity for all stroke subtypes in our cohort. Applying machine learning models to identify stroke subtypes from administrative data sets, can lead to highly accurate models of stroke subtype identification for health services researchers.

Immediate sealing of arterial puncture sites after cardiac catheterization and coronary interventions: initial U.S. feasibility trial using the Duett vascular closure device

The aim of this first U.S. feasibility study was to investigate the safety and efficacy of a novel vascular sealing device, Duett, following percutaneous endovascular procedures. Immediately following a catheterization procedure, the sealing device was deployed at the femoral arterial access site in 43 patients (diagnostic 29, intervention 11, intervention + abciximab 3). Patients were followed up at 1 month with clinical assessment, ankle-brachial index measurement, and Doppler ultrasound of the treated femoral artery puncture site. Successful hemostasis was achieved with the Duett alone in 42/43 (97.7%) patients. There was one uncomplicated crossover to manual compression. The time to hemostasis was 4.0+/-1.5, 6.9+/-4.2, and 5.8+/-1.2 min for diagnostic, interventional, and abciximab patients, respectively. At 1-month follow-up, one patient (2.3%) required ultrasound-guided compression for treatment of a pseudoaneurysm. There were no other major complications. This novel vascular sealing device appears to achieve rapid and safe hemostasis successfully immediately following a wide range of percutaneous endovascular procedures.

[What is the value of biomechanical knowledge for surgery of the hand?]

Cartilage and bone as supportive tissues are submitted to mechanical stresses and react to these in a very specific manner. Functional adaptation to the quality and magnitude of the acting forces is the result. In this article, the basic principles of functional adaptation of cartilage and bone will be presented. On the basis of these principles, promising functional concepts and clinical treatments may be established; this will be shown by some examples concerning the hand.

[Biomechanics of arthrodesis of the major joints of the extremities]

Insufficient movement after an arthrodesis must be compensated for by other joints. Arm movements with an ankylotic shoulder joint can be executed by rotation and tilting of the scapula. The trapezius muscle plays an important role in these movements. Arthrodesis of the hip joint requires an extended range of movement in the intact contralateral joint and sufficient mobility of the lumbar spine. Moreover, every ankylotic joint is stressed by bending because compensation of the torque due to the weight of the corresponding part of the body by the balancing muscles is no longer necessary. The architecture of the spongy bone is adapted to that bending stress. Characteristic examples are anatomic specimens of ankylotic hip and knee joints.

[Basics of Pauwels' theory of the functional adaptation of bones]

Bone is a secondary support tissue. It develops on the base of a preexistent primary scaffold, built up by connective tissue or by cartilage. Bone formation depends on the magnitude of the elastic deformation, due to loading. The skeletal organ "bone" reacts to the actual stress like a feedback system: high stress stimulates new bone formation and incorporation of mineral salts; low stress leads to bone resorption and mobilization of mineral salts. The result of extreme stress is bone resorption (stress fractures, pseudocysts). The radiological density and architecture of the spongy bone reflect exactly the direction and local magnitude of stress.

[Biomechanics of the meniscus]

The menisci of the knee joint enlarge the area of support to more than twice the surface of pure cartilage contact. As a result of the wedge-shaped cross-section, the meniscus is stressed by radially directed shear forces, but because of the bone attachment at both ends, the shear forces are transformed into circular tensile stress. The arrangement of collagen fibres reflects the pattern of tensile stress trajectories. Single chondroma are found in the peripheral zone. The range of displacement of the knee is considerably widened by the menisci. After meniscectomy, this function can be compensated for by the cruciate ligaments, but the stress on the articular cartilage will then increase.

