• Neonatal Medicine
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• 제25권1호
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• pp.1-6
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• 2018

Extremely low birth weight infants remain at increased risk of intraventricular hemorrhage from the fragile vascular bed of the germinal matrix; the roles of hypotension (ischemia) and reperfusion (hyperemia) in the development of intraventricular hemorrhage are still debated. Cerebrovascular pressure autoregulation protects the brain by maintaining constant cerebral blood flow despite changes in blood pressure. The ontogeny of cerebrovascular pressure autoregulation has not been well established and uncertainty remains about the optimal arterial blood pressure required to support brain perfusion. Another important aspect of premature cerebral hemodynamics is the critical closing pressure--the arterial blood pressure at which cerebral blood flow ceases. Interestingly, in premature infants, the critical closing pressure approximates the mean arterial blood pressure. Often in this unique population, cerebral blood flow occurs only during systole when the diastolic arterial blood pressure is equal to the critical closing pressure. Moreover, the diastolic closing margin, a metric of cerebral perfusion that normalizes diastolic arterial blood pressure to the critical closing pressure, may be a better measure than arterial blood pressure for defining cerebral perfusion in premature infants. Elevated diastolic closing margin has been associated with intraventricular hemorrhage. This review summarizes the current state of understanding of cerebral hemodynamics in premature infants.

• Journal of Chest Surgery
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• 제11권3호
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• pp.321-325
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• 1978

Coarctation of the aorta was rare condition among the congenital cardiovascular defects in Korea. We experienced a case of coarctatlon of the aorta [postductal type], which was successfully corrected by resection and end to end anastomosis. This patient, 21 years male patient, was admitted to the medical department for evaluation of hypertension, headache and exertional dyspnea during 4 years, and transferred to the department of chest surgery for operation. On physical examination, blood pressures were measured on both extremity, measuring 190/100mmHg on the arm and 100/80mmHg on the leg. Systolic murmur was heard on 2nd to 3rd left intercostal space and left sternal border. On simple chest x-ray, rib notching was seer/on low border of right 3rd and left 4th rib. Final preoperative diagnosis was made by the retrograde aortic catheterization and aortography, which showed the typical configuration of postductal type of coarctation with poststenotic dilatation of the aorta. On 20th, July, 1978, under the general anesthesia with endotracheal intubation, resection of coarctation of the aorta and end to end anastomosis was performed. During clamp for resection, blood pressure of upper extremity was elevated to 200/140mmHg, and controlled by Arfornad. During recovery, blood pressure over 160ramrig in systole was controlled by Reserpine for 8days postoperatively. At discharge, postoperative 8th day, brachial and femoral artery pressure was 145/85 mmHg and 135/80mmHg. After discharge, there was no evidence of specific symptoms and hypertension without antihypertensive drug.

• Journal of Chest Surgery
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• 제24권3호
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• pp.265-270
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• 1991

Since advent of the prosthetic cardiac valve replacement, much efforts for accurate assessing value function in-vivo have been attempted. To evaluate the postoperative functional and morphological status of the replaced cardiac valve prosthesis, 33 patients with valve replacement were studied by transthoracic and transesophageal 2-dimensional echocardiac imaging as well as by color Doppler flow velocity imaging. Twenty four patients had mitral valve replacement. 6 patients had aortic valve replacement and 3 patients had both mitral and aortic valve replacement. There were 34 mechanical and 2 biological prosthesis. Comparing to transthoracic echocardiography, transesophageal approach showed transvalvular regurgitant jet flow amid the prosthetic mitral valve ring during. systole and much clear visualization of cardiac chamber behind prosthesis which could give shadowing effect to ultrasound beam. According to the quantitative grading by the length and area of mitral regurgitant flow, 24 out of 27 mitral valves revealed mild degree regurgitation considered as physiological after prosthetic bileaflet valve replacement and the other 3 valves including 2 biological prosthesis had moderate degree regurgitation which was regarded as pathologic one. 2 cases of left atrial thromboses and 1 case of paravalvular leakage which were not visible by transthoracic approach were identified by transesophageal echocardiography in patients with mitral valve replacement and patients with aortic valve replacement respectively. We conclude that in patients with prosthetic mitral valve replacement, transesophageal 2-dimensional imaging with color Doppler can suggest reliable information beyond that available from the transthoracic access even though it gives patient some discomfort to proceed.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.109-112
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• 1997

