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Biomedical subjects

D Sander

Publications and source records attributed to D Sander.

At least 37 records · Page 2Linked to original sources
PubMed2001

Enhanced progression of early carotid atherosclerosis is related to Chlamydia pneumoniae (Taiwan acute respiratory) seropositivity.

BACKGROUND: Chlamydia pneumoniae (Cp) infection has been associated with atherosclerosis and has been proposed as a possible additional cardiovascular risk factor. However, the relationship between Cp seropositivity and the progression of early carotid atherosclerosis is not unequivocally clarified. METHODS AND RESULTS: We evaluated the association between serological detection of Cp IgG and/or IgA antibodies and the progression of the intima-media thickness (IMT) of the common carotid artery using duplex ultrasonography in a prospective study with a follow-up of 3 years in 272 consecutive patients with cerebrovascular disease. Cp-seropositive patients showed a significantly enhanced progression of the IMT even after adjustment for other cardiovascular risk factors (0.12 mm/y [95% CI 0.11 to 0.14] versus 0.07 mm/y [0.05 to 0.09]; P:<0.005). Patients with increased C-reactive protein (>/=0.5 mg/dL) and Cp seropositivity showed the most pronounced IMT progression. Multivariate regression analysis revealed Cp seropositivity to be an independent risk factor for progression of early carotid atherosclerosis. Cox proportional-hazard regression analysis demonstrated a significantly increased rate of cerebrovascular and cardiovascular events in patients with Cp seropositivity, particularly in patients with increased C-reactive protein levels. CONCLUSIONS: Our data support the importance of chronic inflammation and infection for the early stages of atherosclerotic development.

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PubMed2001

Altered cerebrovascular response pattern in interictal migraine during visual stimulation.

A dysbalance of the cerebrovascular response during functional activation of the brain has been postulated as a factor in the pathophysiology of migraine. To determine the dynamic pattern of the cerebrovascular response in migraineurs compared with a control group, changes of the cerebral perfusion during cerebral activation were studied with high temporal resolution by functional transcranial Doppler sonography (fTCD). The cerebral blood flow velocity (CBFV) in the right posterior cerebral artery (PCA) and the left middle cerebral artery (MCA) was measured simultaneously during visual stimulation in 19 interictal migraineurs and in 19 age- and sex-matched control subjects. Data were analysed with a previously validated technique based on automated stimulus-related averaging of the CBFV. The MCA migraineurs exhibited a steady increase of CBFV during the stimulation, while normal subjects showed a habituation of the CBFV response. The lack of habituation in migraineurs was significantly (P < or = 0.05) more pronounced across patients with a high attack frequency (> or = 4 per month) compared with migraineurs with a low attack frequency (< 4 per month). In the PCA, compared with normal subjects, migraineurs showed significantly (P < or = 0.05) stronger CBFV changes at the beginning and after the end of stimulation, with a slower decline to baseline. Data are in accordance with electrophysiological findings in migraineurs. It is assumed that a lack of habituation of the cerebrovascular response in migraineurs might contribute to a disturbance of the metabolic homeostasis of the brain that might induce migraine attacks.

Adult↗
PubMed2000

Disturbance of venous flow patterns in patients with transient global amnesia.

Transient global amnesia (TGA) is an inability to form new memories. The pathophysiology and cause of TGA have not been defined. We examined the changes of internal jugular venous flow patterns in 21 patients with TGA and 21 age-matched and sex-matched controls using duplex ultrasonography during two Valsalva manoeuvres (blocking venous return through the superior vena cava). During both manoeuvres a retrograde flow component was seen significantly more frequently in the TGA group than in the controls. Ten patients reported Valsalva-like activities preceding TGA. In these patients a retrograde flow component took place more frequently than in those who did not report preceding Valsalva-like activities. Our results lend support to the hypothesis that TGA may be attributable to venous congestion, and consequent venous ischaemia to bilateral diencephalic or hippocampal structures.

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PubMed2000

Relationship between circadian blood pressure patterns and progression of early carotid atherosclerosis: A 3-year follow-up study.

