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Biomedical subjects

Martin A Ritter

Publications and source records attributed to Martin A Ritter.

10 recordsLinked to original sources
PubMed2006

CT angiography in acute stroke: does it provide additional information on occurrence of infarction and functional outcome after 3 months?

OBJECTIVE: To investigate whether acute phase intracranial CT angiography (CTA) independently predicts infarction and functional outcome in ischemic stroke. METHODS: Hundred and fifty-one consecutive patients with acute (<12 h) ischemic stroke who received intracranial CTA were investigated. Stroke severity on admission was determined using the National Institute of Health Stroke Scale (NIHSS). Reconstructed CTAs were investigated for relevant pathology. Follow-up imaging was performed 24-48 h after admission. Functional outcome was assessed after 3 months using the modified Rankin scale. Single factor and multiple logistic regression analyses were performed to predict infarction and dependency (modified Rankin scale > or = 3) on follow-up. RESULTS: Median NIHSS on admission was 10 (IQR 3-14). Out of the 151 patients, 61 (40%) had pathological CTA findings. Infarction was demonstrated in 60/61 patients (98%) with and in 67/90 patients (74%) without vessel pathology. Presence of infarction on follow-up imaging and dependency at 3 months were correlated with pathological CTA findings on admission in single factor analysis (each p < 0.001). After adjustment for age (> or =/<65 years), NIHSS (> or =/<10), sex, therapy, and time to presentation (> or =/<3 h), only NIHSS > or = 10 on admission was predictive of dependency at follow-up (p < 0.001). CONCLUSIONS: Pathological CTA findings in the acute phase of ischemic stroke do not independently predict a poor outcome at 3 months after acute stroke.

Acute Disease↗
PubMed2006

The use of embolic signal detection in multicenter trials to evaluate antiplatelet efficacy: signal analysis and quality control mechanisms in the CARESS (Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic carotid Stenosis) trial.

BACKGROUND AND PURPOSE: The CARESS (Clopidogrel and Aspirin for Reduction of Emboli in Symptomatic carotid Stenosis) trial proved the effectiveness of the combination of clopidogrel and aspirin compared with aspirin alone in reducing presence and number of microembolic signals (MES) in patients with recently symptomatic carotid stenosis. The present study aimed at installing primary and secondary quality control measures in CARESS because MES evaluation relies on subjective judgment by human experts. METHODS: As primary quality control, centers participating in CARESS evaluated a reference digital audio tape (DAT) before the study containing both MES and artifacts. Interobserver agreement of classifying signals as MES was expressed as proportions of specific agreement of positive ratings (ps+/-values). For all DATs included in CARESS (n=300), online number of MES and off-line number of MES read by the central reader were compared using correlation coefficients. As secondary control, a sample of 16 of 300 DATs was cross-validated by another independent reader (post-trial validator). RESULTS: For the reference tape, the cumulative ps+/-value was 0.894 based on 12 of 14 observers. Two observers with very different results improved after a training procedure. Agreement between post-trial validator and central reader was ps+=0.805, indicating very good agreement. Correlation between online evaluation and off-line evaluation of DATs was very good overall (cumulative rho=0.84; P<0.001). CONCLUSIONS: Multicenter studies using MES as outcome parameter are feasible. However, primary and secondary quality control procedures are important.

Aspirin↗
PubMed2006

Treatment of cremaster synkinesias with botulinum toxin A: a video case report.

Synkinesias secondary to nerve lesions and aberrant re-innervation are well-known phenomena especially after lesions of the facial nerve. Synkinesias can successfully be treated with botulinum toxin A (BTx A). Synkinesias of the cremaster muscle have not been described or treated to date. We present the case of a 62-year-old man who developed synkinesias of both cremaster muscles after extensive laparatomy for esophageal cancer. Treatment of synkinesias with various oral medications had been unsuccessful. Electromyography-guided injections of BTx A in both cremaster muscles (15 MU on the right and 10 on the left) led to significant symptom relief for an average of 8 weeks. We present the case including pre- and posttreatment video clips.

Botulinum Toxins, Type A↗
PubMed2005

Benefit of echocontrast-enhanced transcranial arterial color-coded duplex ultrasound.

OBJECTIVES: Proper assessment of the intracranial arteries by transcranial color-coded duplex sonography (TCCD) 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. MATERIAL AND METHODS: We investigated 67 temporal windows of 47 patients with insufficient native transtemporal insonation conditions before and after the application of the second-generation (gas-filled) microbubble contrast agent Sonovue (in 20 patients out of these 47, both temporal windows were insufficient, in the remaining 27 only one side). RESULTS: As compared to 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). With the help of contrast medium, flow velocity in the middle cerebral artery could be measured through 65 windows as compared to only 26 windows before contrast was applied (p < 0.0001). CONCLUSIONS: In patients with poor precontrast visualization of intracranial arteries, echocontrast-enhanced TCCD is very helpful.

Adult↗
PubMed2004

Platelets in patients with acute ischemic stroke are exhausted and refractory to thrombin, due to cleavage of the seven-transmembrane thrombin receptor (PAR-1).

