P wave recognition and atrial stimulation with fractally iridium coated VDD single pass leads.

Unlabelled: The bottleneck of VDD systems is the reliable detection of the small atrial signals by a floating atrial electrode. Fractally iridium coated electrodes offer excellent sensing and pacing performance. In this study, the performance of such a floating atrial lead in P wave sensing and synchronous ventricular stimulation was examined.

Transesophageal atrial pacing--stimulation and discomfort thresholds: the role of electrode configuration and pulse width.

A balloon catheter with six electrodes has been developed for transesophageal atrial stimulation of the human heart. Introduction is easy and its positioning is simple with the help of six unipolar atrial electrograms. In a group of 20 healthy volunteers, stimulation and discomfort thresholds (intolerable discomfort) were measured for three levels of pulse widths (12, 16, and 20 msec) and for five electrode configurations.

Improved rate responsive algorithm in QT driven pacemakers--evaluation of initial response to exercise.

The QT pacemaker is a rate modulated pacemaker that uses the evoked QT interval as an indicator to determine its optimal pacing rate. Despite the generally favorable clinical results with this form of pacing, some flaws in the system have been reported, such as the frequently observed rather slow initial response of the pacing rate to physical exercise, and the phenomenon of oscillation of the heart rate. These problems can be attributed to the rate adaptive algorithm used in the current QT pacemaker.