Search for: heart-ventricles
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    Evaluation of a novel extra-cardiac Fontan procedure with implantation of a biocompatible membrane

    , Article IRBM ; Volume 36, Issue 5 , 2015 , Pages 287-292 ; 19590318 (ISSN) Rajabzadeh Oghaz, H ; Firoozabadi, B ; Saidi, M. S ; Monjezi, M ; Navabi Shirazi, M. A ; Malakan Rad, E ; Sharif University of Technology
    Elsevier Masson SAS  2015
    Fontan operation is a final palliative surgical treatment for patients with a single ventricle (SV) physiology. One of the common disadvantages of Fontan operation is to generate a non-pulsatile flow instead of the normal pulsatile flow produced by contraction of the ventricle. Theoretically, in SV patients, maintaining the antegrade flow through pulmonary valve can produce flow pulsatility in the right and left pulmonary arteries. However, it not only increases the energy loss in the Fontan of total cavopulmonary pathway (TCPC), but also imposes an extra load on pulmonary arteries as well as the ventricle. In this study, the potential capability of pulmonary valve of the patient that can be... 

    Robust detection of premature ventricular contractions using a wave-based Bayesian framework

    , Article IEEE transactions on bio-medical engineering ; Volume 57, Issue 2 , September , 2010 , Pages 353-362 ; 15582531 (ISSN) Sayadi, O ; Shamsollahi, M. B ; Clifford, G. D ; Sharif University of Technology
    Detection and classification of ventricular complexes from the ECG is of considerable importance in Holter and critical care patient monitoring, being essential for the timely diagnosis of dangerous heart conditions. Accurate detection of premature ventricular contractions (PVCs) is particularly important in relation to life-threatening arrhythmias. In this paper, we introduce a model-based dynamic algorithm for tracking the ECG characteristic waveforms using an extended Kalman filter. The algorithm can work on single or multiple leads. A "polargram"--a polar representation of the signal--is introduced, which is constructed using the Bayesian estimations of the state variables. The polargram... 

    A novel distributed model of the heart under normal and congestive heart failure conditions

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 227, Issue 4 , 2013 , Pages 362-372 ; 09544119 (ISSN) Ravanshadi, S ; Jahed, M ; Sharif University of Technology
    Conventional models of cardiovascular system frequently lack required detail and focus primarily on the overall relationship between pressure, flow and volume. This study proposes a localized and regional model of the cardiovascular system. It utilizes noninvasive blood flow and pressure seed data and temporal cardiac muscle regional activity to predict the operation of the heart under normal and congestive heart failure conditions. The analysis considers specific regions of the heart, namely, base, mid and apex of left ventricle. The proposed method of parameter estimation for hydraulic electric analogy model is recursive least squares algorithm. Based on simulation results and comparison... 

    Investigation of the effect of high +Gz accelerations on human cardiac function

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 27 , 2013 , Pages 54-63 ; 17516161 (ISSN) Jamshidi, M ; Ahmadian, M. T ; Sharif University of Technology
    This study investigates the effect of body acceleration on human cardiac function. Finite element analysis is conducted to simulate geometrical and mechanical properties of human heart. Heart geometrical modeling in three-dimension is performed by segmentation of cardiac MRI images. The nonlinear mechanical behavior of myocardium is modeled by Mooney-Rivlin, Polynomial, Ogden and Yeoh hyperelastic material models. Stress-strain curves of myocardial tissue are obtained from experimental compression tests on bovine heart samples. The experimental results are employed for the evaluation of material coefficients by the nonlinear least squares method. Among hyperelastic models, the Yeoh model... 

    The role of hippo signaling pathway in physiological cardiac hypertrophy

    , Article BioImpacts ; Volume 10, Issue 4 , 2020 , Pages 251-257 Gholipour, M ; Tabrizi, A ; Sharif University of Technology
    Tabriz University of Medical Sciences  2020
    Introduction: The role of Hippo signaling pathway, which was identified by genetic studies as a key regulator for tissue growth and organ size, in promoting physiological cardiac hypertrophy has not been investigated. Methods: Fourteen male Wistar rats were randomly assigned to the exercise and control groups. The exercise group ran 1 hour per day, 5 days/week, at about 65%-75% VO2max on the motor-driven treadmill with 15ºslope, and the control group ran 15 min/d, 2 days/ week at 9 m/min (0ºinclination), throughout the eight-week experimental period. Forty-eight hours after the last session, hearts were dissected and left ventricles were weighed and stored for subsequent RT-PCR analysis.... 

