The Undesirable Communication: A Case of Cerebral Air Emboli in the Setting of Atrio-Esophageal Fistula Following Atrial Fibrillation Catheter Ablation

Atrial-esophageal fistula is an extremely rare condition but is often a deleterious complication following catheter ablation for atrial fibrillation. The associated iatrogenic communication acts as a conduit for air and bacterial translocation, which may lead to cerebral air embolism and polymicrobial sepsis, respectively. Coupled with a history of invasive procedures, the diagnosis is largely based on the accompanying neurological symptoms. In this report, we present the case of a 73-year-old female who presented with neurological deficits attributed to cerebral vascular emboli three weeks after catheter ablation for the treatment of chronic atrial fibrillation

Characterization and modeling of a planar ultrasonic piezoelectric transducer for periodontal scalers

Caries and periodontitis affect the majority of adults during their lifetime. Piezoelectric ultrasonic scalers offer great benefits during the prevention and treatment of periodontal diseases. Our group developed a novel ultrasonic periodontal scaler based on a planar piezoelectric transducer. However, similar to other piezoelectric configurations, the transducer’s characteristics are strongly influenced by operation conditions. In this study, we investigated the influence of driving voltage amplitude and loading force applied using physical calculus models on the novel planar transducer’s input impedance and vibration. Our results show that the resonance frequency, i.e. the frequency at which maximal deflection of the tip occurs, decreases with increasing driving voltage amplitude while it increases with increasing force. Additionally, decreasing driving voltage amplitudes and increasing force both increase the minimal magnitude and reduce the maximal phase of the input impedance near resonance. Based on these observations, we developed a procedure to extend the Butterworth-Van-Dyke (BVD) Model. The extended BVD models allow to simulate the transducer in realistic scenarios and may facilitate the development of dedicated control systems for planar piezoelectric transducers

Characterization and modeling of a planar ultrasonic piezoelectric transducer for periodontal scalers

Caries and periodontitis affect the majority of adults during their lifetime. Piezoelectric ultrasonic scalers offer great benefits during the prevention and treatment of periodontal diseases. Our group developed a novel ultrasonic periodontal scaler based on a planar piezoelectric transducer. However, similar to other piezoelectric configurations, the transducer’s characteristics are strongly influenced by operation conditions. In this study, we investigated the influence of driving voltage amplitude and loading force applied using physical calculus models on the novel planar transducer’s input impedance and vibration. Our results show that the resonance frequency, i.e. the frequency at which maximal deflection of the tip occurs, decreases with increasing driving voltage amplitude while it increases with increasing force. Additionally, decreasing driving voltage amplitudes and increasing force both increase the minimal magnitude and reduce the maximal phase of the input impedance near resonance. Based on these observations, we developed a procedure to extend the Butterworth–Van-Dyke (BVD) Model. The extended BVD models allow to simulate the transducer in realistic scenarios and may facilitate the development of dedicated control systems for planar piezoelectric transducers

Design and realization of a piezoelectric motor for a high temperature automotive application

