No abstract available.
Echocardiography* ; Hemodynamics*

BACKGROUND: Low frequency oscillation of systemic artery pressure was known as the marker of sympathetic modulation. Recently the low frequency oscillation of pulmonay artery pressure in pulmonary hypertensive patient was reported. But no further study about its quantitative relationshop and phasic coupling between the low frequency oscillation of pulmonary artery pressure and systemic artery pressure. Power spectral analysis with autoregressive algorithm and cross spectral analysis are powerful tool for investigation these relationship. METHOD: Analog signals of simultaneous measured left pulmonary and femoral artery pressure in thirty one patients with ventricular septal defect were digitized and stored. After modeling each time series with autoregressive algorithm, power spectral density function was obtained by calculation the frequency response function of each model, and then low frequency power was computed. Cross spectral density function provided squared coherence and phase spectrum. Phase between the low frquency oscillation of the two signal was measured from the phase spectrum when the squared coherence is above 0.5. RESULTS: The advantage of using autoregressive model was that the power spectral density function was continous and sharp spectral peak was usually found. In patients with Rp/Rs<0.25, the low frquency power of pulmonary artery pressure(12+/-12) was significantly smaller than that of the systemic artery pressure(144+/-242). In patients with Rp/Rs>or=0.25, there was no significant difference between the low frequency power of pulmonary artery pressure(384+/-461) and that of the systemic artery pressure(752+/-1241). In patients with Rp/Rs>or=0.25, it was more probable that low frequency oscillation of pulmonary and systemic artery pressure was timely coherent(sqaured coherence>0.5) than in patient with Rp/Rs<0.25. And their phase difference was 0~1.96 radian. CONCLUSION: Autoregressive algorithm is a more powerful tool for spectral analysis than the method of conventional spectrum estimation. When pulmonary vascular resistance remains low, the low frequency oscillation of pulmonary artery pressure was negligible compared to systemic artery pressure. But as pulmonary vascular resistance elevates, the low frequency power of pulmonary artery pressure is much the same as that of systemic artery pressure, and there is a explicit time realtionship that pulmonary artery pressure leads the systemic artery pressure about 0~3 seconds in the low frequency range.
Arteries ; Femoral Artery ; Heart Septal Defects, Ventricular ; Humans ; Hypertension, Pulmonary ; Pulmonary Artery ; Pulmonary Circulation* ; Vascular Resistance

No abstract available.
Female ; Fetal Heart* ; Fractals* ; Heart Rate, Fetal* ; Pregnancy

The mechanism of vasodilation effect of GS-389, 1-(4'-methoxybenzyl)-6,7 -dimethoxy-1,2,3,4-tetrhydroisoquinoline hydrocholoride, a possible cyclic GMP specific phosphodiesterase inhibitor, on rat and mouse thoracic aorta ring has been investigated. GS-389 relaxed rat and mouse thoracic aorta precontracted with phenylephrine and high K+(60mM) in concentration dependent manner. Presence or absence of endothelium did not alter the relaxing effects of it. GS-389 inhibited Ca2+-induced contraction of the high K+ or 1 uM phenylephrine. Initial phasic contraction induced by phenylephrine and caffeine in Ca2+ free solution was inhibited by GS-389. Methylene blue pretreatment suppressed relaxation effect of GS-389. Relaxation by isoproterenol or sodium nitroprusside and by acetylcholine in endotheilium preserved aorta was potentiated by concurrentadministration of GS-389. GS-389 inhibited phenylephrine-induced phosphatidylinositide hydrolysis. It is suggested that inhibition of phosphoinositide turnover associated with elevated cyclic nucleotide by GS-389 may be the possible vascular relaxation mechanism of it.
Acetylcholine ; Animals ; Aorta ; Aorta, Thoracic ; Caffeine ; Cyclic GMP ; Endothelium ; Hydrolysis ; Isoproterenol ; Methylene Blue ; Mice ; Nitroprusside ; Phenylephrine ; Rats ; Relaxation* ; Vasodilation

