Spectral Doppler Waveform Research Articles

Transthoracic Doppler Echocardiography of Normally Originating Coronary Arteries in Children

Transthoracic Doppler color flow and spectral velocity patterns of normal coronary arteries in children have not been well studied. We designed this study to evaluate coronary artery flow velocity characteristics in normal and hypertrophied hearts. Sixty-eight children with optimal two-dimensional echocardiographic images of the left coronary artery (LCA) and right coronary artery (RCA) were prospectively studied. The heart was normal in 45 children, and 23 had left and/or right ventricular hypertrophy assessed by echocardiography (mean age 5.8 versus 5.2 years, p = NS). Color flow signals were detected in the LCA in 63(92%) of the 68 children studied, and pulsed Doppler spectral waveforms were recorded in 47 (69%). The latter were recorded in 26 (58%) of 45 normal children and in 21 (91%) of 23 children with left ventricular hypertrophy. Diastolic RCA flow signals were detected mostly in those with right ventricular hypertrophy (10 of 10). Higher levels of LCA maximum diastolic velocity (42 ± 23 versus 24 ± 6 cm/sec, p = 0.0004), increased diastolic flow (16 ± 15 versus 6 ± 4 ml/min, p = 0.01), and delayed time to peak diastolic velocity expressed as a percentage of diastolic spectral duration (38% ± 14% versus 20% ± 8%, p = 0.0001) were observed in children with left ventricular hypertrophy than in those in normal children. A strong correlation was present between Doppler-derived LCA flow and left ventricular mass/m 2 ( r = 0.7, p = 0.001). In normal hearts, LCA spectral velocity pattern did not change with increasing age, but the time velocity integral became progressively larger, resulting in a strong correlation with weight ( p < 0.001, r = 0.78). This study demonstrates (1) LCA flow signals can be detected and quantitated in the majority of children with and those without left ventricular hypertrophy. (2) Left ventricular hypertrophy is associated with increased LCA flow, higher diastolic velocity, and delayed peak diastolic velocity. (3) RCA flow signals are mostly detected when there is right ventricular hypertrophy. Studies on larger groups of patients are needed to further confirm our observations and to enhance understanding of coronary artery flow reserve. (J Am Soc Echocardiogr 1998;11:409-20.)

Using Doppler ultrasound to detect wall vibrations and flow velocity fluctuations in arteries

Two arterial disorders, stenoses and perforations, result in fluctuations in both wall displacements and blood velocities that are not displayed by conventional ultrasound instruments. Wall vibrations with amplitudes on the order of a micron are too small to be displayed by M-mode. Narrow-band velocity oscillations of less than 50-ms duration can easily be missed in viewing traditional Doppler spectral waveforms. Low-frequency velocity oscillations are attenuated by wall filters. Furthermore, the temporal relationship between flow velocities and wall displacements is not avail- able in conventional systems, yet this relationship provides key information in studying stenoses and locating perforations. To simultaneously examine flow velocities and wall displacements in arteries, a customized ultrasonic, pulse-echo, multigate, quadrature phase demodulation system has been developed. The use of multigate, quadrature phase demodulation in the absence of a wall filter enables exploration of arterial behaviors temporally in the cardiac cycle with sufficient amplitude, frequency, and duration resolution to meet the rigorous demands of the analysis. Wall vibrations as high as 600 Hz with amplitudes less than a micron have been detected simultaneously with arterial jet velocities and flow oscillations. [This work was supported by a grant from DARPA, No. N00014-96-0630.]

Do ultrasonic contrast agents artificially increase maximum Doppler shift? In vivo study of human common carotid arteries.

The aim of this study was to establish whether an increase of maximum Doppler shift occurs in the human common carotid artery after the administration of Levovist, an ultrasonographic echo enhancer. Twenty common carotid arteries of 10 patients were examined. Spectral Doppler waveform examinations were performed before and after administration of Levovist using an Acuson 128 XP 10 and a 7.0 MHz transducer probe. Time averaged mean velocity, peak velocity, maximum Doppler shift, and spectral Doppler indices (pulsatility index, resistive index, systolic-diastolic ratio) were assessed. No significant changes in any of the measured parameters, including maximum Doppler shifts, peak velocity (P = 0.35, Wilcoxon rank sum test), pulsatility indices (P = 0.70), resistive indices (P = 0.98), or other spectral indices, were found. We conclude that an increase in Doppler shift does not inevitably occur after the administration of a signal enhancer when examining the human common carotid artery.

