Biomedical subjects

D W Droste

Publications and source records attributed to D W Droste.

At least 19 recordsLinked to original sources

PubMed2005

Role of cerebral amyloid angiopathy in intracerebral hemorrhage in hypertensive patients.

OBJECTIVE: To assess the interaction of cerebral amyloid angiopathy (CAA) and arterial hypertension as cofactors for intracerebral hemorrhage (ICH). METHODS: The authors investigated 129 postmortem brains of hypertensive patients with and without ICH. Sixty-four patients had had deep (n = 40) or lobar (n = 24) ICH. Sixty-five patients without ICH served as controls. Established risk factors for ICH (age, gender, severity of hypertension, bleeding disorders, intake of anticoagulants, and chronic alcoholism) were identified from medical records. Four specimens per brain were stained with hematoxylin-eosin and Congo red. The entire ICH cohort and subgroups were compared with controls using single-factor and multiple logistic regression analyses. RESULTS: CAA was found in 15 of 64 subjects (23%) with ICH and in five of 65 controls (8%; p = 0.026). In single-factor analysis, CAA was more prevalent in lobar ICH compared with controls (p = 0.007) but not in deep ICH. Poor control of hypertension was more prevalent in the entire ICH group (p = 0.01) and in deep ICH (p = 0.016) but not in lobar ICH. ICH was predictive of the presence of CAA (odds ratio: 5.6, 95% CI: 1.8 to 19.5, p = 0.003), and CAA was more likely to be found in lobar ICH in multivariable-adjusted analysis. After adjustment for conventional risk factors, there was a weak association between CAA and deep ICH. CONCLUSION: Cerebral amyloid angiopathy plays a major role in the pathogenesis of intracerebral hemorrhage even in patients with more evident risk factors.

Aged↗

PubMed2003

Arterial hypertension and ischaemic stroke.

OBJECTIVES: Arterial hypertension is, besides age, the number one risk factor for ischaemic stroke. Patients with arterial hypertension frequently present with additional coexisting vascular risk factors interacting in a complex way. MATERIAL AND METHODS: This paper reviews the benefit of antihypertensive treatment, as well as different treatment options of arterial hypertension and their side-effects. RESULTS: Patients with definite arterial hypertension, but also patients with so-called normal or high-normal blood pressure are at increased risk to develop stroke and other cardiovascular complications. Vascular remodelling of small and large vessels provoked by arterial hypertension is the initial step in the development of atherosclerosis and lipohyalinosis. Vascular remodelling can be improved or even normalized by antihypertensive treatment with angiotensin-converting-enzyme inhibitors and angiotensin-I-receptor antagonists showing the most convincing effects. Angiotensin-converting-enzyme inhibitors and angiotensin-I-receptor antagonists have the lowest rate of side-effects, however, economic restraints hinder their general application. Statins are needed to treat dyslipidaemia. They also lower blood pressure and have a synergistic effect with the above two antihypertensive components in lowering blood pressure. In hypertensive patients, risk of stroke and other cardiovascular complications is determined by the blood pressure level and the presence or absence of target organ damage and the interaction with other risk factors, such as cigarette smoking, dyslipidaemia, and diabetes. These high-risk patients should be treated even more aggressively than usual. CONCLUSIONS: In the vast majority of patients and healthy individuals, target blood pressure should be as high as or below 120/80 mmHg to minimize the occurrence of stroke and other cardiovascular complications.

Angiotensin Receptor Antagonists↗

PubMed2002

Effects of the ultrasound contrast-enhancing agent Levovist on the detection of intracranial arteries and stenoses in chinese by transcranial Doppler ultrasound.