No abstract available.
Heart Septal Defects, Ventricular* ; Tetralogy of Fallot*

No abstract available.
Purpura, Schoenlein-Henoch* ; Scarlet Fever*

BACKGROUND: We studied how periodic and complex heart rate dynamic changes as pulmonary artery pressure increases in 32 infants with ventricular septal defet. In addition, we tested the possibility that the dynamical changes can be used to noninvasively predict the pulmonary artery pressure. METHODS: During cardiac catherterization, mean pulmonary artery pressure was measured and, at the same time, 5minute segments of continous electrocardiographic recording was stored. High-(>0.15 hertz) and low-(0.03-0.15 hertz) frequency components of heart rate variability were computed using spectral analysis. Yhe overall complexity of heart rate time series was quantified by its approximate entropy. RESULT: Pulmonary hypertensive infants(mean pulmonary artery pressure>20mmHg, n=17) had significantly lower low-(p<0.05)and high-(p<0.05) frequency power and lower approximate entropy(p<0.0001) than pulmonary normotensive infants(mean pulmonary artery pressure20mmHg, n=15). The mean pulmonary artery pressure was significantly correlated not with the spectral powers but with approximate entropy(=-0.51, P=0.0001). Conclusion: It can be concluded that, in infants, pulmonary hypertension induced by left-to-right shunt lesions suppress both periodic and complex heart rate oscillation and that mean pulmonary artety pressure can be predicted by calculating approximate entropy of heart trate variability.
Electrocardiography ; Entropy ; Heart Rate* ; Heart Septal Defects, Ventricular* ; Heart* ; Humans ; Hypertension, Pulmonary ; Infant* ; Pulmonary Artery*

OBJECTIVES: This study is aimed to quantify the complex dynamics of beat-to-beat fetal heart rate(FHR) fluctuations by using approximate entropy(ApEn) which is a recently developed mathematical formula quantifying regularity and also to determine the differences between normal fetuses and growth retarded fetuses. BACKGROUND: Recently, some measures of heart rate variability and nonlinear "complexity" of heart rate dynamics have been used as indicators fetal well-being. Approximate entropy is a new mathematical approach and formula to quantify regularity in data. It has been shown to provide new information in fetal heart rate analysis. Because growth retarded fetus accounts for a significant increase in perinatal morbidity and mortality, than normal fetus, we postulated that there existed important differences between normal fetuses and growth retarded fetuses. METHODS: We analyzed FHR tracings for 40 minutes, and approximately 5,000 points in normal fetuses(n=315) and growth retarded fetuses(n=76). The overall "complexity" of each FHR time series was quantified by its approximate entropy, measure of regularity derived from nonlinear dynamics, "chaos theory". RESULTS: Mean baseline FHR increased in growth retarded fetuses than normal fetuses. And the FHR ApEn significantly decreased in growth retarded fetuses(ApEn=0.623) compared to that of the normal fetuses(ApEn=0.868) throughout all gestational ages(p < 0.001). CONCLUSIONS: The ApEn of FHR decreased in growth retarded fetuses throughout all gestational ages. These findings indicated that decreased ApEn values of FHR are associated with sickness and the greater perinatal morbidity risks. Therefore ApEn quantifies subtle changes in FHR regularity and promises for new information in FHR analysis.
Entropy* ; Female ; Fetal Heart* ; Fetus* ; Gestational Age ; Heart Rate ; Heart Rate, Fetal* ; Mortality ; Nonlinear Dynamics ; Pregnancy

