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D W Droste

Publications and source records attributed to D W Droste.

66 records · Page 4Linked to original sources
PubMed1994

The effect of velocity on the appearance of embolic signals studied in transcranial Doppler models.

BACKGROUND AND PURPOSE: Transcranial Doppler ultrasound can be used to detect circulating cerebral emboli. Recent studies have demonstrated that embolus size is significantly related to both the relative intensity increase and duration of an embolic signal. This may allow information about embolus size to be obtained by analysis of Doppler embolic signals. However, theoretically duration will be inversely related to velocity, and therefore velocity may need to be accounted for if information on embolus size is to be derived from the duration of Doppler embolic signals. METHODS: The relation between velocity and both relative intensity increase and duration of embolic signal was investigated in an in vitro flow model, a sheep carotid artery model, and in patients with prosthetic heart valves. The same standard transcranial Doppler ultrasound machine was used for all studies. Embolic signals resulting from 99 glass microspheres (size, 210 to 250 microns) were studied in the in vitro model, as were those from 64 glass microspheres (size, 105 to 150 microns) in the sheep model. Embolic signals recorded from the six middle cerebral arteries of three patients with prosthetic cardiac valves were also studied. RESULTS: There was a significant (P < .001) inverse relation between velocity and duration of high-intensity signal (in vitro model, r = -.82; sheep model, r = -.43); the exact relations were described using best-fit equations. Correlation coefficients for this relation in patients varied between -.30 and -.55. There was also an unexpected significant positive relation between velocity and intensity in the sheep model (r = .44, P < .001) but not in the in vitro model (P > .05). This relation was also seen in some, but not all, patients. CONCLUSIONS: When the duration of embolic signals is used to provide information about the relative size of an embolus, the velocity of the embolic signal should be taken into account. A relation between velocity and relative intensity increase was found in the sheep model and in some patient recordings. It is suggested this relation may result from greater power being supplied to emboli traveling at higher velocities in the center of the vessel; this may occur under certain recording conditions.

Animals↗
PubMed1993

Simultaneous recording of cerebrospinal fluid pressure and middle cerebral artery blood flow velocity in patients with suspected symptomatic normal pressure hydrocephalus.

CSF pressure (intracranial pressure, in one patient lumbar pressure) was monitored continuously for one night in 23 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunt surgery. In 20 patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and CSF pressure were recorded simultaneously. In three patients transcranial Doppler signals were insufficient. Spontaneous changes in CSF pressure always paralleled changes in the TCD signal. Equivalents of B-waves as well as intermediate waves (in between B- and A-waves), and C-waves could be identified easily and always appeared in phase. The Doppler signal, however, could not be used to evaluate the absolute changes in CSF pressure. Fast Fourier Transform of the Doppler signal was a useful tool to indicate the relative frequency of B-wave equivalents. In five patients the injection of 10ml saline into the ventricle raised intracranial pressure considerably, but hardly affected the MCA blood flow velocity. Continuous TCD monitoring might be useful as a noninvasive screening procedure in patients with suspected symptomatic NPH before continuous invasive CSF pressure measurements are performed.

Aged↗
PubMed1993

Middle cerebral artery blood flow velocity in healthy persons during wakefulness and sleep: a transcranial Doppler study.

In 10 normal young adults, middle cerebral artery blood flow velocity was measured continuously over one night by transcranial Doppler sonography. Polysomnography was used to assess the different sleep stages and waking state. During rapid eye movement (REM) sleep, middle cerebral artery blood flow velocity was higher than in any other sleep stage and wakefulness. During the waking state the velocity was higher than in sleep stage 2. Spontaneous rhythmic oscillations of cerebral blood flow velocity were found related to different stages of sleep. A fast Fourier's transformation of the Doppler wave forms revealed a periodicity of 20-75 seconds, which was most prominent during REM sleep and to a lesser degree during sleep stages 1, 2 and 3 and the waking state. These waves may correspond to intracranial pressure changes referred to as B-waves.

Adult↗
PubMed1989

Two transcranial Doppler studies on blood flow velocity in both middle cerebral arteries during rest and the performance of cognitive tasks.

While the middle cerebral artery (MCA) blood flow velocity changes relative to rest were assessed with transcranial Doppler sonography (TCD), 28 right-handed subjects with no sign of cerebrovascular disease performed two series of 6 cognitive tasks (two series = right and left MCA). The tasks included "reading", "finding nouns with a given first letter", and "multiplication" in four comparable versions to be performed aloud and silently in each of the two series. All of the tasks increased the MCA blood flow velocity bilaterally (2.7-12.1%). A significant left-right difference was present during "noun finding aloud" (left greater than right by 4.7%). A statistically insignificant tendency in the same direction was also present for the five other tasks. During loud reading the increase was higher bilaterally than during silent reading. Blood flow velocity changes in the right MCA for the three tasks performed aloud were lower in older than in younger people. It is posited that older people perform the tasks more slowly and under less stress requiring less right-hemispheric participation. Averaging the results for each of the four subjects involved leads to the conclusion that future TCD-lateralization studies should be done bilaterally at the same time to assess lateralization in a single person.

