The currently required surgical procedure for implantable defibrillator implantation is a limiting factor and several groups are therefore investigating transvenous approaches. Our electrode system consists of a nondistal right ventricular catheter electrode and two or three subcutaneously (SC) placed electrodes. An optimal location for these SC electrodes is important to obtain the lowest possible defibrillation threshold (DFT) by allowing a more homogeneous current distribution within the thorax. An empirical approach consists of placing randomly the SC electrodes to find out the lowest possible DFT. A mathematical approach is to calculate the SC electrode locations for an optimal electric field distribution by using magnetic resonance images of thorax cross-sections and a specially designed computer program. Our recent experimental results are based on a series of 15 pigs weighing between 60 and 102 Kg. DFT ranged between 10 and 26 joules. We conclude that an electrode system with a right ventricular electrode and two or three subcutaneous electrodes can be optimized to reach a DFT for pigs with human-near body weights which is compatible with the energy capabilities of our implantable device.

Animals↗

PubMed1987

[Calculating electric fields in biologic tissues based on classified NMR image data].

Explore the source record for details and available documents.

Brain↗

PubMed1986

Influence of NMR measuring sequences and gradient variation on signals from flowing systems. Magnetic resonance tomography on experimental models.

The influence of flow on MR tomography images and signal intensities has been studied using experimental model tubes and an aqueous NiCl2 solution having the same relaxation time as human blood. We applied the inversion recovery (IR) and the spin-echo (SE) sequence on a .15T MR tomography system. The influence of RF pulse distance (tau) in the IR and SE experiment as well as the influence of magnetic z-gradient strength on the flow images has been investigated. IR images revealed that signals from flowing systems recover more rapidly due to influx of non-inverted longitudinal magnetization into the scan slice. SE images in presence of flow are characterized by signal intensity loss with increasing time caused by the outflow and dephasing of transverse magnetization. With increasing strength of the z-gradient, the MR signals of flowing fluids decrease drastically. Thus for detection of flow, all the above mentioned parameters are of importance.

Blood↗

PubMed1985

Acceleration of ossification by means of interferential current.

Dynamic interferential current ossification system (DICOS) is a new non-invasive method to accelerate bone growth and repair successfully applied in Europe. As all evaluation methods of clinical bone repair models are too subjective and statistically unreliable, we base our statement on well defined animal experiments with standardized artificial fractures on sheep. Histological, chemical, radiological and electron-microscopic evaluations showed that the higher the interferential current density, the higher: The mineralization of the new bone; The extracellular alkaline phosphatase and The earlier the weight bearing. The electrical field was cross-calculated with computer-aided programs. 4000 Hz alternating current, using the interferential principle; Pleasant current sensation Non-invasive transcutaneous application; Electrode application at any distance from the fracture, even outside the cast; The application is not contraindicated with metal implants being used; No chemical burning under the electrodes; Post-traumatic oedema resorption; Pain relief for patients in cases where analgetics are contraindicated; Acceleration of reinnervation and improvement of microcirculation.

Alkaline Phosphatase↗

PubMed1975