Biomedical subjects

M Lichtenstein

Publications and source records attributed to M Lichtenstein.

At least 37 records · Page 2Linked to original sources

PubMed1996

Assessment of left ventricular function after radiofrequency and direct current atrioventricular node ablation.

BACKGROUND: There is limited information available regarding the effect of catheter ablation of the antioventricular (AV) junction on left ventricular (LV) function. Both deterioration and improvement in LV function have been reported following direct current (DC) ablation of the AV junction. The deterioration of LV function following DC ablation of the AV junction may be due to the accompanying barotrauma, DC arcing and direct coagulation, or even the effects of chronic ventricular pacing. If this deterioration of LV function was a result of the accompanying effects of DC shock, the use of radiofrequency ablation (RF) should not result in deterioration of LV function. AIM: To study LV function before and after different methods of AV junction ablation and in patients with chronic ventricular pacing without AV junction ablation. MATERIAL: This study assessed LV function in patients following RF ablation, low energy DC ablation of the AV junction and compared the results with our previously reported finding in patients who had AV junction ablation using high energy DC shock. A group of patients undergoing permanent single chamber ventricular pacemaker implantation without AV junction ablation were selected as controls. METHODS: All patients were paced in the ventricle at 110 beats/minute during LV function assessment by radionuclide angiography. Global LV function and segmental wall motion abnormalities were assessed before, immediately following and three months after ablation. RESULTS: In the high energy DC ablation group, a fall in global LV function (50 +/- 3.0% to 43 +/- 3.0%, p = 0.02) and impairment of segmental wall motion were detected. Low energy DC ablation resulted in segmental wall motion impairment similar to high energy DC but without affecting global ejection fraction (47.0% +/- 6.7 to 45.5% +/- 3.1, p > 0.05). Neither RF ablation (44.0% +/- 3.3 to 45.3% +/- 3.5, p > 0.05), nor chronic pacing (46.7% +/- 4.9 to 47.0% +/- 2.9 p > 0.05) had any effect on global or segmental LV function. CONCLUSIONS: Low energy DC or RF ablation of the AV junction does not affect global LV ejection fraction. The deterioration of global LV function after high energy DC shock ablation appears to be related to the accompanying effects of DC energy and not to the effects of chronic ventricular pacing.

Adult↗

PubMed1996

Streptokinase increases luxury perfusion after stroke.

BACKGROUND AND PURPOSE: Recent acute stroke trials have reported that intravenous streptokinase is associated with an increased risk of adverse outcomes. We aimed to study the effect of streptokinase on the nature of reperfusion and the relation between reperfusion and clinical outcome. METHODS: We studied 24 patients in the Australian Streptokinase Trial with acute middle cerebral cortical infarction using 99mTc-hexamethylpropyleneamine oxime single-photon emission CT. Eleven of the 24 patients were scanned before therapy and again 24 hours later. The remaining 13 were scanned once either before therapy (1 patient) or after therapy (12 patients). All patients had outcome scans after 3 months. Infarct hypoperfusion was measured with a validated volumetric technique. Neurological impairment and functional outcome were assessed with the Canadian Neurological Scale and the Barthel Index, respectively. RESULTS: Fifteen patients received streptokinase and 9 received placebo. There was no difference in early reperfusion between streptokinase and placebo. However, streptokinase was associated with a greater amount of nonnutritional reperfusion than was placebo (P = .04). This luxury perfusion was associated with poor functional outcome (P = .02). CONCLUSIONS: This study suggests that streptokinase augments luxury perfusion after stroke. Luxury perfusion is associated with a worse outcome, which might be due in part to reperfusion injury.

Adult↗

PubMed1995

A controlled trial of cisapride in anorexia nervosa.

