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PubMed1982

A quantitative method for the evaluation of spectral analysis patterns in carotid artery stenosis.

Duplex scanning in conjunction with Fast Fourier Transform Spectral Analysis offers a means of identifying stenotic internal carotid arteries, but few quantitative algorithms for interpretation of the spectral analysis patterns have been described. We first developed two objective parameters for analyzing carotid artery spectral analysis patterns which included a total of three peak frequencies in diastole and a ratio of spectral pattern areas between the internal and common carotid vessels. We then devised a formula for interpretation of the test results based on a computerized, best-fit, step-wise, discriminate analysis performed on 196 angiographically studied carotid vessels. This formula was then prospectively applied to 154 other carotid arteries with independently interpreted angiograms. 103/109 (94%) of the carotid arteries with less than 50% angiographic stenosis were correctly identified as were 40/50 (89%) of the vessels with 50% or more narrowing. Combining these groups with 16/17 (94%) properly classified total occlusions resulted in an overall accuracy rate of 93%. Application of the formula to smaller subgroups also showed significant differences in the formula means as they related to the degree of angiographic stenosis. Duplex scanning in conjunction with spectral analysis offers a reliable screening test for the evaluation of patients with suspected carotid artery stenosis.

Carotid Artery Diseases↗
PubMed1998

Automated spectral analysis I: formation of a priori information by spectral simulation.

A spectral simulation method is described for generating a priori information for use in parametric spectral analysis. The method makes use of GAMMA (S. A. Smith, T. O. Levante, B. H. Meier, R. R. Ernst, J. Magn. Reson., 106A, 75-105, 1994), a programming environment that facilitates simulation of magnetic resonance phenomena. The input parameters consist of the chemical shifts and scalar spin-coupling constants for the compounds to be analyzed, the acquisition pulse sequence, and the field strength used. The resultant spectral information consists of the relative amplitude, frequency, and phase of all resonances, which are stored in a spectral database. This procedure can be rapidly and conveniently modified to reflect different acquisition parameters and data analysis requirements.

Aspartic Acid↗
PubMed1996

Assessment of autonomic nervous function by power spectral analysis of heart rate variability in the horse.

We studied power spectral analysis of heart rate (HR) variability in the horse, with the hypothesis that the quantitative information provided by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, electrocardiogram, blood pressure (BP) and respiratory (Resp) waveform were simultaneously recorded from Thoroughbred horses (3-5 years old) and analyzed by power spectrum. There were two major spectral components at low-frequency (LF) and high-frequency (HF) bands for HR variability. The peak of Resp variability clearly occurred at the HF range. In contrast to Resp variability, the power spectra of BP variability occurred at lower frequencies. The maximum coherence between HR and Resp variabilities and HR and BP variabilities occurred at approximately 0.15 and approximately 0.03 Hz, respectively. These relationships were similar to the ensemble spectra. On the basis of these data, we have defined two frequency bands of interest: LF (0.01-0.07 Hz) and HF (0.07-0.6 Hz). Therefore, we believe that power spectral analysis of HR variability provides a very powerful technique for assessing autonomic nervous activity in the horse.

Animals↗
PubMedDate not supplied

Alteration in the low-frequency domain in power spectral analysis of fetal heart beat fluctuations.

OBJECTIVE: Spectral analysis was conducted on fetal heart rate fluctuations for the purpose of investigating the change in gestational age and examining the usefulness as a method of estimating fetal blood gas. STUDY DESIGN: Five hundred and twenty-nine pregnant women with a single normal fetus and 26 women with intrauterine growth restriction (IUGR) were studied during the 20th to 38th gestational weeks. In cases of IUGR, fetal blood gas levels were evaluated with percutaneous umbilical blood sampling. A time series of fetal heart rate fluctuation was obtained with a 1. 15-MHz ultrasonic transducer, and power spectral analysis of 200 consecutive stable beats was performed with an autoregression method. Integrated areas of 0.025-0.125 cycles/beat were defined as low-frequency areas (LFAs) and were examined in normal fetuses. In addition, the relation between LFA and fetal blood gas values was studied. RESULTS: As pregnancy progressed, LFA increased with a cubic regression equation (Y = 6.484 - 0.764X + 0.029X2 - 0.00034X3). The correlation coefficient was 0.625 (p < 0.05). In the cases of IUGR, DeltaLFA was highly correlated with DeltapO2 and DeltapH (correlation coefficient, 0.650 and 0.618, respectively). CONCLUSIONS: Measurement of LFA provides insight into the development of fetal autonomic function and also may serve as a quantitative index of fetal well-being in mid-pregnancy.

