• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.1-6
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• 2017

Stents are widely used as the most common method of treating coronary artery disease with implants in the form of a metal mesh. The blood flow is normalized by inserting a stent into the narrowed or clogged areas of the human body. In this study, the mechanical characteristics of a stent are investigated according to the variations of its design parameters by the Taguchi method and finite element analysis. A stent model of the Palmaz-Schatz type was used for the analysis. In the analysis, an elasto-plastic material model was adopted for the stent and a hyper-elastic model was used for the balloon. The main interest of this study is to investigate the effects of the design parameters which reduce the possibility of restenosis by adjusting the recoil amount. A Taguchi orthogonal array was constructed on the model of the stent. The thickness and length and angle of the slot were selected as the design parameters. The amounts of radial recoil and longitudinal recoil were calculated by finite element analysis. The statistical analysis using the Taguchi method showed that optimizing the shape of the stent could reduce the possibility of restenosis. The optimized shape showed improvements of recoil in the radial and longitudinal directions of ~1% and ~0.1%, respectively, compared to the default model.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.321-328
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• 2018

The purpose of this study was to investigate factors affecting the heart rate, to analyze the relevance and to use it as a management index of factors of increase in heart rate. A total of 204 adults from November, 2016 to March, 2017 who responded to a personal questionnaire among the adults who underwent coronary computed tomography scans for health screening, were the target of the investigation. In the study, there was a statistically significant difference (p <.05) between the heart rate and the gender, CACS, Stenosis and the forces affecting cardiovascular disease. CACS, Stenosis had a statistically significant difference (p <.05) compared with the other groups in the group with a heart rate of 80 bpm or more, the ability to influence cardiovascular disease was different from that of other groups There was a meaning difference in the heart rate below 60 bpm group compared (p <.05). In conclusion, it is important and desirable to maintain heart rate below 60 bpm in order to prevent having cardiovascular disease history, and below 80 bpm to prevent CACS and stenosis.

• Journal of Chest Surgery
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• v.25 no.1
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• pp.1-16
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• 1992

The quantitatively measured local myocardial perfusion rates with microspheres are used as an objective indicator of even distribution of cardioplegic solution, and the efficacy of the retrograde right atrial route of cardioplegia is evaluated in hearts with various levels of coronary arterial obstruction. After initial antegrade cardioplegia under the median sternotomy and aortic cannulation, 60 hearts from anesthetized New Zealand white rabbits are divided in random order as normal group [ligated left main coronary artery ; MA, MR] and diagonal group [ligated proximal diagonal artery ; LA, LR]. Half of each group [N=10] are perfused with antegrade cardioplegia[A] under the pressure of 100 cmH2O and the other half with retrograde right atrial route[R] under the pressure of 60 cmH2O[St. Thomas cardioplegic solution mixed with measured amount of microspheres]. The myocardium is subdivided into segments as A[atria], RV[right ventricle]. S[septum], LV[normally perfused left ventricular free wall], ROI[ischemic myocardium of left ventricular free wall]. LV and RQI are further divided into N[subendocardium] and P[subepicardium]. The resulting local myocardial perfusion rates and N /P of each group are compared with Wilcoxon rank sum test. The weight of the hearts is 5.94$\pm$0.66g, and there are no statistically significant dif-ferences[p>0.05, ANOVA] between six compared group. The mean flow rate[F: ml /g / min] of MR group is comparable with MA group[p>0.05], but in N and L group, there are significantly depressed F with right atrial route of cardioplegia, which means elevated perfusion resistance with this route. In spite of no significant differences in delivered doses of microsphere[DEL] between compared groups[p>0.05, ANOVA], there are significantly depressed REC and NF in hearts with right atrial cardioplegia which suggests increased requirement of cardioplegic solution with this route. The interventricular septum shows poor perfusion with right atrial route of cardioplegia without obstruction of supplying coronary arteries. But, with obstruction of coronary artery supplying septum as in M group, the flow rate is superior with right atrial route of infusion. The left ventricular free wall perfusion rates of every RQI with R route are superior to that of A route[p<0.05]. But, in LV segments, there are unfavorable effects of right atrial cardioplegia in L group, although the subendocardial perfusion is well maintained in N group. The LV free wall of left main group shows depressed perfusion rates with antegrade route as compared with RQI segments of diagonal group. But, by contraries, there are increased perfusion rates and superior N /P ratio with retrograde right atrial route. It implies more effective perfusion with right atrial route of cardioplegia in more proximal coronary arterial obstruction[i.e., M group as compared with L group]. As a conclusion, all region of ischemia have superior perfusion rates with right atrial car-dioplegia as compared with antegrade route, and especially excellent results can be obtained in hearts with more proximal obstruction of coronary arteries which would otherwise result in more severe ischemic damage. But, the depressed perfusion rates of the segments with normal coronary artery in hearts with coronary arterial obstruction may be a problem of concern with right atrial cardioplegia and needs solution.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.713-720
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• 2019

