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H Schieffer

Publications and source records attributed to H Schieffer.

132 records · Page 8Linked to original sources
PubMedDate not supplied

Myocardial perfusion measured by dual-isotope acquisition of 81rubidium/81mkrypton: an experimental verification of the method.

PURPOSE: The purpose of the study was to verify that the 81Rubidium/81mkrypton (81Rb/81mKr) method allows the quantitative measurement of myocardial perfusion. PRINCIPLE: The potassium analogous cation 81Rb is accumulated in the myocardium by the cell membrane-bound Na-K-ATPase. After accumulation an intracellular equilibrium establishes between 81Rb and its radioactive daughter nuclide 81mKr. The flow-sensitive method evaluates the disturbance of this equilibrium by perfusion which washes out the short-lived diffusable daughter nuclide 81mKr while the mother nuclide 81Rb remains cell-bound. METHODS: Isolated rabbit hearts were prepared in a modified Langendorff technique which allowed quantitative collection of the coronary sinus efflux. The myocardium was labeled with pure 81Rb by bolus injection into the aortic cannula. Spectroscopic measurements of 81Rb and 81mKr gamma radiation were performed using a germanium detector. Perfusion was varied in the range between 0 and 4 ml/min/g. The activity ratio 81Rb/81mKr was determined and compared with coronary sinus effusion. RESULTS: 81Rb/81mKr activity ratio was closely related (r = 0.98) to perfusion as described by the predicted equation Rb/Kr = (F/2.96 P) + 1. (Rb/Kr = activity ratio between 81Rb and 81mKr in the myocardium; F = myocardial perfusion (ml/min/g); P = partition coefficient (myocardium/perfusate) for Krypton gas). The constant P was found to be 1.14 +/- 0.06 (mean +/- SEM). No saturation of this ratio at high flow rates was observed. CONCLUSION: The activity ratio 81Rb/81mKr is a valid quantitative measure for myocardial perfusion in isolated hearts. The main limitation of the method before application in man is the correction of the different gamma ray tissue absorption of both nuclides.

Animals↗
PubMedDate not supplied

Experimental validation of a new coronary guide wire labeled with rubidium 81/krypton 81m for continuous assessment of myocardial blood flow.

BACKGROUND: The rubidium 81/krypton 81m method was suggested for assessment of myocardial blood flow (MBF) three decades ago. This study investigates the novel concept of using 81Rb-/81mKr-labeled coronary guide wires with wire-attached 81Rb activity and diffusable 81mKr gas for assessment of lesion-specific impairment of MBF by evaluation of the 81Rb/81mKr activity ratio. The feasibility of wire production is tested, and application of the method is investigated in the canine model. METHODS AND RESULTS: Conventional coronary guide wires for angioplasty (0.014 in) were labeled with radioactive 81Rb/81mKr by ion bombardment of the wire tip. A total of 16 of the 18 wires labeled in series showed successful 81Rb fixation in combination with free 81mKr gas diffusability during quality control measurements. The suitability of the wires to assess MBF in combination with an external gamma ray detector was investigated in open-chested dogs. Electromagnetic measurement of coronary blood flow (CBF) was used as reference, providing a signal that is directly linked to volumetric MBF. The 81Rb/81mKr ratio tracked changes in CBF reliably in all 6 dogs. The found linear dependence of measured 81Rb/81mKr count rates on measured CBF supports the modeling assumptions made to apply the theoretic basis of the 81Rb/81mKr technique to 81Rb-labeled coronary guide wires. CONCLUSION: 81Rb-/81mKr-labeled coronary guide wires provide a signal that indicates volumetric MBF directly. This unique capability may qualify the technique as a valuable tool for research purposes and as an attractive method for invasive cardiology at centers where the logistic arrangements for short-lived isotope supply are provided.

Animals↗
PubMedDate not supplied

Electrophysiological effects of a new antiarrhythmic agent, nicainoprol, in humans.

The electrophysiological effects of nicainoprol, a new antiarrhythmic drug, were evaluated in a heterogeneous group of 23 patients aged 59 +/- 15 (mean +/- standard deviation) years. Nicainoprol was administered intravenously as a bolus of 1-2 mg/kg followed by continuous infusion at two dose levels. Electrophysiologic study was performed before and during the infusion at a steady-state drug level on each dose. The sinus node recovery time was unaltered in patients with normal sinus node function and was markedly prolonged in three of six patients with sinus node dysfunction. The intranodal conduction time (p less than 0.01) and the infranodal conduction time (p less than 0.001) increased, and the QRS duration (p less than 0.05) lengthened significantly even during 1 mg/kg/h. During 2 mg/kg/h, these times were further prolonged and, in addition, the intra-atrial conduction time (p less than 0.05), atrioventricular nodal effective and functional refractory periods (p less than 0.01), as well as the Wenckebach cycle length (p less than 0.001) also increased significantly. Similar depressant effects on the retrograde ventriculoatrial conduction system were also produced by nicainoprol. Retrograde His-atrioventricular nodal conduction was blocked in six of eight patients with this condition and was prolonged in the remaining two. Sustained supraventricular tachycardia was induced in seven patients, five of whom received nicainoprol during the tachycardia. The termination of supraventricular tachycardia was exclusively due to ventriculoatrial block in all five subjects, three with orthodromic circus movement tachycardia and two with atrioventricular nodal reentrant tachycardia of the slow-fast type. The reinducibility of supraventricular tachycardia could be prevented in five of seven patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Walk training and drug treatment in patients with peripheral arterial occlusive disease stage II. A review.

On the basis of the present studies physical therapy is the most effective basis therapy of peripheral arterial occlusive disease stage II according to Fontaine. The consequent integration of the patients into widespread vascular training groups would be desirable. All present studies with so-called vasoactive drugs led to a statistically significant increase in pain-free walking distance. This is especially true for the substances naftidrofuryl, pentoxifylline, and buflomedil. Nevertheless, these studies do not fully meet the standards set by the GCP or the FDA guidelines. It must also be said that the increase in walking distance by vasoactive substances is less pronounced than the effect obtained by walk training alone. Both the vasoactive therapy and controlled walk training aim at an increase in pain-free walking distance. It is, however, still unclear whether the modes of therapy described influence the primary disease. Angiographically controlled studies are momentarily not available.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Influence of neutrophil separation on the expression of adhesion molecules.

In many assays of polymorphonuclear neutrophil (PMN) function the first step is separation of PMN from whole blood. In the present investigation it was examined if PMN separation leads to an altered expression of neutrophil surface membrane adhesion molecules. Samples have been taken from 20 healthy volunteers (10 male, 10 female; 39.7 +/- 11.8 years of age). PMN activation was measured cytometrically using the following antibodies against PMN surface membrane receptors: L-selectin (CD 62 L), beta-2-integrin Mac-1 (CD 11b) and Intercellular Adhesion Molecule 1 (CD54). PMN activation was determined in whole blood and after separation of PMN using density gradients. After PMN separation all three adhesion molecules appeared increased but the effect was only statistically significant for CD 54 (Wilcoxon test). Data (mean fluorescence intensity in arbitrary units) were: CD 62 L: 62 +/- 37 in whole blood, 82 +/- 28 after separation; p = 0.0674, CD 11b: 94 +/- 55 in whole blood, 111 +/- 47 after separation; p = 0.1454, CD 54; 13 +/- 12 in whole blood, 81 +/- 35 after separation; p < 0.0001. With the present data available it can be assumed that separation of PMN from whole blood can influence the results of flow cytometric assays.

Adult↗