• 대한의용생체공학회:의공학회지
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• 제12권1호
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• pp.29-34
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• 1991

Ventricular assist device(VAD) has been clinically applied as a temporary circulatory sup- porting system in the patients with severe heart failure, but small sized VAD for infant is not available. The purpose of tilis paper is to introdIAce small sized VAD and presents the result of in vitro test. Sejong VAD is diaphragmatic type of pneumatic pump and stroke volume is 11cc. Cardiac outputs of the Sejong VAD were measured by overflow tank under variable conditions of driving parameters. The cardiac output was 1.3 1/min at the heart rate of 120 per minute, left atrial pressure of $15cmH_2O$, percent systole of 43%, driving pressure of 240 mmHg, vacuum pressure of -40 mmHg, and mean aortic pressure of 70 mmHg. No mechanical problem was developed during the continuous in vitro test for 3 months.

• Journal of Chest Surgery
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• 제12권3호
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• pp.183-190
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• 1979

A 23-year-old male patient complained dyspnea on exertion and orthopnea since December 1977. On examination, he was tall and slender. There was grade IV/VI to-and-fro murmur on the left sternal border especially on Erb`s point. The liver was descended 2 fingers breadth below right costal margin. There were no signs of Marfan`s syndrome. Echocardiography demonstrated partial closure of aortic valve and dilated aortic root with enlargement of ascending aorta. Left heart cardiac catheterization revealed moderately elevated pulmonary wedge pressure and right ventricular pressure. The left ventricular end diastolic pressure was markedly elevated to 26 mmHg. On aortography, the aortic regurgitation was severe and it was belonged to angiographically Grade IV. The aortic valve was replaced with Carpentier-Edwards valve without excision and replacement of ascending aorta, under the impression of rheumatic valvular heart disease. After closure of aortotomy, blood pressure was transiently elevated and bleeding from the site of inserting air vent needle of ascending aorta was developed. The bleeding was not controlled by any means. On postmortem microscopic study, the histologic changes were strikingly limited to the ascending aorta from the region of the aortic valve ring.

• 대한의용생체공학회:의공학회지
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• 제27권2호
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• pp.78-82
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• 2006

The ventricular assist device(VAD) helps to reduce the overload against the patient's native heart(NH). The pulsatile VAD pumps out the ventricular blood to the aorta with pulsatile flow. If the VAD pulsates simultaneously with the NH, the ventricle of the NH could confronts abnormally elevated aortic pressure, and this could deteriorate the ventricle rather than assist to recover it. Thus counterpulsation algorithms to avoid copulsation have been adopted by many VADs, but these methods utilize electrocardiography or arterial pressure signals, which may have difficulties to acquire consistently for a long period. In this study, the copulsation estimation algorithm for the counterpulsation is developed using the VAD outlet pressure signal. The VAD outlet pressure signal is good to maintain for a long time and the sensor part could be integrated to the VAD as a built-in module. From the VAD outlet pressure signal and its pump rate information calculated with Fast Fourier Transform, pulse peaks by the VAD and the NH were extracted and the next copulsation time at which the VAD and the NH would pulsate simultaneously was estimated. This estimation algorithm was implemented by using PC MATLAB software and tested for various pump rate conditions with mock circulation system. For each condition, the copulsation time was estimated successfully. Consequently, the results showed the possibility to use the outlet cannula pressure signal in the copulsation estimation.

• 대한의용생체공학회:의공학회지
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• 제35권5호
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• pp.119-124
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• 2014

A Ventricular assist device (VAD) is one of the most efficient treatments to raise the survivability of the end stage heart failure patient. However, some of LVAD patients have died for the failures and improper control of LVAD. To detect critical dangers in LVAD, the monitoring methods of LVAD outflow have been requested, because it can be affected by patient's hemodynamic states and abnormal conditions of LVAD. In the case of an external pulsatile LVAD, the air movement through the air line can be used to estimate LVAD outflow. In this study, the air movement in the air-line of the extracorporeal pulsatile LVAD was measured with a differential pressure sensor between different points. The precise estimation of air movement could be achieved by additional measurement of air pressure. In a series of in-vitro experiments, the LVAD outflow were changed according to the afterload of LVAD and the differential pressure of LVAD didn't have close correlation with the LVAD outflow that were measured with an ultrasonic flowmeter at the same time. However, new precise estimation with the data from differential pressure and one point pressure in the air-line showed higher correlations with LVAD outflow.

