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Biomedical subjects

M Sitzer

Publications and source records attributed to M Sitzer.

70 records · Page 4Linked to original sources
PubMed1994

Cerebral microembolism in symptomatic and asymptomatic high-grade internal carotid artery stenosis.

Using transcranial Doppler (TCD) ultrasonography in patients with high-grade (> or = 70%) internal carotid artery (ICA) stenosis, we examined the relation between the rate of TCD-detected silent microembolism of the ipsilateral middle cerebral artery and a history of recent (< 121 days) ischemic symptoms attributable to the diseased ICA. In the so-defined neurologically symptomatic group (n = 33 patients), silent microembolic events occurred in 27 subjects (overall mean rate, 14/h +/- 29). Among 56 neurologically asymptomatic patients matched for the degree of ICA stenosis, only nine showed such events (overall mean rate, 0.35/h +/- 1.4). Across all 89 patients studied, an individual microembolic event rate > or = 2/h had a positive predictive value of 0.88 for a history of recent symptoms. Our data suggest that TCD monitoring can provide reliable paraclinical evidence of "unstable ICA disease."

Aged↗
PubMed1994

Deficiency of both protein C and protein S in a family with ischemic strokes in young adults.

Protein C and protein S deficiencies increase the risk of venous thrombosis and pulmonary embolism, but their role in arterial thrombosis or embolism is controversial. We describe cerebral ischemia in two young women in a family with inherited deficiencies of both proteins C and S and provide evidence that a combined deficiency of proteins C and S may be a high risk factor for ischemic stroke in young adults.

Adult↗
PubMed1993

[Quantification of extracranial carotid stenosis. Magnetic resonance angiography and Doppler sonography versus intra-arterial angiography].

UNLABELLED: To assess various non-invasive techniques for quantifying internal carotid artery CA stenosis, per cent luminal diameter reduction on intraarterial angiograms (IAA) was measured in 63 patients with ICA stenosis or occlusion. These data were compared with independent measurements based on MR-angiography, continuous-wave (cw) Doppler ultrasonography, systolic peak flow velocity and colour Doppler assisted duplex imaging. Correlations with IAA were equally strong for MR angiography, cw Doppler and colour Doppler analysis (0.95; 0.92; 0.92). Positive predictive values for > or = 70% ICA stenosis were lower and negative predictive values were higher for cw Doppler (0.85; 0.92) and colour duplex analysis (0.81; 0.94) than for MR angiography (0.86; 0.88). Statistical analysis showed non-linear correlations between percentage of lumen diameter narrowing and the length of the zone of signal intensity loss (0.72) and maximum systolic peak flow velocity (0.77). CONCLUSION: Several non-invasive methods do compare with IAA in identifying and quantifying high-grade ICA stenosis and may suffice for decisions on treatment.

Adult↗
PubMed1993

[The hemodynamics and anatomy of the circle of Willis. The technic and clinical value of selective MR angiography].

This study evaluates the usefulness of MR angiography in analysing the individual collateral flow dynamics and anatomy of the circle of Willis in 56 patients with high-grade extracranial carotid stenosis or occlusion. Selective MRA of the carotid or vertebrobasilar area was performed by means of presaturation up to the brain-supplying arteries at the level of the middle neck (angled presaturation slabs). Results obtained with selective and non-selective MRA in 56 consecutive patients were compared with the findings at transcranial Doppler ultrasonography and arterial angiography. Ischaemic cerebral infarctions were classified by computerized tomography and correlated with the results of collateral flow analysis: Sensitivity of selective MRA in detecting intracranial collateral flow via anterior or posterior communicating artery was 96 and 97%, respectively; sensitivity in depicting extracranial transorbital flow was lower (71%). Non-selective MRA was 100% sensitive in detecting a non-filling of the horizontal (A1) segment of the anterior cerebral artery and in identifying an origin of the posterior cerebral artery from the intracranial carotid artery. Slow flow infarctions occurred more frequently in patients with transorbital and posterior-to-anterior collateral flow than in patients with collateral flow via anterior communicating artery.

Angiography↗
PubMed1993

Silent cerebral embolism caused by neurologically symptomatic high-grade carotid stenosis. Event rates before and after carotid endarterectomy.

