Biomedical subjects

A Brüls

Publications and source records attributed to A Brüls.

3 recordsLinked to original sources

PubMed1998

First experience with an automatic sensing algorithm in single-lead VDD stimulation.

UNLABELLED: An "Autosensing" algorithm available in SSI(R) and DDR(R) pacemakers automatically adapts the device's sensitivity to changing intracardiac signals. The atrial sensing function of this algorithm was tested for the first time with a VDD pacing system in which large variations of the atrial signal may occur because the atrial electrodes float in the atrial blood pool. METHODS: 15 patients with a VDD pacing system were studied (Unity 292-07, lead 425; Sulzer Intermedics). The atrial sensing threshold was measured, and the atrial sensitivity was programmed with a 2:1 safety margin. The autosensing algorithm and sensitivity profile were temporarily activated, and an ambulatory ECG with continuous marker annotation was recorded. All patients underwent a 30-minute daily life activities protocol. A beat-to-beat analysis of the ambulatory ECG was correlated with the changes in atrial sensitivity. RESULTS: The algorithm changed the baseline sensitivity from 0.57 +/- 0.23 mV during the test to 0.39 +/- 0.20 mV after the final rest period (P < 0.05). During the test 12.6 +/- 10.2 adaptations of the sensitivity occurred (range 0-33). In eight patients atrial undersensing occurred in 4.4% +/- 7.5% of the cycles (4-458 unsensed P waves). In these patients, the algorithm continuously adjusted the sensitivity towards more sensitive values, operating 19.1 +/- 18.3 changes compared with 5.4 +/- 7.3 changes in patients without undersensing (P = 0.009). Oversensing did not occur. CONCLUSION: The autosensing algorithm effectively optimized atrial sensitivity in VDD pacing. In patients with atrial undersensing the algorithm continuously remained near the most sensitive settings, thus reacting as intended. A faster sensitivity adjustment of the system would be desirable.

Activities of Daily Living↗

PubMed1996

Evaluation of a new sensor-based algorithm to protect against atrial arrhythmias.

UNLABELLED: The SmarTracking (ST) algorithm (Marathon 294-09, Intermedics Inc.) uses the sensor-calculated rate (SCR) to define a "variation band" for the intrinsic sinus rate. If the sinus rate exceeds the upper limit of the band, the ventricular pacing rate is limited by the ST rate (STR) and Wenckebach behavior is observed. The present study was aimed at evaluating the behavior of the ST mechanism in patients with healthy sinus node, during exercise and at rest. METHODS: Twenty-one patients (15 men; mean age 67.8 +/- 9.7 years) with normal sinus function were studied. Heart rate was recorded via the rate profile of the implanted pacemaker (Relay 294-03, Intermedics Inc.), and STR and SCR were obtained via a previously calibrated strap-on pacemaker. A 15-minute protocol was used during which subjects alternated periods of walking with periods of rest. RESULTS: The relative difference between the average STR and the average sinus rate (DST) was calculated for each phase of the protocol as well as the maximum number of patients showing inappropriate Wenckebach behavior (#W). At nominal settings, DST was always positive and did not fall below 20%. #W was maximum at rest (5) and during heavy exercise (3). By increasing the STR at rest to 95 ppm and the maximum pacing rate to 150 ppm, the #W was reduced to zero for all types of activity except during very fast walk where #W was 1. CONCLUSION: In general, there was no competition observed between the STR and the intrinsic rhythm. In some cases, the STR at rest and the maximum pacing rate had to be reprogrammed for optimal performance.

Acceleration↗

PubMed1996

Holter recordings with continuous marker annotations: a new tool in pacemaker diagnostics.

UNLABELLED: Pacemakers provide marker annotations to facilitate the interpretation of pacemaker electrocardiograms (ECGs) and can be used in cases of suspected pacemaker malfunction or to understand pacemaker behavior. Due to the need for a programmer, only short-term evaluations are possible. We evaluated a prototype Telemetry Data Logger (TDL) designed to continuously transfer markers from the pacemaker to a conventional Holter recorder. A miniaturized telemetry receiving coil was attached to patient's skin above the pacemaker, which was programmed to transmit markers continuously. The TDL, which receives and converts markers into eight positive and eight negative deflections, ranging from -2.5 to +2.5 mV in amplitude, was connected to one channel of a conventional Holter recorder (Tracker 2). We performed 20 Holters in 13 patients who had implanted VDDR or DDDR devices from the same manufacturer and evaluated three versions of software. Marker transmission was possible in all patients, producing Holter ECGs with complete marker annotations. Artifacts occurred < 4% of the time. A 50-ms rectangular pulse was optimal for marker interpretation. The device, which was easy to use and well accepted by the patients, assisted in the diagnosis of inappropriate pacemaker programming, even when the surface ECG seemed to show regular pacemaker function. In the presence of low quality surface ECGs, marker annotations allowed the assessment of pacemaker function. The capability to annotate the onset of special algorithms, like tachycardia termination algorithms or mode switching, facilitates interpretation of pacemaker behavior, enabling a reliable assessment of the appropriateness of such algorithms. CONCLUSION: The TDL effectively enables pacemaker markers to be inscribed onto a conventional Holter recording, facilitating the interpretation of pacemaker ECGs and the diagnosis of inappropriate pacemaker programming even when not discernible from the surface ECG alone.

Algorithms↗