• Journal of Biomedical Engineering Research
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• v.26 no.2
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• pp.87-93
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• 2005

A new method for real-time estimating left ventricular relaxation time constant (T) from the left ventricular (LV) pressure waveform, based on the isovolumic relaxation model, is proposed. The presented method uses a recursive least squares (RLS) algorithm to accomplish real-time estimation. A new criterion to detect the end-point of the isovolumic relaxation period (IRP) for the estimation of T is also introduced, which is based on the pattern analysis of mean square errors between the original and reconstructed pressure waveforms. We have verified the performance of the new method in over 4,600 beats obtained from 70 patients. The results demonstrate that the proposed method provides more stable and reliable estimation of τ than the conventional 'off-line' methods.

• Biomolecules & Therapeutics
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• v.10 no.2
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• pp.89-98
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• 2002

In this study general pharmacological profiles of KI-60606 on the central nervous system, the cardiovascular system and the other organs were investigated. The dosages given were 0,5, 10 and 25 mg/kg and drugs were administered intravenously. The animals used for this study were mice, rats, cats and guinea pigs. KI-60606 showed no effects on general behavior, motor coordination, spontaneous locomotor activity, hexobarbital-induced hypnosis time, body temperature, analgesic activity, anticonvulsant activity and contraction of nictitating membrane in cats. Furthermore KI-60606 showed no effects on blood pressure, heart rate, LVP (left ventricular peak systolic pressure), LVEDP (left ventricular end diastolic pressure), LVDP (left ventricular developing pressure), DP(double product), CFR(coronary flow rate), smooth muscle contraction using guinea pig ileum and gastric secretion at all dosage tested except the increase of gastrointestinal transport and urinary $K^+$ excretion.

• Biomolecules & Therapeutics
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• v.7 no.2
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• pp.170-177
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• 1999

PEG-hemoglobin SB1 (SB1), which is a hemoglobin-based oxygen carrier, is intended to use as a safe blood substitute against brain ischemia and stroke. The general pharmacological profiles of SB1 were studied. The doses given were 0, 5, 10, 20 ml/kg and drugs were administered intravenously. The animals used for this study were mouse, rat and guinea pig. SB1 showed no effects on general behavior, motor coordination, spontaneous locomotor activity, hexobarbital sleeping time, anticonvulsant activity, analgesic activity, blood pressure and heart rate, left ventricular peak systolic pressure, left ventricular end diastolic pressure, left ventricular developing pressure, double product, heart rate, coronary flow rate, smooth muscle contraction using guinea pig ileum, gastrointestinal transport, gastric secretion, urinary volume and electrolyte excretion at all doses tested except the decrease of body temperature. These findings demonstrated that SB1 possesses no general pharmacological effects at all doses tested.

• YAKHAK HOEJI
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• v.55 no.3
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• pp.247-250
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• 2011

An increase in ventricular pressure can alter cardiac excitation and contraction. Recent report has demonstrated that fluid pressure (FP) suppresses L-type $Ca^{2+}$ current with acceleration of the current inactivation in ventricular myocytes. Since the L-type $Ca^{2+}$ channels known to be regulated by intracellular pH ($pH_i$), this study was designed to explore whether pressurized fluid flow affects pHi in isolated rat ventricular myocytes. A flow of pressurized (~16 dyne/$cm^2$) fluid, identical to that bathing the myocytes, was applied onto single myocytes, and intracellular $H^+$ concentration was monitored using confocal $H^+$ imaging. FP significantly decreased $pH_i$ by $0.07{\pm}0.01$ pH units (n=16, P<0.01). Intracellular acidosis enhances the activity of $Na^+-H^+$ exchanger (NHE). Therefore, we examined if the NHE activity is increased by FP using the NHE inhibitor, HOE642. Although HOE642 did not alter $pH_i$ in control conditions, it decreased $pH_i$ in cells pre-exposed to FP, suggesting enhancement of NHE activity by FP. In addition, FP-induced intracellular acidosis was larger in cells pre-treated with HOE642 than in cells under the control conditions. These results suggest that FP induces intracellular acidosis and that NHE may contribute to extrude $H^+$ during the FP-induced acidosis in rat ventricular myocytes.