L’objectif de cette thèse est deconcevoir et de réaliser un moteurpiézoélectrique destiné à une application derécupération de chaleur du gaz d’échappement.Cette application nécessite un couplerelativement élevé, une compacité importante,une endurance thermique et un coût acceptable.Afin d’atteindre ce but, la conception du moteurpasse par le choix de son mode defonctionnement. Ce choix est fait en se basantsur des critères comme bas coût, fort couple etcompacité importante.Après la détermination de l’architecture dumoteur piézoélectrique, la modélisation estabordée. Le but du modèle est de calculer lescaractéristiques couple/vitesse connaissantses dimensions et ses matériaux, l’état desurface du contact, la précontrainte et la tensiond’alimentation.La modélisation développée était validée pardes mesures expérimentales.Dans la dernière partie, le moteur dimensionnéest réalisé et testé. Son comportementdynamique et ces caractéristiquescouple/vitesse étaient mesurés. A l’exceptiondu couple à l’arrêt et celui de blocage, toutes lesperformances requises par l’application étaientremplies.Finalement, les résultats de modèle sontcomparés aux mesures faites sur le prototype.Le comportement dynamique était bienreproduit par la modélisation. Néanmoins, uneimprécision du calcul des déplacements dustator était constatée. Cela implique uneimprécision du calcul des caractéristiquesmoteur. Il s’avère que cette imprécision est liéeà l’absence du coefficient d’amortissement decontact.The goal of this thesis is to designand build a piezoelectric motor for an exhaustgas heat recovery application. This applicationrequires relatively high torque, highcompactness, thermal endurance and acceptablecost.In order to achieve this goal, the design of theengine passes by the choice of its mode ofoperation. This choice is made based on criteriasuch as low cost, high torque and compactness.After the determination of the architecture ofthe piezoelectric motor, the modelling isaddressed. The purpose of the model is tocompute the torque/speed characteristicsknowing the motor dimensions and materials,the surface state of the contact, the precompressionforce and the supply voltage.The modeling developed was validated byexperimental measurements.In the last part, the motor is build and tested. Itsdynamic behavior and torque/speedcharacteristics were measured. With theexception of the peak and blocking torque, allthe performances required by the applicationwere fulfilled.Finally, the model results are compared to themeasurements done on the prototype. Thedynamic behavior is well predicted by themodel. However, the model is not able tocompute accurately the stator displacements.This implies inaccuracy in the motorcharacteristics computation. It turns out thatthey are related to the absence of the coefficientof contact damping

3D reconstruction of coronary artery bifurcations from intravascular ultrasound and angiography

Abstract Coronary bifurcation lesions represent a challenging anatomical subset, and the understanding of their 3D anatomy and plaque composition appears to play a key role in devising the optimal stenting strategy. This study proposes a new approach for the 3D reconstruction of coronary bifurcations and plaque materials by combining intravascular ultrasound (IVUS) and angiography. Three patient-specific silicone bifurcation models were 3D reconstructed and compared to micro-computed tomography (µCT) as the gold standard to test the accuracy and reproducibility of the proposed methodology. The clinical feasibility of the method was investigated in three diseased patient-specific bifurcations of varying anatomical complexity. The IVUS-based 3D reconstructed bifurcation models showed high agreement with the µCT reference models, with r2 values ranging from 0.88 to 0.99. The methodology successfully 3D reconstructed all the patient bifurcations, including plaque materials, in less than 60 min. Our proposed method is a simple, time-efficient, and user-friendly tool for accurate 3D reconstruction of coronary artery bifurcations. It can provide valuable information about bifurcation anatomy and plaque burden in the clinical setting, assisting in bifurcation stent planning and education

Patient-specific computational simulation of coronary artery bypass grafting

INTRODUCTION: Coronary artery bypass graft surgery (CABG) is an intervention in patients with extensive obstructive coronary artery disease diagnosed with invasive coronary angiography. Here we present and test a novel application of non-invasive computational assessment of coronary hemodynamics before and after bypass grafting. METHODS AND RESULTS: We tested the computational CABG platform in n = 2 post-CABG patients. The computationally calculated fractional flow reserve showed high agreement with the angiography-based fractional flow reserve. Furthermore, we performed multiscale computational fluid dynamics simulations of pre- and post-CABG under simulated resting and hyperemic conditions in n = 2 patient-specific anatomies 3D reconstructed from coronary computed tomography angiography. We computationally created different degrees of stenosis in the left anterior descending artery, and we showed that increasing severity of native artery stenosis resulted in augmented flow through the graft and improvement of resting and hyperemic flow in the distal part of the grafted native artery. CONCLUSIONS: We presented a comprehensive patient-specific computational platform that can simulate the hemodynamic conditions before and after CABG and faithfully reproduce the hemodynamic effects of bypass grafting on the native coronary artery flow. Further clinical studies are warranted to validate this preliminary data