Abstract 106: A Simple Screening Tool to Identify Stroke or TIA Patients With Moderate or Severe Obstructive Sleep Apnea: The CHA2TS2 Score

Introduction: The frequency of obstructive sleep apnea (OSA) among stroke and TIA patients varies from 14% to 72% depending on apnea-hypopnea index (AHI) cut-off points and the study population. Various screening tools have been validated in unselected patients referred for diagnostic polysomnography (DP) but a screening tool that identifies stroke/TIA patients at highest risk of moderate-severe OSA is lacking.

Hypothesis: A simple screening tool that considers medical comorbidities and sleep-related symptoms can identify stroke/TIA patients who are most likely to have moderate-severe OSA.

Methods: Consecutive stroke and TIA patients referred by vascular neurology for DP from September 2012 to February 2015 were included in a retrospective analysis. Baseline clinical characteristics, DP results and outcomes were collected retrospectively. Moderate-severe OSA was defined as AHI≥15.

Results: Of 65 patients (mean age 61±14 years, 48% female, 51% African-American) included in this analysis, 19 (29.2%) were diagnosed with moderate-severe OSA. In multivariable analysis using backward elimination (entry and exit thresholds 0.15), predictors of moderate-severe OSA included history of Coronary artery disease, Hyperlipidemia, older Age, history of Atrial fibrillation, former or current Tobacco use and self- or family-reported Snoring or daytime Sleepiness (CHA2TS2). Variables excluded were sex, race, hypertension, diabetes, depression, chronic obstructive pulmonary disease, patent foramen ovale, body mass index, stroke subtype and wakeup onset . The CHA2TS2 model had excellent predictive power for moderate-severe OSA (AUC= 0.91). CHA2TS2 ≥5 had 100% sensitivity and 54% specificity for detecting moderate-severe OSA.

Conclusions: We developed a simple screening tool that can identify stroke and TIA patients who have high likelihood of having moderate or severe OSA identified on their DP. Prospective validation of CHA2TS2 score is currently underway.

Abstract 206: High False Positive Rates of Atrial Fibrillation Detection Among Stroke Patients who Receive Medtronic Implantable Loop Recorders

Introduction: Atrial fibrillation is a known risk factor for the development of stroke. Implantable loop recorders (ILRs) have specific algorithms to detect occult atrial fibrillation and can be used in patients with cryptogenic stroke. There is limited data on the frequency of false positive atrial fibrillation detected by the Medtronic ILR.

Hypothesis: Medtronic ILRs have a high rate of false positives but despite this are still effective at detecting atrial fibrillation in patients with cryptogenic stroke.

Methods: All stroke patients who underwent ILR placement from Jan 1, 2013 to June 30, 2015 were prospectively collected through an administrative database. Baseline and clinical characteristics were retrospectively obtained. A random sampling of ILR tracings identified as atrial fibrillation by the Medtronic algorithm was adjudicated by a board certified electrophysiologist for accuracy.

Results: Among 52 patients with a history of ischemic stroke or TIA (mean age 68±14 years, 58% male, 83% white), there were 166 rhythm strips identified as atrial fibrillation by the Medtronic algorithm which were adjudicated. Of the 166 strips reviewed, 140 (84%) were incorrectly identified as atrial fibrillation; of those false positives, adjudication identified 57% as premature atrial complexes(PACs), 22% as T wave over-sensing, 10% due to noise, 5.0% due to premature ventricular complexes (PVCs), 2.9% due to under-sensing, and 2.9% due to sinus arrhythmia. Of the 38 (73%) patients who had ILR implantation for cryptogenic stroke, 4 (11%) were identified as having true atrial fibrillation by ILR after adjudication over 413 patient-months of monitoring; mean time to atrial fibrillation detection was 93 days after implantation.

Conclusions: Stroke patients who undergo Medtronic ILR placement have high false positive rates of atrial fibrillation detected with the Medtronic algorithm. When adequately reviewed by a trained cardiologist for accuracy, the Medtronic ILRs remain effective at detecting atrial fibrillation in cryptogenic stroke patients.

Distal tibial fractures are a poorly recognised complication with fibula free flaps

The fibula free flap is ideal for complex jaw reconstructions, with low reported donor and flap morbidity. We discuss a distal tibial stress fracture two months following a vascularised fibula free flap procedure. Despite being an unrecognised complication, a literature review produced 13 previous cases; only two were reported in the reconstructive surgery literature, with the most recent claiming to be the first. The majority of these studies treated this fracture non-operatively; none reported their patient follow-up. Each case presented with ipsilateral leg pain, which has been cited as an early donor site morbidity in as many as 40% of fibula free flap cases. It is known that the fibula absorbs at least 15% of leg load on weight bearing. Studies have shown severe valgus deformities in up to 25% of patients with fibulectomies. We treated our patient operatively, first correcting his worsening valgus deformity with an external fixator, then reinforcing his healed fracture with a long distal tibial plate. We believe that this complication is underreported, unexpected and not mentioned during the consenting process. By highlighting the management of our case and the literature, we aim to increase awareness (and thus further reporting and appropriate management) of this debilitating complication.