Proper assessment of intracranial arteries by transcranial Doppler sonography (TCD) in patients with intracranial stenoses is occasionally made difficult by an insufficient temporal bone window, an unfavourable insonation angle, or low flow velocity or volume. This condition is frequently found in Chinese. In these cases, echocontrast could be helpful. We investigated 48 temporal windows of 24 acute Chinese stroke patients with insufficient native transtemporal insonation conditions before and after the application of the echo enhancer Levovist (galactose/palmitic acid) by an injection pump. We classified the signal quality from four segments of the main intracranial arteries: anterior cerebral artery (A1), main stem of the middle cerebral artery (MCA, M1), intracranial segment of the carotid artery (C1), and posterior cerebral artery (P1). The signal quality was classified as follows: 0 = no signal, 1 = poor, envelope curve does not follow spectrum, 2 = adequate, envelope curve follows spectrum. As compared to the pre-contrast scans, echocontrast allowed for more segments to be evaluated by pulsed Doppler sonography. Before Levovist, only 12% of the segments could be detected, after Levovist 63%. For all arteries, signal quality was better after Levovist, p between 0.0180 and 0.0003. In 3 patients, MCA stenoses with peak systolic Doppler flow velocities above 160 cm/s were found only after Levovist. In patients with poor pre-contrast detection, echocontrast-enhanced TCD allows for more arterial segments to be insonated and for the detection of stenoses unnoted during the non-enhanced investigation.

Aged↗

PubMed2001

Automatic classification of HITS into artifacts or solid or gaseous emboli by a wavelet representation combined with dual-gate TCD.

BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) can detect high-intensity transient signals (HITS) in the cerebral circulation. HITS may correspond to artifacts or solid or gaseous emboli. The aim of this study was to develop an offline automated Doppler system allowing the classification of HITS. METHODS: We studied 600 HITS in vivo, including 200 artifacts from normal subjects, 200 solid emboli from patients with symptomatic internal carotid artery stenosis, and 200 gaseous emboli in stroke patients with patent foramen ovale. The study was 2-fold, each part involving 300 HITS (100 of each type). The first 300 HITS (learning set) were used to construct an automated classification algorithm. The remaining 300 HITS (validation set) were used to check the validity of this algorithm. To classify HITS, we combined dual-gate TCD with a wavelet representation and compared it with the current "gold standard," the human experts. RESULTS: A combination of the peak frequency of HITS and the time delay makes it possible to separate artifacts from emboli. On the validation set, we achieved a sensitivity of 97%, a specificity of 98%, a positive predictive value (PPV) of 99%, and a negative predictive value (NPV) of 94%. To distinguish between solid and gaseous emboli, where positive refers now to the solid emboli, we used the peak frequency, the relative power, and the envelope symmetry of HITS. On the validation set, we achieved a sensitivity of 89%, a specificity of 86%, a conditional PPV of 89%, and a conditional NPV of 89%. CONCLUSIONS: An automated wavelet representation combined with dual-gate TCD can reliably reject artifacts from emboli. From a clinical standpoint, however, this approach has only a fair accuracy in differentiating between solid and gaseous emboli.

Adult↗

PubMed2001

[Detection of circulating cerebral microemboli by transcranial Doppler ultrasonography].

Thromboembolic events represent a major complication of cardiovascular diseases and interventions. Although general risk factors and predictors for thromboembolic events are well known from population-based studies, hardly any therapeutic consequences for the individual patient can be drawn, e.g. for a well-balanced therapy with anticoagulants. A new approach towards an optimised therapy adapted to the individual risk of each patient may be based on the detection of circulating microemboli by transcranial Doppler sonography. With this technique, gaseous or solid microparticles circulating in the blood can noninvasively be detected. Due to their small size, they do not induce thromboembolic events themselves. However, several studies demonstrate that they indicate an increased thromboembolic activity and correlate directly with manifest stroke or emboli. From a transcranial Doppler probe positioned on the temporal plane at the patient's skull, the middle cerebral artery's blood flow is recorded and is analysed acoustically and optically for circulating microemboli. This technique has already been used for risk stratification of high-risk patients and therapeutic decision-making in neurologic routine, e.g. for the indication to anticoagulate the patient or for carotis surgery. Data to evaluate its value in cardiology are limited and based on few clinical studies. In this review, the basic principles and the methodological and technical background for the detection of microemboli, as well as current limitations, are discussed. Furthermore, clinical studies and their results evaluating this technique in patients with cardiological diseases and during cardiovascular interventions are reviewed.

