Atrial Amplitude Mapping to Avoid P Wave Sensing Failure
Physiological pacemaker implantations are increasing in number. However, P wave sensing failure is still a major problem. To determine the best atrial electrode positioning for P wave sensing, the atrial amplitude was measured in 10 dogs, from various epicardial sites, including the endocardium of both appendages. During sinus rhythm, maximum amplitude was obtained from the left atrial free wall. High amplitude was also obtained from the right atrial free wall. However, only low amplitudes were obtained from both appendages. During junctional rhythm, which was obtained by cryosurgery of the sinus node area, patterns of atrial and amplitude mapping changed, but maximum amplitude areas were present on the atrial free walls. Also, atrial amplitude mapping was tried in four clinical cases of WPW -syndrome, during surgery. The maximum amplitude area of the right atrium was located, not on the appendage, but on the free wall, in all cases. These results suggest that J shaped electrode fixation is not adequate to P wave sensing. Even if left a atrial free wall fixation is advisable, this requires a left thoracotomy. Therefore, transvenous fixation to the right free wall should be selected, possibly using a screw-in method.
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