Fourteen symptomatic patients with severe extracranial internal carotid artery stenosis (> or = 70% of luminal narrowing) were monitored using long-term transcranial Doppler ultrasonography to determine the rate of clinically silent embolism of the ipsilateral middle cerebral artery. Before carotid endarterectomy (all patients being treated with intravenous heparin), 462 such events occurred during a total monitoring time of 45 h. Statistical analyses of the inter-event intervals and of the relationship between events and cardiac cycle revealed random occurrence. While the ipsilateral events were found in each subject, silent embolism of the contralateral middle cerebral artery occurred in only four patients each of whom had angiographically proven intracranial cross-flow from the symptomatic carotid territory (39 embolic events during 7 h monitoring time). The other 10 patients showed no contralateral embolism (10 h monitoring time). Five or more days (median 10 days) after surgery and cessation of intravenous anticoagulation the ipsilateral event rate had dropped to 13 in 33 h (P < 0.001) and the contralateral rate to zero. This suggests that the stenosed arterial segment is the main source of cerebral embolism detectable with ultrasound in symptomatic patients with high-grade internal carotid stenosis, and that carotid endarterectomy substantially reduces the rate of these events. Since reduction of ipsilateral stroke risk by successful endarterectomy is known to be of a similar degree in patients as those studied here, transcranially detected embolism may represent a new marker of disease activity of extracranial carotid artery stenosis.

Adult↗
PubMed1993

Between-method correlation in quantifying internal carotid stenosis.

BACKGROUND AND PURPOSE: The degree of internal carotid stenosis has emerged as the most important predictor of ischemic stroke in extracranial carotid artery disease. The purpose of this study was to assess the validity of the noninvasive techniques for quantifying internal carotid stenosis with respect to the accepted standard of intra-arterial angiography. METHODS: We measured the maximum percentage reduction in luminal diameter on the intra-arterial digital subtraction angiograms of 56 symptomatic patients with extracranial internal carotid stenosis (n = 77) or occlusion (n = 20). These data were compared with independent measurements based on continuous-wave Doppler ultrasonography, pulsed-wave Doppler spectrum analysis, color Doppler-assisted duplex imaging, and magnetic resonance angiography. RESULTS: Correlations with intra-arterial angiography were equally strong (r > .90) for magnetic resonance angiography, continuous-wave Doppler, and color duplex analysis. Positive and negative predictive values for (therapeutically relevant) 70% to 99% stenosis were higher for continuous-wave Doppler (.82, .97) and color duplex (.84, .98) than for magnetic resonance angiography (.79, .81). Also, accuracy in quantifying high-grade stenosis was better for both of these ultrasonographic techniques, mainly due to the frequent occurrence of a "flow gap" on the magnetic resonance angiograms. Continuous-wave Doppler and magnetic resonance angiography, but not color duplex, failed to detect slow residual arterial flow in one and two cases of symptomatic "pseudo-occlusion" of the internal carotid, respectively. CONCLUSIONS: (1) Several noninvasive methods compare well with intra-arterial angiography in identifying and quantifying high-grade internal carotid stenosis; (2) the use of these noninvasive methods may suffice for treatment decisions; and (3) because residual between-method disagreement is partly explained by principles of physics, the validity of continuous-wave Doppler and color duplex in quantifying 60% to 99% stenosis is likely to be underestimated by correlation with intra-arterial angiography.

Blood Flow Velocity↗
PubMed1992

Detection of intracranial emboli in patients with symptomatic extracranial carotid artery disease.

BACKGROUND AND PURPOSE: Cerebral embolism from extracranial sources is an important cause of ischemic stroke. The purpose of this limited study using long-term transcranial Doppler ultrasonographic monitoring was to estimate the frequency of clinically silent intracranial embolisms in patients with symptomatic extracranial carotid artery disease. SUMMARY OF REPORT: By means of a 2-MHz pulsed-wave transcranial Doppler instrumentation, three consecutive patients with extracranial internal carotid artery stenosis (n = 2) or occlusion (n = 1) and recurrent ipsilateral ischemic events were monitored (19 hours total recording time). In addition, 10 control subjects without cerebrovascular disease were studied (25 hours total recording time). Formed-element emboli were defined as distinct signals within the fast Fourier-transform Doppler spectrum that were < 70 msec in duration and > 9dB greater in intensity than the background signal. Clinically silent formed-element embolism of ophthalmic or cerebral arteries was demonstrated in all three patients. Embolic events occurred only in the territory of the symptomatic internal carotid artery. The average rate of cerebral embolization at transcranial Doppler ultrasonography was 4.1/hr, with a mean signal duration of 47 msec. No emboli were found in control subjects. CONCLUSIONS: The observed high frequency of silent embolism of the intracranial arteries detected by transcranial Doppler monitoring in patients with recurrently symptomatic extracranial carotid artery disease should encourage studies of the prognostic and therapeutic implications of this method.

Adult↗
PubMed1991

Spontaneous oscillations in cerebral blood flow velocity in normal humans and in patients with carotid artery disease.