To determine the efficacy of cisapride, 10 mg three times daily, in improving gastric emptying, reducing distress during meals, and facilitating weight gain in anorexia nervosa, we conducted an 8-week, randomized, double-blind, placebo-controlled trial on 29 inpatients. Measures included scintigraphic gastric emptying studies at 0, 2, 4, and 8 weeks; subjective distress during meals measured by visual analogue scales; self-rating of degree of global improvement in symptoms associated with eating at end of study; and weight measured weekly. Gastric emptying improved significantly but equally in both groups over the study period. Yet subjective measures were better in the cisapride group; they rated themselves as more hungry (p = .02) and more improved on the global measure of change in symptoms (p = .02). Even so, the cisapride group did not gain more weight. The correlation between gastric emptying and weight gain was modest (r = .30; p = .11), and between gastric emptying and the subjective measures, virtually absent.

Adolescent↗

PubMed1995

Do Australian women have greater spinal bone density than North American women?

The interpretation of bone mineral densitometry results for a particular individual relies on valid reference data from a representative population sample. To establish local reference data, 411 Australian female volunteers had bone mineral densitometry performed at a single medical centre at the proximal femur and lumbar spine using a Hologic QDR 1000-W dual-energy X-ray absorptiometer. These data were compared with reference material from North American women compiled by Hologic. The Australian volunteers had, on average, 7% greater bone mineral density at the lumbar spine for the age range 25-55 years. Possible explanations for this include an actual population difference or the presence of a differential selection bias between the two samples.

Adolescent↗

PubMed1995

Crossed cerebellar diaschisis and brain recovery after stroke.

BACKGROUND AND PURPOSE: Although crossed cerebellar diaschisis is well recognized after stroke, there is controversy concerning its clinical correlations and serial changes, and little is known about its prognostic value. METHODS: We studied crossed cerebellar diaschisis and cerebral hypoperfusion in 47 patients with acute middle cerebral cortical infarction using 99mTc-hexamethylpropyleneamine oxime and single-photon emission computed tomography within 72 hours of stroke onset. Thirty-one of these patients had outcome studies at 3 months; 15 of the 31 underwent an additional scan after acetazolamide injection. Tissue loss was determined with computed tomography, performed at outcome in 28 patients. Clinical stroke severity was assessed with the Canadian Neurological Scale and Barthel Index. Cerebellar blood flow asymmetry was studied in 22 healthy, age-matched control subjects. RESULTS: Cerebellar blood flow asymmetry was significant in patients (mean +/- SE, 9.76 +/- 0.78%; P < .001) but not in control subjects (-0.22 +/- 0.56%). Crossed cerebellar diaschisis was strongly associated with infarct hypoperfusion volume at both acute (regression coefficient +/- SEb, b = 6.76 +/- 0.65; P < .001) and outcome stages (b = 6.13 +/- 0.63; P < .001). Cross-sectionally over the first 72 hours, infarct hypoperfusion volume decreased by 2% for each hour from onset (P < .05), while crossed cerebellar diaschisis remained unchanged. Canadian Neurological Scale score at the acute stage was negatively associated with acute crossed cerebellar diaschisis (b = -0.10 +/- 0.05; P < .05) after allowing for infarct hypoperfusion volume. Crossed cerebellar diaschisis did not change between acute-stage, outcome, and postacetazolamide scans. Acute-stage crossed cerebellar diaschisis predicted outcome Barthel Index score (b = -0.28 +/- 0.14; P = .05) and tissue loss (b = 3.81 +/- 0.96; P < .001) but was no longer an independent prognostic factor after allowing for acute-stage infarct hypoperfusion volume. CONCLUSIONS: This study shows that crossed cerebellar diaschisis is a functional phenomenon that correlates with both stroke severity and infarct hypoperfusion volume and persists despite neurological recovery. Although acute-stage crossed cerebellar diaschisis has no prognostic value independent of acute-stage hypoperfusion volume, it might indicate the proportion of nutritional to nonnutritional perfusion at the infarct site and hence be useful in the evaluation of reperfusion therapies in the acute stage.

Acetazolamide↗

PubMed1995

A prospective study of cortical scarring in acute febrile pyelonephritis in adults: clinical and bacteriological characteristics.