Use of Doppler sonography for revealing hepatic artery stenosis in liver transplant recipients.

The goal of our study was to evaluate the use of duplex Doppler sonography for revealing hepatic artery stenosis (HAS) in patients who have undergone liver transplantation. Forty-six patients with spectral Doppler waveforms obtained from the hepatic artery and with subsequent arteriography were reviewed retrospectively. Arterial waveforms, resistive indexes (RIs), and systolic acceleration times (SATs) were evaluated by one reviewer who was unaware of the arteriographic findings. The mean interval between the two examinations was 2.8 days. Arteriograms that revealed a stenosis of greater than 50% were classified as abnormal. Of the 46 patients, 21 (46%) had a significant stenosis. Patients who had HAS had significantly (p < .05) prolonged SATs (0.08 +/- 0.03 sec versus 0.06 +/- 0.02 sec) and reduced RIs (0.49 +/- 0.05 versus 0.66 +/- 0.05) compared with patients who did not have HAS. Optimal thresholds for HAS detection were RIs less than 0.55 and SATs greater than 0.08 sec. HAS was found in 14 of 15 patients who had both abnormal RIs and SATs. Of the remaining 31 patients, 12 had abnormal values for RI or SAT. Of these 12 patients, three had HAS. Thus, 19 patients had normal RIs and SATs; however, four of these patients were found to have an arterial stenosis. In our 46 patients, abnormal values for both RI and SAT were 67% sensitive and 96% specific for stenosis. When at least one abnormal value was found on Doppler imaging, sensitivity and specificity for stenosis were 81% and 60%, respectively. Duplex Doppler imaging can noninvasively reveal HAS. Abnormal values for both RI and SAT proved to be a more accurate predictor of stenosis than either RI or SAT as independent parameters.

Tardus-parvus Doppler signals in the renal arteries: a sign of pediatric thoracoabdominal aortic coarctations.

W e report two cases of coarctation of the descending aorta in patients who underwent Doppler wave analysis for suspected renal artery stenosis. Both patients had bilateral tardus-parvus patterns on imaging of their renal arteries and an abnormal waveform in the aorta. From these findings we suspected proximal aortic obstruction. The spectral Doppler waveform in the aorta distal to the coarctation varied with the type of proximal stenosis but was always abnormal.

Cellulitis and the Prevalence of Deep Vein Thrombnosis

From February, 1994, to August, 1995, we reviewed the venous duplex ultrasound findings of 207 consecutive patients who presented with clinically evident lower leg cellulitis to determine if thrombophlebitis plaued a role in this entity. All patients had a recent onset of intense erythema of the lower leg with associated pitting edema and diffuse painful cutaneous or subcutaneous tenderness. One hundred ninety-one patients (92%) had normal venous duplex ultrasound examinations, with no evidence of any acute or chronic disease. Four patients (2%) had superficial thrombophlebitis involving the greater saphenous vein in the lower leg only, and 10 patients (5%) had evidence of chronic obstructive disease with recanalizattion and post-thrombotic popliteal venous insufficiency. In a subset of 73 patients aged more than 60 years, arterial evaluation with Doppler spectral waveform analysis showed significant obstructive disease in 41 (56%); 17 of the 19 patients with diabetes in this subset (89%) were noted to have positive arterial examinations. Theae data indicate that when the clinical diagnosis of cellulitis can be made, there is no associated significant acute deep venous thrombosis, and venous duplex ultrasound testing is not indicated. In oldet patients, particularly patients with diabetes, arterial testing for obstructive disease appears to be most appropriate.

