Biomedical subjects
Publications and source records attributed to E Zanette.
Right-to-left shunt due to patent foramen ovale is a well-established risk factor for ischemic stroke, especially in young subjects and in patients with cryptogenic stroke. We report a detailed method for the diagnosis of a right-to-left shunt by means of transcranial Doppler as established at a recent consensus conference, and review the literature on the indications for the test.
We investigated the effects of apomorphine administration at two different doses (2-10 micrograms/kg, s.c.) in 35 migraineurs in headache-free period and in 20 age-matched healthy control subjects, with and without pretreatment with domperidone. Neither patients or controls complained of headache at either dose, whereas at the dose of 10 micrograms/kg migraineurs showed a statistically significant higher incidence of dopaminergic symptoms (nausea, vomiting, drowsiness, yawning, dizziness, sweating) than controls. Furthermore, symptoms due to postsynaptic dopamine receptors activation (i.e., nausea and vomiting) only appeared in migraineurs. No symptom, however, resembled those characterizing a spontaneous migraine attack. In conclusion, migraineurs show a lower threshold for dopamine receptor activation than normal subjects.
OBJECTIVE: To estimate the prevalence and outcome of symptomatic internal carotid artery lesions in young adults. DESIGN: Multicentre hospital based observational study with five year follow up. SETTING: Seven neurological departments in northern and central Italy. SUBJECTS: 240 patients (115 men) aged 15-44 with a recent transient ischaemic attack or stroke in the carotid territory. MAIN OUTCOME MEASURES: (a) Prevalence of symptomatic internal carotid artery stenosis or occlusion detected by continuous wave Doppler ultrasonography at entry; (b) incidence rates of cerebral, cardiac, and non-vascular death; non-fatal stroke; and non-fatal myocardial infarction. RESULTS: Carotid stenoses of 50-99% and occlusions were found in 38 patients (15.8%). Both conditions were significantly more frequent in patients aged over 35 and in those with hypertension, diabetes mellitus, and stroke at entry. The standardised mortality ratio at five years was 10.5 (95% confidence interval 5.0 to 19.3). Survival of patients with stenoses of 0-49% and occlusions was significantly better than that of patients with stenoses of 50-99%. Carotid stenosis of 50-99% was an independent predictor of death (hazard ratio 7.9; 95% confidence interval 2.2 to 29) and non-fatal stroke (hazard ratio 7.4; 1.5 to 37.4). CONCLUSIONS: The prevalence of carotid stenosis or occlusion in young adults after a cerebrovascular event is low. Though patients with high grade symptomatic carotid stenosis are at risk of non-fetal and fetal events, patients with internal artery occlusion apparently have a benign prognosis.
A compression method is presented for medical images based on neural networks and vector quantisation (VQ). The neural net is a perceptron and it is followed by some expressly designed VQ algorithms. The method devotes special attention to the quality of the reconstructed images and to the reduction of artefacts. The compression ratio obtained in the long run with echographic images is greater than 50:1 with good quality.
There are different approaches to the assessment of acute stroke. Its causes, its severity, and/or its final prognosis may be investigated. The traditional approach is anatomoclinical. It is basically limited to finding out if the lesion is a hemorrhage or an ischemia, and its location. This approach is derived from and supported by the fact that acute stroke is still without a valid therapy. In our opinion, not stroke but individual patients presenting with stroke should be treated. The pathophysiology of the individual stroke should be investigated by means of new techniques: magnetic resonance, emission tomography, and transcranial Doppler. These new techniques will be important in the future, making it possible to create effective therapeutic strategies, designed for treating a particular subgroup of patients, as in the case of fibrinolytic agents. The main aspects of these new techniques for evaluating acute ischemic stroke have been reviewed in this article.
In assessing the level of stenosis in extracranial Doppler analysis, spectral analysis has until now been used qualitatively, for the most part. Owing to the many variables affecting the measurements (mainly noise level and instrument setting made subjectively by the operator), the reliability of the inferences on the degree of stenosis is not clearly definable. Under such conditions the need arises for algorithms and systems that can estimate spectral parameters with a higher degree of accuracy, to verify whether reliable inferences can indeed by made or if this technique is only a qualitative one. In the paper a real-time spectral analysis system is described. The system relies on a new spectral estimation algorithm which gives estimates with good robustness with respect to noise. Moreover, a clear measurement procedure which eliminates the many subjective factors affecting the estimates has also been proposed and used. The system has been evaluated with simulated signals and in clinical trials and has shown better performance than the commonly used commercial analysers.