• Journal of Chest Surgery
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• v.19 no.1
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• pp.68-74
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• 1986

15 patients with constrictive pericarditis who underwent interphrenic pericardiectomy from January, 1981 to April, 1983 and 11 patients who underwent radical pericardiectomy from May, 1983 to September, 1984 were compared to the clinical improvement and the results of pre- and postoperative cardiac catheterization. In the group of partial pericardiectomy the pericardium was removed anteriorly from the left phrenic nerve to the right phrenic nerve and in the group of radical pericardiectomy the pericardium was removed from almost entire surface of the heart including diaphragmatic surface and posterior wall of the left ventricle. The following results were obtained. 1. Both group of the patients showed marked symptomatic improvement early after operation. 2. The central venous pressure was decreased significantly after operation in both group of the patients. 3. The right atrial mean pressure and pulmonary arterial mean pressure decreased significantly after operation in both group of the patients and there was no significant difference in the amplitude of decrease between the two groups. 4. The right ventricular end-diastolic pressure and left ventricular end-diastolic pressure were decreased postoperatively in both group of the patients and the patients of the radical pericardiectomy showed more decrease than the patients of interphrenic pericardiectomy, and in the group of radical pericardiectomy the right and left ventricular end-diastolic pressure were normalized postoperatively but in the group of partial pericardiectomy they showed abnormally high pressure persistently. 5. The ejection fraction showed normal level pre- and postoperatively in both group of the patients.

• Journal of Chest Surgery
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• v.12 no.1
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• pp.50-55
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• 1979

The development of aortic insufficiency radically alters the physical findings which are generally associated with ventricular septal defect that was not hemodynamically significant, and the combination of the two lesions produces a typical clinical picture, that may be serious and life-threatening when it is left untreated. Therefore, the selection of patients, type and timing of surgical treatment is considered to be important. Among 114 cases of ventricular septal defect treated surgically utilizing cardiopulmonary bypass in the Department of Thoracic Surgery, Seoul National University Hospital, 7 cases were associated with aortic insufficiency. 1. Five cases were male, and 2 cases were female. Ages were from 4 years to 24 years, and mean age was 11.9 years. 2. In all cases, ventricular septal defect was closed with Teflon patch. In a case, a aortic valvuloplasty and in another, a aortic valve replacement with Hancock valve 23 mm., 5 months after the closure of ventricular septal defect were done. 3. Four cases were type I ventricular septal defect by Kirklin`s classification, 3 cases were type II ventricular septal defect, and diameters of ventricular septal defect were from 3.5 cm. to 0.7 cm. A PDA. was combined to a type I ventricular septal defect. 4. In 5 cases, herniation of the aortic cusp through the ventricular septal defect and in a case, annulus dilatation on the aortic valve was noted. 5. Two cases with type I ventricular septal defect and severe pulmonary hypertension expired. A re-opened case with type II ventricular septal defect expired. 6. Four cases were alive, and all of them show decrease of pulse pressure and aortic insufficiency.

• Journal of Chest Surgery
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• v.26 no.2
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• pp.122-128
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• 1993

This series compromised 31 patients with pulmonary hypertension of 282 patients of ventricular septal defect(VSD) who underwent operation at the department of Thoracic and Cardiovascular Surgery in Chonnam University Hospital, from January, 1986 to December, 1991. Pulmonary hypertension was noted in 59 of 280 cases of VSD. Of them, 31 cases underwent cardiac catheterization on postoperative 8th to 77th month. Age at operation was ranged from 10 months to 29 years (mean 9.13 years). 17 patients were male and 14 patients were female. Results of follow-up studies were as follows: Cardiothoracic ratio was decreased from 0.59${\pm}$0.04 to 0.54${\pm}$0.03 (p=NS). Postoperative systolic pulmonary arterial pressure (PAPs), mean pulmonary arterial pressure (PAPm), and systolic right ventricular pressure (RVPs) were decreased significantly (p<0.001). And also Rp/Rs was decreased from 0.37${\pm}$0.21 to 0.14${\pm}$0.06 (p<0.02). However, systemic arterial pressure (SAP), right atrial pressure (RAP), and pulmonary capillary wedge pressure (PCWP) were changed insignificantly. There were significant relations of follow-up period with the decrement of PAP(p<0.005). In contrary, ther were no relations between the decrement of PAP and the age at operation. These data suggested that the long-term hemodynamic changes remained to be determined in some of the patients, even though they Were asymptomatic, with pulmonary hypertension.