Angioplasty, Balloon, Coronary↗

PubMed2001

Absence of circulating microemboli in patients with atrial fibrillation undergoing electric cardioversion.

Electrical cardioversion (CV) of atrial fibrillation (AF) is associated with an increased risk of stroke, and its appropriate prevention is still a matter of debate. It is known that, besides dislodgement of pre-existing intra-atrial thrombi, the "stunned" atrium after CV is an important cause of thrombus formation and subsequent embolism. We investigated whether CV of AF is associated with occurrence of circulating microemboli (ME) representing a sensitive marker of the actual thromboembolic activity. Twenty-nine patients (22 men) aged 54 +/- 13 years suffering from valvular (n = 5) or nonvalvular (n = 24) AF were studied. All but 1 patient (with recent-onset AF) had been put on oral anticoagulation (INR >2.0) for at least 3 weeks before and 4 weeks after successful CV. In all patients, exclusion of internal carotid artery stenosis and atrial thrombus was performed prior to CV. Five unilateral 1-hour transcranial Doppler ME monitorings over the middle cerebral artery were performed (1) before CV, and (2) immediately, (3) 4-6 h, (4) 24 h, and (5) 2-4 weeks after CV. Total absence of circulating ME was found before CV as well as during a cumulative monitoring time of 115 h after successful CV. Electrical CV of AF after at least 3 weeks of effective anticoagulation is not associated with occurrence of cerebral circulating ME. This finding requires further investigation including high-risk patients with AF undergoing CV based on different treatment protocols.

Aged↗

PubMed2001

Clinically silent circulating microemboli in 20 patients with carotid or vertebral artery dissection.

BACKGROUND AND PURPOSE: Carotid and vertebral artery dissections are frequently complicated by cerebral embolism. Detection of clinically silent circulating microemboli by transcranial Doppler sonography (TCD) is now widely investigated in patients with carotid artery disease in the hope to identify patients at increased risk for stroke. METHODS: In 20 patients with carotid (n = 17) or vertebral (n = 2) artery dissection, or both (n = 1), we performed a 1-hour microembolus detection downstream to the dissection in the middle or in the posterior cerebral artery, respectively. RESULTS: Five patients with a carotid artery stenosis of > or = 90% or with carotid artery occlusion showed microembolic signals at a rate of up to 15 events/h. In all these patients, the onset of the dissection was within the last 58 days. Patients with lower degrees of stenosis or onset of symptoms beyond 58 days did not show microembolic signals at all. Three patients who had presented with recurrent ischaemic events prior to TCD monitoring unexceptionally had microembolic signals. CONCLUSION: Microembolic signals occur in patients with high-grade stenosis or occlusion due to acute cervical artery dissection. Patients with microemboli seem to be at increased macroembolic risk, i.e. stroke recurrence, and may require close-meshed clinical follow-up and possibly stronger antithrombotic treatment.

Adult↗

PubMed2001

Accuracy of in vivo carotid B-mode ultrasound compared with pathological analysis: intima-media thickening, lumen diameter, and cross-sectional area.

BACKGROUND AND PURPOSE: This study aimed to determine the correlation of in vivo ultrasound measurements of intima-media thickening (IMT), lumen diameter, and cross-sectional area of the common carotid artery (CCA) with corresponding measurements obtained by gross pathology and histology. METHODS: Sixty-six moribund neurological patients (mean age 71 years) underwent B-mode ultrasound of the CCA a few days before death. During autopsy, carotid specimens were removed in toto. Carotid arteries were ligated and cannulated for injection of a hydrophilic embedding material under standardized conditions. The carotid bifurcation was frozen and cut manually in 3-mm cross slices. Digital image analysis was carried out to determine the diameter and the cross-sectional area of the frozen slices of the CCA. IMT was assessed by light microscope. Ultrasonic and planimetric data were compared. RESULTS: Mean measurements of lumen diameter and cross-sectional area were 7.13+/-1.27 mm and 0.496+/-0.167 cm(2), respectively, by ultrasound, and 7.81+/-1.45 mm and 0.516+/-0.194 cm(2), respectively, by planimetric analysis of the unfixed redistended carotid arteries (R(2)=0.389 and 0.497). The mean IMT was 1.005+/-0.267 mm by ultrasound and 0.67+/-0.141 mm histologically, resulting in a mean difference of -31%. CONCLUSIONS: Transcutaneous B-mode ultrasound provides a reliable approach for in vivo measurements of the cross-sectional area and, less exactly, of the lumen diameter of the CCA. Compared with histological results, in vivo ultrasound measurements of the IMT are systematically larger.