The Hydrodynamic performance of the trileaflet polymer prosthetic valves depends on the design of the leaflet and the physical properties of the leaflet membrane. In order to study the effect of leaflet membrane elasticity on the hemodynamic performance of trileaflet prosthetic valve, leaflet membranes are manufactured using two different polymers - Biospan and Tecoflex SG-93A. The hemodynamic performance parameters are measured under steady and physiological pulsatile flow, and compared with monoleaflet polymer valve(floating valve) and bileaflet mechanical valve(St. Jude Medical valve). Well designed trileaflet valve shows the lowest mean pressure drop among the tested valves. The trileaflet valves with Biospan membrane show lower pressure drop and back low comparing to those with Tecoflex membrane. More elastic membrane may provide wide opening area during systole and close membrane ree edge contact during diastole. Durability of trileaflet valves are also tested in vitro. Trileaflet valves with non-uniform membrane thickness ail within 17 days because of stress concentration. Trileaflet polymer valves with uniform membrane thickness perform well over 55 days without failure.

• 대한기계학회논문집B
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• 제26권1호
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• pp.39-44
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• 2002

The arterial stenosis related to the intimal thickening of the arterial wall is the main cause of many diseases in human cardiovascular system. Hemodynamic behavior of the blood flow is influenced by the presence of the arterial stenosis. In this study, effects of the pulsatile flow, caused by the periodic motion of the heart, on the blood flow and its interaction with the arterial stenosis are analyzed by the FEM-based computational fluid dynamics. As a result, it was found that the characteristics of the pulsatile flow in the artery with stenosis are quite different from those of the steady flow. And, the pulsatile flow condition affects the wall shear stress, which is one of the most important physiological parameters in the hemodynamics.

• 한국임상수의학회지
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• 제34권1호
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• pp.54-57
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• 2017

A 1-year-old castrated male Schnauzer dog was presented with heart murmur. Auscultation revealed systolic murmur located at the left heart base (grade 5/6). There were no remarkable findings on thoracic radiographs. Two-dimensional echocardiography revealed subaortic tunnel-like obstruction at the entrance to the left ventricular outflow tract. Anterior mitral valve leaflet appeared to be tethered to septum with minimal motion. Chordae tendineae was abnormally thickened. Color Doppler analysis revealed turbulent flow starting below the aortic valve. Mitral regurgitation was presented during systole. Spectral Doppler recordings revealed high velocity flow through the aorta and mitral regurgitation. Based on echocardiographic examination, the dog was diagnosed with subaortic stenosis concurrent with mitral dysplasia. The patient was medicated with ${\beta}-blocker$ and diuretics. It has been doing well without apparent clinical signs at 2 year after the diagnosis.

• 한국가시화정보학회지
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• 제20권1호
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• pp.52-63
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• 2022

Direct numerical simulation of blood flow in a stenosed, patient-specific carotid artery was conducted to explore the transient behavior of blood flow with special emphasis on the wall-shear stress distribution over the transition region. We assumed the blood as an incompressible Newtonian fluid, and the vessel was treated as a solid wall. The pulsatile boundary condition was applied at the inlet of the carotid. The Reynolds number is 884 based on the inlet diameter, and the maximum flow rate and the corresponding Womersley number is approximately 5.9. We found the transitional behavior during the acceleration and deceleration phases. In order to quantitatively examine the wall-shear stress distribution over the transition region, the probability density function of the wall-shear stress was computed. It showed that the negative wall-shear stress events frequently occur near peak systole. In addition, the oscillatory shear stress index was used to further analyze the relationship with the negative wall-shear stress appearing in the systolic phase.

• 대한한의학회지
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• 제23권3호
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• pp.1-10
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• 2002

Objective: There exist gender differences in pulsatile contour waveform. Women have a greater age-related increase in left ventricular mass than do men and more likely to experience symptomatic heart failure after infarction. SDPTG (the second derivative of photoplethysmogram waveform) is a noninvasive method for evaluating the pulse wave and is correlated with age and other risk factors for atherosclerosis. We studied the effect of gender on SDPTG and made clear why the gender differences appear. Methods: To study the effects of effect factors, including height and blood pressure, on SDPTG in the fourth decade, data on height, weight, PTD (pulse transit distance), blood pressure, serum lipid levels, and SDPTG were collected in 115 laboratory healthy men and women. SDPTG is derived from double-differential processing of fingertip photoplethysmography and consists of a, b, c, and d waves in systole and an e wave in diastole; SDPTG aging index (AI) was calculated as (b-c-d-e)/a. Results: There were significant gender-related differences of SDPTG AI, height, and blood pressure. Age, height, and mean blood pressure were respectively and significantly correlated with SDPTG AI. SDPTG is dependent upon age, height, and blood pressure. Restricting analysis to SDPTG AI, age, height, and mean blood pressure, yielded that there were gender-related differences in SDPTG AI (P<0.05) which were derived from those of height (F<0.001, df=l, P=0.994). Conclusions: These new data may help to explain previous findings about age-related differences in pulsatile contour waveforms and why gender differences of SDPTG appear. The results of this study suggest that SDPTG AI, used for evaluation of biological vascular aging, should be calibrated by height as well as age and blood pressure.

