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At least 55 records · Page 3Linked to original sources
PubMed1992

[Modification of the sympatho-vagal interaction in mitral valve prolapse syndrome. Evaluation of heart rate variability by spectrum analysis].

To determine whether clinical manifestations in patients with mitral valve prolapse (MVP) are associated with altered sympatho-vagal tone, 46 patients (mean age 27 +/- 6, range 20-45 years; 18 males and 28 females) were studied by power spectrum analysis of RR variability. Patients were divided in 2 groups, according to echocardiographic criteria: Group A: 11 patients with classical MVP; Group B: 35 patients with non classical MVP. These patients were compared with 30 healthy subjects (Group C) well matched for age, body surface area and heart rate. Our findings indicate that at rest there is a significant difference in the high-frequency component between Group A and Group C. Similarly, during the increase in sympathetic activity induced by 70 degrees head-up tilt all groups showed an increase in the low-frequency component, that was more evident in Group A. The data generated from our laboratory suggest that mitral regurgitation (Group A) is a probable cause of vagal tone increase and that there is an adaptive long-term mechanism towards sympathetic conditions. In addition, probably the normalization, demonstrable by the effect of sympathetic activity in tilt, can mask a dysfunction that may be differently evoked.

Adult↗
PubMed1978

Spectrum analysis of transient phenomena of the left ventricular pressure.

The application of "real time" spectrum analysis to left ventricular pressure during transient phenomena is described. Transient phenomena generated by the injection of drugs (norepinephrine-isoproterenol), anoxia and occlusion of aorta and carotids show sudden changes in the frequency of heart contraction. Propranolol stabilizes the heart rate in similar circumstances.

Animals↗
PubMed1984

[Doppler frequency spectrum analysis of extracranial carotid artery lesions].

Signals registered from the extracranial carotid artery by direct Doppler-ultrasound with a MHz transducer were subjected to real-time frequency spectrum analysis. A systolic maximal frequency over 3500 Hz was considered abnormal, together with a broadened spectrum. The study was made on 157 subsequently operated carotid arteries, not all of which had previous angiographic studies. Of 47 with a normal angiogram 45 were correctly classified non-invasively (specificity 96%). The non-invasive diagnosis was correct in 16 of 17 occlusions of the internal carotid artery demonstrated angiographically. An abnormal Doppler frequency analysis was present in only 7 of 14 stenoses with a decreased vessel lumen below 25%. An abnormal Doppler frequency analysis was present in 78 of 79 stenoses with more than 25% reduction in lumen diameter, diagnostic sensitivity for all stenoses being 91%.

Adult↗
PubMed1990

A C version of Fourier-derived affinity spectrum analysis (FASA) to resolve binding heterogeneity.

The computer program described in this paper facilitates resolution of binding affinity heterogeneity by transforming binding curve data (bound versus free) into affinity spectra (density versus affinity). The original program, written in FORTRAN, is extended and presented here in the language C. New applications include an ability to transform competition curves into affinity spectra and to evaluate the effects of sampling and experimental error on spectrum analysis. We propose that this program be incorporated in the routine evaluation of binding systems.

Binding, Competitive↗
PubMed1981

Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control.

Power spectrum analysis of heart rate fluctuations provides a quantitative noninvasive means of assessing the functioning of the short-term cardiovascular control systems. We show that sympathetic and parasympathetic nervous activity make frequency-specific contributions to the heart rate power spectrum, and that renin-angiotensin system activity strongly modulates the amplitude of the spectral peak located at 0.04 hertz. Our data therefore provide evidence that the renin-angiotensin system plays a significant role in short-term cardiovascular control in the time scale of seconds to minutes.

Angiotensins↗
PubMed1992

Power spectrum analysis of heart rate fluctuations and respiratory movements associated with cooling the human skin.

