Biomedical subjects

S O Strömblad

Publications and source records attributed to S O Strömblad.

3 recordsLinked to original sources

PubMed1995

Closed-line integral optimization edge detection algorithm and its application in equilibrium radionuclide angiocardiography.

UNLABELLED: Automatic evaluation of left ventricular (LV) function using equilibrium radionuclide angiocardiography requires an edge detection algorithm to correct and reproducibly delineate the left ventricle. Available algorithms, usually based on differentiation of a radial profile, generally suffer from low precision due to low signal-to-noise ratios and overlapping structures, for example, the left atrium. METHODS: An edge detection algorithm was developed based on the assumption that the LV border can be defined as the maximum, normalized, closed-line integral of a closed curve in a vector field derived by image differentiation. It is further assumed that the closed curve can be described by a Fourier expansion with a limited number of harmonics. Regions of interest (ROIs) generated by this algorithm were compared with ROIs generated by an algorithm based on a combination of thresholding and second-order derivatives. RESULTS: This algorithm delineates the left ventricle and gives results more closely related to ROIs generated manually than the algorithm combining thresholding and the second-order derivative. Our algorithm can also handle the problem of overlapping structures, as demonstrated in phantom simulations. CONCLUSION: The concept of a maximum, normalized closed-line integral will improve the delineation of the LV in an equilibrium radionuclide angiocardiography study. The problem of overlapping structures is overcome by this algorithm because it takes into consideration global edge information.

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PubMed1990

Thoracic epidural anesthesia improves global and regional left ventricular function during stress-induced myocardial ischemia in patients with coronary artery disease.

The aim of the present investigation was to study the effects of high thoracic epidural anesthesia (TEA), including the cardiac sympathetic segments, on ischemic ST-segment changes and left ventricular global and regional wall motion abnormalities. Ten patients with a two- or three-vessel coronary artery disease, all treated with the beta-adrenergic blocker metoprolol because of severe stable angina pectoris, performed two identical exercise stress tests, the first without TEA (control exercise) and the second with TEA (TEA exercise). Before each stress test, intravenous metoprolol was given to achieve maximal or near maximal beta-adrenoceptor blockade. Systolic and diastolic arterial pressures (radial artery cannula), heart rate, and rate-pressure product, as well as global and regional ejection fractions, using equilibrium radionuclide angiography in the left anterior oblique projection, were measured at rest and during maximal exercise. ST-segment analysis (V3 or V5) was performed, and the regional wall motion score was calculated at control exercise and TEA exercise. Intravenous metoprolol or intravenous metoprolol plus TEA at rest did not cause any significant changes of any of the variables. During TEA exercise, systolic arterial pressure, diastolic arterial pressure, and rate-pressure product, but not heart rate, were significantly lower compared to control exercise. The global and anterolateral ejection fractions were significantly higher (52.8% versus 46.5% and 53.2% versus 46.0%, respectively, P less than 0.05), and the regional wall motion score was significantly lower (8.8 versus 11.8, P less than 0.01) during TEA exercise than during control exercise. ST-segment depression was significantly lower during TEA exercise (-1.03 versus -1.84 mV, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1990

Thyrotoxic atrial fibrillation: an underdiagnosed or overdiagnosed condition?

Hyperthyroidism has been considered to be underdiagnosed as a pathogenetic factor for atrial fibrillation, according to results of thyroliberin stimulation tests. We assessed, clinically and biochemically, thyroid function in 110 ambulatory patients with atrial fibrillation [mean age 64 (SD 11) years] from a group of consecutive cases referred to a specialist cardiology unit during one year. Patients finally categorized as euthyroid (n = 100) commonly presented with one or more symptoms or signs considered to be typical for thyrotoxic patients. Three patients (2.7%; 95% confidence interval, 0-7.5%) fulfilled criteria for hyperthyroidism, but only one was identified from clinical examination. The thyroliberin stimulation test (performed in all patients) identified another seven patients who might have been classified as hyperthyroid according to commonly used criteria for an abnormal thyrotropin response. However, none of these seven patients was judged as hyperthyroid after follow-up. Their thyrotropin concentrations were all above the detection limit for the immunoenzymometric assay. With few exceptions, they had thyroid hormone concentrations within reference limits calculated from the results for the 100 euthyroid subjects, and their concentration ratio for free 3,5,3'-triiodothyronine to free thyroxin, 0.31 (SD 0.05), was lower than that found in the euthyroid group [0.38 (SD 0.08), P less than 0.05]. We conclude that (a) criteria for evaluating results of the thyroliberin stimulation test should be revised, (b) this test is still useful in evaluating suspected cases of hyperthyroidism, for which results of current, improved methods for thyrotropin determination are equivocal, and (c) improved diagnostic methods should be used to characterize the relative importance of hyperthyroidism as a causal factor for atrial fibrillation.

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