Improved Detection and Analysis of Sensed and Paced Events in Dual Chamber Pacemakers with Extended Memory Function A Prospective Multicenter Trial in 626 Patients

PATIENTS AND METHODS: This prospective study analyzed the incidence of atrial arrhythmias in a population of 626 patients in 173 medical centers of eleven European countries and Japan with indication for a dual chamber pacemaker system. The accuracy of the new Automatic Interpretation for Diagnosis Assistance (AIDA) program which is included in Chorus pacemakers was evaluated and the AIDA analysis was compared to and proven with Holter monitoring. Data stored in the pacemakers' memories for the first 24 hours (D1) were compared with simultaneously recorded 24-hour surface electrocardiograms, and data stored over the following 28 days (D28) were examined against reported intercurrent symptoms. RESULTS: At D1, atrial arrhythmias were detected by AIDA in 60 of 626 patients (12%), consisting of atrial fibrillation (n = 29), atrial flutter (n = 4), and miscellaneous arrhythmias (n = 17), and closely corroborated by Holter monitoring (sensitivity 93.7%, specificity 94.9%). At D28, 149 of 386 patients (49%) had had episodes of automatic mode switch prompted by atrial arrhythmias. Symptoms were reported by 81 patients (54%), 92 (62%) had no histories of atrial arrhythmias, and 57 patients (38%) were neither symptomatic nor had histories of atrial arrhythmias. An inverse relationship was found between the number of atrial paced events and the occurrence of atrial arrhythmias (p < 0.001). A history of atrial arrhythmias and older age were associated with a higher risk of atrial arrhythmias (p < 0.05). In contrast, gender, hypertension, concomitant heart disease, or type of atrial lead fixation system were not related with the occurrence of atrial arrhythmias. CONCLUSION: AIDA allowed to confirm, or disprove, the occurrence of atrial arrhythmias as a source of symptoms reported during long-term follow-up. It could also be used to examine the efficacy of antiarrhythmic therapy, and be of assistance when weighing the needs for anticoagulation in patients experiencing asymptomatic atrial arrhythmias.     

Bilayers merge even when exocytosis is transient

During exocytosis, the lumen of secretory vesicles connects with the extracellular space. In some vesicles, this connection closes again, causing the vesicle to be recaptured mostly intact. The degree to which the bilayers of such vesicles mix with the plasma membrane is unknown. Work supporting the kiss-and-run model of transient exocytosis implies that synaptic vesicles allow neither lipid nor protein to escape into the plasma membrane, suggesting that the two bilayers never merge. Here, we test whether neuroendocrine granules behave similarly. Using two-color evanescent field microscopy, we imaged the lipid probe FM4-64 and fluorescent proteins in single dense core granules. During exocytosis, granules lost FM4-64 into the plasma membrane in small fractions of a second. Although FM4-64 was lost, granules retained the membrane protein, GFP-phogrin. By using GFP-phogrin as a probe for resealing, it was found that even granules that reseal lose FM4-64. We conclude that the lipid bilayers of the granule and the plasma membrane become continuous even when exocytosis is transient.     

An improved loose patch voltage clamp method using concentric pipettes

A method for noninvasive voltage-clamp recording from large cells is described. A firepolished pipette having two concentric barrels is pushed against the cell membrane, thereby electrically isolating a circular patch subdivided into an inner and an annular outer region. Both regions are held isopotential, but current is collected from the inner region only. The method electrically simulates a high resistance seal between pipette and cell membrane, allowing accurate and rapid voltage-clamp recording under conditions where the seal resistances actually obtained are low (near 1 M). This is useful in applications where one wishes to avoid enzymatic treatment.We provide details of electrode construction and voltage-clamp electronics, and present results obtained from frog skeletal muscle and leech neurons. For sodium channels of frog muscle, extensive data were previously obtained with other methods. There is good agreement between the earlier results and the measurements presented here.     

Status and perspectives of non invasive cell tracking

The interaction of different cells is an important regulator in the development of many diseases, including cancer. Some cells are recruited directly from the local tissue environment, others reach the pathological focus via the circulation. Using non-invasive cell tracking methods, the distribution and migration of labeled cells can be studied in experimental animal models, and the role of these cells on the pathogenesis of disease can thus be elucidated. Scintigraphy and SPECT, and especially MRI and optical imaging, are frequently used for this purpose. Studies are mostly performed with macrophages and granulocytes (inflammatory cells), which accumulate in nephritis, encephalitis, and tumors. At present, the understanding of progenitor cell migration and differentiation is gaining increasing interest in neurological disorders (for example Parkinson's disease) and in cardiac diseases (for example myocardial infarction). Non-invasive cell tracking is already established in basic research; in the future, a clinical application of cell tracking is foreseeable in the framework of cell therapy.     