Spontaneous oscillations in cerebral blood flow velocity (CBFV) in normals and in patients with stenoses or occlusions of the internal cerebral artery were measured using transcranial Doppler sonography. In normal subjects, large oscillations of up to +/- 30% from the mean CBFV were found with low frequencies between 0.4 and 9 cycles/min. No correlations between CBFV oscillations and systemic circulatory parameters were detected. In patients with carotid artery obstructions the CBFV oscillations were significantly reduced in the middle cerebral artery ipsilaterally to a hemodynamically significant lesion, but not contralaterally. Our results support the hypothesis that spontaneous oscillations (B-waves) of small pial vessels are responsible for the CBFV fluctuations.

Adult↗
PubMed1988

Injuries related to all-terrain vehicular accidents: a closer look at head and neck trauma.

Morbidity and mortality associated with all-terrain vehicular accidents is climbing at a steady rate. These accidents frequently result in multiorgan system trauma. A retrospective study of all victims involved in three-wheel motor vehicle accidents admitted to the UCSD Trauma Unit between July 1980 and July 1985 is presented. Injury severity was assessed using the Abbreviated Injury Scale (AIS) and the Injury Severity Score (ISS). The average patient age was 23.3 years with 30% under 16 years of age. There was a male to female ratio of 14:1. The average hospital stay was 12.4 days. Six percent died as a result of their injuries. Injuries to the head and neck were sustained by 83.3% of patients, facial injuries by 46.6%, injuries to the chest by 13.3%, and injuries to the pelvis and abdomen by 13.3%. Thirty percent suffered injuries to the extremities and over 50% had abrasions, contusions, and/or lacerations. Physicians, the public, and state and federal agencies are urged to promote safer use of these recreational vehicles.

Accidents↗
PubMed1987

Intracerebral hemorrhage after experimental embolic infarction. Anticoagulation.

Embolic stroke was induced in rabbits using autologous blood clot. One hour after stroke, animals received heparin anticoagulation (AC) for five hours (acute AC) or five days (chronic AC). Animals received excessive AC (partial thromboplastin time greater than 3.0 times control), adequate AC (partial thromboplastin time, 1.2 to 2.5 times control), or saline. After the animals were killed, the brains were examined for macroscopic evidence of intracerebral hemorrhage. There was no significant increase over control in the incidence or severity of hemorrhage in any of the four treatment groups. The data suggest that heparin AC does not promote intracerebral hemorrhage after experimental embolic stroke.

Animals↗
PubMedDate not supplied

Selective MR angiography and intracranial collateral blood flow.

This study evaluates the usefulness of MR angiography (MRA) in analyzing the individual collateral flow dynamics and anatomy of the circle of Willis in patients with high-grade extracranial carotid stenosis or occlusion. Selective MRA of the carotid or vertebrobasilar territory was performed by means of presaturation of up to three of the brain-supplying arteries at the level of the middle or lower neck (angled presaturation slabs). Results obtained with selective and nonselective arterial MRA in 45 consecutive patients were compared with findings at transcranial Doppler ultrasonography and intraarterial angiography, the latter serving as the "gold standard." Sensitivity of selective MRA in detecting intracranial collateral circulation via the anterior and posterior communicating artery was 95 and 97%, respectively; sensitivity in depicting extracranial to intracranial transorbital flow was lower (67%). Nonselective arterial MRA was 100% sensitive in detecting a nonfilling of the horizontal (A1) segment of the anterior cerebral artery and in identifying an origin of the posterior cerebral artery from the intracranial carotid artery. Visibility of the posterior communicating artery at MRA predicted for pathological collateral flow via this vessel in all cases. We conclude that selective and nonselective MRA of the cerebral arteries as used here is the most powerful noninvasive method to demonstrate collateral circulation via the basal communicating arteries and to identify hemodynamically relevant anatomic variants of the circle of Willis.

Adult↗
PubMedDate not supplied

Quantification of carotid blood flow velocity using MR phase mapping.