Previous reports have demonstrated lesions on computerized axial tomography (CT), and nuclear scintigraphy (DMSA) in acute pyelonephritis (PN). We undertook a prospective study of all patients presenting to our hospital with PN over 40 months. Patients who fulfilled diagnostic criteria, were treated with intravenous antibiotics. Excluding two who were pregnant, all patients had imaging by intravenous urography (IVU), CT and DMSA during their admission. Urine samples were collected prior to treatment. Patients without IVU evidence of cortical scarring but with parenchymal defects on CT and/or DMSA underwent a repeat DMSA three or more months after the acute episode. Of the 164 patients, 142 were female. E. coli was found in 116 patients. Forty-six patients had an abnormality on IVU. Of the 106 patients without IVU evidence of cortical scarring, 59 had a defect on CT and/or DMSA. Late DMSA scans in 35 of these 59 patients showed a persistent abnormality in 77%. E. coli characteristics such as P-fimbriae and Type 1 fimbriae were not predictive of acute imaging abnormalities. Inhibition of E. coli growth by the addition of EDTA was highly predictive of acute CT and DMSA abnormalities with a sensitivity of 83.3% and a specificity of 82.8%. Acute pyelonephritis is often associated with acute CT and/or DMSA abnormalities which may evolve into renal cortical scars. Acute scan abnormalities can be predicted by the presence of E. coli which were susceptible to EDTA in culture. Late scarring could not be predicted by clinical features, response to treatment or antibiotic used.

Acute Disease↗

PubMed1994

B cell-specific demethylation: a novel role for the intronic kappa chain enhancer sequence.

We studied the molecular mechanism of demethylation and its role in kappa chain gene regulation. Following transfection into B cell cultures, this gene undergoes regional demethylation in a process that is developmentally regulated in a lineage- and stage-specific manner. Although a germline V kappa promoter is not required for the demodification activity, a fragment containing the intronic kappa chain transcriptional enhancer and the nearby matrix attachment region is essential. In its natural location downstream to the J kappa 5 sequence, this element induces bidirectional demodification of plasmid constructs in a distance- and orientation-independent manner. When this enhancer is placed in an upstream position, however, the kappa gene remains modified and transcriptionally inactive, demonstrating that demethylation is required for kappa chain activation. These studies suggest that the kappa enhancer plays a dual role in regulating B cell differentiation by inducing demethylation and by promoting tissue-specific transcription.

Animals↗

PubMed1994

The Sickness Impact Profile for nursing homes (SIP-NH)

BACKGROUND: Valid, feasible measures of functional status are needed to evaluate the expanding nursing home population. This study attempts to increase relevance and reduce respondent burden of the Sickness Impact Profile (SIP) for nursing home residents while maintaining internal consistency and validity. METHODS: 231 residents from one academic and four community nursing homes, aged > or = 60 with a Mini-Mental State Exam score > or = 11, were study participants. Nominal group process was used to identify items and/or categories for removal. Candidate items were those that: represented restrictions of the nursing home environment, had weak item-total score correlations, and/or made minimal contribution to category internal consistency. Reduction was constrained by: minimum correlation of r = .90 between SIP and Sickness Impact Profile for Nursing Homes (SIP-NH) scores, coefficients alpha that fell within 95% confidence regions about predicted alpha. Convergent and discriminant validity were evaluated with the Katz Activities of Daily Living, Physical Disability Index, Geriatric Depression Scale, and Folstein Mini-Mental State Exam. RESULTS: The SIP-NH contains 66 items, a 51.5% reduction. Correlations between the SIP-NH and SIP were: total score r = .98, Physical dimension r = .97, and Psychosocial dimension r = .97. Alpha coefficients all fell within the 95% confidence regions. The SIP and the SIP-NH did not differ in correlations with validating instruments. CONCLUSIONS: The SIP-NH reduces respondent burden and has acceptable internal consistency and external validity. Potentially useful for discriminatory and predictive purposes, responsiveness to change will require longitudinal evaluation.

Activities of Daily Living↗

PubMed1993

A comparative study of radionuclide venography and contrast venography in the diagnosis of deep venous thrombosis.