Is the Pauwels' theory of hip biomechanics still valid? A critical analysis, based on modern methods

The Pauwels' theory of hip biomechanics assuming bending stresses of the proximal femur has been critisized by recent authors. Therefore, the fundamentals of the classic theory have been reviewed, analysed by means of modern methods, and completed. The conclusion is that, hypothetically, a totally bending-free skeletal scaffold could be obtained by muscular tear strings. The analysis of anatomical specimens and considerations on optimisation show, however, that the bending theory of the proximal femur gives still the best explanation for the observations. Furthermore, the classic model has to be completed by two important conditions: 1. The supporting foot must be positioned on the action line of the gravity force of the body, and 2. the abductorial forces on the hip (to balance the momentum of the body weight) is composed by the forces of the lesser glutei (70%) and the muscles tending the tractus iliotibialis (30%).

[The clinical relevance of biomechanical analysis of the hip area]

Some diseases of the hip are due to mechanical causes or are influenced in a positive or negative sense by mechanical factors. In every case, the balance between stressing and biological reaction of the tissues of the locomotor system plays a decisive role. A careful biomechanical analysis should therefore be made at the beginning of any prognostical or therapeutical consideration. This means respective to the hip joint analyses of magnitude and distribution of the articular pressure and of the stressing of the femoral neck. The normal hip joint is characterised by a nearly evenly distributed articular pressure, and this is expressed in a bone condensation of equal thickness in the acetabular roof (sourcil). The consequence of an uneven stress distribution is a triangular shape of the sourcil, increasing either to the lateral or to the medial border of the acetabular roof. The lateral triangle is in general steeper and therefore more dangerous than the medial one. The stress concentration alters first the articular cartilage and then the subchondral bone. The aim of a causal surgical therapy is the decrease and the equal distribution of the articular pressure. It can be attained by increasing the weight-bearing surface of the joint and by centralisation of the stressing force (joint resultant) within this surface. The neck of the normally shaped femur is stressed in the sense of bending, and the magnitude of this stress depends on the neck/shaft angle. In consequence of this result shearing forces at the level of neck fractures, thus preventing the bony reunion. The therapeutical intervention tries either to strengthen the resistance against the shearing force (by nailing) or to eliminate it--as for example in the case of non-union of a neck fracture--(valgisation osteotomy). The reduction of the shearing stress by a valgisation osteotomy (Y-osteotomy, Pauwels) is the decisive factor in the treatment of the congenital coxa vara, a disease, due to a reduced resistance of the tissues of the epiphyseal plate against the normal bending stress. Valgisation osteotomies include the danger of increasing stresses in the hip joint. However, this can be prevented by lateralisation of the greater trochanter.

[The function-dependent morphogenesis of the visceral cranium]

The growth pattern of the facial skull is described by the method of coordinate transformation and simulated in a computer model under the presumption of different growth gradients. The law of functional adaptation of the bone, as it has been proved for the postcranial skeleton, has been applied to the skull. The mechanical stress of the facial skull results from the masticatory function. Due to the complex architecture of the facial skeleton, the stress pattern cannot be determined with sufficient accuracy, needed for a detailed prediction of the growth processes. However, the exact knowledge of the mechanical stresses of single teeth allows the explanation of their positional changes by remodeling processes on the alveolar wall.

Physiological regulation of circadian and pulsatile thyrotropin secretion in normal man and woman

The circadian and pulsatile TSH secretion profiles were investigated in 5 females at the time of menstruation and 21 healthy males by sampling blood every 10 min for 24 h. Computer-assisted analysis, i.e. the Cluster and Desade programs, revealed means of 9.9 +/- 1.7 (Cluster) and 11.4 +/- 3.9 (Desade) pulses/24 h. More than 50% of the TSH pulses were detected between 2000-0400 h. Male and female subjects showed no significant difference in the basal mean and pulsatile secretion of TSH or in the TSH response to TRH (200 micrograms). Repetition of the TSH secretion analysis in 4 healthy subjects after 1, 2, and 6 months (2 subjects) revealed a significantly better cross-correlation within than between individuals (P less than 0.0001). We modulate the circadian TSH secretion pattern by acute sleep withdrawal or prolonged sleep after a night of sleep withdrawal in six healthy male volunteers. Sleep withdrawal augmented the nightly TSH secretion (mean serum TSH, 2.1 +/- 1.3 mU/L; mean TSH in sleep, 1.3 +/- 0.5 mU/L; P less than 0.05), whereas sleep after sleep withdrawal almost completely suppressed the circadian variation (mean TSH, 1.1 +/- 0.7 mU/L; P less than 0.01). This modulation is due to a significant decrease in pulse amplitude, but not to an alteration in the frequency or temporal distribution of TSH pulses.