Identification of toxicants in cinnamon-flavored electronic cigarette refill fluids

In a prior study on electronic cigarette (EC) refill fluids, Cinnamon Ceylon was the most cytotoxic of 36 products tested. The purpose of the current study was to determine if high cytotoxicity is a general feature of cinnamon-flavored EC refill fluids and to identify the toxicant(s) in Cinnamon Ceylon. Eight cinnamon-flavored refill fluids, which were screened using the MTT assay, varied in their cytotoxicity with most being cytotoxic. Human embryonic stem cells were generally more sensitive than human adult pulmonary fibroblasts. Most products were highly volatile and produced vapors that impaired survival of cells in adjacent wells. Cinnamaldehyde (CAD), 2-methoxycinnamaldehyde (2MOCA), dipropylene glycol, and vanillin were identified in the cinnamon-flavored refill fluids using gas chromatography–mass spectrometry and high-pressure liquid chromatography (HPLC). When authentic standards of each chemical were tested using the MTT assay, only CAD and 2MOCA were highly cytotoxic. The amount of each chemical in the refill fluids was quantified using HPLC, and cytotoxicity correlated with the amount of CAD/product. Duplicate bottles of the same product were similar, but varied in their concentrations of 2MOCA. These data show that the cinnamon flavorings in refill fluids are linked to cytotoxicity, which could adversely affect EC users.

Medial submuscular plating of the femur in a series of paediatric patients: a useful alternative to standard lateral techniques

We describe the technique and results of medial submuscular plating of the femur in paediatric patients and discuss its indications and limitations. Specifically, the technique is used as part of a plate-after-lengthening strategy, where the period of external fixation is reduced and the plate introduced by avoiding direct contact with the lateral entry wounds of the external fixator pins. The technique emphasises that vastus medialis is interposed between the plate and the vascular structures. A total of 16 patients (11 male and five female, mean age 9.6 years (5 to 17)), had medial submuscular plating of the femur. All underwent distraction osteogenesis of the femur with a mean lengthening of 4.99 cm (3.2 to 12) prior to plating. All patients achieved consolidation of the regenerate without deformity. The mean follow-up was 10.5 months (7 to 15) after plating for those with plates still in situ, and 16.3 months (1 to 39) for those who subsequently had their plates removed. None developed a deep infection. In two patients a proximal screw fractured without loss of alignment; one patient sustained a traumatic fracture six months after removal of the plate. Placing the plate on the medial side is advantageous when the external fixator is present on the lateral side, and is biomechanically optimal in the presence of a femoral defect. We conclude that medial femoral submuscular plating is a useful technique for specific indications and can be performed safely with a prior understanding of the regional anatomy.

4D digital subtraction angiography: implementation and demonstration of feasibility

BACKGROUND AND PURPOSE

Conventional 3D-DSA volumes are reconstructed from a series of projections containing temporal information. It was our purpose to develop a technique which would generate fully time-resolved 3D-DSA vascular volumes having better spatial and temporal resolution than that which is available with CT or MR angiography.

MATERIALS AND METHODS

After a single contrast injection, projections from the mask and fill rotation are subtracted to create a series of vascular projections. With the use of these projections, a conventional conebeam CT reconstruction is generated (conventional 3D-DSA). This is used to constrain the reconstruction of individual 3D temporal volumes, which incorporate temporal information from the acquired projections (4D-DSA).

RESULTS

Typically, 30 temporal volumes per second are generated with the use of currently available flat detector systems, a factor of ∼200 increase over that achievable with the use of multiple gantry rotations. Dynamic displays of the reconstructed volumes are viewable from any angle. Good results have been obtained by using both intra-arterial and intravenous injections.

CONCLUSIONS

It is feasible to generate time-resolved 3D-DSA vascular volumes with the use of commercially available flat detector angiographic systems and clinically practical injection protocols. The spatial resolution and signal-to-noise ratio of the time frames are largely determined by that of the conventional 3D-DSA constraining image and not by that of the projections used to generate the 3D reconstruction. The spatial resolution and temporal resolution exceed that of CTA and MRA, and the small vessel contrast is increased relative to that of conventional 2D-DSA due to the use of maximum intensity projections.

Patella distal pole avulsion secondary to osteomyelitis in a healthy adult

Primary haematogenous patella osteomyelitis in an adult is a rare condition. Cases published in the literature relate predominantly to the paediatric population or are associated with risk factors such as intravenous drug abuse, human immunodeficiency virus and penetrating trauma. The rarity of this condition and its atypical presentation should be borne in mind while treating a patient with anterior knee pain. It is crucial to evaluate radiography of diagnostic quality carefully.

Design of Dispersive Mixing Devices

Mixing is one of the main functions of screw extruders. In the analysis of mixing, there are two mixing mechanisms that need to be considered: distributive and dispersive mixing. It is well known that single screw extruders generally have poor dispersive mixing capability, even when dispersive mixing elements are incorporated into the screw design. This paper will discuss the requirements for dispersive mixing, current dispersive mixing elements used in single screw extruders will be analyzed, and the lack of efficient dispersive mixing will be explained. A new generation of dispersive mixing elements will be introduced for use in both single and twin screw extruders and internal mixers. A two and three dimensional flow simulation will be used to analyze the mixing performance of these new mixers. Experimental work on the new mixing elements will be presented in a follow-up paper; the results demonstrate that it is possible to achieve dispersive mixing on single screw extruders that is as good as what can be achieved on twin screw extruders. The implications of these results on the compounding industry will be briefly discussed.

