Samuel Emil Schmidt

Samuel Emil Schmidt
Aalborg University · Department of Health Science and Technology

PhD. MSc. BME

About

98
Publications
23,770
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,517
Citations
Citations since 2017
55 Research Items
1323 Citations
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300

Publications

Publications (98)
Article
Full-text available
Cardiorespiratory fitness expressed as maximal oxygen consumption (V̇O2 max) is a strong predictor of cardiovascular health. However, quantification of cardiorespiratory fitness by cardiopulmonary exercise (CPX) assessment is complex and costly and therefore not suitable in most clinical settings. In the current study we develop and validate an alg...
Conference Paper
Background Peak oxygen uptake (&Vdot;O2peak) predicts all-cause mortality and can indicate the effectiveness of exercise-based cardiovascular rehabilitation (CR) in people living with coronary heart disease (CHD). Maximal cardiopulmonary exercise testing (CPET), the gold standard method of measuring &Vdot;O2peak, is expensive, time-consuming, and r...
Article
Cardiorespiratory fitness expressed as maximal oxygen consumption (V̇O2 max) is a strong predictor of cardiovascular health. However, quantification of cardiorespiratory fitness by cardiopulmonary exercise (CPX) assessment is complex and costly and therefore not suitable in most clinical settings. In the current study we develop and validate an alg...
Article
Full-text available
Introduction Echocardiography is a key diagnostic tool for assessment of myocardial performance and hemodynamics. Seismocardiography can potentially provide fast and reliable assessments of key components related to myocardial performance. Aims The aims of this study were to investigate the correlation between SCG and echocardiographic measures an...
Poster
Full-text available
Seismocardiography (SCG) is a technology where the chest wall vibrations from the beating heart are measured using a highly sensitive accelerometer. SCG offers continuous measurement of cardiac function and potential applications include remote monitoring, diagnostic assessments, prognostic health checks and biventricular pacemaker optimization. A...
Article
Full-text available
Objective: The aim of this study was to find spectral differences of diagnostic interest in heart sound recordings of patients with coronary artery disease (CAD) and healthy subjects. Approach: Heart sound recordings from three studies were pooled, and patients with clear diagnostic outcomes (positive: CAD and negative: Non-CAD) were selected fo...
Article
Seismocardiography (SCG) is a technology where the chest wall vibrations from the beating heart are measured using a highly sensitive accelerometer. SCG offers continuous measurement of cardiac function and potential applications include remote monitoring, diagnostic assessments, prognostic health checks and biventricular pacemaker optimization. A...
Article
Background Validation studies of the 2019 European Society of Cardiology pre-test probability model (ESC-PTP) for coronary artery disease (CAD) report that 35–40% of patients have intermediate pre-test risk (ESC-PTP 5-<15%). A clear strategy for deferral or referral in this group has not been established. Stratification tools with a high negative p...
Poster
Background Low socioeconomic position (SEP) is associated with shorter life expectancy and one of the main drivers is an increase in cardiovascular deaths. A higher prevalence of risk factors only partly explains the complex multifactorial pathogenesis. The aim of this study was to investigate the association between SEP and the development of coro...
Poster
Introduction Low cardiorespiratory fitness expressed as a low maximal oxygen consumption (V̇O2max) is associated with cardiovascular disease and all-cause mortality (1). Thus, V̇O2max is recognised as an important clinical tool in the assessment of patients (1,2). However, assessment of V̇O2max by exercise testing is both physically demanding and m...
Article
Background - Polygenic risk scores (PRSs) are associated with coronary artery disease (CAD), but the clinical potential of using PRSs at the single-patient level for risk stratification has yet to be established. We investigated whether adding a PRS to clinical risk factors (CRFs) improves risk stratification in patients referred to coronary comput...
Article
Full-text available
Background Recent technological advances enable diagnosing of obstructive coronary artery disease (CAD) from heart sound analysis with a high negative predictive value. However, the prognostic impact of this approach remains unknown. Objective To investigate the prognostic value of heart sound analysis as two scores, the Acoustic-score and the CAD...
Article
Recent guidelines recommend a risk-adjusted, non-invasive work-up in patients presenting with chest discomfort to exclude coronary artery disease (CAD). However, a risk-adjusted diagnostic approach remains challenging in clinical practice. An acoustic detection device for analyzing micro-bruits induced by stenosis-generated turbulence in the corona...
Article
Full-text available
Background The prevalence of obstructive coronary artery disease (CAD) in symptomatic patients referred for diagnostic testing has declined, warranting optimization of individualized diagnostic strategies. Objectives This study sought to present a simple, clinically applicable tool enabling estimation of the likelihood of obstructive CAD by combini...