Adult↗

PubMed2000

Serial CT and MRI of ischaemic cerebral infarcts: frequency and clinical impact of haemorrhagic transformation.

The frequency, predisposing factors and clinical consequences of haemorrhagic infarcts and damaged blood-brain barrier as shown by contrast enhancement (CE) in ischaemic cerebral infarcts are controversial. We prospectively compared the sensitivity of CT and MRI to haemorrhagic transformation (HT) and CE. We also wished to investigate the clinical significance of HT and factors possibly associated with it. We studied 36 patients with acute ischaemic infarcts in the middle cerebral artery territory during the first 2 weeks after the ictus. After CT and rating of the neurological deficit on admission, serial examinations with clinical neuromonitoring, contrast-enhanced CT and MRI were done on the same day. The occurrence and severity of HT were correlated with CE, stroke mechanism, infarct size, development of neurological deficits and antithrombotic treatment. The frequency of HT detected by MRI was 80%. CE usually preceded HT or was seen simultaneously. MRI had a higher sensitivity than CT to HT and CE. Severity of HT was positively correlated with infarct size (P < 0.01). HT had no influence on patient's neurological status. Neither the type of antithrombotic treatment nor the stroke mechanism was associated with the severity of HT. No parenchymal haemorrhage occurred.

Adolescent↗

PubMed2000

Preoperative B-mode ultrasound plaque appearance compared with carotid endarterectomy specimen histology.

In carotid artery stenosis both the degree of the lesion and its plaque morphology are thought to be associated with the carrier's thromboembolic risk. In this study we evaluated the diagnostic preciseness of non-invasively B-mode ultrasound in predicting the histopathological plaque structure. We examined 44 patients with > 50% ICA stenosis by B-mode within 6 weeks prior to carotid endarterectomy. At the affected bifurcations, up to 10 different regions of interest (ROI) per artery were investigated. Plaque appearance was classified according to 6 subtypes considering different ultrasonic plaque features. Postoperatively, plaque specimens were examined histopathologically for their relative content of calcification, fibrous tissue and different soft tissue. B-mode ultrasound was compared with histopathological features in ROI. A total of 265 regions of interest were evaluated. In mainly echolucent types of plaques, atheromatous debris was most frequently seen, whereas fibrosis was rare. Homogeneous echolucent plaques showed a high proportion of cholesterol and/or recent haemorrhage. Thrombosis at the plaque surface was often seen in "completely echolucent" plaque type (each P<0.001). Carotid B-mode ultrasonography is able to predict the histopathological components and the texture of carotid plaques.

Adipose Tissue↗

PubMed2000

Ultrasound contrast enhancing agents in neurosonology: principles, methods, future possibilities.

