Publications by authors named "Arjen van der Horst"

7 Publications

  • Page 1 of 1

Towards patient-specific modeling of coronary hemodynamics in healthy and diseased state.

Comput Math Methods Med 2013 4;2013:393792. Epub 2013 Mar 4.

Cardiovascular Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.

A model describing the primary relations between the cardiac muscle and coronary circulation might be useful for interpreting coronary hemodynamics in case multiple types of coronary circulatory disease are present. The main contribution of the present study is the coupling of a microstructure-based heart contraction model with a 1D wave propagation model. The 1D representation of the vessels enables patient-specific modeling of the arteries and/or can serve as boundary conditions for detailed 3D models, while the heart model enables the simulation of cardiac disease, with physiology-based parameter changes. Here, the different components of the model are explained and the ability of the model to describe coronary hemodynamics in health and disease is evaluated. Two disease types are modeled: coronary epicardial stenoses and left ventricular hypertrophy with an aortic valve stenosis. In all simulations (healthy and diseased), the dynamics of pressure and flow qualitatively agreed with observations described in literature. We conclude that the model adequately can predict coronary hemodynamics in both normal and diseased state based on patient-specific clinical data.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2013/393792DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3603622PMC
August 2013

The impact of downstream coronary stenoses on fractional flow reserve assessment of intermediate left main disease.

JACC Cardiovasc Interv 2012 Oct;5(10):1021-5

Stanford University Medical Center, Stanford, CA 94305, USA.

Objectives: The aim of this study was to assess the validity of measuring fractional flow reserve (FFR) of the left main (LM) coronary artery in the setting of concomitant left anterior descending (LAD) or left circumflex (LCX) stenoses.

Background: The theoretical impact of a stenosis in the LAD on the FFR assessment of intermediate LM disease with the pressure wire in an unobstructed LCX is currently unknown.

Methods: A previously validated in vitro model of the coronary circulation was used to create a fixed intermediate stenosis of the LM and a variable downstream LAD or LCX stenosis. The true LM FFR (FFR(LM true)), with no concomitant downstream disease, was compared to the apparent LM FFR (FFR(LM apparent)), with concomitant downstream disease measured with different degrees of LAD or LCX disease. Additionally, an equation based on a resistors model was derived to predict the effect of downstream stenosis on LM FFR (FFR(LM predicted)).

Results: In the setting of isolated moderate LM disease (FFR 0.72 ± 0.08), mild to moderate proximal LAD or LCX lesions did not significantly affect LM FFR. Lesions with a composite FFR (LM + downstream disease) ≥0.65 resulted in an FFR(LM apparent) that was not significantly different from FFR(LM true) (0.76 ± 0.06 vs. 0.76 ± 0.05, p = 0.124). Our equation for FFR(LM predicted) accurately modeled the effects of concomitant disease (r = 0.95, p < 0.001).

Conclusions: These data suggest that in the presence of proximal mild to moderate LAD or LCX disease, LM FFR can be reliably measured with the pressure wire placed in the uninvolved epicardial artery.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jcin.2012.07.005DOI Listing
October 2012

A combination of thermal methods to assess coronary pressure and flow dynamics with a pressure-sensing guide wire.

Med Eng Phys 2013 Mar 4;35(3):298-309. Epub 2012 Jun 4.

Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

Measurement of coronary pressure and absolute flow dynamics have shown great potential in discerning different types of coronary circulatory disease. In the present study, the feasibility of assessing pressure and flow dynamics with a combination of two thermal methods, developed in combination with a pressure-sensor-tipped guide wire, was evaluated in an in vitro coronary model. A continuous infusion thermodilution method was employed to determine the average flow, whereas a thermal anemometric method was utilized to assess the pressure and flow dynamics, simultaneously. In the latter method, the electrical power supplied to an element, kept at constant temperature above ambient temperature, was used as a measure for the shear rate. It was found that, using a single calibration function, the method was able to assess coronary pressure and flow dynamics for different flow amplitudes, heart rates, and different pressure wires. However, due to the fact that the thermal anemometric method cannot detect local shear rate reversal, the method was unable to reliably measure flow dynamics close to zero. Nevertheless, the combined methodology was able to reliably assess diastolic hemodynamics. The diastolic peak flow and average diastolic resistance could be determined with a small relative error of (8 ± 7)% and (7 ± 5)%, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.medengphy.2012.05.002DOI Listing
March 2013

The fiber orientation in the coronary arterial wall at physiological loading evaluated with a two-fiber constitutive model.

Biomech Model Mechanobiol 2012 Mar 13;11(3-4):533-42. Epub 2011 Jul 13.

Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, The Netherlands.

