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Biomedical subjects

A Antoniou

Publications and source records attributed to A Antoniou.

52 records · Page 3Linked to original sources
PubMed1990

Use of intravenous adenosine in sinus rhythm as a diagnostic test for latent preexcitation.

In a proportion of patients with left free wall accessory connections, preexcitation is apparent only during atrial arrhythmias or atrial pacing (latent preexcitation). These patients may be at risk of a rapid ventricular response to atrial fibrillation despite the absence of preexcitation in sinus rhythm. The ability of intravenous adenosine to unmask latent preexcitation was evaluated in 22 patients with a history of documented supraventricular tachycardia and a normal electrocardiogram during sinus rhythm. Preexcitation was unmasked in response to adenosine in 4 patients: all 4 were shown to have latent preexcitation at electrophysiologic study. In 12 patients atrioventricular (AV) nodal conduction delay or block was induced without preexcitation after adenosine (first-degree AV block in 8, second-degree block in 4): at subsequent electrophysiologic study none of these patients was found to have latent preexcitation. Five patients had little or no PR prolongation in response to adenosine: of these, 2 were shown to have latent preexcitation at electrophysiologic study. Atrial fibrillation was induced in 1 patient and a narrow complex regular tachycardia in another after intravenous adenosine. Intravenous adenosine during sinus rhythm is capable of producing AV nodal conduction delay or block in 73% of patients with a history of supraventricular tachycardia: in these patients adenosine provides a diagnostic test that is both 100% sensitive and 100% specific for latent preexcitation. In those patients in whom adenosine does not produce AV conduction delay or block, further investigation is required to establish or refute the diagnosis of latent preexcitation.

Adenosine↗
PubMed1990

The interaction of criterion and feedback information in learning a drawing task.

Experiments were designed to examine the influence of criterion and feedback information in the learning of a two-dimensional drawing task. Experiment 1 showed that when the task criterion is well known to the subject, the combined presentation of criterion information and information feedback facilitates the rate of acquisition of the skill but not its overall performance level of achievement. Experiment 2 showed that when the task criterion information is not well known to the subject, presentation of criterion information facilitates both the rate of acquisition and the overall performance level and, furthermore, is essential if configuration information feedback is to be utilized effectively. Experiment 3 showed that it is the combined presentation of criterion and configuration information feedback rather than the isolate presentation of either type of information alone, that facilitates learning and performance. Collectively, the findings from the three experiments suggest an interactive effect of prior knowledge by the learner and type of augmented information in facilitating the acquisition of skill, according to the constraints imposed in the task. The data are consistent with the proposal that the degrees of freedom in the information available to support motor skill learning must match the degrees of freedom to be constraint in the perceptual-motor workspace.

Journal Article↗
PubMed1990

Two 46,XX,t(X;Y) females with linear skin defects and congenital microphthalmia: a new syndrome at Xp22.3.

We describe two females with de novo X;Y translocations, who presented at birth with irregular linear areas of erythematous skin hypoplasia involving the head and neck, along with eye findings that included microphthalmia, corneal opacities, and orbital cysts. The features in these children are similar to but distinct from those seen in females with Goltz syndrome and incontinentia pigmenti. Cytogenetic analysis has shown the X chromosome breakpoint in both females to be at Xp22.3. We suggest that this syndrome is the result of a deletion or disruption of DNA sequences in the region of Xp22.3.

Corneal Opacity↗
PubMed1989

Misuse of verapamil in pre-excited atrial fibrillation.

Of 18 patients who attended accident and emergency departments with pre-excited atrial fibrillation, 10 were inappropriately treated with intravenous verapamil. The reason for the inappropriate treatment was misdiagnosis of the arrhythmia, although diagnostic electrocardiograms were available for all patients: in only 3 of the 18 patients was the correct diagnosis made before intervention. Misdiagnosis occurred because of failure to consider pre-excitation as a possible diagnosis, rather than bias towards a single alternative arrhythmia. The use of intravenous verapamil was associated with deterioration in the clinical condition of 6 patients and continued arrhythmia in all 10.

Adolescent↗
PubMed1989

Reliability of minute ventilation as a parameter for rate responsive pacing.

A minute ventilation sensing rate responsive pacemaker was implanted in 11 patients with bradycardias. Their mean age was 59 +/- 4 years (mean +/- SEM). The pacemaker measures minute ventilation by sensing intravascular impedance using a standard bipolar electrode. The rate responsive programming was simple: apart from ascribing an upper and lower rate, the only programmable parameter was the slope of rate response. This could be derived approximately by assessing the suggested slope value during an exercise test in the 'adaptive VVI' mode. Compared with exercise in the VVI mode, symptom limited treadmill tests in the rate responsive mode showed a 33% improvement of exercise capacity and a 44% improvement of cardiac output as determined noninvasively by continuous wave Doppler measurements of the ascending aortic blood flow. The pacing rate was appropriately increased during a variety of daily activities such as walking at different speeds and gradients, and ascending and descending stairs. Voluntary interference of the respiratory pattern such as during coughing and hyperventilation increased the pacing rate from a resting rate of 70 bpm to 111 +/- 10 and 86 +/- 4 bpm respectively. Continuous talking during exercise attenuated the expected rate response. The pacemaker can sense activity induced by arm swinging. In conclusion, the Meta pacemaker improved cardiac output and exercise capacity in patients with bradycardias. Its rate response was related to workload. Although voluntary interference affected the pacing rate, excessive rate acceleration was not encountered.

Adult↗
PubMed1988

The influence of different amounts of clomiphene citrate on follicle-stimulating hormone, luteinizing hormone and estradiol levels and on the number and maturation of follicles.