A computer-based statistical pattern recognition for Doppler spectral waveforms of intracranial blood flow

A computer-based statistical pattern recognition system has been developed for the analysis of transcranial Doppler (TCD) spectral waveforms of the intracranial middle cerebral artery with varying degrees of increased intracranial pressure. This system extracts multidimensional features from TCD waveforms and performs a cluster analysis of those features. The system can automatically recognize the pattern of spectral waveform and classify it as a normal, abnormal, or borderline subclass of TCD spectral waveform. An optimum decision function was generated based on the Bayes Gaussian classifier. The accuracy of the Bayes Gaussian model the spectral waveforms reaches 100% by estimating posterior probability and using the resubstituting method of estimating misclassification in the training TCD data.

What is the tardus parvus spectral Doppler waveform, and what is its usefulness in the detection of hepatic or renal artery stenosis?

What is the tardus parvus spectral Doppler waveform, and what is its usefulness in the detection of hepatic or renal artery stenosis?

Distinction between benign and malignant causes of cervical, axillary, and inguinal lymphadenopathy: value of Doppler spectral waveform analysis.

Vessels in inflamed lymph nodes are dilated compared with vessels in lymph nodes involved with metastases, which may be compressed by tumor cells. Accordingly, we hypothesized that the Doppler spectral waveform might be different in lymph nodes involved by benign disease and those involved by metastases. We compared spectral waveforms of benign and malignant superficial lymphadenopathy to determine the value of color Doppler sonography in distinguishing between the two. Palpable superficial lymph nodes (41 cervical, one axillary, one inguinal) of 43 untreated patients were prospectively evaluated with color Doppler sonography. We measured resistive index, pulsatility index, peak systolic velocity, and end diastolic velocity from the fastest or next fastest arterial signal in the lymph node that showed the most vigorous flow. Final diagnosis was established by pathologic examination (n = 24) and clinical follow-up (n = 19). Color Doppler sonography showed blood flow in all cases. The mean resistive index was 0.92 +/- 0.23 in lymph nodes involved with metastases and 0.59 +/- 0.11 in lymph nodes affected by benign processes. The mean pulsatility index was 2.66 +/- 1.59 in lymph nodes involved with metastases and 0.90 +/- 0.23 in lymph nodes affected by benign processes. Lymph nodes involved with metastases showed a characteristic high resistive index (> 1.0) and a high pulsatility index (> 1.5) in 10 of 13 cases. Lymph nodes affected by benign processes showed a low resistive index (< 0.8) and a low pulsatility index (< 1.5) in all cases. The resistive indexes and pulsatility indexes were significantly different (p < .005) between lymph nodes affected by benign versus malignant disease. The mean peak systolic velocity was 25 +/- 11.7 cm/sec in lymph nodes involved with metastases and 24 +/- 16 cm/sec in lymph nodes affected by benign processes. The mean end diastolic velocity was 2 +/- 6.7 cm/sec in lymph nodes involved with metastases and 10 +/- 9.5 cm/sec in lymph nodes affected by benign processes. Although the peak systolic velocities were not significantly different, the end diastolic velocities were significantly different (p < .005) between the two types of lymph nodes. Our results suggest that superficial lymphadenopathy due to benign and malignant diseases can be distinguished with a high degree of accuracy (p < .005) by means of spectral waveform analysis. Color Doppler sonography is a useful adjunct to routine sonography. Lymph nodes with a high resistive index are almost always involved by metastases.

Normal renal artery spectral Doppler waveform: a closer look.

To characterize the spectral Doppler tracing of the normal renal artery. Doppler tracings were obtained from a phantom of a vessel with variable compliance and from the kidneys of 15 healthy volunteers. In the phantom, vascular compliance had the following effects on systolic flow velocity patterns: low compliance, little change in the sharp appearance of the systolic component of the transmitted pulse; mildly increased compliance, down-stream dampening of early systolic acceleration (ESA) with the appearance of a sharp early systolic transmitted peak and of a more rounded late systolic compliance peak; high compliance, delayed and diminished transmitted peak that eventually disappeared within the enlarging down-stream compliance peak. Healthy subjects with compliant vessels had greater ESA and more frequently visualized early systolic peaks in the renal hilum than in the renal sinus. Absence of a discrete early systolic peak is a normal finding in young patients, especially in the more distal interlobar arteries. Loss of the early systolic peak may be explained on the basis of vascular compliance.

