Diltiazem slow-release and left-ventricular hypertrophy: a volumetric approach of left ventricular mass using magnetic resonance imaging

AIMS: This study was designed to assess the changes in left ventricular mass (LVM) in hypertensive patients with left ventricular hypertrophy under drug therapy with once-daily slow-release diltiazem. Magnetic resonance imaging (MRI) was used for this purpose because of its higher reproducibility than M-mode or two-dimensional echocardiography. METHODS: Patients suffering from essential hypertension were included if their baseline LVM index (LVMI) was > or = 105 g/m2 in male or > or = 85 g/m2 in female patients, ie, equal or higher to the median values observed in hypertensive patients in our institution. MRI consisted in a true short-axis, electrocardiogram (ECG) gated spin-echo slice acquisition at baseline, after 3 and 6 months of therapy (M0, M3, and M6). Data were stored on magnetic tapes and read subsequently under blind conditions and the control of an external auditor. RESULTS: Thirty-five patients were included. Of these, 14 patients (40%) were not previously treated. Inter- and intra-observer variability for LVMI measurement were 5.6 +/- 4.3% and 2.1 +/- 3.0%, respectively. Mean baseline LVMI was 110 +/- 16 g/m2 in male and 96 +/- 16 g/m2 in female patients. It decreased by 3.6% at M3 (P = 0.05) and by 6.0% at M6 (P = 0.02). A trend towards a greater LVMI reduction was observed in previously untreated patients. CONCLUSION: This study confirms that MRI is a reproducible technique for the measurement of LVM. It demonstrates a significant reduction in LVMI as early as the 3rd month of therapy in hypertensive patients treated with once-daily sustained release (SR) diltiazem, although baseline LVMI in the majority of participating patients was only moderately increased.     

MRI semeiology of segmental contraction abnormalities in arrhythmogenic dysplasia of the right ventricle

The diagnosis of localized arrhythmogenic right ventricular dysplasia may be difficult to ascertain. Aside from electrophysiological arguments, visualization of an abnormal right ventricular contraction pattern is of crucial importance for diagnosis. Cine-MR is almost the only examination method which offers detailed informations on the right ventricular contraction pattern. Nine observations of segmental right ventricular contraction abnormalities assessed by cine-MR are described here: dyskinesia of the distal part of the anterior wall (2), of the inferior wall (2), of the right ventricular outflow tract (2); akinesia of the outflow tract (2) and of the inferior wall (1). Morphological abnormalities of the right ventricle are always associated with contraction abnormalities but seem to be less disease specific. Patients should be more readily referred for a cine-MR examination when the diagnosis of localized right ventricular dysplasia is suspected. Cine-MR sequences related to these observations may be reached via Internet at:http:@alsace.u-strasbg.fr/cardio/coeur.htm.     

Secreting paragangliomas of the organ of Zuckerkandl. A report on two cases (author's transl)

The authors describe two cases of secreting paragangliomas of the organ of Zuckerkandl, beinging the number of known cases to 78. They underline the interest of arteriographic and phlebographic explorations which define more accurately the origin and spread of these tumours.     

On roundoff error distributions in floating point and logarithmic arithmetic

Probabilistic models of floating point and logarithmic arithmetic are constructed using assumptions with both theoretical and empirical justification. The justification of these assumptions resolves open questions in Hamming (1970) and Bustoz et al. (1979). These models are applied to errors from sums and inner products. A comparison is made between the error analysis properties of floating point and logarithmic computers. We conclude that the logarithmic computer has smaller error confidence intervals for roundoff errors than a floating point computer with the same computer word size and approximately the same number range.     

Generation of neutron transport benchmark problems using BEAPAC-3T

A method is described how a quantitative measure can be obtained for the accuracy of numerical methods for the solution of neutron transport problems in an arbitrary homogeneous multidimensional medium. An expansion for the combining coefficients of singular eigenfunctions is developed that yields exact elementary plane-wave solutions that can be evaluated very accurately in terms of exponential integral functions. Linear combinations of these solutions are automatically generated which approximate, in the least squares sense, a user specified incident flux distribution on the boundary of a multidimensional benchmark cell domain. The generated solution is exact for a new benchmark problem which has incident flux given precisely by the generated solution. The quantitative error analysis method has been implemented in the code BEAPAC-3T and is illustrated by application to the TWOTRAN-II code for a square domain problem.     

Probabilistic error analysis of gaussian elimination in floating point and logarithmic arithmetic

The probabilistic models for roundoff error in floating point and logarithmic arithmetic discussed in Barlow and Bareiss (1985) are applied to the error analysis of Gaussian elimination and some related algorithms. This new method of error analysis is compared to the standard deterministic error analysis given in Wilkinson (1963, 1965).     

Experimental investigation of melting heat transfer with regard to different geometric arrangements

In the present study melting experiments, performed with different geometric test configurations, are reported. The investigation encompasses the melting process adjacent to a heated vertical surface and inside a vertical as well as horizontal heated cylinder. All studied processes show common features and can be described by two-regime models. In the first stage of the process the conduction regime is valid, directly followed by a quasi-steady convection regime which can be described by a correlation of the form Nu = f(Ste, Ra). An appropriate transition criterion allows for the transition point between both regimes.