BACKGROUND: The value of the radionuclide blood pool venogram in detecting deep venous thrombosis (DVT) has to date been inadequately evaluated. This is despite its lower complication rate than the gold standard of contrast X-ray venography. AIMS: To compare the relative accuracy and inter observer variability of radionuclide blood pool and X-ray contrast venography as well as evaluate previous literature on radionuclide venography. METHODS: Prospective comparison of radionuclide and contrast venography was performed in 39 patients. Sensitivity and specificity of radionuclide venography were compared to contrast venography and confidence intervals were measured using standard error calculations. A meta-analysis of previous studies was also performed. RESULTS: Significant inter observer variation in reports was present in both radionuclide (37%) and contrast (22%) venograms. Using consensus reports sensitivity of radionuclide venography was 87% compared to contrast venography and specificity was 83%. These results are similar to those obtained in previous studies. Furthermore, sensitivity in specificity in the proximal veins were 90% and 92% respectively which were superior to sensitivity and specificity in the distal veins where it was 74% and 90% respectively. CONCLUSION: The radionuclide venogram appears accurate in the proximal veins and in excluding but not diagnosing distal venous thrombosis.

Adult↗

PubMed1993

Cerebral hypoperfusion in stroke prognosis and brain recovery.

BACKGROUND AND PURPOSE: The value of acute cerebral blood flow measurements in stroke prognosis is controversial. No previous study has determined whether acute perfusion deficits independently add to a validated clinical prognostic score. We aimed to compare the value of acute hypoperfusion deficits with a quantitative clinical score in stroke prognosis and to correlate the changes in perfusion with brain recovery. METHODS: Volumetric analysis of regional hypoperfusion was performed in 38 patients with middle cerebral infarction within 72 hours of onset by use of single photon emission computed tomography and 99mTc hexamethylpropylene amine oxime. Stroke severity was assessed by the Canadian Neurological Score and Barthel Index. Allen's prognostic score was determined acutely in all patients. Clinical outcome was evaluated in 36 of 38 patients, of whom 18 had repeat blood flow studies. RESULTS: Acute hypoperfusion correlated with both the outcome Barthel Index (P < .001, r = -.61) and Canadian Neurological Score (P < .001, r = -.64). Allen's score correlated better with both the outcome Barthel Index (P < .001, r = .80) and Canadian Neurological Score (P < .001, r = .81). Acute hypoperfusion deficits, after allowing for Allen's score, independently predicted neurological but not functional outcome. Despite overall neurological improvement, mean hypoperfusion increased on the repeat blood flow studies (P < .05). CONCLUSIONS: Volumetric analysis of acute regional hypoperfusion within 72 hours of onset predicts stroke outcome after 3 months, but Allen's score is a better prognostic method. Neurological recovery is not associated with chronic infarct reperfusion.

Adult↗

PubMed1992

99Tcm-labelled IgG scanning does not predict the distribution of intestinal inflammation in patients with inflammatory bowel disease.

In order to assess the value of 99Tcm-labelled-immunoglobulin G(99Tcm-IgG) in the assessment of the activity and distribution of intestinal inflammation in patients with inflammatory bowel disease (IBD), 99Tcm-IgG scans were performed in 18 patients. Patients were divided clinically into two groups, those with (ten patients) and those without (eight patients), intestinal inflammation. Disease activity and distribution were assessed by 111In-oxine granulocyte scanning and/or histological extent of inflammation at endoscopy or surgery in all patients with IBD and most of those without intestinal inflammation. In the assessment of the presence or absence of inflammation, a sensitivity of 80% and specificity of 87% were achieved. However, when the localization of intestinal inflammation was evaluated, only five of eight true positive scans were concordant with the distribution of intestinal inflammation as determined by other methods. Thus, significant areas of inflammation were missed in five of ten patients with IBD (two false negative, three incorrect localization of inflammation). Although 99Tcm-IgG scanning appears to have moderate sensitivity and acceptable specificity in the detection of intestinal inflammation, it performs poorly in assessing the distribution of inflammation and is, therefore, of little value in the assessment of patients with suspected or proven IBD.