The value of portal vein pulsatility on duplex sonograms as a sign of portal hypertension in children with liver disease.

The purpose of this study was to determine the significance of portal vein pulsatility on duplex Doppler waveforms in children with end-stage hepatic failure undergoing liver transplantation. Thirty-eight children with end-stage hepatic decompensation were examined with color-assisted spectral Doppler waveform analysis of the hepatic artery and the portal vein. Correlation was made with age, duration of illness, clinical and pathologic diagnosis, and presence of portal hypertension. Findings were compared with those for six patients with acute viral hepatitis and 12 healthy control subjects. Portal vein pulsatility was noted in all 36 patients in whom portal vein flow was detected by Doppler imaging. The majority of these (34) had clinical or sonographic evidence of portal hypertension. In two patients, no portal vein flow was identified in the liver hilum; both had a large portosystemic shunt through collaterals or surgical graft. Significantly increased pulsatility of the hepatic artery waveform (resistive index [RI] = 0.89 +/- 0.15, p < .0001) was seen in patients with end-stage liver disease. In contrast, no portal vein pulsatility and normal hepatic artery pulsatility (RI = 0.60 +/- 0.11) was noted in all patients with acute hepatitis and control subjects. Portal vein waveform pulsatility is 94% sensitive and 90% specific for portal hypertension in end-stage liver disease.

Color Doppler sonography of the cystic artery: comparison of normal controls and patients with acute cholecystitis.

Color Doppler sonography was used to evaluate the length and distribution of the cystic artery in the gallbladder wall in 115 normal adults and in 54 patients with surgically proved cholecystitis. All patients were scanned with a 5 MHz curved array transducer optimized for low volume color sensitivity. A specific attempt was made to visualize the cystic artery throughout its course. Spectral Doppler waveforms were obtained to document arterial flow. The length of the cystic artery visualized was analyzed as a quartile percentage length of the anterior gallbladder wall. The distribution of the cystic artery flow also was analyzed in specific quartiles. Of 54 patients with acute cholecystitis, 26% had cystic artery length greater than half of the anterior gallbladder wall, compared with 2% of 115 normal controls (P < 0.001); 19% of patients with cholecystitis had flow in the distal (fundal) quartile, compared to 0% of normal controls (P < 0.0001). Although the presence or absence of flow in the gallbladder is not a reliable finding to establish the diagnosis of acute cholecystitis, length of cystic artery visualized is a potentially useful criterion to suggest the diagnosis of acute cholecystitis, especially in cases in which flow in the distal fundal quartile of the gallbladder. The usefulness of color Doppler sonography in acute cholecystitis is limited owing to the fact that it is insensitive, and many patients with cholecystitis have no detectable flow or have normal flow patterns.

Hepatic artery stenosis and thrombosis in transplant recipients: Doppler diagnosis with resistive index and systolic acceleration time.

To assess the value of resistive index (RI) and systolic acceleration time (SAT) for diagnosis of stenoses and thromboses of the hepatic artery in liver transplant recipients. Doppler sonograms and angiograms in 125 liver transplant recipients were correlated and analyzed for any statistically significant difference in the RI or SAT of patients with and without arterial stenosis or thrombosis. Sensitivity and specificity were calculated for RI, SAT, peak arterial systolic velocity, and absence of arterial flow. Forty-seven patients had a marked stenosis; 16 had thrombosis. There was a statistically significant difference (P < .05) in the RI and SAT of patients with stenosis or thrombosis versus those with normal arteries but not in patients with stenosis versus thrombosis. RI and SAT parameters allowed detection of abnormalities not found with peak velocity and no-flow parameters. Combined parameters produced 97% sensitivity and 64% specificity for marked arterial disease. Doppler spectral wave form analysis provides excellent screening for detection of hepatic allograft arterial stenosis or thrombosis.

