BME2023 Paper Submission & Registration
9th Dutch Bio-Medical Engineering Conference

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10:30   Heart
Chair: Chris de Korte
15 mins
Post-infarct evolution of ventricular and myocardial function
Koen Janssens, Maaike Kraamer, Peter Bovendeerd
Abstract: Introduction Long-term adverse ventricular remodelling following acute myocardial infarction (MI) can lead to ventricular dilation, diastolic dysfunction, loss of global contractile function and may result in heart failure (HF). Synthetic or tissue engineered patches, disposed over the epicardium, have been suggested as a possible treatment for HF, as they might reduce infarct area, reverse ventricular remodelling and enhance cardiac function. The mechanical properties of these patches and their interaction with the native cardiac tissue are important in device functionality. However, infarct material properties vary over time as the scar tissue matures which may have implications for the support that is to be delivered by the patch. In this study, we aim to quantify the evolution of an acutely infarcted ventricle into a chronically remodelled state in terms of global cardiac function and local myofiber mechanics. Method The finite element model of [1] was extended to model both acute and chronic MI. A droplet shaped region was selected in a thick-walled, truncated ellipsoidal geometry to model an infarct induced by occlusion of the Left Anterior Descending artery. Within this region, active stress generation was eliminated to model acute MI and passive material stiffness was increased to model chronic MI. Pressure-volume plots were used to assess global cardiac function and local stress and strain patterns were analysed to quantify local myofiber function in the infarct, the infarct border zone and the remote region. Results & Conclusions Simulations showed that the relative loss in pump function exceeded the relative loss in the amount healthy tissue by about two-fold, irrespective of infarct age. This disproportional loss was attributed to unfavourable mechanical interactions between healthy and infarcted tissue. With increasing infarct stiffness, myofiber functionality is partially restored in one region of the myocardium though it is depressed in another, resulting in a limited gain in overall cardiac function. These changes were related to the local orientation of myofibers with respect to the infarct region.
15 mins
Estimation of cardiac fibre direction based on activation maps
Johannes de Vries, Miao Sun, Natasja de Groot, Richard Hendriks
Abstract: Estimating tissue conductivity parameters from electrograms (EGMs) could be an important tool for diagnosing and treating heart rhythm disorders such as atrial fibrillation (AF). One of these parameters is the fibre direction, often assumed to be known in conductivity estimation methods. In this abstract, a novel method to estimate the fibre direction from EGMs is presented. This method is based on local conduction slowness vectors of a propagating activation wave. These conduction slowness vectors follow an elliptical pattern that depends on the underlying conductivity parameters. The fibre direction and conductivity anisotropy ratio can therefore be estimated by fitting an ellipse to the conduction slowness vectors in the least squares sense. Applying the presented method on simulated data shows that it can estimate the fibre direction more accurately than existing methods. The estimation performance depends mostly on the range of wavefront directions present in the measurement area, which in turn is influenced by the measurement area size, distance between stimulus and measurement areas, and true fibre direction. The main advantage of the presented method is that it still functions relatively well in the presence of conduction blocks, as long as the surrounding tissue is approximately homogeneous.