BACKGROUND: Arterial hypertension is a major risk factor for cardiovascular damage. The results of several studies suggest that target organ damage is greater in hypertensive persons with high blood pressure variability. METHODS AND RESULTS: During 3.3 years of follow-up, we studied the relationship between circadian blood pressure changes and the progression of early carotid atherosclerosis in 286 patients aged >55 years. Blood pressure patterns were evaluated with a long-term blood pressure monitor, and the extent of atherosclerosis was measured as the intima-media wall thickness (IMT) of the common carotid artery. Patients were subdivided according to blood pressure variability. The progression of IMT was significantly greater in the patients with increased systolic blood pressure variability (0.11 mm/y [95% CI 0.09 to 0.14] versus 0.05 mm/y [0.03 to 0.08]; P:<0.005) even after adjustment for other risk factors. Multivariate regression analysis revealed the daytime systolic blood pressure variability to be the best predictor for the progression of IMT. Raised daytime systolic blood pressure variability (>15 mm Hg) is associated with an increased relative risk of the development of early atherosclerosis (3.9 [1.4 to 11.1]; P:<0.01) and of cardiovascular events (1.87 [1.08 to 3.20]; P:<0.01). CONCLUSIONS: The daytime systolic blood pressure variability is a strong predictor of early carotid atherosclerosis progression and is useful to define the risk-benefit ratio of therapeutic approaches.

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PubMed2000

Extent of cerebral white matter lesions is related to changes of circadian blood pressure rhythmicity.

OBJECTIVE: To evaluate the relationship between circadian blood pressure patterns and the extent of cerebral white matter lesions (WML). DESIGN: Case-control study. PARTICIPANTS: A total of 227 healthy subjects older than 55 years were investigated. Extent and occurrence of WML were evaluated using a computer-supported image analysis system. Circadian blood pressure variation was defined as the average percentage change of nighttime blood pressure compared with the daily blood pressure values. RESULTS: Subjects with WML were significantly older and showed more often a history of hypertension, elevated average systolic daily blood pressure, a reduced systolic circadian blood pressure variation, and an increased incidence of pathological nighttime blood pressure increases. A significant correlation was found between systolic circadian blood pressure variation and the extent of WML. A multiple regression analysis revealed that this parameter was best correlated with the extent of WML. CONCLUSION: In addition to the absolute level of blood pressure, systolic circadian blood pressure variation and in particular a systolic nighttime blood pressure increase may play an important role in the pathogenesis of WML.

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PubMed2000

Evaluation of a method for noninvasive intracranial pressure assessment during infusion studies in patients with hydrocephalus.

OBJECT: A mathematical model previously introduced by the authors allowed noninvasive intracranial pressure (nICP) assessment. In the present study the authors investigated this model as an aid in predicting the time course of raised ICP during infusion tests in patients with hydrocephalus and its suitability for estimating the resistance to outflow of cerebrospinal fluid (Rcsf). METHODS: Twenty-one patients with hydrocephalus were studied. The nICP was calculated from the arterial blood pressure (ABP) waveform by using a linear signal transformation, which was dynamically modified by the relationship between ABP and cerebral blood flow velocity. This model was verified by comparison of nICP with "real" ICP measured during lumbar infusion tests. In all simulations, parallel increases in real ICP and nICP were evident. The simulated Rcsf was computed using nICP and then compared with Rcsf computed from real ICP. The mean absolute error between real and simulated Rcsf was 4.1 +/- 2.2 mm Hg minute/ml. By the construction of simulations specific to different subtypes of hydrocephalus arising from various causes, the mean error decreased to 2.7 +/- 1.7 mm Hg minute/ml, whereas the correlation between real and simulated Rcsf increased from R = 0.73 to R = 0.89 (p < 0.001). CONCLUSIONS: The validity of the mathematical model was confirmed in this study. The creation of type-specific simulations resulted in substantial improvements in the accuracy of ICP assessment. Improvement strategies could be important because of a potential clinical benefit from this method.

Adult↗
PubMed1999

Cerebral vasodilatation causing acute intracranial hypertension: a method for noninvasive assessment.