Adolescent↗
PubMed1980

Proof for the biosynthetic conversion of L-[indole-15N]tryptophan to [10-15N]anthramycin using (13C, 15N) labelling in conjunction with 13C-NMR and mass spectral analysis.

Using 13C-NMR and mass spectral analysis we have demonstrated that the N-10 nitrogen of anthramycin is biosynthetically derived from the indole-nitrogen of tryptophan. Our experimental approach was to bring a 15N atom, which is derived from L-[indole-15N]tryptophan, and a 13C atom which is derived from DL-[1-13C]tyrosine, into adjacent positions of anthramycin. From resonance intensities and 13C-15N spin-spin coupling in the 13C-NMR spectrum of didehydroanhydroanthramycin, a derivative of anthramycin, we could then determine the 13C enrichment at C-11 and the proportion of 13C bonded to 15N at N-10. These results when combined with mass spectral analysis and isotopic dilution measurements proved that the indole nitrogen of tryptophan was completely retained at N-10 of anthramycin.

Amino Acids↗
PubMed1983

Detection of aortic porcine valve dysfunction by maximum entropy spectral analysis.

A high-resolution method of spectral analysis, of the class generally called "maximum entropy method," was used in a study of aortic porcine valve closing sounds in 37 patients (ages 19 to 76). Spectra from 27 normal xenografts, implanted from 2 weeks to 61 months previously, were characterized by a dominant frequency peak, F1, at 89 +/- 15 Hz (mean +/- SD), with a lower amplitude peak, F2, at 154 +/- 25 Hz. Eight of nine patients with aortic porcine valve dysfunction were proved surgically to have leaflet degeneration or infection and had either F1 (139 +/- 54 Hz) and/or F2 (195 +/- 74 Hz) significantly higher than normal (p less than .001). In two patients with paravalvar leak but no leaflet abnormality, F1 and F2 were in the normal range. Estimation of F1 and F2 was highly reproducible and was unaffected by duration of implant up to 5 years. Spectral analysis of aortic porcine valve closing sounds by the maximum entropy method may be useful for detection of intrinsic xenograft dysfunction.

Adult↗
PubMed2002

[Autonomic hyperreflexia induced by sacral root stimulation is detected by spectral analysis of the EEG].

PURPOSE: To compare spectral analysis of the electrocardiogram (ECG) with mean arterial pressure (MAP) and heart rate (HR) monitoring in the detection of autonomic hyperreflexia (AHR) induced by sacral root stimulation. METHODS: Ten spinal cord injured patients scheduled for implantation of a sacral root stimulator for bladder retention were included. Under target controlled anesthesia with propofol 4 micro g*mL(-1) and remifentanil 4 ng*mL(-1), the patients were placed in the knee chest position. The sacral roots were exposed by laminectomy (L2-S1) and their function assessed by electrostimulation under urodynamic and cardiovascular monitoring. Online power spectrum densities were calculated from the ECG R-R interval by the MemCalc(TM) software using the maximum entropy method. Low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-0.4 Hz) spectra were associated with sympathetic and parasympathetic activities respectively. The most extreme value of each variable was noted before and during each stimulation. A difference ( triangle up ) of more than 10% signified AHR. The comparison ( triangle up LF vs triangle up MAP and triangle up HF vs triangle up HR) was done by a concordance test with a kappa coefficient (k): -1 = total discordance to 1 = total concordance. RESULTS: AHR was detected in six patients as an increase in LF and MAP (n = 4); an increase in LF, HF, MAP with a decrease in HR (n = 2). The detection delay was 5.3 +/- 1 sec (LF, HF) and 10.4 +/- 1.2 sec (MAP and HR). Concordance was 85% (LF vs MAP: k = 0.7) and 90% (HF vs HR: k = 0.8). CONCLUSION: AHR induced by sacral root stimulation is detected by spectral analysis of the ECG earlier than MAP and HR. Other studies are needed to confirm these results.