• 약학회지
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• 제50권2호
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• pp.111-117
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• 2006

Cardiac chambers serve as mechanosensory systems during the haemodynamic or mechanical disturbances. To examine a possible role of fluid pressure (FP) in the regulatien of atrial $Ca^{2+}$ signaling we investigated the effect of FP on L-type $Ca^{2+}$ current $(I_{Ca})$ in rat ventricular myocytes using whole-cell patch-clamp technique. FP $(\sim40cm\;H_2O)$ was applied to whole area of single myocytes with electronically controlled micro-jet system. FP suppressed the magnitude of peak $I_{Ca}$ by $\cong25\%$ at 0 mV without changing voltage dependence of the current-voltage relationship. FP significantly accelerated slow component in inactivation of $I_{Ca}$, but not its fast component. Analysis of steady-state inactivation curve revealed a reduction of the number of $Ca^{2+}$ channels available for activity in the presence of FP. Dialysis of myocytes with high concentration of immobile $Ca^{2+}$ buffer partially attenuated the FP-induced suppression of $I_{Ca}$. In addition, the intracellular $Ca^{2+}$ buttering abolished the FP-induced acceleration of slow component in $I_{Ca}$ inactivation. These results indicate that FP sup-presses $Ca^{2+}$ currents, in part, by increasing cytosolic $Ca^{2+}$ concentration.

• Journal of Chest Surgery
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• 제27권7호
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• pp.576-580
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• 1994

For 26 months since August 1991, 10 consecutive patients with congenital left ventricular outflow tract obstruction underwent corrective surgery in Pusan Paik Hospital. Their ages ranged from 2 to 18 years. There were 6 male and 4 female patients. According to stenotic site, obstruction were classified into supravalvular [n = 5], subvalvular [n = 4], valvular stenosis [n = 1]. We have performed patch enlargement of ascending aorta [n = 2], supravalvular membrane resection and patch enlargement of ascending aorta [n = 3], subvalvular membrane resection [n = 2], subvalvular membrane resection and left ventricular myectomy [n = 2] and aortic annuloplasty with Dacron patch and aortic valve replacement [n = 1]. Preoperative mean value of systolic pressure gradient were 85.0 $\pm$29.2mmHg[supravalvular], 70.0mmHg[valvular], 72.5 $\pm$ 22.5mmHg[subvalvular], and 78.5 $\pm$ 24.3mmHg[total]. Postoperative mean value of systolic pressure gradient were 31.0 $\pm$ 8.9mmHg[supravalvular], 0mmHg[valvular], 15.0 $\pm$ 10.8mmHg[subvalvular], and 21.5 $\pm$ 13.9mmHg[total]. Postoperative systolic pressure gradient was decreased significantly[p = 0.001]. Postoperative course and short-term follow up results were good except one case of transient heart failure.

• Journal of Chest Surgery
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• 제22권2호
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• pp.234-245
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• 1989