Background : The approximate entropy of heart rate variability has recently been used as a tool in evaluating cardiovascular health and physiology and in diagnosing pertubated physiologic status, by quantifying the irregularity and the pattern of the heart rate variability. Therefore approximate entropy of the fetal heart rate variability will be used as an important tool in studying the fetal cardiovascular health and disease, but unfortunately there have been no previous systematic studies of the approximate entropy in normal fetuses. This study's aim has been to present the normal approximate entropy values of the fetal heart rate variability according to the gestational age, to demonstrate the developmental maturation of physiology of the control systems of the heart rate, and to quantify the evolution of the pattern of fetal heart rate variability. METHODS: Three hundred and thirty seven mothers with normal singleton pregnancies, who were 20 weeks or more of gestational age, were randomly chosen. For more than 40 minutes fetal heart rates and fetal movements were recorded and were downloaded to a computer. From each heart rate data, 5000 points ('total') of heart rate during which fetal movements occured and 1200 points ('rest') during which no fetal movement occured were selected and the approximate entropy was calculated, and then 2 weeks' average of the approximated entropy of the heart rate were calculated and compared to find the maturational differences of them. RESULTS: The approximate entropy of the rest period showed a tendency to increase with advancing gestation (p=0.0001). It was significantly higher between the 41st-42nd week (0.987 +/-0.017) than the period before the 24 th week (0.864+/-0.032) and between the 25th-26th week (0.868+/-0.022). (p<0.05). The approximate entropy of the total period showed another tendency (p<0.05): from a low level before the 24 th week (0.788+/-0.067) it increased to reach its peak at the 29th-30 th week (0.963+/-0.041) then it gradually decreased again to significantly (p<0.05) lower levels at the 37th-38th week (0.776+/-0.046) and the 39th-40th week (0.786+/-0.047). CONCLUSIONS: Normal value of approximate entropy, which is bound to be used as an index in evaluating the fetal well-being, has been presented from 20th to 42th week of gestation with an interval of two weeks. The systems that control the heart rate seem to mature consistently as gestation advances, but before the 26th week it is significantly more immature than at term. Fetal heart rate variability evolves from an immature oscillating pattern into a transitional patternless pattern during the second trimester and finally consolidates into a mature accelerational pattern during the third trimester.
Entropy* ; Female ; Fetal Heart* ; Fetal Movement ; Fetus ; Gestational Age ; Heart Rate ; Heart Rate, Fetal* ; Humans ; Mothers ; Physiology ; Pregnancy ; Pregnancy Trimester, Second ; Pregnancy Trimester, Third ; Pregnancy* ; Reference Values

BACKGROUND: The effectiveness for vagal stimulation by ice water aplication to face during metronome-controlled respiration of 15 breaths/minute was examed. The importance of basal vagal tone and sympathovagal interaction in the individual variability of responsiveness to the vagal stimulation was investigated. METHOD: Fifty three 12~13 year old healthy volunteers were included. Vagal tone and sympathovagal interaction before and after application of ice water to the face were assessed by power spectral analysis of RR interval(heart rate) variability. RESULT: Basal heart rate, high frequency power, and low to high frequency power ratio were 81+/-13(58~110 beats/min), 791+/-1061(56~4161 msec2) and 1.08+/-1.22(0.04~4.85) during controlled respiration. After ice water application twenty three children developed 5 more nodal escape beats due to severe bradycardia. Minimum heart rate, high frequency power and low to high power ratio changed to 42+/-12(19~72/min), 1890+/-1882(221~7258msec2) and 0.64+/-0.43(0.12~1.46). The increased ratio of high frequency power, maximum heart rate decrement and its percent after stimulation were 5.44+/-5.62(0.63~24.26), 39+/-14(10~81/min) and 47+/-15(16~81%) respectively. The increased ratio of high frequency power was correlated with basal logarithmic high frequency power(r=-0.60, p=0.0004). Maximum heart rate decrement was correlated with basal logarithmic high frequency power(r=-0.41, p=0.0018) and low to high frequency power ratio(r=0.27, p=0.04). CONCLUSION: Application of ice water to the face during controlled respiration produces powerful vagal stimulation and bradycardia, however, there is a wide individual variability of responsiveness to it. The absolute basal vagal tone contribute to this individual variability.
Bradycardia ; Child ; Healthy Volunteers ; Heart Rate* ; Heart* ; Humans ; Ice* ; Respiration* ; United Nations ; Water*