• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1073-1082
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• 2003

Many researchers have investigated the blood flow characteristics through bileaflet mechanical heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets, and pulsatile flow analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simultaneously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole. calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.

• Journal of Veterinary Clinics
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• v.32 no.1
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• pp.101-104
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• 2015

A 4-years-old, intact male Golden retriever dog was presented with abdominal distension and dyspnea. Physical examination revealed arrhythmia and cardiac murmur. Generalized cardiomegaly, pleural effusion and ascites were shown on thoracic and abdominal radiographs. Two-dimensional echocardiography revealed abnormal mitral and tricuspid valve motion, mitral and tricuspid regurgitation, left ventricular eccentric hypertrophy and left atrial dilation. Color-flow Doppler imaging revealed turbulent flow extending into the left ventricle during diastole from the mitral valve orifice, and into the left atrium during systole. Spectral Doppler recordings revealed highly increased early diastolic mitral valve inflow and prolonged pressure half-time of mitral inflow. Based on the echocardiographic examination, the diagnosis was made as the mitral valve dysplasia concurrent with mitral valve stenosis and tricuspid valve dysplasia.

• Journal of Acupuncture Research
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• v.27 no.2
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• pp.23-30
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• 2010

Objectives : The second derivative of photoplethysmogram waveform(SDPTG) is a simple, convenient and non-invasive technique for pulse wave analysis. This study was designed to investigate the differences in the SDPTG between the affected side and the unaffected side in hemiparetic patients after stroke, and the effects of acupuncture at Palsa(BaXie) in hemiparetic patients after stroke. Methods : To evaluate the differences between the affected side and the unaffected side in hemiparetic patients after stroke, their SDPTG were recorded by using a Cardio Peri SA6000. To evaluate the effects of acupuncture at Palsa(BaXie) in 20 hemiparetic patients after stroke and 20 healthy subjects, their SDPTG were recorded 2 times(pre-acupuncture and post-acupuncture). The SDPTG consists of an a, b, c and d wave in systole and an e wave in diastole. Sano aging index was defined as (b-c-d)/a. Results : 1. The affected side in hemiparetic patients after stroke had higher average b/a ratio(p<0.05)and Sano aging index(p<0.05) than the unaffected side 2. In a comparison of pre-acupuncture and post-acupuncture at the Palsa(BaXie), b/a ratio(p<0.05) and Sano aging index(p<0.05) was decreased significantly in both hemiparetic patients and healthy subjects. Conclusions : These findings suggest that acupuncture at Palsa(BaXie) may be effective method of reverting some of the deleterious effects on vascular function produced by stroke.

• Progress in Medical Physics
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• v.10 no.3
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• pp.115-123
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• 1999

The two dimensional echocardiography is widely used to evaluate regional wall motion abnormality, because of its abilities to depict left ventricular wall motion. A number of researches have been processed for evaluation and quantitative analysis of left ventricular wall motion functions. In this paper, we proposed an algorithm which detects automatically and analyze quantitatively endocardial wall motion during systole. The echocardiograms were obtained in the short-axis views in normal subjects. Automated edge detection and endocardial contour tracking algorithm was applied to each frames, quantitative analysis based on segmentation was performed, pre-defined color overlays superimposed on the gray scale images, and the images was animated. The proposed algorithm provided automated, quantitative diagnosis of regional wall motion abnormality.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2002.11a
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• pp.59-62
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• 2002

Wavelength selection and prediction algorithm for determining hematocrit are investigated. A model based on the difference in optical density induced by the pulsation of heart beat is developed by taking approximation of Twersky's theory on the assumption that the variation of blood vessel size is small during arterial pulsing[1]. A device is constructed with a five-wavelength LED array as light source. The selected wavelengths are two isobestic points and three in compensation for tissue scattering. Data are collected from 549 out-patients who are randomly grouped as calibration and prediction sets. The range of percent hematocrit was 19.3∼51.8. The ratio of the variations of optical density between systole and diastole at two different wavelengths is used as a variable. We selected several such variables that show high reproducibility among all variables. Multiple linear regression analysis is made. The relative percent error is 8% and the standard deviation is 3.67 for the calibration set. The relative % error and standard deviation of the prediction set are 8.2% and 3.69 respectively. We successfully demonstrate the possibility of non-invasive hematocrit measurement, particularly, using the wavelengths below 1000nm.

• Journal of Chest Surgery
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• v.23 no.3
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• pp.438-451
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• 1990

Pneumatic total artificial heart[TAH] has been clinically applied for the purpose of permanent or temporary use followed by cardiac transplantation in the patients with end stage heart diseases. In spite of the good durability of the pneumatic TAH, thrombus formation, bleeding and infection resulted in death. The Tomasu heart, which is a type of pneumatic TAH, was used in this study. This model is a modified Jarvik heart and consists of atrial cuffs, outflow vascular grafts and thin-layer seamless diaphragm type of ventricles. Cardiac outputs of the left artificial heart were measured by Donovan`s mock circulation under variable conditions of driving parameters, and an experimental artificial heart implantation was performed in 4 calves to observe the changes of hemodynamic parameters in early postoperative period and hematologic and bio-chemical changes in a long-term survival case. In the mock circulation test, cardiac output of the heart was increased with the increase of the left atrial pressure and left driving pressure. Maximum cardiac output was obtained at the heart rate of 120 to 130/min and percent systole of 40 to 45Zo under the condition of a constant left driving pressure of 180mmHg and left atrial pressure of 10mmHg. During the first 24 hours of TAH pumping, driving pressure ranged from 178$\pm$5mmHg to 187$\pm$8mmHg for the left heart and from 58$\pm$6mmHg to 78$\pm$28mmHg for the right heart. The Mean arterial pressure significantly increased between 2 and 8 hours after the start of pumping. The survival time ranged from 27 hours to 46 days. The causes of death were respiratory failure in 2 cases, mechanical valve failure in one, and left ventricular outflow obstruction due to thrombus in a 46-day survival case. This study demonstrated that Tomasu artificial heart operated effectively during the first 24 hours of artificial heart pumping, but thrombus formation around the valve holding area was the main problem in long-term survival case.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of Veterinary Clinics
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• v.36 no.3
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• pp.159-165
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• 2019

