Sudden rate drop intervention rate level in patients with new 'clarity' pacemakers and carotid sinus syndrome.

BACKGROUND: In patients in whom syncopal episodes are mainly caused by occasional drops in heart rate, Sudden Rate Drop intervention feature intends to provide high rate intervention pacing. New Vitatron Medical B.V. pacemaker system Clarity DDDR, provides AN option FOR recognizing Sudden Rate Drop and responding by intervention pacing until it detects the recovering. MATERIAL AND METHODS: In patients with carotid sinus syndrome it is possible to provoke this situation BY sinus carotidus massage. We have implanted 10 of these devices in our center, 2 of which in patients with hypersensitive carotid sinus syndrome. In both patients, we activated sudden rate drop intervention on DDD mode pacing and applied protocol for testing the necessary level of Sudden Rate Drop Intervention Rate. Both patients gave their informed consent to be submitted to this testing. Pacemaker software assumes rate intervention level of 110 bpm. We tested our patients for rate levels of 90 and 110 bpm. Massaging the carotid sinus during 5 seconds, we provoked Sudden Rate Drop Intervention 10 times, in each patient, 5 times at intervention rate of 90 and 5 times at 110 bpm. Patients were unaware of the programmed intervention rate and were merely expected to report any different sensations experienced during the testing. RESULTS: In all 20 tests, pacemaker responded to sudden rate drop elicited by carotid sinus massage (100%), which was verified by selected event recordings. After the massage, neither of the patients registered any sensations at sudden rate drop intervention rate level of 90 bpm in a total od 10 tests (100%), while 8 out of 10 massages at 110 bpm intervention rate provoked palpitations (80%). On the grounds of this testing, we concluded that lowering of Sudden Rate Drop Intervention Rate Level from 110 BPM to 90 BPM does not affect the reliability of system reaction, but changes patient's awareness of heart beats. CONCLUSION: As a final conclusion, it should be said that basic prerogatives of a pacing system: safety and efficacy with minimal energy consumption, and in this case, quality of life option that a patients practically does not feel intervention when it occurs, are all met.

Full ventricular capture indicated by the QT interval function.

UNLABELLED: The atrioventricular (AV) interval is critical in dual chamber (DDD) pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM) to obtain full ventricular capture (FVC) with maximal reduction of the left ventricular (LV) outflow gradient and optimal LV diastolic filling. We studied the relationship of FVC, fusion, spontaneous AV conduction, and the QT interval. METHODS: 11 patients with various cardiac diseases and stable AV conduction received a QT sensing Diamond, Vitatron, DDD pacemaker. Software was downloaded into the pacemaker. In the DDD pacing mode, with the QT interval measured from the ventricular pacing stimulus to the end of the T wave, the AV interval was shortened from 400 ms, in 20-ms steps, to 90 ms. At 90 ms the stimulation rate was increased by 30 beats/min and the AV interval was increased stepwise. FVC and fusion was examined on the surface ECG. RESULTS: At 400 ms interval, spontaneous AV conduction inhibited the pacemaker. Shortening the AV interval resulted in pacing with a short QT interval. Further reduction of the AV interval resulted in a longer QT interval up to a point where the QT interval became stable. This point, the bending point in the plot of measured QT interval versus shortened AV intervals, coincided with the point of FVC. The relation of the QT-AV interval plot and the point of fusion was comparable when lengthening the AV interval at a 30 beats/min faster stimulation rate. CONCLUSION: The bending point in the QT interval versus AV interval plots showed a good correlation with the FVC and fusion points observed on ECG. The results suggest that automatic discrimination between fusion and full capture using QT interval measurements may be feasible.

[Caries prevalence among schoolchildren in Zoetermeer. A study performed by primary health doctors]. / Cariësprevalentie onder Zoetermeerse schoolkinderen. Een onderzoek uitgevoerd door JGZ-artsen.

In a study performed by primary health doctors among 10- and 11-year-olds in Zoetermeer (the Netherlands), 72% of the children were found to possess four healthy permanent first molars. The examination was exclusively based on visual inspection by means of mouth mirrors.

Long-term treatment with 5,5-diphenylhydantoin reduces lymphadenopathy and anti-ssDNA autoantibodies in C57BL/6-lpr/lpr mice.