Deep spontaneous vasodilatatory events are frequently recorded in various cerebral diseases, causing dramatic increases (A-waves) in intracranial pressure (ICP) and subsequently provoking ischemic brain insults. The relationship between fluctuations in CBF, ICP, and arterial blood pressure (ABP) is influenced by properties of cerebrovascular control mechanisms and the cerebrospinal pressure-volume compensation. The goal of this study was to construct a mathematical model of this relationship and to assess its ability to predict the occurrence and time course of A-waves. A group of 17 severely head-injured patients were included in the study. In our model ICP was derived from the ABP waveform using a linear signal transformation. The transformation was modified during the simulation by a relationship between ABP and flow velocity, i.e., by the characterization of the cerebrovascular bed. In this way the ICP could be calculated from the ABP waveform. This model was verified by comparison of simulated and directly measured ICP during A-waves recorded in seven of the patients. In all simulations, plateau elevations of ICP were well replicated. The mean absolute error between real and simulated ICP was 8.3 +/- 5.4 mm Hg at the baseline and 7.9 +/- 4.3 mm Hg at the top of plateau waves. The correlation coefficient between real and simulated increase in ICP was R = 0.98; P < .001. Similarly, correlation between real and simulated increase in pulse amplitude of ICP was highly significant (R = 0.94; P < .001). The mathematical model of the relationship between ABP, flow velocity, and ICP is of potential clinical use for the noninvasive detection of A-waves in patients in whom invasive ICP assessment is not conducted.

Adolescent↗
PubMed1999

Methodological parameters influence the detection of right-to-left shunts by contrast transcranial Doppler ultrasonography.

BACKGROUND AND PURPOSE: Contrast transcranial Doppler ultrasonography is a new method to detect intracardiac right-to-left shunts, such as the patent foramen ovale. However, the methodology of the procedure varies considerably among investigators. This study was undertaken to assess the influence of methodological parameters on the results of the contrast transcranial Doppler examination in the detection of right-to-left shunts. METHODS: A total of 72 patients (mean age, 58.2+/-14.7 years) had a contrast transcranial Doppler ultrasonography examination. To study the influence of methodological factors, patients with evidence of a right-to-left shunt underwent repeated examinations with modified procedures. Parameters under investigation were the timing of the Valsalva maneuver, the dose of the contrast medium, and the patient's posture during the examination. RESULTS: The median contrast signal count was 58.5 and 48.0 (P<0.001) and the median latency of the first intracranially detected contrast signal was 12.5 and 8.5 seconds (P=0.05) when the Valsalva maneuver was performed 5 and 0 seconds after the start of the injection, respectively. Reducing the contrast medium dose from 10 to 5, 2.5, and 1.2 mL resulted in a decline of the median signal count from 54.5 to 28.5, 20.5, and 12.0 (P<0.01), respectively, while the latency of the first contrast signal increased from 13.3 to 14.0, 14.6, and 15.0 seconds (P<0.05). The sitting position also produced a lower signal count than the supine position (P<0.02). CONCLUSIONS: This study demonstrates that several essential methodological parameters influence the results of the contrast transcranial Doppler ultrasonography examination. Therefore, it is necessary to standardize the procedure to permit comparable quantitative assessments of the shunt volume. The findings of the present study suggest that 10 mL of contrast medium be injected with the patient in the supine position and that the Valsalva maneuver be performed 5 seconds after the start of the injection.

Adult↗
PubMed1998

Changes of circadian blood pressure patterns are associated with the occurence of lucunar infarction.

BACKGROUND: The occurrence of lacunar infarction is closely related to arterial hypertension. However, there is only limited and partly controversial knowledge regarding the possible pathogenetic role of circadian blood pressure changes. OBJECTIVE: To evaluate the relationship between circadian blood pressure rhythm, occurrence, and extent of lacunar infarction. METHODS: We analyzed circadian blood pressure patterns, other cardiovascular risk factors, and occurrence of lacunar infarction in 118 hospitalized patients older than 55 years. Noninvasive 24-hour blood pressure measurements and magnetic resonance or computed tomographic brain imaging were performed in 61 patients with lacunar infarction and in 57 control patients. Daytime blood pressure variability was defined as the within-subject SD of all systolic and diastolic blood pressure readings during the daytime measurement period. Circadian blood pressure variation was defined as the average percentage change of nighttime blood pressure values compared with the daytime blood pressure values. RESULTS: Patients with lacunar infarction were significantly older and showed more often a history of arterial hypertension, elevated average daytime blood pressure values, an increased systolic daytime blood pressure variability, and a reduced circadian blood pressure variation due to an increased incidence of a pathologic nighttime blood pressure increase. No significant correlation was found between these parameters and the number of lacunae. A logistic regression analysis revealed that a reduced systolic circadian blood pressure variation, age, systolic average daytime blood pressure, and a history of arterial hypertension were best correlated with the occurrence of lacunar infarction. CONCLUSION: Reduced nighttime decline in systolic blood pressure may be an important risk factor for the development of lacunar infarction in addition to the absolute level of blood pressure and age.