15 mins
On the design of a novel portable ECG device for the recording of A 4-precordial electrode arrangement
Alejandra Zepeda-Echavarria, Rutger van de Leur, Nynke de Vries, Rien van der Zee, Joris Jaspers, Thierry Wildbergh, Pieter Doevendans, René van Es
Abstract: The ECG is a fundamental diagnostic tool in the everyday practice of clinical medicine. The 12-lead ECG is commonly used by physicians to diagnose, monitor, record and understand the electrical activity of the heart. Technological advances have allowed to bring medical devices to home environments. To investigate if an arrangement of 4- precordial electrodes could provide enough evidence to detect ECG changes, we developed a smartphone-sized ECG recording device, the miniECG, aiming to detect the full spectrum of ECG abnormalities. The miniECG has the following components: four dry electrodes, a microcontroller unit, and an app. The four electrodes are stainless steel electrodes with peaks that could enable a low impedance contact. The design of the microcontroller unit is based on the ADS1298 (Texas Instruments, USA). Eight differential channels are recorded for 10 seconds, with a 24-bit resolution and a programmable gain up to 12V/V. The recordings and connection to app via Bluetooth is managed by the microcontroller NRF52840 (Nordic Semiconductor, Norway) featuring an Arm® Cortex ® -M4F CPU. The app designed to start and collect data on the recordings was designed on React Native. Finally, the high-level software for the processing and visualization of the ECG data was developed in python. A first clinical study to determine if the miniECG is capable to detect ST-elevation was performed from May 2021 to February 2022 at UMC Utrecht and Meander Medical Center. A total of 252 patients were included, 36 of whom demonstrated ST-elevation at hospital arrival. In 30 of these patients the ST-elevation was also present on the miniECG recordings while in 2 patients ST-elevation had resolved on the follow up 12 lead ECG and the other 4 ST-elevation was not present on miniECG recordings. Further analysis showed that the miniECG can record anterior, lateral, and inferior ST-elevation. The miniECG can record high-quality multi-lead ECGs. Analysis of clinical study data shows that the miniECG can accurately detect ischemic ST-elevation in patients with inferior, lateral, and anterior myocardial infarction. Further research is required to demonstrate non-inferiority of the miniECG to the standard 12-lead ECG in the detection of other common cardiac (ab)normalities.
15 mins
Prognostic value of combined biomarkers in patients with heart failure: the heartmarker score
Jonna van der Stam, Sjoerd Bouwmeester, Saskia van Loon, Natal van Riel, Arjen-Kars Boer, Lukas Dekker, Patrick Houthuizen, Volkher Scharnhorst
Abstract: Objective In clinical practice the classification of patients suffering from Heart Failure (HF) is done using the New York Heart Association (NYHA) Classification [1]. The NYHA is used by cardiologists to classify patients into four groups (NYHA I-IV) based on complaints during normal physical activity. However, this classification is subjective and has a significant inter-observer variability [2]. This research explores a HF -biomarker based classification for risk classification of HF patients. Methods HF biomarkers were analyzed in a population of HF outpatients and expressed relative to their cut-off (NT-proBNP>1000pg/mL, ST2>35ng/mL, GDF-15>2000pg/mL and FGF-23>95.4pg/mL). Biomarkers that remained significant in multivariable analysis were combined into a Heartmarker score. The performance was compared to the New York Heart Association (NYHA) classification, which is widely used and accepted in clinical practice to classify HF patients. Results HF biomarkers of 245 patients were analyzed of whom 45 (18%) experienced the composite endpoint of HF hospitalization, appropriate ICD shock, or death. HF biomarkers were elevated more often in patients with the composite endpoint (NT-proBNP: 78% vs 31% p<0.01; GDF-15: 73% vs 34% p<0.01; ST-2: 31% vs 6% p<0.01; FGF-23: 42% vs 20% p=0.04). NT-proBNP, ST2, GDF-15 were independent predictors and were used to build the ‘Heartmarker’ score. Percentage of event-free survival and distance covered in 6-minutes of walking decreased with increasing ‘Heartmarker’ score (0: 97%, 1: 83%, 2-3: 56%; 0: 380m,1:340m,2-3:290m) Conclusion The Heartmarker score can be used as an intuitive model for risk stratification in HF outpatients. Compared to the NYHA classification, it was better at discriminating between different risk classes and had a comparable relation to functional capacity. It can be calculated automatically from results of biomarker measurements providing a reproducible and objective score for risk-classification of HF patients that could provide an additional tool for physicians.