    Time-dependent analysis of leaflets in mechanical aortic bileaflet heart valves in closing phase using the finite strip method

    , Article Medical Engineering and Physics ; Volume 28, Issue 2 , 2006 , Pages 122-133 ; 13504533 (ISSN) Mohammadi, H ; Ahmadian, M. T ; Wan, W. K ; Sharif University of Technology
    Background and aims of the study: Mechanical heart valves (MHV) are widely used to replace dysfunctional and failed heart valves. The bileaflet MHV design is very popular due to its superior hemodynamics. Since their introduction in 1977, the hemodynamics of bileaflet prostheses has been extensively studied. In this study the dynamic behaviour during the closing phase of a bileaflet MHV under normal physiological conditions has been investigated. Methods: Fluid analysis is based on the control volume with moving boundaries in the vicinity of the occluder. Unsteady continuity equation, unsteady momentum equation on the control volume and unsteady Bernoulli's equation have been used to... 

    Polymer/metal composite 3D porous bone tissue engineering scaffolds fabricated by additive manufacturing techniques: A review

    , Article Bioprinting ; Volume 25 , 2022 ; 24058866 (ISSN) Mohammadi Zerankeshi, M ; Bakhshi, R ; Alizadeh, R ; Sharif University of Technology
    Elsevier B.V  2022
    The employment of tissue engineering scaffolds in the reconstruction of the damaged bone tissues has shown remarkable promise since they significantly facilitate the healing process. Fabrication of highly porous biocompatible scaffolds with sufficient mechanical strength is still challenging. In this regard, polymers have been widely utilized to construct three-dimensional (3D) porous scaffolds due to their excellent processability and biocompatibility. However, insufficient mechanical strength and inappropriate degradation rate of the monophasic polymer scaffolds in the bone regeneration process, as the main challenges, limit their extensive clinical application. The incorporation of... 

    LSTM-Based ecg classification for continuous monitoring on personal wearable devices

    , Article IEEE Journal of Biomedical and Health Informatics ; Volume 24, Issue 2 , 2020 , Pages 515-523 Saadatnejad, S ; Oveisi, M ; Hashemi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Objective: A novel electrocardiogram (ECG) classification algorithm is proposed for continuous cardiac monitoring on wearable devices with limited processing capacity. Methods: The proposed solution employs a novel architecture consisting of wavelet transform and multiple long short-term memory (LSTM) recurrent neural networks (see Fig. 1). Results: Experimental evaluations show superior ECG classification performance compared to previous works. Measurements on different hardware platforms show the proposed algorithm meets timing requirements for continuous and real-time execution on wearable devices. Conclusion: In contrast to many compute-intensive deep-learning based approaches, the... 

    Clinical validation of a smartphone-based handheld ECG device: A validation study

    , Article Critical Pathways in Cardiology ; Volume 21, Issue 4 , 2022 , Pages 165-171 ; 1535282X (ISSN) Ahmadi-Renani, S ; Gharebaghi, M ; Kamalian, E ; Hajghassem, H ; Ghanbari, A ; Karimi, A ; Mansoury, B ; Dayari, M. S ; Khatmi Nemati, M ; Karimi, A ; Zarghami, M. H ; Vasheghani Farahani, A ; Sharif University of Technology
    Lippincott Williams and Wilkins  2022
    Background: Remote cardiac monitoring and screening have already become an integral telemedicine component. The wide usage of several different wireless electrocardiography (ECG) devices warrants a validation study on their accuracy and reliability. Methods: Totally, 300 inpatients with the Nabz Hooshmand-1 handheld ECG device and the GE MAC 1200 ECG system (as the reference) were studied to check the accuracy of the devices in 1 and 6-limb lead performance. Simultaneous 10-second resting ECGs were assessed for the most common ECG parameters in lead I. Afterward, 6-lead ECGs (limb leads), were performed immediately and studied for their morphologies. Results: Of the 300 patients, 297 had...