Norbert Benda

Cardiac output and central distribution of blood flow in the human fetus

BackgroundThe objectives of this study were to establish reference ranges for left and right cardiac output and to investigate blood flow distribution through the foramen ovale, ductus arteriosus, and pulmonary bed in human fetuses. Methods and ResultsA prospective study was performed in 222 normal fetuses from 13 to 41 weeks of gestation with high-resolution color Doppler ultrasound. Cardiac output and ductal flow were calculated by use of vessel diameter and the time-velocity integral. Pulmonary blood flow was expressed as the difference between right cardiac output and ductal flow. Foramen ovale flow was estimated as the difference between pulmonary flow and left cardiac output. Gestational age-specific reference ranges are given for left, right, and biventricular output and volume of ductal blood flow, showing an exponential increase with gestational age. Median ratio of right to left cardiac output was 1.42 and was not associated with gestational age. Right cardiac output was 59% and left cardiac output was 41% of biventricular cardiac output. Median biventricular cardiac output was estimated to be 425 mL · min−1 · kg−1 fetal weight. Ductal blood flow was 46%, estimated pulmonary flow was 11%, and estimated foramen ovale flow was 33% of biventricular output. ConclusionsThe study establishes reference ranges for fetal cardiac output and offers insights into the central blood flow distribution in human fetuses from 13 weeks to term. There is a clear right heart dominance. The estimated ratio of pulmonary blood flow to cardiac output is higher than in fetal lamb studies.

Preserved endothelial function in IDDM patients, but not in NIDDM patients, compared with healthy subjects.

OBJECTIVE To examine endothelial function (EF) noninvasively in IDDM and NIDDM patients with long diabetes duration. RESEARCH DESIGN AND METHODS We studied EF in 17 IDDM patients without diabetic complications and in 25 NIDDM patients with comparable glycemic control and with diabetic complications and compared both with nondiabetic control subjects matched for age, sex, and lumen diameter. Using high-resolution ultrasound, we measured the endothelialdependent (FAD%) and independent vasodilation (GTN%); the blood flow at rest, postocclusive, and after application of 400 μg glyceroltrinitrate of the brachial artery; and the intima media thickness (IMT) of the common carotid artery. RESULTS In the IDDM patients, neither FAD% (8.2 ± 4.6 vs. 7.6 ± 4.2%), GTN% (16.3 ± 4.9 vs. 18.4 ± 6.4%), nor postocclusive blood flow (40.6 ± 19.1 vs. 39.3 ± 23.6 cm/s) differed from the control subjects. IMT (0.59 ± 0.10 vs. 0.55 ± 0.14 mm) was slightly, but not significantly, elevated. In contrast, the NIDDM patients showed an impaired FAD% (3.8 ± 3.3 vs. 6.9 ± 4.4%, P < 0.01), no difference in GTN%, and a decreased postocclusive blood flow (18.5 ± 13.8 vs. 32.7 ± 20.0 cm/s, P < 0.01). IMT was significantly increased in NIDDM patients (0.77 ± 0.14 vs. 0.62 ± 0.10 mm, P < 0.001). CONCLUSIONS In contrast to NIDDM patients with cardiovascular complications, IDDM patients with long diabetes duration and good long-term metabolic control do not have impaired EF compared with control subjects.

Insertion/Deletion Polymorphism of the Angiotensin I-Converting Enzyme Gene Is Associated With Coronary Artery Plaque Calcification As Assessed by Intravascular Ultrasound

OBJECTIVESnWe evaluated the influence of the insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene on coronary plaque morphology and calcification in patients with angiographically documented coronary artery disease (CAD).nnnBACKGROUNDnThe ACE I/D polymorphism has been associated with an increased risk of myocardial infarction in patients with the DD genotype but not with the presence of native CAD.nnnMETHODSnWe studied 146 patients undergoing percutaneous transluminal coronary angioplasty for stable angina pectoris by means of preinterventional intravascular ultrasound (IVUS). Qualitative and quantitative criteria were used to classify the target lesions as poorly or highly echoreflective or as calcified. Genomic deoxyribonucleic acid was analyzed by polymerase chain reaction (PCR) to identify the I/D polymorphism, with a second insertion-specific PCR in DD genotypes to prevent mistyping.nnnRESULTSnThe ACE genotype groups (DD 46, ID 68, II 32) were well matched for the basic characteristics. Patients with the DD genotype had significantly more calcified lesions (DD 80%, ID 57%, II 66%; unadjusted odds ratio [OR] 2.88, 95% confidence interval [CI] 1.30 to 6.92, p = 0.008) and more calcifications >180 degrees of the vessel circumference (DD 22%, ID 10%, II 6%; OR 2.80, 95% CI 1.05 to 7.63, p = 0.03). The prevalence of myocardial infarction was not significantly associated with coronary calcification (OR 1.44, 95% CI 0.72 to 2.88, p = 0.31).nnnCONCLUSIONSnPatients with CAD and the ACE DD genotype have a significantly higher incidence and greater extent of coronary lesion calcification, as determined by IVUS. This finding indicates that the ACE I/D gene polymorphism is related to the development or progression of atherosclerotic plaque calcification.