OBJECTIVE: The purpose of this study was to determine the feasibility of a two-dimensional phase-sensitive MR technique [phase mapping (PM)] for the quantification of carotid blood flow velocity (CBFV) and pulsatility in normal subjects and patients with extracranial carotid disease. MATERIALS AND METHODS: Using PM, we measured the systolic peak, minimum diastolic, and mean CBFV and the pulsatility index in both common carotid arteries (CCAs) of 22 normal subjects and 32 patients. In addition, the CBFV was quantified in the internal carotid arteries (ICAs) of 25 patients. These data were compared with independent measurements based on pulsed-wave Doppler ultrasonography. RESULTS: Correlations between PM and pulsed-wave Doppler were strong for systolic peak CBFV in both the CCA (r = 0.91) and the ICA (r > or = 0.82). Slightly lower correlations were obtained for mean CBFV (r > or = 0.79) and minimum diastolic CBFV (r > or = 0.75), both measured in the CCA. Velocity waveform comparison revealed high between-method correlations for the CCA (r = 0.90 for normals; r > or = 0.88 for patients) and slightly lower correlations for the ICA (r > or = 0.75). Agreement was lower (r = 0.63) for measurements in the ICA distal to high grade stenosis. CONCLUSION: Phase mapping compared well with Doppler ultrasonography in quantifying CBFV and pulsatility in patients with extracranial carotid artery disease. Except for poststenotic measurements in high grade obstructive lesions, PM is capable of providing quantitative hemodynamic information on the severity of ICA stenosis.

Adult↗
PubMedDate not supplied

Factors influencing flow-induced signal loss in MR angiography: an in vitro study.

OBJECTIVE: Signal loss due to poststenotic turbulence is one remaining limitation in the clinical use of MRA. The objective of this study was to determine the factors influencing poststenotic signal loss (PSL) in a stenotic tube system. MATERIALS AND METHODS: With use of a two-dimensional gradient echo sequence (FLASH), the influence of (a) the degree of stenosis (50, 75, and 91% cross-sectional area reduction), (b) flow velocity (12, 47, 71, and 94 cm/s), (c) TE (3, 6, 13, and 20 ms), and (d) flip angle (5, 10, 20, ... , 90 degrees) on the length of PSL was measured in a nonpulsatile stenotic tube system. To quantify the effect of first-order gradient motion refocusing (GMR), the signal intensity ratio from flow-compensated and -uncompensated images was calculated. For statistical analysis, multiple regression analysis and unpaired Student t test were used. RESULTS: In the flow model used, the length of PSL increased significantly with the degree of stenosis (beta ST' = 0.483 mm/%, beta ST" = 0.447 mm/%, p < 0.0001), flow velocity (beta v' = 0.297 s, beta v" = 0.213 s, p < 0.0001), and TE (beta TE = 1.88 mm/ms, p < 0.0001), respectively, whereas no correlation emerged for varying flip angles (beta alpha = 0.0214, p = 0.29). First-order GMR reduced significantly PSL in through-plane measurements (p < 0.0001). Maximal signal-enhancing effects of first-order GMR were observed 1-3 cm distal to the stenosis. CONCLUSION: Flow model parameters (i.e., degree of stenosis, flow velocity) markedly influenced the length of PSL that could be compensate for by use orf shortened TEs and first-order GMR. Varying flip angles had no significant influence on PSL.

Acrylic Resins↗
PubMedDate not supplied

Diffusion-weighted MR imaging lesions after filter-protected stenting of high-grade symptomatic carotid artery stenoses.

BACKGROUND AND PURPOSE: The clinical efficacy of filter devices in internal carotid artery (ICA) stent placement has been a matter of controversy. The aim of this retrospective study was to assess the number and extent of cerebral emboli, as represented by new lesions on diffusion-weighted MR imaging (DWI), in patients treated with filter-protected carotid stent placement. METHODS: Standard DWI (B0 = 1000) was performed within 48 hours before and 48 hours after filter-protected carotid stent placement in 50 patients with symptomatic, high grade (>70%), atherosclerotic ICA stenosis. Number, extent, and vascular territory of new DWI lesions after stent placement were assessed by consensus of 2 experienced neuroradiologists. Multifactorial statistical analysis was performed to determine risk factors associated with DWI lesions. RESULTS: New punctate DWI lesions with a median diameter of 2 mm were detected in 14 of 50 cases in the territory of the stented ICA and in 7 of 50 cases in other vascular territories. Median lesion load was 1 lesion (range, 1-15) per positive case in the stented ICA and 1 lesion (range, 1-7) in other vascular territories. All DWI lesions were clinically asymptomatic. Because of 1 hyperperfusion syndrome with temporary brain swelling, the 30-day stroke and death rate was 2%. Age >or =70 years was the only significant predictor for new DWI lesions, whereas sex, degree and site of stenosis, vascular risk factors, and stent and filter type showed no significant correlation. CONCLUSIONS: New DWI lesions after filter-protected carotid stent placement are substantially more frequent in the ipsilateral ICA territory compared with other vascular territories. Therefore, intraluminal filters cannot completely protect the brain from procedure-related embolization. However, individual lesion load and the risk of clinically relevant ischemia is low.

Aged↗