A length of respiratory movement and instantaneous heart rate was divided into 32 segments to adopt computerized power spectrum analysis. An array of frequency spectrum across all the segments was then constructed to demonstrate sequential changes in the respiratory rhythm (0.4 Hz), low (less than 0.1 Hz) and high (0.2-0.4 Hz)-frequency components of heart rate fluctuations associated with lowering the skin temperature. A significant increase in the power for the low and high frequency components of heart rate fluctuations accompanying bradycardia occurred by cooling the face to 0 and 10 degrees C, while cooling the foot to 0 degrees C yielded a significant increase and decrease in the power for the former and latter component, respectively, without change in heart rate. The spectral power for respiratory movements was not altered by these stimuli. The maximal change in the power for low- and high-frequency components as well as in the heart rate during cooling the face and foot to 0 degrees C was found to correlate negatively with the relative resting magnitude of the respective parameter in the pre-stimulus period. Similar relationship existed only with the power for low-frequency component of heart rate fluctuations when lowering the temperature of foot to 10 degrees C. The power spectrum array employed in this study thus enabled us to estimate the effectiveness of skin cooling on the three hemodynamic parameters.

Adult↗
PubMed1984

Pulsed Doppler imaging and spectrum analysis for detection of carotid artery disease.

One hundred carotid arteries in 53 patients suffering from transient cerebral ischaemia or amaurosis fugax have been studied prospectively. Internal carotid arteries were assessed by a six-channel pulsed Doppler imaging system combined with Doppler spectrum analysis and the findings compared with those obtained by X-ray contrast arteriography. Stenosis (greater than 25% diameter reduction) was correctly diagnosed by ultrasonography with a sensitivity of 93% and a specificity of 96%. Occlusion was correctly diagnosed with a sensitivity of 92% and a specificity of 97%. The ability to recognize arterial stenosis and occlusion with this noninvasive system suggests that it has a major part to play in screening patients with suspected carotid artery disease.

Adult↗
PubMed1991

Revision of the amino acid sequence of the smallest bc1 complex subunit: use of fast atom bombardment mass spectrometry and mass-analysed ion kinetic energy spectrum analysis.

We have isolated the smallest bc1 complex subunit from an acidic chloroform/methanol extract of bovine cardiac muscle. The identification of the polypeptide was made possible by classical Edman degradation and amino acid analysis. The measurement of its exact molecular weight by fast atom bombardment mass spectrometry (m/z 6519.8), the characterization of a tryptophan cleavage peptide and pepsic peptides by mass measurements and by mass-analysed ion kinetic energy spectrum analysis allow rectification of the amino acid sequence of the smallest bc1 complex subunit. We found a serine residue instead of Gln 22 and tryptophan residues in place of Ser 34 and Ser 38.

Amino Acid Sequence↗
PubMed1973

Spectrum analysis in ultrasonic Doppler blood flow monitoring: experience in its application to deeply situated vessels.

Ultrasonic Doppler monitoring of pulsatile flow patterns in the major systemic arteries has been rendered possible by the development of intravenous and intra-esophageal probes, thereby obviating major surgery or arterial catheterization. The information provided by Doppler flow signals obtained in this way is considerably enhanced by the use of spectrum analysis. The advantages include immunity from interference from noise or extraneous signals, the separation of two or more superimposed flow signals, and superposition of pressure and flow signals for time correlation and comparison.

Abdomen↗
PubMedDate not supplied

Doppler spectrum analysis and vascular imaging in the diagnosis of extracranial carotid artery disease.

Ultrasound methods are well suited for the exploration of the carotid system. High resolution echography can visualize atheromatous defects on the vessels walls with a resolution better than one mm, whereas Doppler examination detects haemodynamic disturbances due to these plaques. Conventional Doppler examination can reveal moderate or severe stenosis (greater than 60%); the recent development of frequency analysis of the Doppler audio signal makes now possible the detection of very light haemodynamic disturbances due to low grade stenosis even as small as 15%. Spectral distribution abnormalities have been classified in four grades according to their amplitude. The combination of the morphological and functional data provided by echography and Doppler spectrum analysis has drastically increased the diagnostic possibilities of the ultrasound methods in the field of the extracranial vascular pathology. With a new duplex system which combines echography and C.W. Doppler examination (duplex probe) it is possible to detect, and quantify carotid stenosis (in percentage of the lumen reduction), and to evaluate blood flow volume in ml/mn.