A method for rapid dose-response screening of environmental chemicals using human embryonic stem cells

INTRODUCTION

Human embryonic stem cells (hESC) provide an invaluable model for assessing the effects of environmental chemicals and drugs on human prenatal development. However, hESC are difficult to adapt to 96-well plate screening assays, because they survive best when plated as colonies, which are difficult to count and plate accurately. The purpose of this study is to present an experimental method and analysis procedure to accomplish reliable screening of toxicants using hESC.

METHODS

We present a method developed to rapidly and easily determine the number of cells in small colonies of hESC spectrophotometerically and then accurately dispense equivalent numbers of cells in 96-well plates. The MTT assay was used to evaluate plating accuracy, and the method was tested using known toxicants.

RESULTS

The quality of the plate set-up and analysis procedure was evaluated with NIH plate validation and assessment software. All statistical parameters measured by the software were acceptable, and no drift or edge effects were observed. The 96-well plate MTT assay with hESC was tested by performing a dose-response screen of commercial products, which contain a variety of chemicals. The screen was done using single wells/dose, and the reliability of this method was demonstrated in a subsequent screen of the same products repeated three times. The single and triple screens were in good agreement, and NOAELs and IC(50)s could be determined from the single screen. The effects of vapor from volatile chemicals were studied, and methods to monitor and avoid vapor effects were incorporated into the assay.

DISCUSSION

Our method overcomes the difficulty of using hESC for reliable quantitative 96-well plate assays. It enables rapid dose-response screening using equipment that is commonly available in laboratories that culture hESC. This method could have a broad application in studies of environmental chemicals and drugs using hESC as models of prenatal development.

Two galantamine titration regimens in patients switched from donepezil

OBJECTIVES

In addition to inhibiting acetylcholinesterase, galantamine has allosteric-modulating activity at nicotinic receptors. This may make galantamine an attractive option for patients starting treatment for Alzheimer's disease (AD), but also for those who have not benefited from their current therapy. This study explored outcomes in subjects with AD transitioning from donepezil because of insufficient tolerability or efficacy.

MATERIALS AND METHODS

Subjects previously receiving donepezil for mild-to-moderate AD were enrolled in a 12-week randomized, open-label study. After screening and a 7-day washout, subjects were randomly allocated to galantamine fast (8 mg/week increments) or slow (8 mg/4 week) titration to 16-24 mg. Efficacy outcomes included the Alzheimer's Disease Assessment Scale - cognitive subscale (ADAS-cog/11), Mini-Mental State Examination (MMSE), Clinician's Interview-Based Impression of Change - Plus Caregiver's Input (CIBIC-plus) and Alzheimer's Disease Cooperative Study - Activities of Daily Living Inventory (ADCS-ADL).

RESULTS

Eighty-six of 89 patients (fast titration, n = 44; slow titration, n = 45) completed the study. At week 12, ADAS-cog/11 score improved from screening by 2.6 and 0.6 in the fast- and slow-titration arms, respectively (overall, -1.6; P = 0.002). MMSE scores improved slightly in both arms (overall, +0.9; P = 0.002). Two-thirds of patients had improvement or no change on the CIBIC-plus at week 12. ADCS-ADL scores did not change significantly from screening in either treatment arm. Galantamine was generally well tolerated; nausea (5.6%) and bradycardia (4.5%) were the most commonly reported adverse events.

CONCLUSIONS

Patients in whom donepezil is ineffective or poorly tolerated may benefit from a switch to galantamine.

Endoscopic image analysis in semantic space

A novel approach to the design of a semantic, low-dimensional, encoding for endoscopic imagery is proposed. This encoding is based on recent advances in scene recognition, where semantic modeling of image content has gained considerable attention over the last decade. While the semantics of scenes are mainly comprised of environmental concepts such as vegetation, mountains or sky, the semantics of endoscopic imagery are medically relevant visual elements, such as polyps, special surface patterns, or vascular structures. The proposed semantic encoding differs from the representations commonly used in endoscopic image analysis (for medical decision support) in that it establishes a semantic space, where each coordinate axis has a clear human interpretation. It is also shown to establish a connection to Riemannian geometry, which enables principled solutions to a number of problems that arise in both physician training and clinical practice. This connection is exploited by leveraging results from information geometry to solve problems such as (1) recognition of important semantic concepts, (2) semantically-focused image browsing, and (3) estimation of the average-case semantic encoding for a collection of images that share a medically relevant visual detail. The approach can provide physicians with an easily interpretable, semantic encoding of visual content, upon which further decisions, or operations, can be naturally carried out. This is contrary to the prevalent practice in endoscopic image analysis for medical decision support, where image content is primarily captured by discriminative, high-dimensional, appearance features, which possess discriminative power but lack human interpretability.