The Annals of Thoracic Surgery, Vol 27, 63-69, Copyright © 1979 by The Society of Thoracic Surgeons
Myocardial stimulation impedance: the effects of electrode, physiological, and stimulus variables
GF Tyers, RR Brownlee, HC Hughes Jr, CW Shaffer, EH Williams and RL Kao
With exposed metal at the electrode tissue interface (8 mm2, 28 mm2, 57
mm2), myocardial threshold stimulation impedance increased as pulse
duration was lengthened, with left ventricular intramyocardial stimulation,
and with the smaller surface area electrode. An 0.5 mm2
differential-current-density electrode, which eliminated direct metal-
to-tissue contact at the electrode-myocardial interface, was associated
with notably higher impedances than each of the three metal tip electrodes
and did not show increasing impedance levels with changes in pulse
duration, confirming the minimization of polarization energy losses with
this device. The majority of electrode, electrode tissue interface, and
myocardial variables that are characterized by high threshold stimulation
impedance are associated with low threshold energy requirements for pacing
and reduced pacemaker power source drain. No accurate information about
sensing impedances can be derived from current knowledge of pacing
impedance.