The validity of Doppler-derived spectral analysis in the presence of multiple stenoses.

It has been suggested that mathematical analysis of ultrasonic Doppler spectral waveforms allows non-invasive quantification of arterial stenoses proximal to the Doppler probe. Less emphasis has been placed on the influence of distal stenoses or distance to the ultrasonic probe. A bench-top electromechanical model with multiple stenoses was constructed to evaluate the effects on spectral waveforms of variations in the severity of proximal and distal stenosis, length of stenoses, distance between stenoses, and distance between ultrasonic probe and stenoses. The following analytic indices, descriptive of spectral waveforms, were evaluated: pulsatility index, spectral broadening index, Laplace damping factor, mode frequency, mean frequency, arithmetic mean frequency, maximum envelope frequency and minimum envelope frequency. All these indices, except the mode frequency, were influenced by the degree of distal as well as proximal stenosis. They were also affected by the distance between the Doppler probe and the upstream and downstream stenoses. The length of stenoses did not influence the flow waveform. Of the model variables, the distal stenosis had the greatest influence on the calculated indices. However, none of the analytic techniques could detect a stenosis smaller than a 70% reduction in cross-sectional area. It was concluded that Doppler-derived spectral waveforms between sequential stenoses are inevitably influenced by events other than the degree of proximal stenosis alone. Therefore, ultrasonic spectral waveforms obtained at a single point of the arterial tree in patients with multi-segment arterial disease should be interpreted with caution.

Variance mapping in colour flow imaging: What does it measure?

Flow disturbance is known to occur in association with high grade carotid stenosis and cause spectral broadening and fluttering in the Doppler spectral waveform distal to the stenosis. Colour flow variance mapping has been proposed as a means of documenting its presence. We prospectively evaluated this hypothesis by studying 15 patients with high grade (> 50%) stenotic lesions in the internal carotid artery. In all 15 cases, the site of increased variance on the colour Doppler map corresponded to the point of maximum velocity. In 10 cases of greater than 75% stenosis, the point of aliasing on the traditional colour Doppler map and the site of maximal variance occurred at the stenotic jet (length 7.3 +/- 2.3 mm) and not along the full length of disturbed flow (19.3 +/- 5.5 mm). In five patients with stenoses between 50-75% diameter narrowing, decreasing the colour Doppler pulse repetition frequency (PRF) created a region of abnormal variance corresponding to the site of aliasing. In all 15 stenoses, the site of maximum flow disturbance, defined as fluttering in the Doppler spectral waveform, was not apparent on the variance map. We conclude that the variance map does not reflect flow disturbance and is most likely to occur at sites of aliasing.

Budd-Chiari syndrome: detection with color Doppler sonography.

The value of color Doppler sonography in evaluating newly diagnosed Budd-Chiari syndrome in five patients was studied. Hepatic venous findings included absence of vessels (one patient), flow reversal (two patients), narrowing (four patients), and tortuosity (three patients). Detected collaterals included hepatic venous to hepatic venous (four patients), hepatic venous to subcapsular systemic venous (two patients), and portosystemic (three patients). Hepatic venous spectral Doppler waveforms were flat and essentially aphasic in four patients, indicative of distal hepatic venous compression. The inferior vena cava was markedly compressed in two patients and slightly compressed in one. Color Doppler sonography allowed more reliable and confident identification of irregular, compressed, or otherwise abnormal hepatic veins than did conventional sonography. Color Doppler sonography also showed collateral vessels that were undetected with conventional sonography or other imaging techniques. Our results suggest that color Doppler sonography may be a valuable tool in the initial diagnosis and evaluation of suspected Budd-Chiari syndrome.