Adult↗
PubMed1989

A transcranial Doppler study of blood flow velocity in the middle cerebral arteries performed at rest and during mental activities.

While changes in blood velocity in the middle cerebral artery relative to rest were assessed by transcranial Doppler sonography, 70 volunteers with no sign of cerebrovascular disease performed two (left and right middle cerebral artery) series of six cognitive tasks. The tasks are assumed to be processed predominantly by either the left (verbal and mathematical tests performed aloud) or the right hemisphere (dot/distance estimation, spatial perception, and face recognition performed silently). All tasks were shown to increase middle cerebral artery blood flow velocity on both sides, by 1.6-10.6%. After an initial maximum at approximately 8 seconds, velocity decreased then increased again. A steady state was reached after approximately 24-42 seconds. The initial minimum during the following rest phase was reached some seconds later, followed by a slow increase to the reference rest steady state. A difference according to side could be determined only during the three right-hemispheric tasks (right greater than left, 2.5-2.9%). Left-handedness/ambidexterity, familial sinistrality, and profession seemed to have no influence on the results. The middle cerebral artery blood flow velocity increase on both sides was higher in women than in men during the dot/distance estimation and was also higher bilaterally in older than in younger subjects during the dot/distance and the spatial perception tasks. Habituation in performing the tasks was an important factor associated with a decrease of blood flow velocity, especially in the right middle cerebral artery. The habituation more pronounced on the right side possibly reflects the role of the right hemisphere in attention and arousal. The absolute blood velocities at rest decreased bilaterally with age.

Adult↗
PubMed1989

Brain activity and blood flow velocity changes: a transcranial Doppler study.

Seventy volunteers with no sign of cerebral vascular disease performed two series of 6 cognitive tasks, 3 of which are assumed to be processed predominantly by the left and 3 by the right hemisphere. During the tasks, blood flow velocity changes in the middle cerebral artery were recorded every 3 seconds by the transcranial Doppler method (TCD). All tasks increased blood flow velocities in both MCAs, but only the "right hemispheric" tasks resulted in a statistically significantly higher increase than the left MCA. The time course of velocity changes reflects the increase in blood flow caused by increased brain metabolism during brain activity. During stimulation of the right and/or left visual field, blood flow velocity changes were recorded in the P2-segment of the corresponding hemisphere. In 76 volunteers, the study was performed. The time course of velocity changes was similar to that in the MCA study. Velocity rose as a result of increasing complexity of the visual stimulus. The velocity changes are similar to blood flow increases reported in the literature and rose by as much 2 to 25%. Assuming that the diameter of the large branches of the circle of Willis does not change during mental activity, blood flow velocity changes reflect blood flow volume changes. With the TCD method the close relationship among brain activity, metabolism, and blood flow can be reliably investigated. The high spatial resolution enables information to be given about the onset of autoregulation.

Adolescent↗
PubMedDate not supplied

A novel method of macropathologic and arteriographic examination of carotid specimens obtained from autopsy.

Twenty carotid bifurcations were examined. During autopsy, carotid bifurcations were removed in toto. Unfixed carotids were ligated and cannulated for injection of an angiographic contrast medium followed by injection of a tissue-embedding medium at physiologic pressure and temperature. The carotid bifurcation was frozen and cut manually in 3-mm cross-sections. Photographs were then taken of every slice. Angiography, filling with tissue-embedding material, and sectioning were successful in all cases. In the macropathologic sections, the extent, configuration and location of atherosclerotic lesions could be identified.

Aged↗
PubMedDate not supplied

Microembolic load in asymptomatic patients with cardiac aneurysm, severe ventricular dysfunction, and atrial fibrillation. Clinical and hemorheological correlates.

Transcranial Doppler sonography has become a widely used method for detecting cerebral circulating microemboli (ME) arising from the carotid arteries or the heart. Yet, studies on subgroups of patients with distinct cardiac sources of embolism are still limited. The same holds true for investigation on the relationship between microembolization and hemorheological parameters. A total of 142 patients suffering from left ventricular aneurysm (LVA, n = 52), severe left ventricular dysfunction (LVD, n = 43), or chronic atrial fibrillation (AF, n = 47) were enrolled in this study. All patients had been neurologically asymptomatic for at least 1 month. Further relevant embolic disorders of the carotid arteries and the heart had been excluded. Unilateral monitoring for ME over the middle cerebral artery was performed for 30 min. Blood was drawn after each monitoring for determination of plasmatic coagulation parameters, as well as plasma viscosity, and platelet reactivity. The overall prevalence of ME was 31%, with a slightly higher prevalence in patients with LVA (37%) compared to patients suffering from AF (30%) or LVD (26%). With single-factor analysis, a trend towards higher ME prevalences was found with (a) a history of remote embolic events, (b) ineffective anticoagulation, (c) increased platelet aggregation, or (d) increased plasma viscosity (all p > 0.1). The combination of ineffective anticoagulation in conjunction with increased platelet aggregation, however, was significantly associated with higher ME rates even after adjustment for other factors by logistic regression analysis. Our results demonstrate a low ongoing microembolic activity in asymptomatic patients suffering from LVA, LVD and AF. An activated plasmatic coagulation system together with increased platelet aggregation contributes to ME generation.

