What are the electrophysiological characteristics of the Medtronic 6991 transvenous atrial lead over four weeks post-insertion?
The Medtronic 6991 atrial transvenous lead shows a significant decrease in P wave amplitude during the first week and an increase in stimulation threshold over four weeks post-insertion.
Despite some reports on the use of the atrial transvenous endocardial lead, Medtronic 6991, there is still very little information on the electrophysiological properties of the lead. A lead extension wire was connected to the atrial lead, passed subcutaneously, and brought through the abdominal skin. P wave amplitude, threshold of stimulation, and electrode resistance were repeatedly determined through the atrial lead during four weeks after the electrode insertion in 17 patients. Mean P wave amplitude at insertion was 3-7 1 0 (mean SD) mV. It decreased significantly to a lowest mean level of 2-3 09 mV after one week. From that time there were only small variations. In the supine position and with normal breathing there was a spontaneous variation in the P wave amplitude of 15 per cent. P wave amplitude was only to a minor extent influenced by body position and maximum breathing movements. The threshold of stimulation was 1-7 0-7 V (impulse duration 0 5 mi) at the time of electrode insertion. It increased to 2 7 1 0 V after four weeks. The electrode resistance varied about 600 ohms.
Kruse et al. (Thu,) studied this question.