Article
Aims Estimation of pre-test probability (PTP) of disease in patients with suspected coronary artery disease (CAD) is a common challenge. Due to decreasing prevalence of obstructive CAD in patients referred for diagnostic testing, the European Society of Cardiology suggested a new PTP (2019-ESC-PTP) model. The aim of this study was to validate that...
Article
Full-text available
Objective: Seismocardiography is the measurement of vibration waves caused by the beating heart with accelerometer(s) placed on the chest. Investigating the nature and the behavior of these vibration waves, by comparing measurements from multiple sites, would help to understand the heart's mechanical contraction activity. Approach: Using newly d...
Article
Full-text available
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
The real time high frame rate (HFR) 2-dimensional ultrasound system, T5, at Duke University is capable of imaging at up to 1000 images per second for adult cardiac imaging. A method for detecting and visualizing the mechanical contraction fronts using HFR echocardioagraphy-derived Strain Rate Image (SRI) was described in 26 patients. The Tissue Sho...
Article
The purpose of this study was to investigate the correlation between the seismocardiogram and cardiorespiratory fitness. Cardiorespiratory fitness can be estimated as VO2max using non-exercise algorithms, but the results can be inaccurate. Healthy subjects were recruited for this study. Seismocardiogram and electrocardiogram were recorded at rest....
Preprint
This paper presents the image-quality-guided strategy for optimization of bicubic interpolation and interpolated scan conversion algorithms. This strategy uses feature selection through line chart data visualization technique and first index of the minimum absolute difference between computed scores and ideal scores to determine the image quality g...
Article
Full-text available
In August 2019, ESC published new guidelines on Chronic Coronary Syndromes including a new risk assessment paradigm for estimation of pre-test-probability. The CAD-score is an acoustic-based score for ruling-out of coronary artery disease (CAD). In the current letter to the editor we re-evaluate the re-classification potential the CAD-score in the...
Article
Full-text available
To determine the potential of a non-invasive acoustic device (CADScor®System) to reclassify patients with intermediate pre-test probability (PTP) and clinically suspected stable coronary artery disease (CAD) into a low probability group thereby ruling out significant CAD. Audio recordings and clinical data from three studies were collected in a sin...
Article
Full-text available
Background: Liver fibrosis is a well-known complication of long-term use of parenteral nutrition in patients with intestinal failure associated to the nutrient composition in parenteral nutrition. This study investigates the prevalence of significant liver fibrosis and identifies risk factors for liver fibrosis. Methods: This was a retrospective...
Article
Full-text available
Cardiac time intervals are important hemodynamic indices and provide information about left ventricular performance. Phonocardiography (PCG), impedance cardiography (ICG), and recently, seismocardiography (SCG) have been unobtrusive methods of choice for detection of cardiac time intervals and have potentials to be integrated into wearable devices....
Article
Background: Coronary computed tomography angiography (CTA) is the preferred primary diagnostic modality when examining patients with low to intermediate pre-test probability of coronary artery disease (CAD). Only 20-30% of these have potentially obstructive CAD. Because of the relatively poor positive predictive value of coronary CTA, unnecessary i...
Article
Aims: European and North American guidelines currently recommend pre-test probability (PTP) stratification based on simple probability models in patients with suspected coronary artery disease (CAD). However, no unequivocal recommendation has yet been established. We aimed to compare the ability of risk factors and different PTP stratification mod...
Article
Recently, we developed a high-frame-rate echocardiographic imaging system capable of acquiring images at rates up to 2500 per second. High imaging rates were used to quantify longitudinal strain parameters in patients with echocardiographically normal function. These data can serve as a baseline for comparing strain parameters in disease states. Th...
Chapter
Over the past century, extensive research has been conducted on interpretation of vibration signals created by the heart and their potential use in noninvasive cardiology. Today, new microelectronics and signal processing technologies have provided unprecedented opportunities to reintroduce some of these techniques as useful cardiovascular assessme...
Conference Paper
A preliminary study of a non-reference aliasing artefact index (AAI) metric is presented in this paper. We focus on the effects of combining a full-reference metric and interpolation algorithm. The nearest neighbor algorithm (NN) is used as the gold standard against which test-algorithms are judged in terms of aliased structures. The structural sim...
Article
Full-text available
The purpose of this work is to define fiducial points in the seismocardiogram (SCG) and to correlate them with physiological events identified in ultrasound images. For 45 healthy subjects the SCG and the electrocardiogram (ECG) were recorded simultaneously at rest. Immediately following the SCG and ECG recordings ultrasound images of the heart wer...