A patient-specific mechanical description of the coronary arterial wall is indispensable for individualized diagnosis and treatment of coronary artery disease. A way to determine the artery's mechanical properties is to fit the parameters of a constitutive model to patient-specific experimental data. Clinical data, however, essentially lack information about the stress-free geometry of an artery, which is necessary for constitutive modeling. In previous research, it has been shown that a way to circumvent this problem is to impose extra modeling constraints on the parameter estimation procedure. In this study, we propose a new modeling constraint concerning the in-situ fiber orientation (β (phys)). β (phys), which is a major contributor to the arterial stress-strain behavior, was determined for porcine and human coronary arteries using a mixed numerical-experimental method. The in-situ situation was mimicked using in-vitro experiments at a physiological axial pre-stretch, in which pressure-radius and pressure-axial force were measured. A single-layered, hyperelastic, thick-walled, two-fiber material model was accurately fitted to the experimental data, enabling the computation of stress, strain, and fiber orientation. β (phys) was found to be almost equal for all vessels measured (36.4 ± 0.3)°, which theoretically can be explained using netting analysis. In further research, this finding can be used as an extra modeling constraint in parameter estimation from clinical data.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10237-011-0331-1DOI Listing
March 2012

Thermal anemometric assessment of coronary flow reserve with a pressure-sensing guide wire: an in vitro evaluation.

Med Eng Phys 2011 Jul 2;33(6):684-91. Epub 2011 Feb 2.

Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

Assessment of coronary flow reserve (CFR) with a commercially available pressure-sensor-tipped guide wire using the principle of thermal anemometry could provide major clinical benefits both in determining and in distinguishing between epicardial and microvascular coronary artery disease. In constant-temperature thermal anemometry, the electrical power required to maintain an element at a constant temperature is a measure for the local shear rate. Here, the feasibility of applying this thermoconvection method to a pressure-sensing guide wire is investigated using an in vitro model. A theoretical relation between electrical power and steady shear rate based on boundary layer theory was tested in an experimental set-up. In steady flow, a reproducible relation between electrical power and shear rate was obtained with an overheat temperature of 20K, which was in good agreement with theory. The relation between shear rate and flow, however, depends on geometry of the artery and position of the guide wire inside the vessel. Although this means that this thermoconvection method is less useful for absolute flow measurements, CFR could be assessed even for unsteady flow using the steady calibration curve with a mean relative difference of (3±5)% compared to CFR derived from the golden standard using an ultrasonic flow measurement device.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.medengphy.2011.01.004DOI Listing
July 2011

A generic constitutive model for the passive porcine coronary artery.

Biomech Model Mechanobiol 2011 Apr 17;10(2):249-58. Epub 2010 Jun 17.

Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

Constitutive models describing the arterial mechanical behavior are important in the development of catheterization products, to be used in arteries with a specific radius. To prove the possible existence of a constitutive model that, provided with a generic set of material and geometric parameters, is able to predict the radius-specific mechanical behavior of a coronary artery, the passive pressure-inner radius (P-r ( i )) and pressure-axial force change (P-ΔF ( z )) relations of seven porcine left anterior descending coronary arteries were measured in an in-vitro set-up and fitted with the model of Driessen et al. in J Biomech Eng 127(3):494-503 (2005), Biomech Model Mechanobiol 7(2):93-103 (2008). Additionally, the collagen volume fraction, physiological axial pre-stretch, and wall thickness to inner radius ratio at physiological loading were determined for each artery. From this, two generic parameter sets, each comprising four material and three geometric parameters, were obtained. These generic sets were used to compute the deformation of each tested artery using a single radius measurement at physiological loading as an artery-specific input. Artery-specific P-r ( i ) and P-ΔF ( z ) relations were predicted with an accuracy of 32 μm (2.3%) and 6 mN (29% relative to ΔF ( z )-range) on average compared to the relations measured in-vitro. It was concluded that the constitutive model provided with the generic parameters found in this study can well predict artery-specific mechanical behavior.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10237-010-0231-9DOI Listing
April 2011

Continuous infusion thermodilution for assessment of coronary flow: theoretical background and in vitro validation.

Med Eng Phys 2009 Jul 23;31(6):688-94. Epub 2009 Feb 23.

Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.

Direct volumetric assessment of coronary flow during cardiac catheterization has not been available so far. In the current study continuous infusion thermodilution, a method based on continuous infusion of saline into a selective coronary artery is evaluated. Theoretically, volumetric flow can be calculated from the known infusion rate (Q(i)), the temperatures of the blood (T(b)), the saline (T(i)), and the mixture downstream to the infusion site (T). We aimed to validate and optimize the measurement method in an in vitro model of the coronary circulation. Full mixing of infusate and blood was found to be the main prerequisite for accurate determination of the coronary flow. To achieve full mixing the influence of catheter design, infusion rate, and location of temperature measurement were assessed. We found that continuous infusion thermodilution slightly overestimated coronary flow determined by directly measured reference flow by 7+/-8%, over the entire physiological flow range of 50-250 ml/min. These results were found using a specially designed infusion catheter (infusion mainly through distally located sideholes), a high enough infusion rate (25 ml/min), and measurement of the mixing temperature between 5 and 8 cm distal from the tip of the infusion catheter. Absolute coronary flow rate can be measured reliably by the continuous infusion method when full mixing is present, under the conditions mentioned above.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.medengphy.2009.01.006DOI Listing
July 2009
-->