Adult↗
PubMedDate not supplied

Abundance of microembolic signals detected by transcranial doppler ultrasound in a patient with Eisenmenger's syndrome.

BACKGROUND: Clinically silent circulating microemboli can be detected by transcranial Doppler sonography. CASE DESCRIPTION: We report the case of a 45-year-old man with congenital cyanotic heart disease, elevated haematocrit, low platelet count and decreased protein C and protein S activity. Before and following several haemodilutions, we performed 5 1-hour transcranial Doppler recordings from one or both middle cerebral arteries (MCAs) on different days. The number of microembolic signals per hour varied from 54 to 134. During the bilateral recording, the microemboli occurred on both sides (55 in the right and 45 in the left MCA, respectively). There was no relation to red blood cell count, platelet count, the spontaneously lowered prothrombin time or the spontaneously prolonged activated partial thromboplastin time. CONCLUSIONS: The origin of the large number of microembolic signals found in this patient remains unclear, but may be presumed in the intra-abdominal or crural venous system.

Eisenmenger Complex↗
PubMedDate not supplied

The carotid compression test for therapeutic occlusion of the internal carotid artery. Comparison of angiography with transcranial Doppler sonography.

BACKGROUND: The anterior communicating artery is a key collateral pathway in patients with internal carotid artery (ICA) occlusions. Diagnostic balloon or manual occlusion of the ICA is a qualified test for the collateral function of the circle of Willis. The aim of our study was to test whether transcranial Doppler sonography (TCD) with manual carotid compression is able to predict the degree of cross-over flow and tolerance of ICA occlusion. METHODS: A prospective study was performed on 88 patients suffering from neck tumors or inoperable ICA aneurysms with planned ligation or permanent balloon occlusion of the ICA. Preceding a balloon occlusion lasting 20 min we performed TCD with manual carotid compression test. Insufficient cross-over flow during transient carotid occlusion was defined angiographically as missing opacification of the middle cerebral artery (MCA) after selective injection of contrast media in the contralateral ICA, and sonographically as a decrease greater than 60% in flow velocity of the MCA ipsilateral to the carotid occlusion. RESULTS: TCD and angiography could be compared in 70 of 88 patients. Angiography showed no or insufficient collateral flow in 26%. All patients (n = 10) with a decrease in MCA velocity greater than 60% on angiography showed missing or poor cross-over flow. A greater than 50% increase in the anterior cerebral artery (ACA) predicted moderate or good cross-over flow in 98%. Clinical observation revealed 11 transient neurological deficits. Eight of them showed insufficient cross-over flow angiographically and sonographically. In 2 of 11 only TCD revealed such low collateral supply. Neither technique predicted hemodynamic ischemia in only 1 of the 11. CONCLUSION: TCD with carotid compression test is a valid method for predicting interhemispheric flow and clinically relevant hemodynamic compromise in cases of occlusion of the ICA.

Aneurysm↗
PubMedDate not supplied

Microembolus detections at follow-up in 19 patients with acute stroke: correlation with stroke etiology and antithrombotic treatment.

The present study was designed to perform follow-up transcranial Doppler investigations for microembolic signals (MES) in acute stroke patients by means of a strict protocol. The number of MES was correlated with stroke etiology and the strength of antithrombotic treatment. Concurrently, we wanted to demonstrate that MES in acute stroke patients are solid in nature and not gaseous. Nineteen patients with middle cerebral artery ischemic events, 16 with completed stroke and 3 with transient ischemic attack (TIA) were investigated within 24 h following the onset of symptoms. Six 1-hour recordings on days 1, 2, 3, 4, 7 and 14 were performed from the affected middle cerebral artery. The four-gate technique and recently established criteria for the identification of MES were used. Eight of 19 patients showed MES in at least one recording. Variability was high and showed no uniform tendency with respect to time since onset of symptoms or treatment. All 3 patients with internal carotid artery dissection showed MES. In 3 patients with lacunar stroke, no MES were detected. Two patients with MES suffered recurrent TIAs during the observation period, whereas none of the patients without MES suffered a recurrent ischemic event. In the acute phase following stroke, ongoing, emerging and vanishing embolization in some patients may reflect individual active processes of remodelling, healing and disruption or disappearance of the embolic source.

Acute Disease↗