Pimobendan is an inodilator used to treat canine heart failure, and pentoxifylline is reported to be beneficial for microcirculation and heart disease. The purpose of this study was to evaluate the pharmacokinetic and pharmacodynamic profiles of a novel pimobendan-pentoxifylline liquid mixture after oral administration to dogs. Eight healthy Beagle dogs were included in the study. The dogs were divided into the control group (orally administered water; n = 4) and experimental group (orally administered pimobendan-pentoxifylline liquid mixture [pimobendan 0.25 mg/kg, pentoxifylline 15 mg/kg]; n = 4). Plasma samples were obtained and echocardiographic indices were measured for 24 hours after administration. The concentrations of pimobendan and pentoxifylline were quantified by using a liquid chromatography-mass spectrometer (LC-MS). The elimination half-life ($T_{1/2}$) was $32.96{\pm}9.80mins$ for pimobendan and $29.49{\pm}6.67mins$ for pentoxifylline. The time to reach maximum concentration ($T_{max}$) were $52.50{\pm}31.22mins$ for pimobendan and $41.25{\pm}18.87mins$ for pentoxifylline. The maximum blood concentration ($C_{max}$) was $96.92{\pm}75.64ng/mL$ for pimobendan and $7074.07{\pm}3261.1ng/mL$ for pentoxifylline. Of the echocardiographic indices, fractional shortening (FS) and left ventricular internal diameter at end systole (LVIDs) were significantly altered at 1-3 hours after the administration of pimobendan-pentoxifylline liquid mixture. The pimobendan-pentoxifylline liquid mixture was well tolerated by the dogs, with no adverse effects observed during the study.

• Journal of Cardiovascular Imaging
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• v.26 no.4
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• pp.201-213
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• 2018

BACKGROUND: Children with significant adenotonsillar hypertrophy (ATH) may show right ventricular (RV) dysfunction. We aimed to evaluate RV dysfunction in such children before adenotonsillectomy by evaluating peak longitudinal right atrial (RA) strain (PLRAS) in systole. PLRAS, electrocardiogram (ECG) and conventional echocardiographic parameters were compared to distinguish children with significant ATH with sleep-related breathing disorder (ATH-SRBD) from controls. METHODS: Fifty-six children (23 controls and 33 children with ATH-SRBD without symptoms of heart failure) were retrospectively studied. Preoperative echocardiograms and ECGs of children with ATH-SRBD who underwent adenotonsillectomy were compared to those of controls. Available postoperative ECGs and echocardiograms were also analyzed. RESULTS: Preoperatively, prolonged maximum P-wave duration (Pmax) and P-wave dispersion (PWD), decreased PLRAS, and increased tricuspid annulus E/E' were found in children with ATH-SRBD compared to those of controls. From the receiver operating characteristic curves, PLRAS was not inferior compared to tricuspid annulus E/E', Pmax, and PWD in differentiating children with ATH-SRBD from controls; however, the discriminative abilities of all four parameters were poor. In children who underwent adenotonsillectomy, echocardiograms $1.2{\pm}0.4$ years after adenotonsillectomy showed no difference in postoperative PLRAS and tricuspid annulus E/E' when compared with those of the preoperative period. CONCLUSIONS: Impaired RA deformation was reflected as decreased PLRAS in children with ATH-SRBD before adenotonsillectomy. Decreased PLRAS in these children may indicate subtle RV dysfunction and increased proarrhythmic risk. However, usefulness of PLRAS as an individual parameter in differentiating preoperative children with ATH-SRBD from controls was limited, similar to those of tricuspid annulus E/E', Pmax, and PWD.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.51-56
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• 2021

The brachial systolic blood pressure and pulse pressure are the predictors of cardiovascular disease in individuals over 50 years of age. As the stiffness increases, the reflex amplitude and pressure in the late systole increase, resulting in an increase in left ventricular load and myocardial oxygen demand. Therefore, it is necessary to study how stiffness affects blood pressure. In this study, the blood pressure pulse waves were measured before and after taking the drug, and the blood pressure pulse wave was measured before and after myocardial heart transplantation in patients with heart failure. The correlation between R, L, and C components of the Windkessel model was estimated by increasing blood pressure. As a result of modeling the parameters of the Windkessel model using the curve fitting method, the increase in blood pressure and decrease in systolic rise time were due to the increase in the L component in the RLC Windkessel model. Among the various mechanical characteristics of blood vessels, the most important parameter affecting high BP waveform is the inertance.