[Densitometry of the bony structures of the human TMJ]

Four millimeter sagittal section of 65 formalin-fixed human TMJs were prepared. The X-rays of these specimen were evaluated numerically in a densitometer. The distribution of bone material and densities in condyle and fossa led to a classification of condylar and fossa types. In 48 specimen a combination of increased density of the condyle on the facial aspect with a thin bony lamella in the roof of the fossa, which either shows high density or very little material of low density, a so-called parchment fossa, was observed. The varying degrees of density as a function of mechanical stresses are discussed. The transfer of forces in the human TMJ during mastication exposes the superio-anterior or superio-facial segments of the condyle and the posterior slope of the articular tubercle to loading forces, while at the same time the roof of the fossa remains free of load.

[Biomechanical aspects of hip dislocation]

The stress distribution in the subluxated hip joint is analyzed by means of a two-dimensional computer model. Luxation becomes manifest if the action line does not intersect with the contour of the socket. Pathological stress with overloading of the bone and cartilage tissue appear if the articular resultant force is shifted towards the acetabular edge. The important parameter is the CE angle. The coxa valga per se has no pathological meaning as long as the femoral head is covered sufficiently by the acetabular roof.

[Anatomy and biomechanics of the meniscus of the knee joint]

The menisci enlarge the weight-bearing surface to an extension twice of the pure contact surface between the femur condyles and the tibia plateau. Furthermore they widen the range of the articular resultant force. Consequently, the balancing muscular forces can be implemented more economically. The menisci are adapted to their functional stressing: circular tension is resisted by circularly arranged collagen fiber bundles. Split lines, however, show a more complex arrangement.

[MR of the shoulder joint with surface coils at 1.5 tesla. Its anatomy and possible clinical use]

High spatial resolution magnetic resonance images of the shoulder were obtained in axial, sagittal and coronal orientations using a 1.5 T imaging system and anatomically shaped, wrap-around surface coils. Variations in scapular position induced by patient positioning change the relationship of the planes to the shoulder anatomy and make reproducibility of sagittal and coronal planes difficult. We, therefore, use--after axial orientation--image-oblique planes perpendicular and parallel to the glenoid fossa. In this manner MRI can visualise the anatomic structures of the shoulder including rotator cuff, long biceps tendon, articular capsule, articular cartilage, muscles and bones due to the high soft tissue contrast of MRI.

[Biomechanical principles of the statics of the hip joint. Critical appraisal of a new theory]

Graphical analysis of forces, acting on the hip joint and the study of x-ray pictures show clearly, that there exist no shifting components, pushing the femoral head out of the acetabulum as described by Bombelli in several publications. Therefore, shifting forces cannot have any causal effect on the development of primary arthrosis.

[Basic biomechanics of "stress-correction" by osteotomies in the region of the knee joint (author's transl)]

A recent suggestion by Izadpanah and Keönch-Fraknóy (1977) for the correction of the stressing of the knee-joint, is an epiarticular transpositary osteotomy with either a medial or lateral displacement of the condyle block, thus causing neither valgisation nor varisation. With the aid of compression tests on specimens and a photoelastic test, the authors try to prove the effect of this osteotomy. The tests give a false positive result. The submitted investigation deals with basics of correction osteotomies at the knee-joint. It shows that the effect of Izadpanah and Keönch-Fraknóy osteotomy is essentially slighter that the authors think and that furthermore, Maquet's subarticular rotation osteotomy is so far the best method available for centralisation of the force resultant in the joint.