Duplex Ultrasonographic Insonation and Visualization of Intracerebral Arteries

Until now, clinical, noninvasive interrogation of intracranial vessels has consisted only of insonation via transcranial Doppler. Such devices have utilized a 2.0 MHz, continuous wave probe with Doppler spectral waveform display. Clincial aapplication of these techniques has required precise location of cranial "windows" and has been hampered by the extreme anatomic variability of both cranial bony structures and intracerebral arteries. The lack of simultaneous intracranial arterial visualization has limited the clinical pplicability of transcranial Doppler technology. Recently, the authors have utilized a 2.25 MHz curved phased array probe with a pulsed Doppler to image and insonate simultaneously the intracerebral arteries. Colorflow imaging of both near- and far-field regions is the necessary first step for vessel localization and identification. Once this is accomplished, the image of each artery in turn is amplified and gray scale tuning is employed to permit direct visualization of the arterial walls and lumen. Pulsed Doppler waveform analysis is perfomred simultaneously and along the entire visible artery length. In this manner the arteries of both right and left hemispheres are examined in detail. We have found the duplex technique to be superior to the use of Doppler alone in the examination on intracerebral vessels. The ability to visualize and insonate simultaneously eliminates the uncertainty caused by anatomic variation. These advantages, long applied to the evaluation of peripheral vessels, are now available for use in the diagnosis of intracranial arterial disease.

Towards an ideal blood analogue for Doppler ultrasound phantoms

If a phantom is to produce Doppler spectral waveforms accurately matching those that would be obtained in vivo, it is necessary to use a fluid that behaves like blood in vivo, both acoustically and rheologically. An alternative to blood is described that uses finely powdered nylon suspended in a mixture of glycerol and water. The nylon particles used have dimensions and density close to those of erythrocytes and they aggregate at low shear rates to give non-Newtonian behaviour. Viscosity may be varied over a wide range by the addition of liquid detergent. Consideration is given to the importance of haematocrit in modelling pulsatile and disturbed flows as it affects the haemodynamics of flow and the backscattered power of an ultrasound beam. This adaptable blood analogue is suitable for use in models of both large structures and fine vessels.

Duplex Ultrasonographic Insonation and Visualization of Intracerebral Arteries

Until now, clinical, noninvasive interrogation of intracranial vessels has con sisted only of insonation via transcranial Doppler. Such devices have utilized a 2.0 MHz, continuous wave probe with Doppler spectral waveform display. Clinical application of these techniques has required precise location of cranial "windows" and has been hampered by the extreme anatomic variability of both cranial bony structures and intracerebral arteries. The lack of simultaneous in tracranial arterial visualization has limited the clinical applicability of transcranial Doppler technology. Recently, the authors have utilized a 2.25 MHz curved phased array probe with a pulsed Doppler to image and insonate simultaneously the intracerebral arteries. Colorflow imaging of both near- and far-field regions is the necessary first step for vessel localization and identification. Once this is accomplished, the image of each artery in turn is amplified and gray scale tuning is employed to permit direct visualization of the arterial walls and lumen. Pulsed Doppler waveform analysis is performed simultaneously and along the entire visible ar tery length. In this manner the arteries of both right and left hemispheres are examined in detail. We have found the duplex technique to be superior to the use of Doppler alone in the examination of intracerebral vessels. The ability to visualize and insonate simultaneously eliminates the uncertainty caused by anatomic varia tion. These advantages, long applied to the evaluation of peripheral vessels, are now available for use in the diagnosis of intracranial arterial disease.

Transcranial Doppler ultrasound studies of cerebral autoregulation and subarachnoid hemorrhage in the rabbit

The authors describe a method for Doppler ultrasound recording of flow velocity in the basilar artery of normal rabbits and rabbits with experimental subarachnoid hemorrhage (SAH). With this transcranial Doppler (TCD) model, clinical assumptions regarding flow velocity/cerebral blood flow (CBF) relationships, autoregulatory responses, and Doppler spectral waveform analysis can be tested under controlled conditions and compared with established methods of CBF measurement (hydrogen clearance). The time course of changes in flow velocity following SAH (cerebral vasospasm) is successfully demonstrated using the experimental TCD method. There are significant differences in the flow velocity and CBF responses to hypercapnia, hypocapnia, and trimethaphan-induced hypotension which indicate that TCD cannot be considered a simple alternative to CBF measurement for the study of cerebrovascular reactivity and cerebral autoregulation.