Sixty-eight anovulatory women were divided into three groups according to the administered doses of clomiphene citrate (CC) (A 250 mg, B 500 mg, C 750 mg). Daily follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2) measurements were performed. Follicular maturation was monitored by ultrasound. In the high-CC dose group, a statistically significant FSH rise was noted. As a result, earlier selection of the dominant follicle (DF), faster increase in the DF diameter and increased E2 production was found.

Adult↗
PubMed1988

Initial clinical experience with a minute ventilation sensing rate modulated pacemaker: improvements in exercise capacity and symptomatology.

A minute ventilation sensing rate modulated pacemaker was implanted in nine patients with bradycardia. Minute ventilation is sensed in this pacemaker by means of a standard bipolar pacing electrode. Compared with exercise in the constant rate ventricular pacing (VVI) mode at 1 month after pacemaker implantation, rate responsive pacing resulted in an improvement of exercise capacity of 33 +/- 5% (from 437 +/- 42 s in the VVI mode to 593 +/- 57 s in the rate modulated mode, P less than 0.01, Bruce protocol). This improvement was maintained in the seven patients in whom an exercise test was repeated at 3 months after implantation. The pacing rate was significantly correlated with oxygen consumption (r = 0.84 +/- 0.04) and measured minute ventilation (r = 0.76 +/- 0.06). Symptomatology in these patients was assessed by means of self-assessment questionnaires in a double blind, randomized cross-over study in which the pacemaker was alternatively programmed into the VVI and rate modulated modes. Significant improvements in "shortness of breath" and "energy during daily activities" were documented during rate modulated pacing and "palpitations" and "chest pain" were not worsened. Most patients preferred the rate modulated mode during the study. In conclusion, rate modulated pacing by sensing minute ventilation resulted in better exercise capacity and symptomatology. The pacing rate also showed good correlation with the individual's oxygen requirement.

Adult↗
PubMedDate not supplied

Imaging and localization of pancreatic insulinomas.

For pancreatic insulinomas, the treatment of choice is surgical excision, which when successful is curative. Intraoperative palpation combined with ultrasonography theoretically depict almost all tumors, however the accuracy of palpation is improved by the preoperative localization. All recent advances in imaging have improved the likelihood for curative surgical resection. Our purpose is to demonstrate the characteristics of all modalities, which may be used in the preoperative localization algorithm.

Algorithms↗
PubMedDate not supplied

Male breast myofibroblastoma and MR findings.

Myofibroblastoma of the breast is a rare benign tumor seen predominantly in men in the sixth to seventh decades of life. We present a case of breast myofibroblastoma in a man and describe the mammographic, sonographic, and MR findings.

Aged↗
PubMedDate not supplied

Surgical outcome of carotid artery disease: analysis of 367 carotid endarterectomies.

Carotid endarterectomy is a method of prophylaxis. A total of 367 carotid endarterectomies in 335 patients were performed during the period of 1989-1997: 222 (66.3%) were symptomatic and 113 (33.7%) asymptomatic patients. In all, 262 (78.2%) had unilateral, 41 (12.2%) contralateral occlusion and 32 (9.6%) bilateral artery disease. All were operated on under general anesthesia without using shunt or patch. Of the patients with bilateral occlusive disease, 17 underwent simultaneous and 15 staged endarterectomy. The mortality rate of the first 30 postoperative days was 1.19% and the mortality/stroke rate 2.38%. Transient neurogenic dysfunction occurred in 3.68%, myocardial ischemia in 0.89%, and postoperative hypertension in 16.7%. Endarterectomy of symptomatic and asymptomatic patients with unilateral localisation, contralateral occlusion or bilateral occlusive disease remains a highly acceptable prophylactic method. The future will show whether other endovascular procedures affect the broad application of carotid endarterectomy.

Aged↗
PubMedDate not supplied

Hepatic epithelioid hemangioendothelioma: MR imaging findings.

We describe the sonographic, computed tomography and magnetic resonance imaging findings of two patients with histologically proven hepatic hemangioendothelioma. Both patients presented with multiple liver nodules. Color Doppler ultrasound demonstrated moderate vascularity at the periphery of the nodules, as well as central neovascularity. On enchanced computed tomography images, the lesions showed peripheral enhancement only. On magnetic resonance images, tumor signal was low on T1-weighted and moderately high on T2-weighted images. The distinction between normal liver and tumor was difficult on all sequences. Administration of superparamagnetic iron oxide particles delineated well the tumor by suppressing the signal of the normal liver and better depicted areas of remaining healthy parenchyma.

Adolescent↗
PubMedDate not supplied

MRI and ultrasonographic findings in the investigation of lymphedema and lipedema.

METHODS: Twenty-four healthy subjects and 16 patients with lymphedema and lipedema were studied with MRI and ultratomography. RESULTS: In chronic lymphedema, ultrasonography revealed a statistically significant increase of the subcutaneous fat without difference in skin thickness as compared to the healthy subjects. MRI revealed in lymphedema a statistically significant increase of skin thickness + subcutaneous tissue + muscular mass (p = 0.048); in lipedema, a statistically significant increase of skin thickness and subcutaneous tissue (p < 0.0001) as compared to the healthy controls. CONCLUSIONS: MRI offers strong qualitative and quantitative parameters in the diagnosis of lymphedema and lipolymphedema, while ultrasonography is expected to improve its diagnostic efficiency with the aid of high frequency echo with more sophisticated resolution apparatus. Age, weight and height of the patient as well as duration of the disease do not seem to affect the above-mentioned parameters.

Adipose Tissue↗