OBJECTIVES: Ultrasound of the brain supplying arteries is a standard diagnostic procedure in patients with suspected and definite acute and chronic cerebrovascular occlusive disease. Anatomical and pathological limitations led to the development of echocontrast agents which are able to survive pulmonary and capillary transit and improve the echogenicity of the flowing blood. MATERIAL AND METHODS: This article reviews present and future applications of echocontrast agents in conjunction with personal experiences. RESULTS: Currently, echocontrast is used for the differentiation of internal carotid artery occlusion and pseudoocclusion, better delineation of the maximal narrowing in high-grade stenoses, and better visualization of the extracranial vertebral artery and its collaterals. Transcranial applications include the insufficient foraminal or temporal window, assessment of arteriovenous malformations, thrombosis of cerebral veins and sinuses, and intracranial aneurysms. The use of echocontrast can have direct diagnostic and therapeutic consequences. Harmonic imaging, perfusion imaging, stimulated acoustic emission, and drug delivery are possible future domains of the technique. DISCUSSION: Besides the support of conventional neurovascular ultrasound in poor examination conditions due to the patients' anatomy or pathology, echocontrast agents may allow for novel applications in the diagnosis and treatment of cerebrovascular patients.

Carotid Artery Diseases↗

PubMed2000

Benefit of echocontrast-enhanced transcranial color-coded duplex ultrasound in the assessment of intracranial collateral pathways.

BACKGROUND AND PURPOSE: Although clinically important, proper assessment of intracranial arterial collateral pathways by transcranial color-coded duplex sonography (TCCD) in patients with internal carotid artery (ICA) high-grade stenosis or occlusion is occasionally made difficult by an insufficient temporal bone window, an unfavorable insonation angle, or low flow velocity or volume. In these cases, echocontrast could be helpful to increase the diagnostic confidence or to make the diagnosis at all. METHODS: We investigated 50 temporal windows of 44 patients with ipsilateral high-grade (>/=70%) ICA stenosis or occlusion and insufficient native transtemporal insonation conditions before and after the application of the echo enhancer Levovist with an infusion pump. RESULTS: Compared with the precontrast scans, echocontrast allowed for more segments to be evaluated by pulsed Doppler sonography (P<0. 0001) and for longer lumen segments to be displayed on color mode (P<0.0001). Also, collateral flow via the anterior and posterior communicating artery could be demonstrated in 25 and 32 scans, respectively, compared with only 1 demonstration of each collateral pathway before the application of contrast medium (both P<0.0001). Similarly, with the help of contrast medium, flow velocity in the middle cerebral artery could be measured in 45 cases compared with only 26 cases before contrast was applied (P<0.0001). CONCLUSIONS: In patients with poor precontrast visualization of intracranial arteries, echocontrast-enhanced TCCD is very helpful in the assessment of intracranial collateral pathways recruited downstream to ICA stenoses and occlusions.

Adult↗

PubMed2000

Visualization of the basilar artery by transcranial color-coded duplex sonography : comparison with postmortem results.

BACKGROUND AND PURPOSE: Transcranial color-coded sonography (TCCS) via the suboccipital approach allows direct and continuous visualization of the basilar artery (BA). In this study, we intended to evaluate the ability of native TCCS in visualizing the length of the BA by means of a comparison with postmortem measurements. METHODS: The BA was prospectively studied by TCCS shortly before death (median 3 days) in 46 moribund neurological patients (mean+/-SD age 71.1+/-13.1 years). The length of the BA was determined by measuring the distance between the vertebrobasilar junction and the deepest available flow signal in the top of the BA. During autopsy, photos of the vertebrobasilar system were taken to evaluate the true anatomic length and variations of the course of BA in situ, eg, straight, curved, or S-shaped. RESULTS: Comparison of the in vivo ultrasound measurements of BA length and postmortem data was possible in 44 of 46 cases. In the 2 remaining patients, the BA was occluded. The mean insonation depth of the vertebrobasilar junction was found at 66.9+/-7.1 mm. The mean BA length was 21.5+/-6. 8 mm by color-coded duplex and 32.9+/-6 mm anatomically (P<0.0001). The mean difference between color mode and anatomic findings was 11. 3+/-6.4 mm in the case of a straight BA (35 cases) and 16.3+/-4.8 mm in an anatomically tortuous course of the BA (9 cases). CONCLUSIONS: Color duplex imaging enables correct visualization of the proximal two thirds of the BA, but only exceptionally of its distal one third. A tortuous course of the BA leads to an underestimation of its anatomic length.