Physical and biological characterization of superparamagnetic iron oxide- and ultrasmall superparamagnetic iron oxide-labeled cells: a comparison

RATIONALE: Superparamagnetic iron-oxide particles are used frequently for cellular magnetic resonance imaging and in vivo cell tracking. The purpose of this study was to compare the labeling characteristics and efficiency as well as toxicity of superparamagnetic iron oxide (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO) for 3 cell lines. METHODS: Using human fibroblasts, immortalized rat progenitor cells and HEP-G2-hepatoma cells, dose- and time-dependence of SPIO and USPIO uptake were evaluated. The amount of intracellular (U)SPIO was monitored over 2 weeks after incubation by T2-magnetic resonance relaxometry, ICP-mass-spectrometry, and histology. Transmission-electronmicroscopy was used to specify the intracellular localization of the endocytosed iron particles. Cell death-rate and proliferation-index were assessed as indicators of cell-toxicity. RESULT: For all cell lines, SPIO showed better uptake than USPIO, which was highest in HEP-G2 cells (110 +/- 2 pg Fe/cell). Cellular iron concentrations in progenitor cells and fibroblasts were 13 +/- 1pg Fe/cell and 7.2 +/- 0.3pg Fe/cell, respectively. For all cell lines T2-relaxation times in cell pellets were below detection threshold (<3 milliseconds) after 5 hours of incubation with SPIO (3.0 micromol Fe/mL growth medium) and continued to be near the detection for the next 6 days. For both particle types and all cell lines cellular iron oxide contents decreased after recultivation and surprisingly were found lower than in unlabeled control cells after 15 days. Viability and proliferation of (U)SPIO-labeled and unlabeled cells were not significantly different. CONCLUSIONS: The hematopoetic progenitor, mesenchymal fibroblast and epithelial HEP-G2 cell lines accumulated SPIO more efficiently than USPIO indicating SPIO to be better suited for cell labeling. However, the results indicate that there may be an induction of forced cellular iron elimination after incubation with (U)SPIO.     

Microsurgical excision of symptomatic sacral perineurial cysts: a study of 15 cases

BACKGROUND: The widespread use of magnetic resonance imaging (MRI), now the first line investigation for back and leg pain, reveals cystic sacral lesions more often than myelography did in the past. There is agreement that symptomatic perineurial sacral cysts should be treated surgically. However, it is still debated whether the preference should be given to the curative option, consisting of excision of the cyst with duraplasty, or to drainage of the cyst to relieve symptoms. In this retrospective study the efficacy of microsurgical cyst resection with duraplasty is evaluated. METHODS: In 15 patients presenting with pain and neurologic deficits, myelography and/or MRI detected sacral cysts. The clinical features suggested that the space-occupying lesions caused the disturbances. Microsurgical excision of the cyst along with duraplasty or plication of the cyst wall was performed in all the cases. Postoperative care included bed rest and CSF drainage for several days. RESULTS: In 13 out of 15 patients the preoperative radicular pain disappeared after surgery. The 2 patients with motor deficits and the 6 patients with bladder dysfunction recovered completely. In all except 1 of the 10 patients complaining of sensory disturbances a significant improvement was achieved. No complications were observed. CONCLUSION: Microsurgical excision of the cyst combined with duraplasty or plication of the cyst wall is an effective and safe treatment of symptomatic sacral cysts and, in the view of the authors, the method of choice.     

Kardiale Defibrillation durch Laien- und Ersthelfer „First-Responder”–Überlegungen zu einem neuen Rettungskonzept gegen den plötzlichen Herztod

Zusammenfassung Nach wie vor ist die Letalit?t des pl?tzlichen Herztodes, beim Vorliegen von Kammerflimmern oder pulsloser ventrikul?rer Tachykardie, erschreckend hoch. Neue technische M?glichkeiten und das Verst?ndnis neuzeitlicher notfallmedizinischer M?glichkeiten und Hilfeleistung erm?glichen ein optimiertes Behandlungskonzept für Notfallpatienten. Da allein die rasche kardiale Defibrillation die definitive Interventionsm?glichkeit zur Terminierung von Kammerflimmern oder pulsloser ventrikul?rer Tachykardie darstellt, sollte die Anwendung der modernen externen Defibrillationstechnik nicht erst durchgeführt werden, wenn der Notarzt oder das qualifizierte Notfallteam beim Patienten eintrifft. Auch nicht?rztliches Personal und trainierte Laien k?nnen (und dürfen!) diese lebensrettende Ma?nahmen mittels halbautomatischen Defibrillatoren durchführen. Diese M?glichkeiten sollten zu überlegungen und Empfehlungen der Fachverb?nde eingehen, die zu neuen Rettungskonzepten führen. Eingegangen: 10. April 2001 Akzeptiert: 21. Mai 2001