Adolescent↗
PubMed2001

Spectral analysis of circadian rhythms in heart rate variability of dogs.

OBJECTIVE: To determine characteristics of power spectral analysis of heart rate variability (HRV) during a 24-hour period in dogs and to evaluate the effects of vagal and sympathetic tone on HRV ANIMALS: 16 healthy adult Beagles. PROCEDURE: Power spectral analysis of HRV was conducted, using 24-hour ambulatory ECG recordings. Circadian rhythms were evaluated in terms of absolute units of low-frequency (LF) and high-frequency (HF) powers, their ratio (LF:HF), and their adjusted (normalized) units (LF[norm] and HF[norm]). Three or 4 dogs were used for simultaneous measurement of heart rate and respiratory waveform as well as to evaluate treatment (propranolol, atropine, or both) administered to cause blockade of the autonomic nervous system. RESULTS: Values for LF and HF powers, LF:HF, LF(norm), and HF(norm) had obvious rhythmicity in clinically normal dogs. The HF power of HRV in dogs was extremely high, compared with that of other species, and HF peaks corresponded to peaks obtained from respiratory waveforms. Blockade of the autonomic nervous system documented that HRV in dogs was mostly attributable to vagal activity. CONCLUSION AND CLINICAL RELEVANCE: We determined characteristics of power spectral analysis of HRV in dogs, including circadian rhythm of the autonomic nervous system. Power spectral analysis of HRV may provide a useful noninvasive technique for assessing the effect of drugs on activity of the autonomic nervous system in dogs.

Animals↗
PubMed1990

Spectral analysis of short-term heart rate variability in diabetic patients.

Spectral analysis of short term R-R variability estimated by autoregressive modelling is a recently developed method for the evaluation of cardiovascular autonomic function. This new test also allows to study the interaction on heart rate variability of parasympathetic and sympathetic system. The sensitivity of the method for detection of cardiovascular autonomic neuropathy has been evaluated in a group of diabetic patients in comparison with the sensitivity of a battery of the most commonly used cardiovascular autonomic tests (deep-breathing, lying-to-standing, Valsalva Manoeuvre, postural hypotension and hand grip). Spectral analysis of heart rate variability resulted in a very sensitive method for early detection of diabetic autonomic neuropathy, about one-fourth of diabetic patients with normal traditional cardiovascular autonomic tests had abnormal results at spectral analysis. Both sympathetic and vagal control of heart rate resulted alterated in diabetic autonomic neuropathy.

Adult↗
PubMed1993

A comparison of cardiovascular reflex tests and spectral analysis of heart rate variability in healthy subjects.

Determination of whether results of cardiovascular reflex tests and spectral analysis of heart rate variability are age dependent and whether there is correlation between results of both, cardiovascular reflex tests (the Valsalva manoeuvre, deep breathing test, handgrip test, cold face stimulus test, orthostatic test) and spectral analysis of heart rate variability were performed on 83 healthy volunteers of both genders, aged 21 to 70 years. We found that results of all heart rate based tests and results of spectral analysis decreased with aging, while results of blood pressure based tests did not. Parasympathetic activity predominated in younger subjects, while in older subjects sympathetic activity was dominant. Valsalva, deep breathing, and orthostatic ratios correlated with integrals of amplitude spectra in the standing posture and deep breathing and cold face stimulus ratios with integrals of amplitude spectra in the supine posture, whereas blood pressure changes during handgrip and orthostatic test did not correlate with integrals of the amplitude spectra. These findings suggest that tests based on heart rate may be more sensitive than tests based on blood pressure changes. This study supports the use of spectral analysis as an additional clinical test of autonomic nervous system function and stresses the importance of age in the evaluation of the results of autonomic nervous system function testing.

Adult↗
PubMed1995

Insight into blood-pressure control in SHR via the response to acute hemorrhage: a spectral analysis approach.