Motor skill learning in patients with cerebellar degeneration

To explore the role of the cerebellum in learning a complex motor task, we studied nineteen patients with cerebellar degeneration and sixteen healthy subjects who attempted to improve their performance in generating a trajectory connecting five via points on a data tablet. Multijoint arm movements were performed at a constant total movement time, and spatial error was measured. Subjects performed 100 trials at a movement time of 3.5 s (slow movements), and another 100 trials at maximum speed (fast movements). With slow movements, patients and normal subjects reduced the error over trials to the same extent, but in patients, the rate of improvement was slightly slower. With fast movements, patients showed less improvement than normal subjects. When tested 24 h later, patients demonstrated significant retention of acquired skill and tended to improve more rapidly when performing both slow and fast movements than during the first session. We conclude that patients with cerebellar degeneration can exhibit almost normal performance in skill learning with slow movements, but with fast movements, their performance improves to a lesser extent. The problem may be difficulty in the refinement of motor execution, which is more of a requirement for fast movements than for slow ones.

Angioscotoma detection with fundus-oriented perimetry: A study with dark and bright stimuli of different sizes

Fundus-oriented perimetry (FOP) was used to evaluate the effectiveness of different-sized bright and dark stimuli in detecting and quantitatively measuring angioscotoma. The foveolas and optic disks of digitized fundus images were aligned with their psychophysical counterparts to construct individual grids of perimetric stimuli. Each grid included a linear set of test point locations crossing a retinal vessel. Angioscotomas immediately became visible in nine of 13 healthy normal volunteers tested with FOP. Additional mathematical processing of local loss of differential light sensitivity (dls) disclosed an angioscotoma for at least one stimulus condition in all persons tested. The angioscomas were usually deeper for small (12) targets than for large (32) ones. On the other hand, the overall noise at dls thresholds was generally higher for small than for large stimuli regardless of whether the stimuli were bright or dark. No noteworthy differences were found in detection rates or signal-to-noise ratios under different stimulus conditions (dark/bright/small/large). FOP permits the individual arrangement of stimuli for specific morphological conditions and is thus capable of detecting even minute visual field defects such as angioscotomas.

Pre-test estimation and design in the linear model

As a robust method against model deviation we consider a pre-test estimation function. To optimize a continuous design for this problem we give an asymptotic risk matrix for the quadratic loss. The risk will then be given by an isotonic criterion function of the asymptotic risk matrix. As an optimization criterion we look for a design that minimizes the maximal risk in the deviation model under the restriction that the risk in the original model does not exceed a given bound. This optimization problem will be solved for the polynomial regression, the deviation consisting in one additional regression function and the criterion function being the determinant.

An explicit no response instead of time-out in automated visual-field testing.

Abstract. Background: To evaluate the effect of response-acquisition technique on psychometric performance in visual-field testing, the conventional one-button yes/time-out method was compared with a two-button yes/no method for responding whether or not the stimulus was detected. There are a number of situations in which the single-button technique leads to ambiguous results. In this study, we thus expected the yes/no method to reduce tendencies towards habituation and automatic responding. Our hypothesis was that the two-button technique could reduce the rate of erroneous responses. Methods: Luminance-difference sensitivity for bright stimuli (32) on a photopic background was evaluated at 26 locations within the central visual field (30°) using a specially equalised video display unit and a modified 4/2-dB staircase strategy (six reversals, maximum-likelihood threshold estimation). Sixty-one ophthalmologically normal subjects (aged 20–30 years) were examined twice with each method. Results: Mean sensitivities with the two-button yes/no method were found to be, on average, 0.13 dB above those measured with the one-button yes/time-out technique – a difference without clinical relevance. Within-subject variability did not differ between the two methods. However, the less intuitive two-button yes/no method had a slightly higher number of false responses in catch trials. Conclusion: Compared to the conventional one-button yes/time-out method, the two-button yes/no method in normal young subjects thus showed little difference in mean sensitivities and equivalent within-subject variabilities. Concerning our initial hypothesis, the yes/no method is of somewhat higher complexity and is not able to reduce the rate of erroneous responses. The one-button yes/time-out method fared a little better in error rate. In summary, the yes/no method is an alternative and additional possibility of response acquisition in visual-field testing, which is worthy of being tested in a clinical study with elderly subjects.

Models for the description of angioscotomas.

To describe small scotomas in visual field examinations several statistical models are proposed and applied to the evaluation of angioscotoma in 13 ophthalmologically normal subjects. A special perimetric grid is used where thresholds can be estimated along a line of narrow-spaced test points which crosses the predicted location of the retinal vessel. A two-stage analysis employs single estimations to fit a threshold curve by means of a special parametric description of the luminance difference sensitivity threshold as a function of stimulus position. An alternative model incorporates the threshold as a function of position into the probabilistic description of the binary response (stimulus seen/not seen).