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P Schwindke

Publications and source records attributed to P Schwindke.

5 recordsLinked to original sources
PubMed1991

["QT" pacemaker in aggregate exchange. Do old electrodes impair functional ability?].

A "QT"-interval driven rate responsive pacemaker can also be implanted on the occasion of pacemaker replacement. To evaluate the electrophysiological properties and limitations of chronic leads, in 30 patients the evoked intracardiac electrogram was recorded via the chronic lead during pacemaker replacement (14 different types, mean interval after implantation 111 (25-171 months). T-wave detectability was evaluated with different pulse amplitudes (2.5 and 5.0 V) and two pacemaker systems (TX 915, Rhythmyx) with different "fast recharge" mechanisms. In particular, the T-wave signal was influenced by capacitor discharge effects. At 2.5 V output T-wave amplitude was greater than or equal to 1.5 mV in all (19) patients, who could be paced at this voltage. However, at 5 V in 9/30 patients T-wave was less than 1 mV and detection was not possible in 6/30 cases. During pacing with the newly developed "QT"-interval driven, rate-responsive pacemaker (Rhythmyx) with two fast recharge pulses, in nine investigated patients the T-wave was markedly better discriminable compared to the TX 915 pacemaker. Accordingly, in 37 patients with implanted "QT"-controlled pacemakers (TX 911): n = 13; TX 915: n = 21; Rhythmyx: n = 3. Indication for pacemaker therapy: high degree AV block: n = 24, sick-sinus syndrome: n = 13) reliable T-wave sensing was possible at 2.5 V/0.2 ms output, whereas at 5 V/2 ms no T-wave sensing could be achieved in 8/37 cases. On the occasion of pacemaker replacement the "QT"-controlled pacemaker can be implanted without intraoperative measurements, whenever a pulse amplitude less than 2.5 V is sufficient for stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗
PubMed1986

Low temperature light microscopy and its application to study freezing in aqueous solutions and biological cell suspensions.

The freezing of biological cell suspensions can be understood in terms of ice formation in the external suspension medium and the cellular reactions to the changing environment. Cryomicroscopy allows a quantitative analysis of both categories of phenomena. Besides freezing stages of appropriate thermal design, the components used for that purpose include a microcomputer (PSI 80) based control system, an image analysis system (Intellect 100) and a spectrophotometer (MPV compact). The investigation of extracellular ice formation is focused on the following effects: The redistribution of solutes in the residual liquid and the resulting concentration profiles are determined photometrically or densitometrically. The transitions between various morphologies of the ice-liquid phase boundary (planar-cellular-dendritic) can be related to interface instability theories. With respect to solute segregation, the studies also involve the formation of bubbles from supersaturated gaseous solutes and freezing potentials resulting from the differential incorporation of cations and anions into the solid phase. The interaction between particles or cells and the advancing ice front is determined from critical interface velocities marking the transition between repulsion and entrapment. The effects of freezing on biological cells are studied mainly with blood cells, especially lymphocytes. The water efflux due to osmotical gradients across the membrane yields volume shrinkage curves which are recorded and analysed from video images for various cooling rates. Beyond a certain threshold cooling rate, intracellular ice starts to form, and different crystallization morphologies can be detected. The intracellular crystallization temperatures depend on cooling and warming rates as well as on the presence of penetrating cryoadditives. A fluorescence viability is used to determine the percentage of damaged cells immediately after thawing.

Cells↗