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Sixty-three patients (115 carotid arteries) have been examined first by Dopplersonography, then by echotomography and finally by angiography using the Seldinger technique. The comparison between echotomography and angiography showed a sensitivity of 0.9, a specificity of 0.7 and a accuracy of 0.8. There have been 15 false positive results; in 14 of them the lesions were lower than 10% of lumen reduction and in one case there was a 10-45% stenosis. It seems that echotomography can better estimate lower degree lesions. It was difficult for echotomography to detect correctly the presence of an occlusion and to evaluate the surface aspect mainly in the presence of ulcerations.
Near infrared spectroscopy, a recently developed optoelectronic technique, has been studied as a possible method of monitoring the adequacy of cerebral perfusion in 22 patients who were candidates for carotid endarterectomy. Using this technique, changes in haemoglobin volume, haemoglobin oxygen saturation and redox level of cytochrome-c-oxidase were recorded from the frontoparietal region during routine carotid compression tests performed under continuous electroencephalographic (EEG) monitoring. A highly significant association was found between EEG slowing, indicating impaired cerebral function, and a fall in haemoglobin volume and oxygen saturation, indicating a reduced blood and oxygen supply to the brain (Fisher exact test, P less than 10(-5]. In a few tests haemoglobin volume and oxygen saturation were reduced without changes in the EEG recording. This study raises new issues concerning the compensatory mechanisms taking place during carotid occlusion and suggests that near infrared spectroscopy might be useful in monitoring the blood and oxygen supply to the brain during carotid endarterectomy.
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The present study has been devoted to the analysis of 120 patients presenting with reversible focal cerebral ischemia without conventional signs of cardiopathy and/or relevant atherosclerotic disease. In 77% of the patients vascular risk factors, such as hypertension or hyperlipemia, were present. In 23% of the patients, no abnormal finding was discovered at clinical, hematochemical and cardiological examinations. In these patients a further cardiological evaluation was performed with echocardiography. Dynamic electrocardiography was performed in 52 patients. Echocardiography and dynamic electrocardiography revealed the occurrence of 6 cases of mitral valve prolapse (MVP), 2 cases of frequent premature ventricular beats, and 1 proximal atrial arrhythmia. All 6 cases of MVP were detected in the subgroups of patients without vascular risk factors. In our patients younger than 45 years, the relative frequency of MVP attains 21.5%. This study confirms that MVP has to be regarded as a risk factor for focal cerebral ischemia in young patients.
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An international Consensus Meeting to determine a standard in the examination technique for the detection of right-to-left shunt (RLS) using contrast transcranial Doppler sonography (TCD) led to the following recommendations to standardize the examination procedure: The patient should be prepared with an 18-gauge needle inserted into the cubital vein and should be in the supine position. Insonation of at least one middle cerebral artery (MCA) using TCD is performed. The contrast agent is prepared using 9 ml isotonic saline solution and 1 ml air mixed with a three-way stopcock by exchange of saline/air mixture between the syringes and injected as a bolus. In case of little or no detection of microbubbles (MB) in the MCA under basal conditions, the examination will be repeated using the Valsalva maneuver (VM). Contrast agent will be injected 5 s before the start of the VM; the overall VM duration should be 10 s. The patient should start the VM on examiner's command. The strength of the VM can be controlled by peak flow velocity of the Doppler curve. The time when the first MB appears at the MCA level will be noted. A four-level categorization according to the MB count should be applied: (1) 0 MB (negative result); (2) 1-10 MB; (3) >10 MB and no curtain, and (4) curtain. ('Curtain' refers to a shower of MB, where a single bubble cannot be identified.) The results should be documented for basal condition and VM testing separately. The clinical significance of the diagnosis of a RLS in a particular patient is not fully evaluated and requires further studies. A minimum amount of MB suggestive of a clinical relevant RLS is not yet established. It probably depends on interindividual differences in hemodynamics that are currently not fully understood. Transesophageal echocardiography remains the gold standard for detection of a patent foramen ovale or an atrial septum defect. However, TCD with a contrast agent has been turned out as a potential method to diagnose a RLS in several studies which have been published during the last years, and a RLS other than at the atrial level may be detected only by this method. Furthermore, the VM can be applied more comfortably and more reliably during Doppler examination than during transesophageal echocardiography.