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At least 73 records · Page 4Linked to original sources
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↗
PubMed1981

Myocardial infarction diminishes both low and high frequency QRS potentials: power spectrum analysis of lead II.

Previous studies based primarily on counts of QRS notches and slurs have suggested that myocardial infarction (MI) increases high frequency QRS components. However, this technique does not quantitatively measure total high frequency voltage. To further study this problem, a microprocessor ECG system was employed capable of averaging multiple QRS complexes to reduce noise. Power spectrum analysis of the QRS using a Fast Fourier Transform was then performed in lead II in ten normal subjects and ten patients with prior inferior MI. The infarct group showed a decrease in QRS potentials over a broad frequency range (7.81-304.7 Hz). Therefore, contrary to previous estimates, MI may attenuate high as well as low frequency QRS potentials as part of a general decrease in electromotive force.

Adult↗
PubMed1989

Power spectrum analysis of myometrial electromyogram and intrauterine pressure changes in the pregnant rhesus monkey in late gestation.

Various methods have been used to quantify myometrial activity in the pregnant rhesus monkey during the last third of gestation. A precise definition of activity must retain the characteristics of epoch duration, amplitude, and the repetitive frequencies of active epochs. We used Fast Fourier Transform and power spectrum analysis to determine whether the patterns of myometrial contractility consist predominantly of contractions or contractures. This analysis allows quantification of activity represented by each of these patterns of activity. We applied these methods to myometrial electromyogram and intrauterine pressure recordings in pregnant rhesus monkeys to characterize the changes in myometrial activity that occur after surgery, after intravenous indomethacin administration, and when food is withdrawn for 48 hours. We conclude that changes in the frequency pattern of myometrial activity provide important information in relation to labor and delivery contractions.

Animals↗
PubMed1991

[Spectrum analysis of heart rate. A method of studying the role of the autonomic nervous system in the regulation of blood circulation].

Spectral analysis of heart rate variability has recently been shown to be a reliable noninvasive test for quantitative assessment of cardiovascular automatic regulatory responses. In 12 ambulant normotensive healthy young males (mean age 23 +/- 1 years) after a period of 10 min. for stabilisation, a continuous ecg recording (lead CM-5) for 8 min. was obtained in the supine and standing position, with a controlled respiration rate 15/min. Power spectrum of 512 point time series (R-R intervals) in both positions was calculated using a fast Fourier transform-based window periodogram method. Based upon results from the literature the power spectrum analysis was performed on two components: low frequency LF (0.05-0.15 Hz) and high frequency HF (0.15-0.50 Hz). Mean R-R interval decreased on standing position from 0.79 +/- 0.10 s to 0.59 +/- 0.11 s (p less than 0.001). The ratio HF/LF in supine was 0.63 +/- 0.70 and on standing position 2.54 +/- 0.73 (p less than 0.001). The relative LF component of the total HR power spectrum increased from 22.8% +/- 12.1% to 42.9 +/- 14.4% (p less than 0.001) after changing the position from supine to standing, and the relative HF component decreased from 56.3 +/- 22.4% to 25.5 +/- 16.2 (p less than 0.001). The total power was significantly lower when standing in comparison to supine position (681 +/- 519 s2, 1188 +/- 963 s2 respectively, p less than 0.05). Our results suggest that heart rate fluctuations in supine position in normal men are mainly vagally determined (HF power spectrum component).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Determination of the value of spectrum analysis of the Doppler signal in the assessment of the carotid artery bifurcation].

A prospective trial was set up in 100 patients, who underwent arteriography of the cerebropetal and cerebral arteries, to determine the value of the direct examination of the Carotid arteries using a continuous wave bidirectionnal Doppler with spectrum frequency analysis. The results of this non-invasive direct technique are compared with the biplane arteriography and with the indirect noninvasive oculoplethysmography (OPG-Gee). The conclusions of this study are that the direct Doppler examination with spectrum frequency-analysis is a very good tool in detecting lesions in the Carotid arteries, and is superior to the indirect OPG-Gee examination, especially in stenoses of 30-69%.

Angiography↗
PubMed1991

Validity of catheter-tip Doppler technique in assessment of coronary flow velocity and application of spectrum analysis method.

Measurement of coronary flow velocity in clinical cases contributes to understanding the pathophysiology of coronary circulation. To determine absolute coronary flow velocity, coronary blood flow was assessed with an end-mounted Doppler catheter (3Fr, 20 MHz), which was combined with a custom-designed fast-Fourier transformation analysis system. In vitro study using model circuit, actual flow velocity (8 to 96 cm/s) was well correlated with that determined by this catheter system (y = 1.01 X +1.5, r = 0.988). In a clinical study of 12 patients with normal coronary arteriograms, the Doppler catheter was positioned at the proximal left anterior descending artery. Clear flow velocity patterns, which consisted of predominant diastolic components and preceding small systolic components, were obtained in all cases. The peak flow velocity was 17 +/- 8 cm/s (mean +/- standard deviation) during systole and 44 +/- 12 cm/s during diastole in this portion. In 5 patients, the great cardiac vein flow, which reflects the left anterior descending artery flow, was simultaneously measured during rapid atrial pacing. During pacing, percent increases in flow velocity were well correlated with those in great cardiac vein flow (y = 0.90 x +6.4, r = 0.935). These results indicate that catheter-tip Doppler technique with fast-Fourier transformation analysis may be useful in quantitatively determining coronary flow velocity in clinical cases.

Aged↗
PubMedDate not supplied

[Detection and quantification of carotid atheroma. Respective value of vascular ultrasonography, spectrum analysis and digital intravenous angiography].

This retrospective study involved 37 subjects who were examined by means of intravenous digitalised angiography, vascular ultrasonography and spectral analysis of the Doppler signal. The last two examinations were found to give the most precise images and functional information. The concordances between angiography and ultrasonography on the one hand and spectral analysis on the other were 82 and 90 per cent. The authors have established a protocol in order to limit and systematize these examinations during screening for carotid atheroma: the risk factors are weighted; a score is obtained by summation; depending on the value of this score and the patient's age, the investigation procedure is pursued or not. The sequence always consists of ultrasonography followed by spectral analysis when plaque is detected and by angiography when the plaque is stenotic or ulcerated. In symptomatic patients, ultrasonography and digitalised angiography are performed routinely.

Arteriosclerosis↗