Aged↗
PubMed1998

A method for a simulation of continuous intracranial pressure curves.

The study introduces a method to simulate continuously an intracranial pressure (ICP) wave form. In a system analysis approach the intracranial compartment was viewed as a black box with arterial blood pressure (ABP) as an input signal and ICP as an output. A weight function was used to transform the ABP curve into the ICP curve. The output ICP waveform was generated using a weight function derived from the transcranial Doppler blood flow velocity (FV) and ABP curves. In order to establish the relationship between TCD characteristics and weight functions simultaneous recordings of FV, ABP, and ICP curves of a defined group of patients were used. A linear function between the TCD characteristics and the weight functions was obtained by calculating a series of multiple regression analyses. Given examples demonstrate the procedure's capabilities in predicting the mean ICP, the pulse and respiratory waveform modulations, and the trends of ICP changes.

Computer Simulation↗
PubMed1997

Assessment of functional hemispheric asymmetry by bilateral simultaneous cerebral blood flow velocity monitoring.

The aim of this study was to investigate side-to-side differences of simultaneously measured middle cerebral artery (MCA) blood flow velocities during various hemisphere-specific tasks. Using a transcranial Doppler device, flow velocity changes of 24 healthy, right-handed subjects were monitored simultaneously in the left and right MCA during different hemisphere-specific tasks. Mean flow velocity (MFV) curves were averaged for each individual subject and task. Simultaneously, heart rate, blood pressure and end-tidal carbon dioxide (CO2) were measured in a subgroup of six subjects. When compared with the resting state, all stimuli produced significant (p < 0.001) bilateral MFV increases, ranging from 2.5-9.2%. A lateralization of MFV increases with a significantly (p < 0.001) more pronounced increase in MFV in the hemisphere contralateral to the performing band was observed both during simple sequential finger movements and a complex spatial task. During the complex spatial task, consistently higher MFV increases were observed in the right MCA (p < 0.001), regardless of the side of task performance. Recognition of pictorial material presented as part of a memory task, also resulted in a side-to-side difference of respective MFV increases (right > left, p < 0.001), whereas memorization did not. Whereas bilateral MFV elevations observed during stimulation with white noise were only discrete and not lateralized, exposure to overt speech produced significantly higher (p < 0.001) MFV increases in the left MCA. The time course of the MFV reaction showed a rapid increase with an initial maximum after 4-5 s. Heart rate, blood pressure, and end-tidal CO2 showed only subtle changes during the stimulation periods. In conclusion, the observed side-to-side differences of MFV reaction in the left and right MCA concur with current functional imaging data. Bilateral simultaneous repetitive transcranial Doppler monitoring is a sensitive method to detect cerebral perfusion asymmetries caused by hemisphere-specific activation, and thus may be helpful for noninvasive assessment of hemispheric dominance for language.

Adult↗
PubMed1997

Noninvasive prediction of intracranial pressure curves using transcranial Doppler ultrasonography and blood pressure curves.

BACKGROUND AND PURPOSE: Until now the assessment of intracranial pressure (ICP) required invasive methods. The objective of this study was to introduce an approach to a noninvasive assessment of continuous ICP curves. METHODS: The intracranial compartment was considered a "black box" system with an input signal, the arterial blood pressure (ABP), and an output signal, the ICP. A so-called weight function described the relationship between ABP and ICP curves. Certain parameters, called transcranial Doppler (TCD) characteristics, were calculated from the cerebral blood flow velocity (FV) and the ABP curves and were used to estimate this weight function. From simultaneously sampled FV, ABP, and (invasively measured) ICP curves of a defined group of patients with severe head injuries, the TCD characteristics and the weight function were computed. Multiple regression analysis revealed a mathematical formula for calculating the weight function from TCD characteristics. This formula was used to generate the ICP simulation. FV, ABP, and ICP recordings from 11 patients (mean age, 46 +/- 14 years) with severe head injury were studied. In each patient, ICP was computed by a simulation procedure, generated from the data of the remaining 10 patients. The simulation period was 100 seconds. RESULTS: Corresponding pressure trends with a mean absolute difference of 4.0 +/- 1.8 mm Hg between computed and measured ICP were observed. Shapes of pulse and respiratory ICP modulations were clearly predicted. CONCLUSIONS: These results demonstrate that this method constitutes a promising step toward a noninvasive ICP prediction that may be clinically applicable under well-defined conditions.

