Changes of the unipolar right ventricular impedance during the cardiac cycle are related to the changing content of blood (low impedance) and tissue (high impedance) around the tip of the pacing electrode. During myocardial contraction, the impedance continuously increases reaching its maximum in late systole. This impedance increase is thought to correlate with right ventricular contractility, and thus, with the inotropic state of the heart. In the new Inos2 DDDR pacemaker, integrated information from the changing ventricular impedance (VIMP) is used for closed-loop regulation of the rate response. The aim of this study was to analyze the effect of increasing dobutamine challenge on RV contractility and the measured impedance signals. In 12 patients (10 men, 68 +/- 12 years) undergoing implantation of an Inos2 DDDR pacemaker (Biotronik), a right ventricular pigtail catheter was inserted for continuous measurements of RV-dP/dtmax and simultaneous VIMP signals during intrinsic and ventricular paced rhythm. Then, a stress test with a stepwise increase of intravenous dobutamine (5-20 micrograms/kg per min) was performed. To assess the relationship between RV contractility and measured sensor signals, normalized values of dP/dtmax and VIMP were compared by linear regression. There was a strong and highly significant correlation between dP/dtmax and VIMP for ventricular paced (r2 = 0.93) and intrinsic rhythm (r2 = 0.92), although the morphologies of the original impedance curves differed quite substantially between paced and intrinsic rhythm in the same patient. Furthermore, VIMP correlated well with sinus rate (r2 = 0.82), although there were at least four patients with documented chronotropic incompetence. We conclude, that for intrinsic and ventricular paced rhythms sensor signals derived from right ventricular unipolar impedance curves closely correlate with dP/dtmax, and thus, with a surrogate of right ventricular contractility during dobutamine stress testing. Our results suggest that "inotropy-sensing" via measurement of intracardiac impedance is highly accurate and seems to be a promising sensor principle for physiological rate adaptation in a closed-loop pacing system.
The influence of applied electric fields on the transport properties of weak links in YBa2Cu3O7−δ films has been investigated. It is found that the critical temperature Tc0 of epitaxial films containing weak links can be reduced by 10 K with applied electric fields of 6 MV/cm. In one case, Tc0 shifts of up to 25–30 K were observed. These are by far the largest Tc shifts reported for any superconducting system.
BACKGROUND:There exists only very few data on in vitro and in vivo effects of gamma irradiation of red blood cells (RBCs) that have been leukoreduced by filtration before a subsequent irradiation. Reported studies reflect neither the current Food and Drug Administration (FDA) nor the European recommendations on timing of irradiation and subsequent storage. STUDY DESIGN AND METHODS:We studied 40 RBC units that were prepared from inline filtered whole blood and 40 RBC units that were filtered after component separation. All RBCs were stored in the additive solution saline-adenine-glucose-mannitol and leukoreduced on the collection day. In both groups, 20 components were irradiated on Day +14 with 30 Gy, and 20 served as nonirradiated controls. In vitro evaluation of both irradiated and nonirradiated RBC units was performed before and after irradiation on Days +1, +7, +14, +21, +28, +35, and +42 from the collection day. RESULTS: Gamma irradiation induced enhanced leakage of potassium ions and lactate dehydrogenase and an enhanced in vitro hemolysis rate in the irradiated components. However, in vitro hemolysis rate of both nonirradiated and irradiated components was remarkably lower than 0.8 percent, and the preservation of adenosine triphosphate over 42 days was satisfying. CONCLUSIONS: This study reflects the current FDA and European recommendations on timing of irradiation and subsequent storage. Our findings together with recent results of other investigations on the effect of gamma irradiation on leukoreduced RBCs allow the proposal that a storage time up to 28 days after irradiation is allowable.
Reducing women's anxiety of blood donation, reminding medical professions more intensively on blood donation and appealing to personal experience or a free health check may be the most promising approaches to increase BDs' return rates.
We have performed MeV-ion irradiation of high-quality epitaxial YBa2Cu307 & films (thickness =200 nm) at low temperatures (60 to 80 K) with in situ measurements of the resistivity p and the critical temperature T,o. The increase of p and the decrease of T,o observed for irradiation with 6-MeV He and 25-MeV ' 0 are proportional to the calculated number of atoms displaced by processes of the nuclear energy loss S". For 25-MeV ' S, 120-MeV ' Kr, 173-MeV, and 360-MeV ' Xe, however, a much stronger sensitivity to irradiation is observed than would be expected from these calculations. Furthermore, p and T,o depend nonlinearly on ion fluences in the cases of 173and 360-MeV " Xe. The enhanced sensitivity to irradiation and the deviations from linearity are attributed to effects of additional defects induced by the electronic energy loss S,. If S, exceeds an 4 effective threshold S,o of 2000 eV/A, latent tracks of amorphized material are observed. A model is proposed that qualitatively describes the effects of these tracks on transport properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.