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Biomedical subjects

M Simons

Publications and source records attributed to M Simons.

At least 235 records · Page 13Linked to original sources
PubMedDate not supplied

Non-equilibrium dynamics as an indispensable characteristic of a healthy biological system.

Healthy systems in physiology and medicine are remarkable for their structural variability and dynamical complexity. The concept of fractal growth and form offers novel approaches to understanding morphogenesis and function from the level of the gene to the organism. For example, scale-invariance and long-range power-law correlations are features of non-coding DNA sequences as well as of healthy heartbeat dynamics. For cardiac regulation, perturbation of the control mechanisms by disease or aging may lead to a breakdown of these long-range correlations that normally extend over thousands of heartbeats. Quantification of such long-range scaling alterations are providing new approaches to problems ranging from molecular evolution to monitoring patients at high risk of sudden death. We briefly review recent work from our laboratory concerning the application of fractals to two apparently unrelated problems: DNA organization and beat-to-beat heart rate variability. We show how the measurement of long-range power-law correlations may provide new understanding of nucleotide organization as well as of the complex fluctuations of the heartbeat under normal and pathologic conditions.

Animals↗
PubMedDate not supplied

The impact of clinical data on interpretation of thallium scintigrams.

BACKGROUND: The availability of clinical information often influences the interpretation of diagnostic imaging information. METHODS AND RESULTS: In this study we examined the impact of such data on interpretation of exercise thallium scans and the differences in analysis of such information between radiologists and clinicians. Two hundred thirty-seven exercise tolerance test-thallium scans (122 in patients with suspected coronary disease and 115 in patients with documented coronary disease) were read prospectively, first without and then with the knowledge of clinical information. Test scores, the readers' and clinicians' interpretations of historic data, and any changes in readings or interpretation of scintigraphic data were recorded. We found that the addition of clinical information resulted in changes in interpretation of 63 test results (27%), 20 (8%) of them major. Furthermore, clinical data significantly affected final test scores in 26 patients (11%), potentially affecting clinical management in this group. The changes in test scores were triggered predominantly by differences in interpretation of perfusion abnormalities rather than thallium lung uptake or left ventricular dilation with exercise. The impact of clinical data on overall test scores was greater in patients with suspected than documented coronary disease (p < 0.05). There was good agreement in assessment of clinical information between scan readers and a clinician in tests done in patients with suspected coronary artery disease but not in patients with known coronary disease. CONCLUSIONS: We conclude that clinical information has major influences on the interpretation of thallium scans, and interpretation of data can vary significantly between cardiologists and radiologists depending on the nature of the clinical data.

Coronary Disease↗
PubMedDate not supplied

Serial motion assessment by reference tracking (SMART): application to detection of local functional impact of chronic myocardial ischemia.

PURPOSE: To compare measurements of wall motion and thickening with and without correcting for cardiac twisting and shortening. METHOD: Inversion recovery Gd-DPTA perfusion and cine motion MRI were performed on 12 pigs with chronic ischemia induced by ameroid occluder. Analyses were based on conventional fixed plane imaging and serial motion assessment by reference tracking (SMART). RESULTS: Normal motion was 31.3 +/- 1.9%, and normal wall thickening was 41.4 +/- 2.2%. At the maximum perfusion defect, SMART wall motion was 10.5 +/- 2.4% and fixed wall motion was 20.6 +/- 1.7% (p < 0.004), SMART wall thickening was 20.1 +/- 4.4%, and fixed wall thickening was 32 +/- 1.9% (p < 0.03). CONCLUSION: SMART measurements of wall thickening and motion detect much smaller thickening and motion in ischemic myocardium than fixed radial metrics. SMART data, covering the entire heart, should prove twice as sensitive to abnormalities in motion and thickening, such as any produced by ischemic heart disease or improved by treatment.

Animals↗
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Occupational therapy and physiotherapy for the patient with burns: principles and management guidelines.

Clinical practice guidelines are a tool to assist with clinical decision making. They provide information about the care for a condition and make recommendations based on research evidence, which can be adapted locally. A focus group within the Allied Health Interest Group of the Australian and New Zealand Burn Association has compiled the "Occupational Therapy and Physiotherapy for the Patient with Burns--Principles and Management Guidelines." These guidelines are designed as a practical guide to the relevant clinical knowledge and therapy intervention techniques required for effective patient management. Content areas include respiratory management, edema management, splinting and positioning, physical function (mobility, function, exercise), scar management, and psychosocial and mutual elements. The document has undergone extensive review by members of the Australian and New Zealand Burn Association to ensure clarity, internal consistency, and acceptability. The guidelines have been endorsed by the Australian and New Zealand Burn Association. An abridged version of the guidelines is included in this article, with the full document available from www.anzba.org.au.

Burns↗
PubMedDate not supplied

Aortic root dimension measurement by first-pass radionuclide angiography.

A method for measuring the ascending aortic cross-sectional dimension is reported. First-pass radionuclide angiocardiography was performed in 53 patients with various cardiac diseases. The number of pixels from superior vena cava/right atrium junction to the main pulmonary artery were counted horizontally and converted to distance in centimeters. Aortic root size was also measured in these patients by M-mode echocardiography performed within 6 months of the radionuclide study. The two methods were compared by regression analysis. The correlation coefficient between the methods was 0.76, and the standard deviation of the regression was 0.23 cm. This radionuclide method has an accuracy which can be clinically useful for size assessment of the ascending aorta.

Adult↗
PubMedDate not supplied

[Flat crossleg flaps in the repair of large skin, muscle and bone defect of the leg. Present indications, new techniques (author's transl)].

This is a report on a patient who suffered a large skin, muscle and bone defect of the leg following a Volkmann's ischemia. The author's indications for a flat crossleg flap are explained : extended skin defect at the anterior and inner aspect of the broken tibia or a skin defect associated to a tibial defect making a secondary bone graft necessary. Finally the authors describe an original technique of crossleg flap : this consists in a trapezoidal flap with the large side being the implantation basis.

Adolescent↗
PubMedDate not supplied

Effect of adenosine on transmural flow gradients in normal canine myocardium.

Previous reports suggest that in comparison to epicardial flow the response of endocardial blood flow to systemic adenosine is limited. However, intravenous adenosine results in reflex tachycardia and hypotension, which we avoided in six anesthetized dogs by infusing adenosine into the left circumflex (LCx) artery to evaluate the endocardial/epicardial ratio during partial and full vasodilation. The mean (+/- SD) LCx endocardial/epicardial ratio was 1.37 +/- 0.18 with partial vasodilation and 0.81 +/- 0.06 with full vasodilation, which represents an initial increase followed by a decrease when compared with the normal left anterior descending values (p less than 0.05). This biphasic response in the endocardial/epicardial ratio with increasing vasodilation was a direct effect of adenosine, as no hemodynamic alterations occurred during the protocol. These data suggest that in an experimental model with a relative tachycardia the endocardial layer is more sensitive to adenosine but there is a greater capacity to increase flow in the epicardial layer.

Adenosine↗