• The Korean Journal of Pharmacology
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• v.19 no.1
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• pp.61-69
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• 1983

Hypothermia is an essential preparatory procedure for cardiac surgery, which lows the metabolic rate and myocardial oxygen demand. However, hypothermia itself is a stress enough to change the tonus of sympathoadrenal system, especially the cardiovascular responses to the catecholamines. It is reported that the positive chronotropic and inotropic response of catecholamines is exaggerated during hypothermia because of decreased norepinephrine uptake at the junctional cleft or decreased catecholamine metabolism. On the other hand, there are evidences of diminished catecholamines responses in low temperature ana further, interconversion of adrenergic receptors is also suggested. Present investigation was planned to observe the cardiovascular changes and its responses to catecholamines during surface hypothermia in cat. Healthy mongrel cats, weighing $2{\sim}3\;kg$, anesthetized with secobarbital(30 mg/kg), were permitted to hypothermia by external cooling technic. Esophageal temperature, ECG (lead II), heart rate, left ventricular pressure with dP/dt, carotid artery pressure and left ventricular contractile force were monitored with Polygragh (Model 7, Grass), and the respiration was maintained with artificial respirator (V 5 KG, Narco). Followings are summarized results. 1) Surface cooling caused progressive decrease of body temperature and reached $l8.8{\pm}0.8^{\circ}C$ and $16.9{\pm}0.6^{\circ}C$ in 120 and 150 min respectively, after immersion into ice water, and ventricular fibrillation was developed at $20.4{\pm}0.65^{\circ}C$. 2) Heart rate, blood pressure and myocardial contractility were decreased after initial increase as the body temperature falls. 3) Systolic and diastolicdd P/dt of left ventricular pressure were decreased and that the decrement of diastolic dP/dt was more marked. 4) On ECG, ST depression, Twave inversion and prolongation of PR interval were prominent in hypothermia, and moreover, the prolongation of PR interval was marked just prior to the development of ventricular fibrillation. 5) The cardiovascular responses to catecholamines, especially to isoproterenol, were suppressed under hypothermia.

• Journal of Chest Surgery
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• v.18 no.1
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• pp.79-85
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• 1985

The effect of graded increments in positive end-expiratory pressure [PEEP] on hemodynamics required to ventilate 8 critically ill patients is reported. Acute respiratory insufficiency was a cause of death in only one patient of drug inoxication among the 8 patients studied. The cardiac output was not changed significantly after the increment of PEEP to the level of 20 cm H2O. The heart rate was increased significantly from 15 cm H2O PEEP [P<0.01] as compared to 0 cm H2O PEEP; and the stroke volume was decreased significantly from 15 cm H2O PEEP [P<0.05]. The blood pressure was not affected at any level of PEEP, but the pulmonary artery pressure was elevated significantly at 10 cm H2O PEEP [P<0.01]. The right ventricular transmural filling pressure was not affected at the level of 10 cm H2O PEEP, but from 15 cm H2O PEEP it was increased significantly. With the increment of PEEP, the left ventricular stroke work index was decreased slightly; and at 20 cm H2O PEEP, it was decreased significantly. The right ventricular stroke work index was increased only at 10 cm H2O PEEP. The systemic vascular resistance was decreased significantly from 15 cm H2O PEEP [P<0.01].

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.387-394
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• 1996

This paper presents a Neural Network Identification(NNI) method for modeling of highly complicated nonlinear and time varing human system with a pneumatically driven mock circulatory system of Left Ventricular Assist Device(LVAD). This system consists of electronic circuits and pneumatic driving circuits. The initiation of systole and the pumping duration can be determined by the computer program. The line pressure from a pressure transducer inserted in the pneumatic line was recorded System modeling is completed using the adaptively trained backpropagation learning algorithms with input variables, heart rate(HR), systole-diastole rate(SDR), which can vary state of system. Output parameters are preload, afterload which indicate the systemic dynamic characteristics. Consequently, the neural network shows good approximation of nonlinearity, and characteristics of left Ventricular Assist Device. Our results show that the neural network leads to a significant improvement in the modeling of highly nonlinear Left Ventricular Assist Device.