Abstract
A prolonged refractory period of about 0.55sec, was noted soon after exchange of Arco LI3D demand pacemaker due to electrical leakage which had been implanted 6 days before with sutureless epicardial lead by subxyphoidal approach. When a patient-QRS existed in this prolonged refractory period, demand failure occurred and the next pacing pulse was hazardously generated on T wave.
Our experiment revealed that the refractory period (0.26sec.) could be prolonged to 0.52sec., if a pulse was detected only in the period from 0.15 to 0.26 sec, after the pacemaker pulse, and that demand function did not work when a pulse existed in the refractory period and another in the prolonged refractory period, e. g. noises of very low frequency.
We assumed that the pacemaker detected the high voltage or high slew rate of T wave as a pulse in the period from 0.15 to 0.26sec. in this case. The manufacturer reported that the function of this pacemaker was within acceptable range. We thihk this pacemaker has such excellent function as the pacing pulses may not stop by low frequecy pulse-like noise (as low as 3.2Hz), but has such a weak point as mentioned above. We reimplanted another pacemaker (Medtronic 5973) successfully.