Australia↗

PubMed1992

The effect of aging on intact PTH and bone density in women.

OBJECTIVE: To determine whether age-related bone loss is negatively associated with serum intact parathyroid hormone (PTH). DESIGN: Survey. SETTING: University hospital outpatient department. PARTICIPANTS: 100 community-dwelling women, age 18 to 80, recruited as a convenience sample. MEASUREMENTS: Dependent variables--bone density at the spine and femoral neck by dual-energy X-ray absorptiometry. Independent variables--age, menopausal status (binary) and intact serum PTH by Allegro immunometric assay. RESULTS: Post-menopausal women had higher serum PTH and lower bone density of spine and femoral neck than premenopausal women. Bone density at the spine decreased with age, but this effect was accounted for by menopausal state. Bone density at the femoral neck decreased with age even after adjusting for menopause. Log PTH was negatively associated with bone density at the femoral neck but not significantly at the spine. Multiple regression analysis adjusting for age and menopause showed no significant association between intact PTH and bone density at the spine or the femoral neck. CONCLUSION: Although this study confirmed the rise in intact PTH with age, there is no evidence that this is the mediator of age-related bone loss.

Absorptiometry, Photon↗

PubMed1992

Correlations between cerebral arterial velocities, blood flow, and delayed ischemia after subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Elevated middle cerebral erythrocyte velocities and tissue hypoperfusion have been correlated with delayed ischemia after subarachnoid hemorrhage, but few studies have compared serial arterial velocities with cerebral blood flow and neurological deficits. METHODS: Serial measurements of middle cerebral velocities, using transcranial Doppler ultrasonography, were performed in 34 patients after subarachnoid hemorrhage and correlated with cerebral blood flow, measured in 20 of the 34 using single-photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime and neurological evidence of delayed ischemia. RESULTS: In 16 patients without delayed ischemia, eight had evidence of vasospasm (greater than 120 cm/sec), but only one of seven had hypoperfusion, suggesting that vasospasm might be more common than hypoperfusion in this group (p = 0.1). In 10 patients with delayed ischemia and a lateralizing deficit, both asymmetrical middle cerebral vasospasm (eight of nine with vasospasm) and hypoperfusion (six of six studied) were concordant with the clinically ischemic hemisphere (p less than 0.05). Vasospasm occurred with nonlateralized delayed ischemia in seven of eight patients and with hypoperfusion in five of six, affecting the anterior cerebral territory in three. CONCLUSIONS: Concordant vasospasm and hypoperfusion were most often present in patients with delayed ischemia and lateralizing neurological deficits. Discordant results reflect inherent limitations and the different levels of the circulation monitored by the two techniques.

Adult↗

PubMed1991

Ventricular dysfunction following direct-current shock atrioventricular junction ablation.

Catheter-induced His bundle ablation for refractory supraventricular arrhythmias is most commonly performed with direct-current shock energy of 200-300 joules. The high energy pulse delivered by direct-current shock produces a lesion in the atrioventricular node by fulguration, with the residual energy being dissipated as a pressure wave. The effect of direct-current shock His bundle ablation on global and regional ventricular function was assessed in 14 consecutive patients by radionuclide ventriculography performed before and after ablation and again three months later. All studies were performed with ventricular pacing at 110 bpm. Global left ventricular ejection fraction was found to be significantly reduced at the three month study (0.43 +/- 0.03 vs 0.50 +/- 0.03, pre ablation, p = 0.02). A significant reduction in wall-motion score was also seen in six of the seven patients who had normal wall motion in pacing rhythm prior to ablation. Deterioration was mainly seen at the left and right ventricular apices. The observed reduction in ventricular function that follows direct-current shock His bundle ablation may result from myocardial damage from electro-coagulation or from barotrauma and supports continued investigation into alternative, less traumatic energy sources for the procedure.