Adult↗
PubMed1997

Cardiovascular consequences of clinical stroke.

In clinical stroke cardiovascular abnormalities are frequently neglected although they occur more often than it is generally assumed. However, cardiac arrhythmias, pathological ECG findings, and changes of circadian blood pressure patterns are significantly increased in patients with acute cerebrovascular lesions and are associated with an increased mortality. Several clinical studies have shown that cerebral infarctions may cause different cardiovascular abnormalities depending on the location and the size of the stroke. Hereby, the prolongation of the QT interval and the expansion of the QRS-complex as the most frequent ECG abnormalities are regarded as indicators of the electrical instability of the ventricular myocardium. Furthermore, cardiac enzyme increases are interpreted as an indicator of myocardial damage during the acute phase after cerebral ischaemia. Since the autonomic nervous system plays a major role in the regulation of blood pressure, alterations of sympatho-adrenergic activity can also affect the diurnal blood pressure profile. Some studies report frequent changes of the circadian blood pressure patterns with a decreased night-time blood pressure decline or a pathological night-time blood pressure elevation. Several studies proved the importance of infarct location. The insular cortex in particular has an important role in the genesis of the pathological activation of the sympathetic nervous system. Hence, a highly significant relationship between the extent of circadian blood pressure variation and percentage insular infarction could be found. Some findings implied that the mechanism of cardiovascular instability following stroke relates to the disinhibition of the insular cortex and a reacting augmentation of the sympathetic tone. A further important aspect is given by the strong evidence that sympathetic activation ] is lateralized following hemispheric brain infarction. Accordingly, patients with a right-sided hemispheric infarction showed a significantly diminished circadian blood pressure variation as compared with patients with left-sided hemispheric infarction. The results in patients with brain stem infarction were heterogeneous. On the one hand, patients with brain stem infarction had substantially higher mean plasma norepinephrine levels than did patients with hemispheric infarction; on the other hand, hemispheric lesions were associated with a significantly higher incidence of cardiac arrhythmias when compared to patients with brain stem infarction.

Animals↗
PubMed1996

Extent of autonomic activation following cerebral ischemia is different in hypertensive and normotensive humans.

OBJECTIVES: To evaluate whether the extent of autonomic activation following brain infarction differs between hypertensive and normotensive humans, and to investigate the role of the insular cortex for this sympathetic activation. DESIGN: Prospective, hospital-based study. SETTING: Department of Neurology of a university medical center. SUBJECTS: Forty-two patients with essential hypertension and 45 patients who were normotensive. MAIN OUTCOME MEASURES: Extent of autonomic activation following stroke as indicated by circadian blood pressure patterns, serum norepinephrine levels, and cardiovascular variables. RESULTS: Normotensive patients with insular infarction showed a significantly reduced circadian blood pressure variation and a higher frequency of nocturnal blood pressure increase compared with patients suffering from essential hypertension and insular stroke. These findings were also associated with higher serum norepinephrine concentrations and more frequent electrocardiographic abnormalities. No significant changes in these variables were seen between normotensive and hypertensive patients without insular involvement. CONCLUSIONS: Our findings suggest a difference in cortical control of autonomic function between hypertensive and normotensive patients after stroke and point to a possible role of the insular cortex in the pathogenesis of essential hypertension.

Aged↗
PubMed1996

Increase of posterior cerebral artery blood flow velocity during threshold repetitive magnetic stimulation of the human visual cortex: hints for neuronal activation without cortical phosphenes.

