Article Messung atrial und ventrikulär evozierter Myokardpotentiale zur Detektion neurohumoraler Erregung des Herzens was published on January 1, 1995 in the journal Biomedical Engineering / Biomedizinische Technik (volume 40, issue s1).

The benefit of DDD(R) pacing is proven even in patients with intermittent atrial fibrillation. Atrial fibrillation developing during dual chamber pacemaker implantation creates a difficult problem. Maneuvers to reestablish a stable atrial rhythm often are required if atrial fibrillation sets in. This study was performed to determine if atrial lead placement can be performed with acceptable long‐term results in the presence of atrial fibrillation. Twenty‐one patients in whom atrial fibrillation developed during permanent pacemaker implantation were included in this study. In 12 patients, episodes of intermittent atrial fibrillation had been documented before the procedure. Screw‐in leads were used in 15 patients and J‐shaped passive fixation leads in 6 patients. AH leads were bipolar. The intraoperative atrial fibrillation electrogram amplitudes ranged from 0.9 to 3.2 mV (mean 1.8 ± 0.6 mV). One patient required lead revision due to a high atrial pacing threshold after conversion to SR. One patient remained in atrial fibrillation at 3‐month follow‐up. The other 20 patients converted to SR, 11 of whom had intermittent atrial fibrillation with successful mode switch activation. P wave amplitudes were 2.8 ± 6 mV (range 1.4 to 4.0 mV) after conversion to SR. The mean atrial pacing threshold was 1.1 ± 0.5 V (range 0.5 to 3.5 V). Placement of atrial leads in patients who develop atrial fibrillation during pacemaker implantation is feasible; fibrillatory electrogram amplitudes showed a good correlation with the atrial signal after conversion to an organized atrial rhythm (r = 0.698). Acceptable atrial pacing thresholds can be expected as well.

Electrical stimulation with low amplitudes can be life-threatening in pacemaker dependent patients. On the other hand, it is possible to prolong pacemaker longevity by reducing pacing energy.Based on undistorted detection of the ventricular evoked response (VER) by fractally coated pacing leads an algorithm for automatic ventricular capture control has been developed and intraoperatively tested in a clinical study.In 19 patients (pts) the VER could reliably be measured with an amplitude of 10.1 +/- 3.2 mV. Testing in VVI mode has been successful in all pts. A modified algorithm for ventricular capture control in DDD mode failed in the first 2 of 10 pts due to wrong programming of the blanking time. After modification the newest version of the algorithm has successfully been applied to the last 8 pts.The possibility to reduce the stimulation amplitude to a lower level with respect to the pacing threshold offers an enhancement of pacemaker's longevity. Besides, simultaneous beat-to-beat analysis of the VER guarantees highest safety and the possibility of high-voltage stimulation in case of capture loss.In the meantime, this algorithm has been implemented in a DDD pacemaker device and has also been tested under chronic conditions clinically.

Article Automatische Amplitudenanpassung auf der Grundlage myokardial evozierter Reizantworten - Erste klinische Erfahrungen was published on January 1, 1996 in the journal Biomedical Engineering / Biomedizinische Technik (volume 41, issue s1).

EINLEITUNG Jüngste Fortschritte in der Schrittmacherund Elektrodentechnologie haben es ermöglicht, myokardiale Reizantworten nach elektrischer Stimulation telemetrisch zu delektieren. Für die ventrikulär evozierte Reizantwort (VER) konnte die außerordentliche Zuverlässigkeit und Signalstabilität in den letzten Jahren aufgezeigt werden (1,3). Inzwischen sind erste klinische Anwendungen der VER erfolgreich durchgeführt worden. Im Gegensatz zur VER ist die atrial evozierte Reizantwort (AER) allerdings wesentlich schwieriger zu delektieren (2,3). Die AER stellt ein niederfrequentes Signal mit kleiner Amplitude dar (4,5). Zum Vergleich sind in Abb. l die typischen Kurvenverläufe von AER und VER gegenübergestellt. Dabei muß berücksichtigt werden, daß eine komplette Aufzeichnung einer isolierten AER kaum möglich ist, da es a) bei erhaltener atrioventrikulärer (AV) Überleitung zu einer ventrikulären Eigenaktion kommt, die die zweite Hälfte des AER überlagert, oder b) bei AV-Blockierung der Ventrikel notwendigerweise stimuliert wird Dies führt zu einer deutlichen Verzerrung der AER im weiteren Signalverlauf (abhängig von programmiertem AV-Intervall).