The purpose of this study was to propose a new measurement method for accurate measurement of vessel diameter in computed tomography angiography(CTA). CTA test was performed after non-ionic iodine contrast agent was flowed at a constant rate to self-maded perfusion phantom. After obtaining raw data, images were reconstructed with multi-planar reconstruction(MPR) and maximal intensity projection(MIP). Diameters of vascular models were measured for each technique. Relative and conventional measurements were then compared. The mean diameter of the vascular model was closer to the actual measurement when relative measurement was used compared to that when conventional measurement was used both in MPR and MIP. Relative measurements of MPR and MIP were closer to actual measurement than those of conventional measurement (34% VS, 24%, p<0.05). The relative measurement method proposed in this study was closer to the actual measurement than the conventional measurement method. However, both test methods were still larger than actual results. Therefore, further study of relative measurement method is needed using this study as basic data.

• Journal of Chest Surgery
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• v.31 no.2
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• pp.134-141
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• 1998

Primary lung cancer has recently increased progressively in its incidence in Korea. It is clearly evident that surgical resection offers the best offortunity for cure of non-small cell carcinoma. This study was designed to analyse the clinical data of 100 primary non-small cell carcinoma patients who underwent lung resection surgery from January 1992 to July 1995 at the department of Thoracic and Cardiovascular Sugery, Kyungpook National University Hospital. There were 86 males and 14 females(6:1). In the age distribution, the peak incidence was recorded in the seventh decade(43%). The methods of tissue diagnosis were bronchoscopic biopsy in 53 patients(50.5%), percutaneous needle aspiration in 17 patients(16.2%), transbronchial lung biopsy in 11 patients(10.5%), mediastinoscopic biopsy in 2 patients (1.9%), sputum cytology in 2 patients(1.9%), and thoracotomy in 20 patients(19.0%). Fifty-five lobectomies, 22 pneumonectomies, 15 bilobectomies, 2 segmentectomies, 4 sleeve lobectomies, a sleeve pneumonectomy, and a wedge pneumonectomy were performed. Operative mortality occured in 4 cases(sepsis in 2 cases, respiratory failure in 1 case, and acute myocardiac infarction in 1 case). The histologic types of tumor were 67 squamous cell carcinomas, 26 adenocarcinomas, 6 large cell carcinomas, and an adenosquamous cell carcinoma. Eighteen patients with N2 mediastinal lymph node metastases had 8 squamous cell carcinomas(11.9%), 9 adenocarcinomas(34.6%), and a large cell carcinoma(16.7%). The primary tumors in these patients were in the right upper lobe in 4 patients, the right middle and lower lobe in 9 patients, the left upper lobe in 3 patients, and the left lower lobe in 2 patients. With regard to pathologic stages, 45 patients had stage I disease; 13 patients, stage II; 36 patients, stage IIIa; 5 patients, stage IIIb; and 1 patient, stage IV. The overall actuarial survival rate was 77.5% at 12 months, 56.1% at 24 months and 43.7% at 43 months. The actuarial survival rates at 43 months were 81.3% in Stage I, 20.8% in Stage II, 27.9% in Stage IIIa, 25.0% in Stage IIIb and 33.3% in Stage IV. These facts suggest that early detection and surgical resection are recommended for favorable postoperative survival in non-small cell lung cancer.

• The Korean Journal of Nuclear Medicine
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• v.39 no.1
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• pp.9-14
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• 2005