Carotid Artery Diseases↗
PubMed1983

Duplex ultrasound scanning of the carotid arteries with velocity spectrum analysis.

Duplex ultrasound examination of the carotid arteries using high-resolution realtime imaging and pulsed Doppler flow measurements with velocity spectrum analysis was performed on a series of 50 consecutive patients (100 vessels), and findings were compared with findings of conventional carotid arteriography. The criteria for an abnormal duplex examination included: a velocity ratio of 1.5 or more (ratio of the maximum internal carotid artery [ICA] flow velocity to the maximum common carotid artery flow velocity); turbulence, as indicated by an ICA velocity spectral width of 40 cm per second or more; visible plaque that produced an ICA stenosis of 50% or more; a maximum ICA velocity of 100 cm per second or more; and inability to detect ICA flow. A flow-limiting stenosis was defined arteriographically as a 50% or greater stenosis of the diameter of the arterial lumen. The velocity ratio was the best single duplex criterion, with an overall accuracy of 88%. The sensitivity or specificity of the duplex examination was as high as 97%, depending on the number of duplex criteria that were abnormal.

Arteriosclerosis↗
PubMedDate not supplied

Range-gated pulsed Doppler power frequency spectrum analysis for the diagnosis of carotid arterial occlusive disease.

Carotid arterial disease was investigated with a Duplex Scanner using Power Frequency Spectrum Analysis. Sixty-one carotid systems were evaluated noninvasively and angiographically, while 20 controls were examined and assumed to be normal. Peak frequency and 50% frequency bandwidth, a quantitative index of spectral broadening, were correlated with the percentage of stenosis. Peak frequency predicted the presence or absence of hemodynamically significant stenoses (greater than or equal to 50% diameter reduction) with 90.8% accuracy, while 50% frequency bandwidth correctly identified similar lesions with 93.2% accuracy (p = NS). Also, with the latter results, carotid systems were grouped into less than 25%, 25% to 49%, and greater than or equal to 50% stenosis categories with an 86.4% accuracy. Similar statistical evaluation was attempted for peak frequency results. It was not possible to separate hemodynamically insignificant lesions (less than 50% diameter reduction) into distinct groups because of the overlap of results among those arteries with less than 50% stenosis. Finally, all eight occluded internal carotid arteries were identified with combined Doppler/imaging analysis. However, with imaging alone, only 5 of 8 (63%) occluded arteries were correctly identified.

Carotid Artery Diseases↗
PubMed1990

[Effect on electroacupuncture on experimental epilepsy--power spectrum analysis of EEG].

The present study was undertaken to investigate the effect of electroacupuncture (EA) on electroconvulsive shock (ECS) and penicillin-induced convulsions in rats, using power spectrum analysis technique. Under quiet state, delta and theta bands were found to be predominant in the power spectrum of spontaneous EEG's with the peak of the main power in the delta band. During ECS and penicillin-induced convulsions, the power percentage of the delta band decreased, while those of alpha and beta bands increased. The bands with the peak of the main power shifted to the right, and the total power was distinctly enhanced. No marked change in background EEG activity was observed during EA stimulation. In the case of EA plus ECS or penicillin-induced convulsions, the power percentage of the delta band increased, while those of alpha and beta bands decreased. The peak of the main power returned to the delta band with a decreased total power. The compressed power spectrum array showed distinct suppression of convulsions by EA audio-visually. These results suggest that EA enables the EEG to synchronize and enhances the inhibitory process of the brain, thereby plays its anticonvulsant role.

Animals↗
PubMed1982

Detection of subcritical stenoses by Doppler spectrum analysis.

