• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.715-720
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• 2014

In order to maximize the effect of left ventricular assist device (LVAD) on ventricular unloading, the therapy should be begun at appropriate level of heart failure severity. We predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used 3 dimensional finite element model of ventricle coupled with 6 Wind-kessel compartmental model of vascular system. Using the computational model, we predicted cardiac responses such as contractile ATP consumption of ventricle, left ventricular pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous LVAD. Contractile ATP consumption, which indicates the ventricular energetic loading condition decreased maximally at the $5^{th}$ level heart-failure under LVAD therapy. We conclude that optimal timing for LVAD treatment is $5^{th}$ level heart-failure when considering LVAD treatment as "bridge to recovery".

• Journal of Chest Surgery
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• v.32 no.2
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• pp.124-129
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• 1999

Background: Ventricular septal defect(VSD) that causes pulmonary hypertension increase right ventricular workload. Echocardiographic assessment of right ventricular systolic time interval (RVSTI) has been used to predict pulmonary artery pressure in various cardiopulmonary diseases. This study was undertaken in infants with simple VSD to observe the alteration of the right ventricular workload through the changes of RVSTI after repair of VSD. Material and Method: We evaluated heart rate, the ratio of the left atrium/aortic root diameter (LA/Ao), right ventricular pre-ejection period(RVPEP), right ventricular ejection time(RVET), and its ratio(RVPEP/RVET) as a predictor of right ventricular workload in 12 children with simple VSD. These were measured three times at the preoperative period, at the 3 month and between 6 month and 1 year(average 9.5${\pm}$1.8month) after repair of VSD by M-mode & Doppler echocardiograph from the pulmonic valve echogram. Result: Heart rate was decreased significantly after repair(137.1${\pm}$13.7 vs 114.4${\pm}$21.1 and 104.1${\pm}$10.2, p<0.01). LA/Ao ratio was decreased significantly after repair(1.71${\pm}$0.32 vs 1.47${\pm}$0.33 and 1.39${\pm}$0.23, p<0.05). RVPEP/RVET were decreased after repair (0.38${\pm}$0.09 vs 0.32${\pm}$0.08 and 0.29${\pm}$0.09, p<0.01). Heart rate corrected RVPEP/RVET were significantly decreased only after 6 months(0.32${\pm}$0.03 vs 0.30${\pm}$0.05 and 0.28${\pm}$0.06, p<0.05). Conclusion: We found elevated right ventricular workload was progressively decreased until more than 6 months after repair and the RVSTI may serve a useful guide in postoperative care for children with VSD.

• Journal of Chest Surgery
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• v.36 no.7
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• pp.523-526
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• 2003

A 44-year-old man had been admitted for dyspnea on exertion and abdominal distension. The echocardiography revealed abnormal mass in right atrium and tricuspid valve stenosis with right ventricular obliteration. The operation was performed with mass removal, enlargement of tricuspid valve opening, and right ventricular endocardiectormy. And then, atrial septal defect was made due to inadequate right ventricular volume. The patient's symptom was improved and he discharged without events. The endomyocardial fibrosis was diagnosed with microscopic examination. Eighteen months later, the patient was readmitted due to aggravated dyspnea and cyanosis. The right ventricular obliteration was progressed and pulmonary blood flow was severely decreased in follow up echocardiography. Palliative bidirectional cave-pulmonary shunt was performed due to functional single ventricle. The dyspnea and cyanosis was markedly improved. Bidirectional cavo-pulmonary shunt for advanced and isolated right ventricular endomyocardial fibrosis provided effective palliation at early postoperative period, However, long-term follow up is mandatory.

• Journal of Chest Surgery
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• v.35 no.9
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• pp.664-667
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• 2002

Extracorporeal membrane oxygenation(ECMO) provides stable oxygenation to prevent elevation of pulmonary vascular resistance and bypasses a significant part of cardiac output to the pulmonary vascular bed to reduce pulmonary perfusion pressure. In addition, ECMO prevents right heart failure and low cardiac output by means of ventricular assist and reduction in volume load to right ventricle. As a result, ECMO can be used for the treatment of pulmonary hypertensive crisis after surgery for congenital heart disease, especially when it is refractory to conventional measures. We report a case of postoperative pulmonary hypertensive crisis, developed in a 37-year-old male with patent ductus arteriosus with secondary pulmonary hypertension, which was successfully managed including ECMO.