Purpose: Abnormal myocardial perfusion may be caused by ventricular preexcitation, but its location, extent, severity and correlation with accessory pathway (AP) are not established. We evaluated perfusion patterns on myocardial perfusion SPECT and location of AP in patients with WPW (Wolff-Parkinson-White) syndrome. Materials and Methods: Adenosine Tc-99m MIBI or Tl-201 myocardial perfusion SPECT was performed in 11 patients with WPW syndrome. Perfusion defects (PD) were compared to AP location based on ECG with Fitzpatrick's algorithm or electrophysiologic study and radiofrequency catheter ablation. Results: Patients had atypical chest discomfort or no symptom. Risk of coronary artery disease (CAD) was below 0.1 in 11 patients using the nomogram to estimate the probability of CAD. Coronary angiography was performed in 4 patients (mid-LAD 50% in one, normal in others). In 4 patients, AP localization was done by electrophysiologic study and radiofrequency catheter ablation (RFCA). Small to large extent ($11.0{\pm}8.5%$, range:$3{\sim}35%$) and mild to moderate severity ($-71{\pm}42.7%$, range:$-2l7{\sim}-39%$) of reversible (n=9) or fixed (n=1) perfusion defects were noted. One patient with right free wall (right lateral) AP showed normal. PD locations were variable following the location of AP. One patient with left lateral wall AP was followed 6 weeks after RFCA and showed significantly decreased PD on SPECT with successful ablation. Conclusion: Myocardial perfusion defect showed variable extent, severity and location in patients with WPW syndrome. Abnormal perfusion defect showed in most of all patients, but it did not seem to be correlated specifically with location of accessory pathway and coronary artery disease. Therefore myocardial perfusion SPECT should be interpreted carefully in patients with WPW syndrome.

• Journal of Chest Surgery
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• v.42 no.6
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• pp.696-703
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• 2009

Background: A Comprehensive Aortic Root and Valve Reconstruction (CARVAR) procedure is comprised of aortic root wall reconstruction and corrections of the leaflets for treating various aortic valve diseases. We evaluated our recent early clinical experience with the CARVAR procedure. Material and Method: From October 2007 to September 2008, 114 cases (66 males) of CARVAR procedures were performed, The mean patient age was 53 years (range: 14~84) The patients were divided into 4 groups: 1) the AAR group: aortic regurgitation with aortic root wall deformity such as annulo-aortic ectasia or ascending aortic aneurysm (n=18), 2) the IAR group: isolated AR with leaflet abnormality (n=42), 3) the IAS group: isolated aortic stenosis (n=51) and 4) the PAVR group: previous aortic valve replacement (n=3). Sinotubular junction (STJ) reduction was done in all the patients, leaflet correction was done in 10 of the AAR group patients and in all the patients of the other groups, annulus reduction was done in 14 of the MR group patients and in 6 of the IAR group patients. Aortic dissection was excluded from this analysis. Result: There was no mortality or follow-up death. The diameter of the aortic sinus decreased from $54.6{\pm}8.4$ mm to $38.3{\pm}3.8$ mm in the AAR group, the mean AR grade decreased from 3.2 to 0.2 in the IAR group, the mean aortic valve pressure gradient decreased from $47.1{\pm}24.4$ mmHg to $15.1{\pm}11.7$ mmHg in the IAS group and the mean AR grade decreased to 0 in the PAVR group. Balloon type coronary perfusion cannula-related coronary ostial stenosis developed in 4 patients and this was treated with OPCAB in three patients and with PTCA in one patient. Two patients developed postoperative infectious endocarditis. All the patients were discharged and followed up in a stable condition. Conclusion: The CARVAR procedure showed excellent short term results, but a good further follow up result is required to apply this procedure to most kinds of aortic valve diseases.

• The Korean Journal of Nuclear Medicine
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• v.38 no.6
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• pp.486-491
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• 2004

Purpose: factor analysis and independent component analysis (ICA) has been used for handling dynamic image sequences. Theoretical advantages of a newly suggested ICA method, ensemble ICA, leaded us to consider applying this method to the analysis of dynamic myocardial $H_2^{15}O$ PET data. In this study, we quantified patients' blood flow using the ensemble ICA method. Materials and Methods: Twenty subjects underwent $H_2^{15}O$ PET scans using ECAT EXACT 47 scanner and myocardial perfusion SPECT using Vertex scanner. After transmission scanning, dynamic emission scans were initiated simultaneously with the injection of $555{\sim}740$ MBq $H_2^{15}O$. Hidden independent components can be extracted from the observed mixed data (PET image) by means of ICA algorithms. Ensemble learning is a variational Bayesian method that provides an analytical approximation to the parameter posterior using a tractable distribution. Variational approximation forms a lower bound on the ensemble likelihood and the maximization of the lower bound is achieved through minimizing the Kullback-Leibler divergence between the true posterior and the variational posterior. In this study, posterior pdf was approximated by a rectified Gaussian distribution to incorporate non-negativity constraint, which is suitable to dynamic images in nuclear medicine. Blood flow was measured in 9 regions - apex, four areas in mid wall, and four areas in base wall. Myocardial perfusion SPECT score and angiography results were compared with the regional blood flow. Results: Major cardiac components were separated successfully by the ensemble ICA method and blood flow could be estimated in 15 among 20 patients. Mean myocardial blood flow was $1.2{\pm}0.40$ ml/min/g in rest, $1.85{\pm}1.12$ ml/min/g in stress state. Blood flow values obtained by an operator in two different occasion were highly correlated (r=0.99). In myocardium component image, the image contrast between left ventricle and myocardium was 1:2.7 in average. Perfusion reserve was significantly different between the regions with and without stenosis detected by the coronary angiography (P<0.01). In 66 segment with stenosis confirmed by angiography, the segments with reversible perfusion decrease in perfusion SPECT showed lower perfusion reserve values in $H_2^{15}O$ PET. Conclusions: Myocardial blood flow could be estimated using an ICA method with ensemble learning. We suggest that the ensemble ICA incorporating non-negative constraint is a feasible method to handle dynamic image sequence obtained by the nuclear medicine techniques.