Basilar Artery↗

PubMed2000

Evaluation of new online automated embolic signal detection algorithm, including comparison with panel of international experts.

BACKGROUND AND PURPOSE: The clinical application of Doppler detection of circulating cerebral emboli will depend on a reliable automated system of embolic signal detection; such a system is not currently available. Previous studies have shown that frequency filtering increases the ratio of embolic signal to background signal intensity and that the incorporation of such an approach into an offline automated detection system markedly improved performance. In this study, we evaluated an online version of the system. In a single-center study, we compared its performance with that of a human expert on data from 2 clinical situations, carotid stenosis and the period immediately after carotid endarterectomy. Because the human expert is currently the "gold standard" for embolic signal detection, we also compared the performance of the system with an international panel of human experts in a multicenter study. METHODS: In the single-center evaluation, the performance of the software was tested against that of a human expert on 20 hours of data from 21 patients with carotid stenosis and 18 hours of data from 9 patients that was recorded after carotid endarterectomy. For the multicenter evaluation, a separate 2-hour data set, recorded from 5 patients after carotid endarterectomy, was analyzed by 6 different human experts using the same equipment and by the software. Agreement was assessed by determining the probability of agreement. RESULTS: In the 20 hours of carotid stenosis data, there were 140 embolic signals with an intensity of > or =7 dB. With the software set at a confidence threshold of 60%, a sensitivity of 85.7% and a specificity of 88.9% for detection of embolic signals were obtained. At higher confidence thresholds, a specificity >95% could be obtained, but this was at the expense of a lower sensitivity. In the 18 hours of post-carotid endarterectomy data, there were 411 embolic signals of > or =7-dB intensity. When the same confidence threshold was used, a sensitivity of 95.4% and a specificity of 97.5% were obtained. In the multicenter evaluation, a total of 127 events were recorded as embolic signals by at least 1 center. The total number of embolic signals detected by the 6 different centers was 84, 93, 108, 92, 63, and 78. The software set at a confidence threshold of 60% detected 90 events as embolic signals. The mean probability of agreement, including all human experts and the software, was 0.83, and this was higher than that for 2 human experts and lower than that for 4 human experts. The mean values for the 6 human observers were averaged to give P=0.84, which was similar to that of the software. CONCLUSIONS: By using the frequency specificity of the intensity increase occurring with embolic signals, we have developed an automated detection system with a much improved sensitivity. Its performance was equal to that of some human experts and only slightly below the mean performance of a panel of human experts

Algorithms↗

PubMed2000

Contrast transcranial doppler ultrasound in the detection of right-to-left shunts : time window and threshold in microbubble numbers.

BACKGROUND AND PURPOSE: Cardiac right-to-left shunts can be identified by transesophageal echocardiography (TEE) and by transcranial Doppler ultrasound (TCD) with the use of contrast agents and a Valsalva maneuver (VM) as provocation procedure. Currently, data on the appropriate timing of the VM, the use of a diagnostic time window, and a threshold in contrast agent microbubbles detected are insufficient. METHODS: Fifty-eight patients were investigated by both TEE and bilateral TCD of the middle cerebral artery. The following protocol with injections of 10 mL of the commercial galactose-based contrast agent Echovist was applied in a randomized way: (1) no VM, (2) VM for 5 seconds starting 2 seconds after the beginning of contrast injection, (3) VM for 5 seconds starting 5 seconds after the beginning of contrast injection, (4) VM for 5 seconds starting 8 seconds after the beginning of contrast injection, and (5) repetitive short VMs in between 2 and 13 seconds after the beginning of contrast injection. In addition to the single tests, we also tested the sensitivity and specificity of combined results of the tests with VM. RESULTS: In 21 patients, a right-to-left shunt was demonstrated by TEE and contrast TCD (shunt positive). Twenty-one patients were negative in both investigations, no patient was positive on TEE and negative on TCD, and 16 patients were only positive on at least 1 TCD investigation but negative during TEE. Test 3 was the most appropriate test when combined with the results of 1 of the other tests with VM. The highest sensitivities were achieved with a diagnostic time window of 40 seconds and when the presence of a single microbubble was sufficient for the diagnosis of a shunt. CONCLUSIONS: TCD performed twice with 2 provocation maneuvers with Echovist is a sensitive method to identify TEE-proven cardiac right-to-left shunts. The VM should be performed for 5 seconds starting at 5 seconds after the beginning of contrast injection.