Article
Full-text available
Objective Diagnosing coronary artery disease (CAD) continues to require substantial healthcare resources. Acoustic analysis of transcutaneous heart sounds of cardiac movement and intracoronary turbulence due to obstructive coronary disease could potentially change this. The aim of this study was thus to test the diagnostic accuracy of a new portabl...
Article
Heart sounds have been widely studied and have been demonstrated to have value for detecting pathologies in clinical applications. Over the last few decades, the use of heart sound signals has become increasingly uncommon and its practice in modern medicine somewhat diminished, although research into automated analysis has continued. Unfortunately,...
Article
The electrocardiographic interval between the peak and the end of the T-wave (Tpe) is believed to be an arrhythmic risk marker. However, there are also a number of reports that are inconsistent with the usefulness of Tpe for identifying abnormal repolarization. This study was designed to investigate how the Tpe prolongation is correlated to a prolo...
Article
Objective: To characterize the vascular sounds of the uteroplacental blood flow obtained by microphones. Methods: The present retrospective study took place in an anechoic chamber facility at Aalborg University, Aalborg, Denmark, in 2012, and included pregnant participants aged 18-40 years with a singleton pregnancy at 32-36 weeks and a parity o...
Article
Full-text available
In the past few decades, analysis of heart sound signals (i.e. the phonocardiogram or PCG), especially for automated heart sound segmentation and classification, has been widely studied and has been reported to have the potential value to detect pathology accurately in clinical applications. However, comparative analyses of algorithms in the litera...
Article
Background: Recently, numerous models and techniques have been developed for analyzing and extracting features from the T wave which could be used as biomarkers for drug-induced abnormalities. The majority of these techniques and algorithms use features that determine readily apparent characteristics of the T wave, such as duration, area, amplitud...
Conference Paper
Full-text available
Temporal alignment of signals obtained using different acquisition systems is often complicated by asynchronous sampling. In the current study we aligned 3-lead ECGs recorded in a phonocardiogram setup with 12-lead Holter ECGs. Two signals with common morphology (lead II from both devices, recorded synchronously with closely placed electrodes) were...
Conference Paper
Full-text available
Introduction: Doppler Tissue M-Mode ultrasound facilitates a method for measuring both mitral and aortic valve opening and closing. These measures can be used when assessing global information about the cardiac cycle. The method depends on an operator to manually setting points in the ultrasound image to obtain the timing intervals. We developed an...
Conference Paper
Full-text available
Signal-averaged ECG (saECG) has been used to show delayed ventricular activation and myocardial infarction, but alignment jitter acts as a low-pass filter. Jitter arises due to sampling of the signal, and due to imperfect alignment algorithms. In this study we investigated the influence of the sample rate on the saECG spectrum, i.e. if the jitter c...
Conference Paper
The present work investigates the use of a Laser Doppler Vibrometer (LDV) to record valve sounds and characterizes those recordings. An LDV (Polytec PDV-100) was used to measure the normal component of the velocity of the chest wall at 30 points (grid of 6 × 5 points) in each of seven subjects. The recorded signals were analyzed in the frequency do...
Conference Paper
Full-text available
Introduction: Studies of the movement of the chest wall show their potential in the diagnosis of heart diseases. Few studies have focused on mapping these movements especially in the lower inaudible frequency band. Aims: This study evaluates Body Surface Mapping (BSM) as a method for describing mechanical cardiac activity. Methods: The chest wall's...
Conference Paper
Full-text available
This study aims to describe a feature tracking algorithm tailored to estimate circumferential strain on high frame rate ultrasound (HFR-US) images. The algorithm used the Hungarian assignment algorithm for tracking a basic feature descriptor. A second order Kalman model was used to recursively describe regional myocardial displacement along the myo...
Article
Epicardial ultrasound (EUS) can be used for intra-operative quality assessment of coronary artery bypass anastomoses. To quantify the anastomotic quality from EUS images, the area of anastomotic structures has to be extracted from EUS sequences. Currently, this is done manually as no objective methods are available. We used an automatic anastomosis...
Article
The study describes a novel algorithm for deriving myocardial strain from an entire cardiac cycle using high-frame-rate ultrasound images. Validation of the tracking algorithm was conducted in vitro prior to the application to patient images. High-frame-rate ultrasound images were acquired in vivo from 10 patients, and strain curves were derived in...
Article
This observational study investigated digital auscultation for the purpose of assessing the clinical feasibility of monitoring vascular sounds in pregnancy. The study was performed at the Regional Hospital Viborg, Denmark, and included 29 pregnant women, 10 non-pregnant women and 10 male participants. Digital auscultation was performed with an elec...