In this study we investigated, by means of the spectral analysis approach, the possible alterations in the activity of the pressor-control mechanisms in relation to the development of essential hypertension. Since the maintenance of controlled arterial blood pressure (ABP) levels is achieved by a continuously fluctuating control system, instantaneous ABP varies continuously in direct correlation with the activation of various control branches. The power spectrum of ABP fluctuations thus provides a quantitative measure of the activity of the various controlling mechanisms. Two strains of rats, Spontaneously Hypertensive Rats (SHR) and Wistar-Kyoto normotensive rats (WKY), were subjected to acute hemorrhage, a procedure known to trigger a strong response, of both the neural (autonomic nervous system) and the hormonal (renin-angiotensin and vasopressin) systems. ABP was continuously recorded from the caudal artery in conscious, 1-month-old SHR and WKY. Three groups of rats were studied. Group 1, acute 2-ml hemorrhage; Groups 2, injection of prazosin (2.5 mg/kg) or Group 3, captopril (4 mg/kg), each followed by bleeding as in the group 1. Spectral analysis of ABP fluctuations was performed on time traces of 20 min duration. The low-frequency part of the power spectrum was analyzed. Three frequency bands were investigated: 0.004-0.04 Hz, 0.04-0.07 Hz and 0.07-0.1 Hz. In SHR, although the baseline mean ABP levels were similar to those of WKY, ABP fluctuations were significantly dampened in SHR in each of the three frequency ranges. Hemorrhage induced, in both strains, a similar fall in mean ABP accompanied by an increase in the slow ABP fluctuations. However, in SHR, the response was significantly greater that that of WKY. The steepest response was observed in the slowest, 0.004-0.04 Hz frequency band, 8.7 +/- 1.7 vs. 1.5 +/- 0.4 times the baseline levels. However, this intense increase in power after hemorrhage brought the two strains to similar levels. The difference in the response to bleeding was eliminated, in the three frequency ranges, by alpha 1 blockade. Captopril reduced the response to bleeding in SHR, to the level observed in WKY in all three frequency bands. Spectral analysis of the spontaneous oscillations in ABP unmasks abnormalities which conventional blood pressure measurements cannot detect in 1-month-old, still normotensive SHR. It thus, provides a tool to study the dynamics of the abnormalities which precede the development of hypertension. Bleeding amplifies the malfunction observed in SHR under baseline conditions, since the mean ABP levels were similar in both strains before and after bleeding, SHR seem to retain the ability to respond to a fall in blood volume by requiring a greater recruitment of the control mechanisms than WKY.

Acute Disease↗
PubMed1998

Spectral analysis of heart valve sound for detection of prosthetic heart valve diseases.

The spectral analysis of heart valve sound is a noninvasive diagnostic method known to be useful in evaluating the state of the heart valve function. This may provide early detection of valve calcification, thrombus or destruction, since previous studies have shown that the dominant frequency peak moved to a high frequency area when natural heart valve leaflets were calcified, stiffened or destroyed. However, it is important for a heart valve sound diagnostic system to find a proper spectral analysis method on phonocardiography. Until now, conventional frequency analyses such as the Fourier transform or autoregressive spectral estimation technique have been used to estimate spectral components of a phonocardiogram, but they are inappropriate because the signal frequency is assumed to remain constant during the transform interval. To overcome this problem, in this study, FOS (Fast Orthogonal Search) & MUSIC (MUltiple SIgnal Classification), which both appeared suitable for the analysis of biological data, were applied to prosthetic heart valve sound as the new heart valve sound spectral analysis methods. Five subjects with normally functioning mechanical heart valves and a patient with a malfunctioning one were selected to collect the heart valve sound signals. As a result, the second dominant peak frequency proved to be important along with the first dominant peak frequency in identifying the valve function. This study showed that the new heart valve sound spectral analysis method presented in this paper may be an effective method in heart valve sound analysis. Further study using this system in a large population of patients will aid in providing a diagnostic method in the early detection of valve failure.

Female↗
PubMed2001

Spectral analysis of heart rate variability using the integral pulse frequency modulation model.