15 mins
Utility of a four precordial electrode set-up in the detection of ECG abnormalities
Johanneke ten Broeke, Rutger van der Leur, Alejandra Zepeda Echavarria, Melle Vessies, Pieter Doevendans, Joris Jaspers, René van Es
Abstract: Background. The miniECG, a 9x5cm device equipped with one electrode at each corner, has the potential to function as a low-cost, easy to use alternative for the 12-lead ECG and may facilitate ECG monitoring at home. The device aims to improve time-to-treatment in various cardiac diseases. The utility of the miniECG in detecting the full spectrum of ECG abnormalities should be investigated. Research goal. The aim of this study was to define criteria for evaluation of the miniECG in patients with normal sinus rhythm (NSR), and both left and right bundle branch blocks (LBBB and RBBB). Methods. Next to the acquisition of the 12-lead ECG, measurements with the miniECG were performed at the University Medical Centre Utrecht. The lower two electrodes of the miniECG were positioned in the mid-line at the lower sternal border. In this preliminary analysis, miniECGs of 60 patients (20 patients with NSR, 20 patients with LBBB and 20 patients with RBBB) undergoing a 12-lead ECG were visually inspected. In later research, a total of 15.000 patients will be included. Results. P-, QRS- and T-waves were easily recognized in the miniECG signal. In miniECGs of patients with NSR, P-waves that were positive in lead II (measured from the upper right to the lower left electrode) preceded every QRS complex. For both the LBBB and RBBB patient groups, widened (>120ms) QRS complexes were observed. In patients with LBBB, S-waves were present in lead II. For patients with RBBB, both lead II and lead I2 (measured from the upper left to the lower right electrode) showed R-waves or a typical RSR pattern. Conclusion. This preliminary analysis shows the potential of the miniECG to recognize NSR and cardiac abnormalities such as bundle branch blocks. Structural analysis of 15.000 miniECGs is yet to be performed to extend the criteria for interpretation of the miniECG for cardiac abnormalities.
15 mins
Generation of synthetic aortic valve stenosis geometries for in silico trials
Sabine Verstraeten, Martijn Hoeijmakers, Frans van de Vosse, Wouter Huberts
Abstract: In silico clinical trials are a promising method to increase the efficiency of the development of transcatheter aortic valve implantation (TAVI) devices. With an in silico trial, devices can be tested on virtual patients by computer models. Each patient of the virtual cohort is represented by a synthetic aortic valve geometry. Two important aortic valve morphologies to include are: (1) the shape of the left ventricular outflow tract (LVOT), either convergent or divergent, and (2) the angle between the LVOT and the ascending aorta (∠LVOT-AA). These morphologies influence the occurrence of complications, such as conduction problems [1], and paravalvular leakage [2]. To the best of our knowledge a framework to generate synthetic aortic valve geometries that considers these morphologies is not yet available. Therefore, the aim of this research is to develop a framework to generate synthetic aortic valve geometries, that (1) are physiologically plausible, and (2) allow for selection of the aforementioned morphologies. Non-parametric statistical shape modeling (SSM) [3, 4] was used to extract the mean shape and shape variance (shape modes) from a set of 97 stenotic aortic valve geometries. Each geometry within or outside this data set was approximated by adding a weighted combination of 24 shape modes to the mean shape. With the SSM 500 synthetic geometries were generated by sampling new weight combinations from an inferred distribution [5, 6]. Logistic regression and linear regression models were used to filter synthetic geometries on LVOT morphology and ∠LVOT-AA respectively. A non-parametric multivariate ANOVA test revealed that the 500 synthetic geometries did not differ significantly from the set of 97 real patient geometries (p = 0.47 > 0.05). The LVOT shape filter and the ∠LVOT-AA filter successfully selected the aforementioned morphologies with a sensitivity of 97% and 94% respectively. These results demonstrate that the framework developed in this study, (1) succeeded in generating synthetic geometries that are physiologically plausible, and (2) makes it possible to select geometries with certain morphologies. Consequently, this framework has the potential to generate synthetic data sets for in silico TAVI trials.

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