To analyze the effects of low intensity repetitive transcranial magnetic stimulation over the occipital cortex on regional cerebral perfusion, bilateral simultaneous monitoring of posterior cerebral artery blood flow velocity was performed using transcranial Doppler ultrasonography in 14 healthy subjects. During 20 s of unilateral magnetic stimulation with 3 Hz and 6 Hz a significant increase of ipsilateral flow velocity was observed during both stimulus conditions (3 Hz, 10.2 +/- 3.7%; 6 Hz, 12.8 +/- 4.7%). A significantly smaller flow velocity increase occurred also in the contralateral posterior cerebral artery (3 Hz, 8.6 +/- 4.0%; 6 Hz, 10.6 +/- 4.1%). Flow velocity increases were similar to values reported in the literature for physiological activation paradigms so that excessive excitation of the visual cortex does not seem to occur during repetitive magnetic stimulation. The largest increase of flow velocity was observed in the ipsilateral posterior cerebral artery of 5 subjects who experienced phosphenes in the contralateral visual half-field during stimulation (14.3 +/- 4.1%: mean of 3 and 6 Hz stimulation). In the other 9 subjects significant velocity increases indicated cortex activation in the absence of cortical phosphenes. The occurrence of maximum velocity responses within 2-3 heart beats following the first cortex stimulus points to a fast adjustment of cerebral perfusion in response to transcranial brain stimulation.

Blood Flow Velocity↗
PubMed1996

Relationships between delayed ischemic dysfunctions and intracranial hemodynamics following subarachnoid hemorrhage.

Delayed ischemic dysfunctions (DID) are one of the main complications following subarachnoid hemorrhage. It was the aim of our study to analyse the possible prognostic value of different transcranial Doppler ultrasonography parameters and to elucidate the risk of developing DID with particular reference to the intracranial pressure. The relative change of mean blood flow velocity and of corresponding cerebral circulatory resistance index as well as the intracranial pressure were determined in 44 patients with spontaneous subarachnoid hemorrhage. No relationship was found between the occurrence and extent of DID and the relative change of mean flow velocity during the clinical course. In contrast, there was a significant correlation between the relative change of the cerebral circulatory resistance index and the occurrence of DID. While patients without or with reversible DID showed a decreased resistance index compared to the initial value (without DID: -17% +/- 15%; reversible DID: -3% +/- 14%), patients with irreversible DID had a significant increase of the resistance index (+14% +/- 9%). Accordingly, patients with irreversible DID showed a significant increase of intracranial pressure compared to the patients with reversible DID. We conclude that the evaluation of relative changes of the cerebral circulatory resistance index by bedside monitoring is a useful tool to predict the occurrence of subarachnoid hemorrhage-associated DID and has therapeutic impact.

Adolescent↗
PubMed1996

Diurnal systolic blood pressure variability is the strongest predictor of early carotid atherosclerosis.

We studied the relationship between circadian blood pressure changes and development of early carotid atherosclerosis in 208 hypertensive and 216 normotensive patients older than age 55 years. Blood pressure patterns were evaluated noninvasively with a long-term blood pressure monitor, and extent of atherosclerosis was measured as the intima to media wall thickness (IMT) of the common carotid artery. No significant differences regarding age, sex, smoking, diabetes, cholesterol, and triglycerides were found between both patient groups. The age-adjusted IMT was significantly larger in the hypertensive patients (1.34 mm [95% confidence interval 1.24, 1.44] versus 1.18 mm [1.14, 1.22]; p < 0.05). However, after adjustment for diurnal systolic blood pressure variability, which was significantly increased in the hypertensive group, the significant IMT difference between both patient groups was no longer observed (1.32 mm [1.27, 1.37] versus 1.29 mm [1.25, 1.33]). Multivariate regression analysis revealed the diurnal systolic blood pressure variability as the strongest predictor for IMT. The IMT was most increased in hypertensive patients with increased diurnal systolic blood pressure variability and additional nocturnal blood pressure increase (1.64 mm [1.45, 1.83]. The odds ratio of having early atherosclerosis (age-adjusted IMT > 1.5 mm) increased with raised diurnal systolic blood pressure variability (> 15 mm Hg) in both groups (normotensive: 8.5 [2.30]; hypertensive: 12.6 [4, 43]). The diurnal systolic blood pressure variability is the strongest predictor of early carotid atherosclerosis measured with B-mode ultrasonography and is useful to define the risk-benefit ratio of therapeutic approaches, particularly in patients with only slightly elevated blood pressure levels.

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