To further the insight in the immunomodulating properties of the anticonvulsant 5,5-diphenylhydantoin (DPH), C57BL/6 (B6), C57BL/6-lpr/lpr (B6-lpr/lpr) and MRL/MpJ- +/+ (MRL) mice received DPH orally for six months to determine weekly urinary biopterin levels, a potential T-cell activation marker, by high performance liquid chromatography. At the end of the experiment serum antibody levels were measured by ELISA and relative lymphoid organ weights determined. DPH treatment resulted in reduced body weight in all strains, reduced spleen weights in B6 and MRL mice, profoundly reduced popliteal lymph node weights in B6-lpr/lpr mice and increased thymus weights in MRL mice. DPH treatment decreased serum IgM, IgG and IgA as well as IgM and IgG anti-ssDNA levels in B6-lpr/lpr mice, but did not affect these parameters in other strains. Effects of DPH on IgM rheumatoid factor levels in B6-lpr/lpr mice were inconsistent. Urinary biopterin levels of untreated B6 and B6-lpr/lpr mice were about equal and lower than those of MRL mice. During the first three months of DPH treatment, persistently elevated biopterin levels were observed in B6 and to a lesser degree in MRL mice, and alternately elevated and control levels in B6-lpr/lpr mice. Thereafter, the effects faded in all strains. Results show that long-term DPH treatment causes only minor lymphoid organ weight changes in B6 and MRL mice, but causes a clear reduction of the lymphadenopathy and (auto)antibody formation in B6-lpr/lpr mice. Observed changes could not be related to altered biopterin excretion indicating that the latter is an inappropriate marker of murine autoimmune disease.

Urinary biopterin levels in mice during graft-versus-host reactions and during exposure to 5,5-diphenylhydantoin.

Based on evidence that urinary neopterin levels are useful markers of disordered cellular immunity in man, we investigated murine urinary biopterin excretion during acute and chronic graft-versus-host (GvH)-reactions as well as after oral exposure to drugs with documented immune disregulating potential in man. Biopterin levels were determined in urine spot samples by reversed-phase high performance liquid chromatography and expressed in relation to the urinary creatinine content. Similarly increased and decreased biopterin levels were observed during acute and chronic GvH-disease in (C57BL/6J x DBA/2J)F1 (B6D2F1) mice. Increased and/or decreased levels of urinary biopterin were observed during treatment with 5,5-diphenylhydantoin (DPH), methimazole, propylthiouracil and nitrofurantoin, but no consistent pattern could be distinguished. The DPH-induced alterations were similar in B6 and B6D2F1 mice, were dose-dependent, reversible and independent of mature T-cells, as judged by the pronounced biopterin excretion of B6-nu/nu mice in comparison with their T-cell competent litter mates. The results indicate that monitoring of urinary biopterin excretion in mice does not represent a useful biochemical marker for T-cell activation.

Initial clinical experience with rate adaptive cardiac pacing using two sensors simultaneously.

UNLABELLED: In the rate adaptive pacemakers, all presently available sensors show one or more drawbacks. Combining two sensors in a single pacemaker, we tried to optimize its rate responsive characteristics. In this study, we present the rate adaptive behavior of a two sensor pacemaker system, using both QT interval and activity sensing. In addition, we compared the rate response with that of each sensor alone. Nine patients with an implanted QT interval sensing pacemaker, and an externally attached activity sensing pacemaker performed three exercise stress tests on treadmill. The QT interval, measured by the implanted pacemaker, and the activity level, were transmitted to an external computer. This computer contained the two sensor rate adaptive algorithm, and reprogrammed the implanted pacemaker on beat-to-beat basis. CONCLUSION: In the two sensor mode the rate increases immediately at the onset of exercise, caused by the prompt response of the activity sensor. Further rate increase is driven by the QT interval sensor and therefore proportional to the level of exercise. Furthermore, the rate decay during the recovery phase is more physiological.

Effects of various inhibitors of oxidative phosphorylation on energy metabolism, macromolecular synthesis and cyclic AMP production in isolated rat thymocytes. A regulating role for the cellular energy state in macromolecular synthesis and cyclic AMP production.

Inhibitors of oxidative phosphorylation such as several triorganotin compounds, oligomycin, 2,4-dinitrophenol and carbonylcyanide p-trifluoromethoxyphenylhydrazone suppress energy metabolism of isolated rat thymocytes as indicated by a reduction of ATP levels, an increase in glucose consumption and by a marked accumulation of lactate. Also these compounds effectively inhibit the incorporation of DNA, RNA and protein precursors into acid-precipitable material of thymocytes. Moreover, the prostaglandin E1-induced elevation of cAMP is markedly reduced by these inhibitors. A correlation is observed between the effects on energy metabolism, macromolecular synthesis and cAMP production, since from a series of trialkyltin chlorides, tri-n-propyltin, tri-n-butyltin and tri-n-hexyltin are very effective inhibitors of these functions, while trimethyltin and tri-n-octyltin affect neither of them; other inhibitors of oxidative phosphorylation, each of them with quite different mechanisms of action, also inhibit macromolecular synthesis and cAMP production. The finding that a rise in intracellular ATP concentrations leads to a reversion of the tri-n-butyltin-induced inhibition of cAMP production and uridine incorporation, indicates a regulating role for the cellular energy state in these aspects of cellular function.