• Clinical and Experimental Pediatrics
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• v.45 no.2
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• pp.214-222
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• 2002

Purpose : The aim of this study was to evaluate myocardial injury in children treated with adriamycin by echocardiography, which is non-invasive and safe measurement for children. Methods : Left ventricular dimensions, wall stress, and contractile function were determined by echocardiographic methods in 17 patient recepients with adriamycin chemotherapy at rest(group 1) and during stress(group 2). Twenty age-matched normal subjects were established as control group. Results : End-diastolic dimension was decreased in both groups(group 1; $92{\pm}7%$ of normal, group 2; $87{\pm}8%$ of normal, P<0.05). Left ventricular end diastolic volume and wall mass were also decreased in both groups(group 1; $96{\pm}12mL/m^2$ and $145{\pm}18g/m^2$, group 2; $87{\pm}8mL/m^2$ and $137{\pm}16g/m^2$, respectively, P<0.05 and P<0.05) and group 2 showed lower values than group 1. Meridional end systolic stress(ESSm) was increased in both groups but there was no significant difference between the two groups(group 1; $52.6{\pm}6.2g/cm^2$, group 2; $63.5{\pm}8.5g/cm^2$, P<0.05, normal value $45.7{\pm}3.5g/cm^2$). The load-independent relation of rate-corrected circumferential fiber shortening velocity(Vcfc) to ESSm has a significant abnormal change in 7 out of 17(41%) in group 1 and 12 out of 17(71%) in group 2. Conclusion : The load-dependent systolic index, such as fractional shortening, may fail to show abnormality because of the compensatory changes in preload and afterload which can mask the impaired contractility. Therefore, systolic performance also should be monitored by a load-indepedent contractility index such as slope value of the end-systolic pressure-dimension relation and the position of the left ventricular stress-fiber shortening velocity after exercise.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.4
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• pp.22-28
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• 2013

It is important to begin left ventricular assist device (LVAD) treatment at appropriate time for heart failure patients who expect cardiac recovery after the therapy. In order to predict the optimal timing of LVAD implantation, we predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used LVAD-implanted cardiovascular system model which consist of 8 Windkessel compartments for the simulation study. The time-varying compliance theory was used to simulate ventricular pumping function in the model. The ventricular systolic dysfunction was implemented by increasing the end-systolic ventricular compliance. Using the mathematical model, we predicted cardiac responses such as left ventricular peak pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous and pulsatile LVAD. Left ventricular peak pressure, which indicates the ventricular loading condition, decreased maximally at the 1st level heart-failure under pulsatile LVAD therapy and 2nd level heart-failure under continuous LVAD therapy. We conclude that optimal timing for pulsatile LVAD treatment is 1st level heart-failure and for continuous LVAD treatment is 2nd level heart-failure when considering LVAD treatment as "bridge to recovery".

• Journal of Chest Surgery
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• v.32 no.3
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• pp.299-302
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• 1999

Heart transplantation was planned for a 10-year old boy who had dilated cardiomyopathy with severe congestive heart failure and had been on dopamine for 1month. However, partial left ventriculectomy and mitral annuloplasty were performed instead, because there was no donor heart of the adequate size and the symptoms were aggravated. The clinical symptoms were markedly improved after the surgery. Comparing the postoperative echocardiographic results with the preoperative results, there were remarkable changes in the left ventricular ejection fraction(preoperative LV EF 17% to postoperative 3 months 29%, 6 months 35%, 1 year 36%) and the left ventricular end-diastolic dimension(preoperative 72 mm to postoperative 3 months 59 mm, 6 months 61 mm, 1 year 61 mm). Partial left ventriculectomy and mitral annuloplasty reduced the cardiac loading in the dilated cardiomyopathy. Partial left ventriculectomy and mitral annuloplasty may be considered as one of the alternative surgical metho s to carry over until a heart transplantation can be performed, especially for children.