Little information is available regarding the sensitivity of carotid Doppler signal spectral analysis in documenting flow disturbances caused by subcritical stenotic lesions. We have studied the effects on spectra of stenoses ranging from 10% to 80% diameter reduction using the infrarenal aorta of the dog. Spectral analysis was able to reliably detect stenoses as small as 20% by comparison of the peak systolic frequency at the site of stenosis with that proximal to it; a peak frequency ratio of about 1.5 was typical for this degree of stenosis. This ratio continued to increase in the nearly linear fashion with increasing stenosis, reaching approximately 2.1 for a 50% stenosis. For greater degree of stenosis, turbulent flow patterns and significant spectral broadening were noted a gradual decrease in the peak frequency ratio. Spectra of Doppler signals recorded at sites 1 cm or more distal to the stenosis site were not significantly different from proximal spectra until the stenosis exceeded a 45% diameter reduction and the peak frequency ratio 1.3. At these distal sites this ratio increased with increasing stenosis to a maximum of 1.64 for a 65% stenosis, beyond which the flow was characterized by severe turbulence and a decreasing ratio. Doppler signal spectrum analysis appears to be a potentially quantitative noninvasive technique that has the sensitivity necessary to detect subcritical carotid arterial stenoses and be applicable to the clinical setting.

Animals↗
PubMed1991

Assessment of aortoiliac obstructive disease by Doppler spectrum analysis of blood flow velocities in the common femoral artery at rest and during reactive hyperemia.

Aortoiliac obstructive disease was assessed by Doppler spectrum analysis of blood flow velocities in the common femoral artery measured both at rest and during reactive hyperemia. The intraarterial femoral artery pressure measured at rest and during reactive hyperemia served as the "gold standard" for the definition of a hemodynamically significant aortoiliac stenosis. Our results, obtained from 93 patients (136 limbs), showed that differences between Doppler spectra obtained from limbs with a hemodynamically significant aortoiliac stenosis and those from limbs without were more pronounced during reactive hyperemia than at rest. The best assessment of aortoiliac obstructive disease could be obtained with a combination of parameters derived from Doppler spectra measured at rest and during reactive hyperemia. With these parameters, obtained by multivariate analysis, 85% of the limbs were diagnosed correctly compared with the gold standard. If angiographic data were added to the gold standard, even 91% of the limbs were diagnosed correctly. We conclude that analysis of Doppler spectra-obtained noninvasively from the common femoral artery at rest and during reactive hyperemia provides an accurate hemodynamic assessment of the aortoiliac segment.

Aortic Diseases↗
PubMed1986

Continuous-wave versus range-gated pulsed Doppler power frequency spectrum analysis in the detection of carotid arterial occlusive disease.

Two types of ultrasonic Doppler velocity metering devices currently used in the detection of extracranial carotid artery disease, the continuous-wave (CW) and the range-gated pulsed (RP) Doppler systems, were compared in the present study. Power frequency spectrum analysis (PFSA) was performed on 130 carotid arterial bifurcations with a CW Doppler and 81 carotid arteries with an RP Doppler system. All results were compared with angiographic findings. The frequency bandwidth at 50% peak power (f50%), a quantitative index for defining spectral broadening, detected stenoses equal to or greater than 50% diameter reduction with 93% sensitivity, 92% specificity, and 92% accuracy with the CW system. With the RP Doppler, the same degree of stenosis was identified with 94% sensitivity, 93% specificity, and 93% accuracy. Compared with angiographic classification into 0-24%, 25-49%, and 50-99% diameter reduction categories, CW Doppler PFSA and an 85% overall accuracy, and the RP Doppler overall accuracy was 86%. CW Doppler also correctly identified 15 of 16 internal carotid artery (ICA) occlusions; 8 of 8 ICA occlusions were correctly identified with the RP Doppler. Thus, both techniques detected carotid artery disease with comparable results. For research and ease of operation, an RP Doppler system with a variable sampling volume appears to be most desirable. However, a standard CW system is superior if utility and cost-effectiveness are of prime importance.

Arterial Occlusive Diseases↗