Spectral analysis of heart rate variability (HRV) is a widely accepted approach for assessment of cardiac autonomic function and its relationship to numerous disorders and diseases. As a rule, the non-parametric methods for HRV spectral analysis are tested using the integral pulse frequency modulation (IPFM) model. However, published results with simulated HRV signals show differences requiring further development of the existing methods. With the aim of improving estimation accuracy, an entirely IPFM-based method for HRV analysis is investigated. According to this method, the spectra are computed by finding the least squares solution of two matrix equations that are derived using the IPFM model and involve irregular samples of a signal representing the HRV. The method is validated with various synthesised signals (in all tests, the relative errors of the power estimates at the modulating frequencies are within 3%, and the relative power of the spurious terms is less than 0.8% only) and is furthermore applied to the spectral analysis of R-R interval series obtained from diabetic children. The results, with simulated and real HRV signals, show that the developed method yields very accurate estimations of the spectral region below half the mean heart rate. Moreover, it allows the detection and assessment of certain genuine modulating components beyond the traditional frequency limit of the HRV spectra.

Child↗
PubMed1985

[Exploration of the cervical arteries within the framework of an angiology service. Our experience using Doppler spectral analysis].

Diagnosis and quantification of severity of carotid lesions were assessed by different procedures. Oculoplethysmography was of value only in cases of significant occlusive lesions. Ultrasound methods possessed enhanced sensitivity: Doppler velocimetry, ultrasound imaging and particularly spectral analysis of the Doppler signal. Efficacy of this exploratory method was assessed in a department of angiology, spectral analysis being rated as 5 different grades as a function of degree of arterial stenosis (fig. 1). It was routinely combined with Doppler velocimetry and ultrasound imaging in 35 patients, a total of 64 carotid bifurcations being analyzed. Digital subtraction venous angiography was performed in 28 of these cases. Study of the reading effect on interpretation of the spectral analysis showed 37 agreements and 27 divergences; among the latter the definition of normality in relation to grades I or II appears to be responsible. Greater significance was noted for the reading effect in cases explored by Doppler velocimetry and ultrasonography. Positive findings were obtained with spectral analysis in 41 of 64 patients, either by detection of non-significant lesions or by precise quantification of stenotic lesions. Results of digital subtraction angiography were debatable in 8 of 28 patients and were unconfirmed on ultrasound imaging. Spectral analysis of the Doppler signal has therefore an advantage over Doppler velocimetry and ultrasonography in that more precise data is obtained on stenotic lesions and that those of little significance are detected. It supplies an effective means of diagnosis and surveillance and it establishes the need for angiography. Lack of sensitivity and reproducibility of ultrasound and digital subtraction venous angiography raises the problem of an effective reference test.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid Artery Diseases↗
PubMed2005

Study of low-frequency ultrasonic cavitation fields based on spectral analysis technique.

A kind of new spectral analysis method for analyzing ultrasonic cavitation fields is brought forward in this paper. This method extracts the line spectrum and the continuous spectrum from the cavitation noise spectrum respectively, then obtains estimations of the energy intensities of different cavitation components such as the stable cavitation and the transient cavitation through corresponding calculations. The method is also applied to investigate low-frequency ultrasonic cavitation fields and is compared with spectral level analysis method. The results show that this method can provide adequate information on the course of the cavitation process, give the delicate analysis on the transient cavitation and the stable cavitation, and help to gain an insight into the nonlinear process of cavitation fields. Moreover, it also shows that the criterion for characterization of cavitation intensity presented by Frohly through studying the high-frequency ultrasonic fields can be used to evaluate the low-frequency ultrasonic fields.

Journal Article↗
PubMed2004

Spectral analysis of movement patterns during anesthesia.

UNLABELLED: It remains unclear how anesthetics produce immobility, an end-point used in determining anesthetic potency. Understanding how movement (in response to noxious stimulation) is ablated by anesthetics could be aided by using spectral analysis of the high and low frequency components of complex movement patterns. We therefore applied a spectral analysis to previously published movement data from rats anesthetized with isoflurane and halothane at 0.6, 0.9, and 1.1 minimum alveolar concentration (MAC). We recorded isometric forces of hindlimb movement elicited by noxious mechanical stimulation of the hindpaw. The movement patterns were subjected to spectral analysis to determine force amplitude for each frequency component. When halothane was increased from 0.6 to 0.9 MAC, force amplitude decreased only for the lowest-frequency (<1 Hz) components, in part related to the generally lower high-frequency forces at 0.6 MAC. Between 0.6 and 0.9 MAC isoflurane amplitude was reduced for most frequencies in the 0-10 Hz range. For both halothane and isoflurane at 1.1 MAC, as expected, force amplitude substantially decreased at all frequencies. We conclude that spectral analysis is useful to describe and quantify the effects of anesthetics on complex movement patterns resulting from noxious stimuli applied during anesthesia. IMPLICATIONS: Complex movement can occur when a noxious stimulus is applied to an anesthetized animal. The frequency components of these movement patterns can be described and quantified by spectral analysis, thus providing a useful tool to investigate the immobilizing properties of anesthetics.