• Clinical and Experimental Pediatrics
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• v.46 no.12
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• pp.1274-1278
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• 2003

Syncope in children and adolescents have a common occurrence according for up to 15% before adulthood. Micturition syncope, a kind of situational syncope, can be considered a form of reflex syncope. It can typically occur in healthy young men after rising from bed in the early morning who experience sudden loss of consciousness during or immediately after urination. The mechanism of micturition syncope is not completely understood, but it has been suggested that vasovagal reflex mediated bradycardia and peripheral vasodilation and decreased venous return due to Valsalva effect and standing position lead to the decrease in cerebral blood flow resulting in syncope. The causes of syncope are variable. So complete history taking, physical examination, electrocardiography, exercise stress test, echocardiography, head-up tilt table test, electroencephalography(EEG), brain magnetic resonance image and urodynamic study should be required for the diagnosis of micturition syncope. There were several reports about micturition syncope. However, literature of micturition syncope at the pediatric age has rarely been reported in Korea so far. Therefore, we report a case of a 9-year-old boy with micturition syncope with typical EEG findings of high amplitude delta wave and flattening during syncope.

• Clinical and Experimental Pediatrics
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• v.50 no.5
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• pp.462-468
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• 2007

Purpose : The purpose of this study was to analyze the changes of the late potential of Signal- averaged electrocardiography (SAECG) and Electrocardiography (ECG) parameters during follow up of those who had taken surgical repair of Tetralogy of Fallot (TOF). Methods : Nine patients who had taken surgical repair of TOF since 1985 checked SAECG and standard 12 leads ECG twice in 1999 and 2005 in Kyungpook national university hospital. We evaluated changes of QRS duration, QT interval and JT interval, QRS dispersion, QT dispersion and JT dispersion of standard 12 leads ECG and Filtered QRS (f-QRS), High frequency low amplitude potential (HFLA), Root mean square in terminal 40 ms (RMS) and Mean voltage in terminal 40 ms (MV) of SAECG between in 1999 and 2005. Results : There were significant decrease of JT dispersion ($101.11{\pm}50.11$ vs $71.11{\pm}22.61ms$, P< 0.05) and significant increase of HFLA ($24.67{\pm}13.19$ vs $32.89{\pm}14.21ms$, P<0.05). But there were no significant changes in other parameters. Conclusion : In repaired TOF patients, we evaluated ECG and SAECG to detect possible late complications such as tricuspid regurgitation, right ventricular enlargement, ventricualar arrythmia and sudden death. And there were significant changes of ECG and SAECG in some parameters (JT dispersion, HFLA). But to see the relationships between the changes of these parameters and the long term prognosis, we need to check more patients and longer follow-up.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.30-38
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• 2000

Purpose: We investigated the role of myocardial perfusion SPECT in prediction of ventricular dilatation and the role of revascularization including thrombolytic therapy and PTCA in prevention of ventricular dilatation after an acute myocardial infarction (AMI). Materials and Methods: We performed dipyridamole stress, 4 hour redistribution, and 24 hour reinjection Tl-201 SPECT in 16 patients with AMI two to nine days after attack. Perfusion and wall motion abnormalities were quantified by perfusion index (PI) and wall motion index (WMI). Left ventricular ejection fraction (LVEF), WMI and ventricular volume were measured within 1 week of AMI and after average of 6 months. According to serial changes of left ventricular end-diastolic volume (LVEDV), patients were divided into two groups. We compared WMI, PI and LVEF between the two groups. Relationships among degree of volume, stress-rest PI, WMI, CKMB, Q wave, LVEF and revascularization were analysed using multivariate analysis. Results: Only initial rest perfusion index was significantly different between the two groups (p<0.05). While initial LVEF, stress PI, CKMB, trial of revascularization procedure, presence of Q wave and WMI were not significantly different between the two groups. Eight of 16 patients (50%) showed LV dilatation on follow-up echocardiography. Three of 3 patients (100%) who did not undergo revascualrization procedure documented LV dilatation. And only 5 (38%) of the remaining 13 patients who underwent revascularization revealed LV dilatation. There was no difference in infarct location between the two groups. By multivariate linear regression analysis in patients only undergoing revascularization, rest perfusion index was the only significant factor. Conclusion: Myocardial perfusion SPECT performed prior to revascularization was useful in prediction of LV dilatation after an AMI. Rest perfusion index on myocardial perfusion plays as a significant predictor of left ventricular dilatation after AMI. And revascularization appears to be a valuable procedure in alleviating LV dilatation after AMI with or without viable myocardium in a limited number of patients studied retrospectively.