Between January 1984 and December 1986, sixty nine patients, aged 16 months to 25 years [mean age 10.05*6.40 years], underwent total correction of tetralogy of Fallot in Kyungpook national university hospital. In 66 hospital survivors, 30 patients were followed up for 12 to 48 months [mean 30.10*10.26 months]. These 30 patients were classified in two groups, TAP [transannular patch] and Non-TAP group. There were 9 patients in TAP group, and 21 in Non-TAP group. There were no significant differences between two groups in terms of age at operation, follow up duration, ACC time, and bypass time. All patients were evaluated by two dimensional echocardiography, Doppler echocardiography, standard 12-lead electrocardiography, and plain chest X-ray. Right ventricular systolic pressure, pulmonary arterial systolic pressure, pressure gradient between the right ventricle and the pulmonary artery, presence or absence of pulmonary regurgitation and its grading, fractional shortening of the left ventricle, and Qp/Qs in case of remnant ventricular septal defect were obtained by echocardiographic examination. Cardiothoracic ratio was measured by plain chest film, and ventricular dysrrhythmia was detected by electrocardiogram. Comparing the data between two groups, there was significant difference in incidence of postoperative pulmonary regurgitation [p< 0.05], 100%[9/9] in TAP group and 47.6 %[10/21] in Non-TAP group, but all the regurgitations were not severe. There were no significant differences in other comparisons, despite of higher incidence of cardiomegaly in TAP group [CT ratio: 59.3*5.3% VS 54.7*6, 4 %].

• Journal of Chest Surgery
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• 제27권7호
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• pp.563-570
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• 1994

Effect of ischemic preconditioning on left ventricular function after cardiac arrest in isolated rat heart.Ischemic preconditioning reduces infarct size caused by sustained ischemia. However, the effects of preconditioning on post ischemic cardiac function are not well-known. The objective of the present study was to determine whether preconditioning would improve the recovery of left ventricular functions after cardiac arrest in isolated rat heart model.Isolated rat hearts were allowed to equilibrate for 20 minutes and were then subjected to either 5 minutes of global, normothermic transient ischemia [Group 2 and 4] or not [Group 3]. A stabilization period of perfusion lasting 5 minutes after the termination of transient ischemia was followed by a standard global, normothermic 20 minute-ischemia and 35-minute reperfusion challenge [Group 3 and 4]. These following results were odtained.1. The recovery of left ventricular developed pressures showed no significant differences between Group 3 and Group 4 at 50 [P>0.3] and 85 minute [P>0.2].2. Heart rates showed no significant differences throughout all the course of experiment and between groups [P>0.5].3. The recovery of left ventricular maximum dP/dt showed no significant differences between Group 3 and Group 4 at 50 [P>0.1] and 85 minute [P>0.2].4. The recovery of pressure-rate products showed no significant differences between Group3 and Group 4 at 50 [P>0.5] and 85 minute [P>0.1].These results suggest that ischemic preconditioning does not provide significant benefit for the postischemic left ventricular functions in isolated rat hearts.

• Journal of Yeungnam Medical Science
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• 제34권1호
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• pp.128-131
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• 2017

Mid-ventricular obstruction (MVO) rarely occurs in patients without hypertrophic cardiomyopathy. Increased cardiac contractility may play an important role in causing MVO. We experienced a case of severe chest pain and MVO in a 50-year-old female patient. She had hypertension, diabetes, stroke and peripheral artery disease. Her blood pressure was very high (222/122 mmHg) with severe fluctuation. The transthoracic echocardiography revealed MVO accompanied by hyper-dynamic left ventricular systolic function. We regarded her chest pain and MVO as secondary findings related to other diseases. Coronary angiography and several tests for uncontrolled hypertension were performed, and those evaluations revealed that she had coronary artery disease and hyperthyroidism. We considered that the increase in the myocardial oxygen demand in response to the increase in cardiac contractility and workload associated with hyperthyroidism aggravated her symptoms and MVO. She was treated with methimazole and beta blockers and her symptoms dramatically improved.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.415-419
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• 1997

The left ventricular relaxation rate is used as a golden standard which describes the left ventricular diastolic unction. So far, to get the rate of relaxation one should calculate the data after full recording, that is, off-line method. Therefore one cannot get the rate of relaxation in real-time while changing loading condition or infusing drug. But real time monitoring of the relaxation rate is necessary while changing loading condition or infusing drug to control the mechanics of heart and to get more information. We propose a new criterion to get the left ventricular relaxation rate and a real time algorithm. By comparison, it was turned out that our criterion outperforms others criterion.