Adolescent↗

PubMed1999

Four-gated transcranial Doppler ultrasound in the detection of circulating microemboli.

OBJECTIVE: Embolus detection by transcranial Doppler ultrasound is very time consuming and semi-automated detection is mandatory. The device studied, a TC4040, Nicolet-EME, uses the four-gate technique and allows for audiovisual off-line verification of the recorded events. METHODS: Twenty controls, 10 patients with mechanical prosthetic heart valves and 12 patients with occlusive carotid artery disease were investigated by transcranial colour-coded duplex sonography and, subsequently, underwent a 1-h unilateral embolus detection from the middle cerebral artery using four-gate TCD. We investigated the Doppler spectrum background, microembolic signals (MES) and artefacts produced. A detection threshold of 5 dB or more was defined taking into account natural fluctuations of the Doppler spectrum. RESULTS: Sensitivity of the software was 91.9% and observer-software agreement on MES was 7.8% in the valve patients, and 77.7% and 7.5% in the carotid artery disease patients, respectively. Weaker MES were more likely not to be detected in all four channels. The artefact signal rejection rate was 62%. MES produced either positive or zero time delays in adjacent channels. Artefact signals produced either no delay, or a positive or a negative time delay. Duration of MES ranged from 1-88 ms. CONCLUSIONS: Besides refined recognition of MES using the time delay, four gates give faint MES no less than four opportunities to overcome the detection threshold. With this device's satisfying sensitivity, regions of interest in a 1-h recording can audiovisually be evaluated off-line in a few minutes by an investigator.

Adult↗

PubMed1999

Absence of circulating microemboli in patients with lone atrial fibrillation.

Atrial fibrillation (AF) is a well-recognized independent risk factor of ischemic stroke. The aim of this study was to investigate the amount of microembolic signals (MES) in 15 patients with 'lone' AF representing the subgroup of AF patients with the lowest lifelong risk of stroke. All patients had been put on effective anticoagulation due to a scheduled electric cardioversion. Additional cardiac and arterial sources of embolism were excluded by echocardiography and extracranial color-coded duplex sonography of the carotid arteries. Unilateral one-hour transcranial Doppler monitorings revealed complete absence of MES in this series. This observation fits the concept that the amount of microembolisation is related to the risk of manifest thromboembolism. Further studies on this patient group treated with less intensive antihemostatic therapy should be undertaken to define more clearly the disease-specific microembolic activity.

Aged↗

PubMed1999

Intracranial pressure B-waves precede corresponding arterial blood pressure oscillations in patients with suspected normal pressure hydrocephalus.

B-waves are rhythmic oscillations of intracranial pressure (ICP) with a wavelength of 0.5-2 min. These oscillations are accompanied by corresponding fluctuations of arterial blood pressure (BP). There is controversy in the literature whether the ICP oscillations precede or follow the BP oscillations. This relationship, however, is important for the understanding of the origin and the interactions of ICP B-waves with other parameters. ICP and BP were monitored continuously for one night in nine patients with suspected symptomatic normal pressure hydrocephalus (NPH). Forty-five B-waves were identified and the time delays between the peaks and the onsets of B-waves and their BP-equivalents were measured. The mean (+/- standard deviation) of the time delays between the peaks of ICP B-waves and corresponding BP-oscillations was 4.2 +/- 2.4 sec and between the onsets of the oscillations 10.3 +/- 6.6 sec. In all but two B-waves, the ICP peak preceded the BP peak, in all the 45 B-waves the onset of the ICP increase preceded the BP increase (p < 0.004). Our study demonstrates that ICP B-waves precede concomitant changes in BP by several seconds.

Aged↗