• Journal of Acupuncture Research
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• 제19권3호
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• pp.126-137
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• 2002

Objective : There is accumulating data that cardiovascular diseases, including hypertension, cerebro-vascular accident, coronary heart disease, relate to atherosclerotic changes. Increased serum levels of lipids could play a role in these circumstances. the SDPTG(the second derivative of photoplethysmogram waveform) is noninvasive methods for evaluating the pulse wave and is correlated with age and other risk factors for atherosclerosis. Methods : To study the effects of serum lipid levels on the SDPTG in the middle-age adults, data on serum lipid levels and the SDPTG were collected in 80 healthy middle age with varying serum lipid concentrations. Biological vascular age was assessed using the SDPTG. the SDPTG consists of an a, b, c, and d wave in systole and an e wave in diastole; an SDPTG aging index(Al) was calculated as (b-c-d-e)/a. Results : Serum triglyceride, total cholesterol, total lipid, phospholipid, HDL cholesterol levels were respectively and significantly correlated with SDPTG Al. Serum lipid levels and blood pressure are age-dependent and the SDPTG is blood pressure-dependent. Restricting analysis to age and blood pressure yield strong positive correlations between serum triglyceride, total lipid levels and SDPTG Al, but no correlations between serum total cholesterol, phospholipid levels and SDPTG Al. Conclusion : The results of this study suggest that preventive acupuncture programs or herbal medications for reducing serum lipid, especially triglyceride, levels in middle-age should include a evaluation of biological vascular aging with the second derivative of photoplethysmogram waveform.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2003년도 제27회 추계학술대회
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• pp.49-49
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• 2003

목적 : 심초음파는 비침습적이므로 반복적으로 정확히 심질환의 경과를 관찰하여 치료효과 및 수술시기를 정할 수 있는 검사로서 임상적으로 매우 유용하다. 실시간 심근조영심초음파에 의한 time intensity 평가는 부위별로 수행됨으로 연속적으로 위치하는 관심영역이 intensity에 있어 심장의 움직임 변화에 영향을 받는다. Time intensity 곡선의 최적의 곡선맞춤을 위해 주기적인 심장 운동 매개변수를 조합해 기존의 모델을 보정한 안정적인 측정방법을 제시한다. 방법 : 심장의 운동에 의한 특징적인 정보를 설명하기 위해 기존의 문헌에 제시된 지수 함수에 주어진 심박수로 만들어진 시간에 관한 일반적인 정형파 함수를 추가한다. C(t) = A[1 - exp($\beta$t)] + Dsine(2$\pi$ft + $\theta$) C(t): videointensity A: plateau videointensity (blood volume) $\beta$: capillary blood velocity (rate constant of rise in videointensity) t: pulsing interval (ms) D: displacement from the periodic variance of the curve (estimated motion field from the ejection point for the ratio between systole and diastole) f: heart rate $\theta$: transit time issue A $\times$ $\beta$ : myocardial blood flow 관상동맥의 관류 데이터에 대한 실험이 펄스간격에 대한 비디오 세기로 수행되었다. 그리고 이러한 결과들이 the sum of squares due to error, R square, root mean squared error로 평가되었다. 결과 : 실험결과, 주기적인 심장의 움직임과 심박출 시점으로부터의 변위를 잘 기술하고 곡선에서의 측정 점들이 예측된 심장 움직임에 따라 성공적으로 표시되었다. 뿐만 아니라 보정된 모델이 현저한 적합도의 향상을 보여주었다. 결론 : 제시된 접근방법은 각각의 측정에서 심장 운동 영역의 변화에 독립적이며 측정 시점에 의해 영향받지 않고 심근 관류의 안정적인 측정이 가능하다. 심장의 움직임에 관한 매개변수를 조합한 모델로 곡선접합을 수행함으로써 관류의 정량적 정보를 좀더 정확하게 얻을 수 있으며 임상적 이용을 가능하게 할 것으로 기대된다.