Adult↗

PubMed1991

Value of positive technetium-99m leucocyte scans in predicting intestinal inflammation.

The value of positive scans of autologous 99mTc-labelled leucocytes in the detection of intestinal inflammation was assessed in 29 patients with known inflammatory bowel disease and a high probability of intestinal inflammation and 58 with a low probability of intestinal inflammation comprising 37 with intestinal symptoms and 21 with suspected abscess. Autologous leucocytes were labelled with 99mTc using either of the established methods. In patients with inflammatory bowel disease, 3/13 with ileocaecal and 1/11 with colonic accumulation of 99mTc were incorrectly diagnosed in that there was no histological evidence of inflammation in those regions. In the low probability patients, all 26 positive images were false positives: there were 19 in the ileocaecal and 7 in colonic regions and no differences between the two subgroups. False positives were more common in low probability than high probability patients (p = 0.011). The results were independent of the 99mTc cell labelling technique used. Three false positive patients also had normal scans for 111In-labelled granulocytes. The time of first detection of 99mTc in the bowel was earlier in true than in false positive patients (92% v 33% within 1 h, p = 0.008), the false positive rates in the first hour of imaging being 5% in high and 15% in low probability patients. In 99mTc scintigraphy, the appearance of the isotope in the intestine occurs commonly in the absence of inflammation irrespective of the cell labelling technique used. In high probability patients, imaging at 1 h can more reliably discriminate true from false positives and retain clinical usefulness. In low probability patients specificity remains unacceptable and 99mTc-labelled leucocyte scanning in these patients is of little value as a positive predictor of intestinal inflammation.

Adolescent↗

PubMed1991

The influence of epidural blockade and pethidine administered during delivery on neonatal myocardial performance.

The aim of the present study was to investigate whether obstetric analgesia with an epidural blockade (Marcaine, bupivacaine hydrochloride, 141.5 +/- 56.8 mg) and pethidine (95.0 +/- 30.7 mg) influenced neonatal myocardial function following vaginal delivery. Left ventricular output and other left ventricular function indices were measured 5.6 +/- 4.3 h postpartum with Doppler and M-mode echocardiography in a group of healthy, full-term, appropriate-for-gestational-age infants (n = 10) whose mothers had received both bupivacaine and pethidine during delivery, and in a similar group of newborn infants (n = 10) whose mothers had received only nitrous oxide/oxygen analgesia. In 7 of the 10 infants in each groups, a second assessment of myocardial function was performed 21.7 +/- 4.6 h post partum. There were no significant differences in any of the variables used to assess left ventricular function at either of the measurement points between the group of infants whose mothers had received bupivacaine/pethidine during delivery, and the group of infants whose mothers had received nitrous oxide/oxygen analgesia only.

Anesthesia, Epidural↗

PubMed1990

Demethylation of genes in animal cells.

Tissue-specific animal cell genes are usually fully methylated in the germ line and become demethylated in those cell types in which they are expressed. To investigate this process, we inserted a methylated IgG kappa gene into fibroblasts and lymphocytes at various stages of development. The results show that this gene undergoes demethylation only in the mature lymphocytes and therefore suggest that the ability to demethylate a gene is developmentally regulated. These studies were supported by similar experiments using the rat Insulin I gene, and in this case it appears that the cis-acting elements that control demethylation may be different from those responsible for gene activation. The ability to demethylate the housekeeping gene APRT is also under developmental control, because this occurs only in embryonic cells, both in tissue culture and in transgenic mice.

Adenine Phosphoribosyltransferase↗

PubMed1990

Incorporating severity of illness into estimates of likelihood ratios.

Although severity of illness may affect the usefulness of a diagnostic test, most previous work has considered test performance only in the dichotomous situation where the target disorder is considered present or absent. In this paper, a clinical example is provided and two methods presented whereby illness severity may be incorporated into the determination of likelihood ratios for a diagnostic test. The use of this approach is that given a test result, a clinician may determine the post-test probability of all levels of the illness in the patient under study.

Alcohol Drinking↗