• Journal of Chest Surgery
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• v.21 no.6
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• pp.1020-1029
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• 1988

The authors evaluated 153 patients who had undergone cardiac valve replacement between October 1979 and July 1988. The results are as follows: l. Out of 153 patients, there were 56 males and 97 females ranging from 15 to 62 years of age with a mean of 37 years. 2. Isolated mitral valve replacement took place in 82 patients, aortic valve replacement[AVR] in 16, double valve replacement[DVR] in 34, AVR combined with open mitral commissurotomy in 19, and tricuspid valve replacement[TVR] was done in 2 patients. 3. 153 patients had 187 prosthetic valves replaced with Ionescu-Shiley valves[16], Carpentier-Edwards[36], Bjork-Shiley[19], St. Jude Medical[108], and Duromedics[8]. 4. Our of 98 patients with atrial fibrillation[ 64% of a total 153 patients ] during the preoperative period, 22 patients recovered NSR[ 22/98, NSR recovery rate 22.4%] after valvular surgery and remaining 76 patients revealed persisting atrial fibrillation[76/153, 49.7% ]. 5. Preoperative episodes of systemic arterial embolization were attained in 9 patients[9/153, 6% ], and left atrial thrombi were confirmed in 22 patients intraoperatively[ 22/153, 14% ]. Of these, only one patient, however, demonstrated the correspondence of preoperative embolization and intraoperative existence of LA thrombi. 6. With mechanical prostheses, anticoagulant therapy was begun 48 hours after operation with sodium warfarin[2.5-5.0mg/day], maintaining the prothrombin time between 16 and 18 seconds or 30 to 50% of control values and continued for life. With tissue prostheses, sodium warfarin was continued for 3 to 6 months and converted into buffered ASA[ 325 mg/day ] for one year. 7. The mean follow-up for the survivors was 30.1 months, with a range from 3 months to 9 years. All suspected or confirmed thromboembolic episodes counted as events and occurred in 4 patients[ 1.04%/patient-year] with mechanical valve replacement. No persistent paralysis or death was noted. Late complications have not yet occurred in the patients with isolated MVR and AVR. 8. There were remarkable structural failures of tissue valves in 3 patients[ 1.9%/patient-year ], while no instance of failure of a mechanical valve. 9. There were 10 operative early deaths[10/153, 6.5%] and 5 late deaths[5/153, 3.3%]. Consequently, overall mortality was 9.8%[ 15/153] during follow-up period. 10. We currently favor using the St. Jude Medical valve in all patients requiring valve replacement except in those who can not take warfarin anticoagulation.

• Polymer(Korea)
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• v.34 no.2
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• pp.178-183
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• 2010

Medical metal stents inserted to patients with a cardiovascular disease associated with coronary artery system have relatively increased the survival rate. The development of new stents is, however, urgently required due to restenosis and late thrombosis generated in metal stents. To solve these problems, the biodegradable polymers such as poly(lactide-co-glycolide) (PLGA), poly(L-lactide)(PLLA), and poly ($\varepsilon$-caprolactone)(PCL) were mixed with alpha lipoic acid (ALA), which is well known to inhibit the proliferation of neointimal hyperplasia. Subsequently, the ALA-loaded polymers were coated on stainless steel by electrospray. The drug-eluting behaviors from the coated polymers were investigated according to kinds and concentrations of polymers, spray rates, and kinds of solvents. The drug-eluting rate from PCL with the lowest glass transition temperature was the fastest among three polymers and followed by PLGA and PLLA. The surface roughness increased as the spray rate was increased and also the drug-eluting rate was affected by kinds of solvents with different boiling point. It is expected that drug-eluting stent (DES) coated with ALA-loaded polymers can be applied practically for clinical applications by controlling the behavior of drug release.