Platelet activation is involved in the pathogenesis of cerebrovascular ischemia, but the major agonist involved has yet to be identified. To investigate the role of thrombin in platelet activation in patients with acute ischemic stroke, and while thrombin is the most likely candidate for activation of the thrombin receptor PAR-1 in vivo, we assessed its cleavage and internalization using the antibodies SPAN12, binding to uncleaved PAR-1, and WEDE15, recognizing cleaved and uncleaved, but not internalized PAR-1. In contrast to healthy age-matched controls, platelets from stroke patients exhibited significant cleavage and internalization of PAR-1 (P<0.001) and failed to respond to thrombin in vitro. Enhanced surface expression of CD62P, CD63, TSP-1 and less mepacrine uptake showed platelet degranulation during stroke. Platelets from patients with acute cerebral ischemia are exhausted and desensitized to thrombin through cleavage of PAR-1, indicating that high concentrations of thrombin occur with acute cerebrovascular ischemic events in vivo.

Acute Disease↗
PubMed2002

Microembolus detection by transcranial doppler sonography.

Microembolic signals can be detected by transcranial ultrasound as signals of high intensity and short duration. These signals represent circulating gaseous or solid particles. To optimize the differentiation from artefacts and the background signal and to facilitate the clinical use, several attempts have been made to automatize the detection of microemboli. Microemboli occur spontaneously in various clinical situations but their clinical impact and possible therapeutical implications are still under debate. This article provides a review of the actual literature concerning the current state of technical and clinical aspects of microembolus detection.

Artifacts↗
PubMed2002

Follow-up examinations by transcranial Doppler ultrasound in primary angiitis of the central nervous system.

BACKGROUND: Primary angiitis of the central nervous system (PACNS) is a rare disease. The definite diagnosis is made upon proof of mononuclear inflammation of the vessel wall on brain biopsy. The diagnosis can also be established on clinical grounds, typical findings on intra-arterial angiography and other investigatory grounds excluding other diseases. Therapy comprises an aggressive immunosuppressive approach. Close monitoring of the patients is mandatory. Transcranial Doppler ultrasound (TCD) has not yet been used to follow up the vasculitic lesions in PACNS. CASE: We report on a 32-year-old female with massive cerebral infarctions secondary to multiple large-vessel stenoses because of probable PACNS. The patient was followed closely by means of TCD. During therapy the cerebral blood flow velocities normalized as displayed by TCD. Clinical improvement followed several days after normalization of cerebral blood flow. CONCLUSIONS: TCD is a valuable noninvasive bedside tool to monitor cerebral blood flow velocities and therapy response in patients with cerebral vasculitis, if large arteries are involved.

Adult↗
PubMed2002

The Venturi effect and cerebrovascular ultrasound.

BACKGROUND: One of the most frequent diagnostic pitfalls in cerebrovascular ultrasound is the evaluation of the vertebrobasilar system in the case of vertebral artery (VA) hypoplasia because the diagnostic findings are sometimes suggestive of significant pathologies, but may be completely normal as well. The Venturi effect is a phenomenon of hydrodynamics which describes a drop in hydrostatic pressure along areas of high flow velocities. METHOD: We review the physical background of the Venturi effect and describe how it can explain both physiological and pathological flow phenomena encountered during cerebrovascular ultrasound investigations. We focused on flow phenomena at the vertebrobasilar junction by theoretically calculating conditions with different influx angles and flow velocities on two-dimensional digital subtraction angiography images. In the discussion, we also address other areas of cerebrovascular ultrasound, where the Venturi effect is of particular interest. RESULTS AND CONCLUSIONS: The blood flow velocity within the VAs and the angle between a hypoplastic VA and the basilar artery (BA) are important determinants of the intraluminal pressures of these arteries and thus their resistances. In the case of angles below 90 degrees between the distal VA and the BA, abnormal extracranial flow profiles may suggest downstream VA stenosis or occlusion, whereas in the case of angles above 90 degrees, a diagnosis of an AV fistula downstream to the V4 segment may be assumed. Furthermore, various hemodynamic effects at the site of a stenosis of the brain supplying arteries can also be explained by a transstenotic pressure drop created by the Venturi effect, particularly the generation of musical murmurs. The systolic dip ('systolic deceleration') at the origin of the VA due to subclavian artery stenosis is also a consequence of the Venturi effect.

Blood Flow Velocity↗
PubMed2002

Carotid artery auscultation--anachronism or useful screening procedure?

Carotid bruits are supposed to indicate the presence of high-grade common carotid or extracranial internal carotid artery stenosis in a large proportion of patients. Using a stethoscope, we prospectively auscultated 273 carotid arteries of 145 patients blinded to the results of a complete extracranial and intracranial Doppler investigation including extracranial color-coded duplex ultrasound. Fifty-four arteries showed stenosis of > or = 50%-99%, or occlusion of the extracranial internal or the common carotid artery. In 25 of these arteries, a bruit was present. In 9 out of 16 patients with extracranial stenosis from 70%-99%, a bruit was detected. In one additional patient with a middle-grade external carotid artery stenosis, a bruit was also present. In seven additional patients, a bruit was present in the absence of any carotid artery stenosis, cardiac vitium or goiter. The sensitivity of carotid auscultation for the detection of a 70%-99% stenosis of the common or extracranial internal carotid artery was 56% and specificity was 91%. The positive predictive value of a bruit found during carotid auscultation was 27%, and the negative predictive value of a normal auscultation was 97%. Carotid auscultation is a useful screening procedure in the detection of carotid stenosis or occlusion, but requires confirmation by carotid ultrasound.

Adult↗