Algorithms↗
PubMed1993

Spectral analysis of flow velocity in the contralateral artery during coronary angioplasty: a new method for assessing collateral flow.

OBJECTIVES: The present study was designed to evaluate a new method for assessing coronary collateral flow and resistance in conscious humans. BACKGROUND: Earlier pathomorphologic and invasive studies have indicated that collateral vessels are important for salvage of myocardium at risk in acute myocardial infarction. Only a few clinical studies have attempted to express the development of the collateral vascular bed in terms of flow or resistance. METHODS: Angiography and flow velocity measurements of the contralateral coronary artery were performed in 38 patients undergoing coronary angioplasty for one-vessel disease. Coronary flow velocity was assessed by zero-crossing frequency analysis in 37 patients and, additionally, by fast Fourier transform spectral analysis in 23. Collateral flow was determined by the decrease of flow velocity after balloon deflation. Mean aortic pressure and coronary wedge pressure were assessed for calculation of collateral vascular resistance. RESULTS: Angiography of the contralateral artery during balloon inflation revealed the presence of collateral vessels in 26 patients (recruitable collateral vessels in 19). Fast Fourier transform spectral analysis demonstrated a significant transient increase of flow velocity during brief coronary occlusion in 15 patients with collateral vessels compared with 8 patients without collateral vessels (4.8 +/- 1.3% vs. 23.4 +/- 17.2%, p < 0.001). A transient increase in flow velocity (> 10%) was less evident by zero-crossing frequency analysis than by fast Fourier transform spectral analysis (sensitivity 8% vs. 87%). The relative resistance of the collateral vascular bed was significantly reduced when collateral vessels were present during coronary occlusion (4.4 +/- 3.8 vs. 16.9 +/- 4.6, p < 0.001). Furthermore, electrocardiographic signs of ischemia were less present in those 15 patients with collateral vessels (p < 0.05). CONCLUSIONS: The beneficial effect of collateral vessels during brief coronary occlusion is exerted by a significant increase of flow in the contralateral artery in combination with a reduced resistance in the collateral vascular bed. The method presented is capable of expressing the development of the collateral vascular bed in terms of flow and resistance.

Adult↗
PubMed1990

[Spectral analysis of the arterial pulse during extracorporeal circulation. Experimental study in dogs].

PURPOSE: Spectral analysis of arterial pulse was performed during cardiopulmonary bypass with both pulsatile and continuous flow in order to evaluate the pulse model best suitable to reproduce physiological circulatory conditions. MATERIAL AND METHODS: Ten adult mongrel dogs were submitted to cardiopulmonary bypass with a roller pump for continuous flow and pulsatile flow pump in parallel. The physiological pressure waves, the roller pump waves and the pulsatile pump flow waves were recorded. During the pulsatile flow we varied the ejection period of the pump in relation to the total cycle by 70%, 60%, 50%, 40% and 30%. RESULTS: The roller pump flow showed a bifid wave followed by single peak wave. During spectral analysis we observed three harmonic components of the same amplitude. The using of the pulsatile pump flow proportioned, by spectral analysis, harmonic components whose amplitudes are inversely proportional for ejection/cycle ratio. CONCLUSION: The fundamental component of the pressure wave during the physiological flow, the pulsatile flow, and that of the roller pump stays the same, if the same blood flow is maintained; the pulse of the flow is inversely proportional to the ejection/cycle ratio; the roller pump produces a flow pattern that cannot be described as laminar; the ejection/cycle ratio of 30% seemed ideal for the performance of pulsatile flow perfusion.

Animals↗