Article
Full-text available
Background: Coronary computed tomography angiography (CCTA) is an established method for ruling out coronary artery disease (CAD). Most patients referred for CCTA do not have CAD and only approximately 20-30 % of patients are subsequently referred to further testing by invasive coronary angiography (ICA) or non-invasive perfusion evaluation due to...
Article
Full-text available
Optimizing risk assessment may reduce use of advanced diagnostic testing in patients with symptoms suggestive of stable coronary artery disease (CAD). Detection of diastolic murmurs from post-stenotic coronary turbulence with an acoustic sensor placed on the chest wall can serve as an easy, safe, and low-cost supplement to assist in the diagnosis o...
Article
Full-text available
This paper considers the problem of classification of the first and the second heart sounds (S1 and S2) under cardiac stress test. The main objective is to classify these sounds without electrocadiogram (ECG) reference and without taking into consideration the systolic and the diastolic time intervals criterion which can become problematic and usel...
Article
Earlier studies have documented that coronary artery disease (CAD) produces weak murmurs, which might be detected through analysis of heart sounds. An electronic stethoscope with a digital signal processing unit could be a low cost and easily applied method for diagnosis of CAD. The current study is a search for heart sound features which might ide...
Article
Chercheur), Samy TALHA (Médecin hospitalo-universitaire), Emmanuel ANDRES (Médecin hospitalo-universitaire), Alain DIETERLEN (Enseignant-chercheur) Introduction: The telemedicine E-care project provide an intelligent platform useful for home monitoring by using non-intrusive sensors for patients with heart failure stage 3. It helps the medical stuf...
Conference Paper
Full-text available
In this exploratory study we propose to analyze, in healthy adult volunteers, the heart electrical (electrocardiogram, ECG) and mechanical (phonocardiogram, PCG) activity during exercise. Heart sounds amplitude, frequency content, and RS2, may be important features in the non-invasive assessment of heart activity, such as for the estimation of card...
Article
Purpose: Epicardial ultrasound (EUS) can be used to assess the quality of coronary artery bypass graft surgery (CABG) anastomoses by determining stenotic rates. Currently, no objective quantitative methods are available for the analysis of EUS images. Therefore, surgeons have to be trained in interpreting EUS images, which may limit the use of EUS...
Conference Paper
Full-text available
Traditional apex-cardiography measures chest wall vibrations at the apex beat using an air-coupled microphone. To provide additional insight in apexcardiography and chest vibrations we estimated the three dimensional displacement of the apex beat. A 3-axis accelerometer was placed at the location of the apex beat in 5 healthy subjects in left later...
Conference Paper
Full-text available
The 12-lead ECG can be described as the projection of a time-varying dipole on the lead vectors. This dipole- source assumption implies that the different leads must show a high coherence and that deviations from values close to unity may indicate the presence of noise. We evaluated the average coherence in the band of 5 Hz to 45 Hz in 309 ECGs and...
Conference Paper
Full-text available
Introduction: The first heart sound (S1) carries information about ventricular function which may be clinically useful in optimization of cardiac resynchronization therapy (CRT). We developed a method of measuring the effects of CRT on S1 energy. Methods: For 10 patients with activation induced heart failure (age 64±8.4 years), the heart sound was...
Conference Paper
Full-text available
Early repolarization (ER) in the inferior/lateral leads of 12-lead ECG increases the risk of arrhythmic death. Automatic methods are needed to robustly locate the Jpoint in ER positive ECGs so large databases with electrocardiographic ER patterns can be analyzed. We developed an algorithm (Std-12) to determine Jpoint location in the 12-lead ECG bas...
Patent
A method, system, stethoscope and server for classifying a cardiovascular sound recorded from a living subject. The method comprises the steps of: identifying diastolic and/or systolic segments of the cardiovascular sound; dividing at least one of the identified diastolic and/or systolic segments into a number of sub-segments comprising at least a...
Patent
This invention describes a method for dividing a substantial cycli cardiovascular signal into segments by determining the characteristics of said cyclic signal, wherein each cycle in said signal comprises at least two characteristic segments and wherein the method comprises the steps o identifying segments in a cycle based on prior knowledge of sai...
Conference Paper
Full-text available
Weak murmurs related to coronary artery disease might be masked in ambient noise when heart sounds are recorded in clinical settings. The aim of the current study was to characterize the influx of ambient noise through the chest and through the microphone's coupler house. To estimate the transmission through the coupler house the coupler was placed...