A totally implantable pacemaker which derives its power from ventricular contractions is undergoing animal tests at Western Reserve University.
The current prototype of the subminiature pacemaker, weighing only 10 gm, was described for the Society of Thoracic Surgeons by John H. Kennedy, MD.
It consists of a piezoelectric crystal in contact with the pericardium, converting contractions into alternating current. Pacing stimuli are delivered via electrodes to the left ventricle after passing through a rectifier and storage circuit.
The current model, "the size of a poker chip" (1.5-inch diameter), has performed well during short-term implantations in dogs.
It can produce up to 1.7 volts or 80 pulses/min and stores sufficient energy for three to ten pulses in case of interrupted cardiac function.
Closed chest massage may be used to reactivate the unit, the Cleveland surgeon explained.
An earlier, considerably larger and heavier prototype (about 30 gm) was used in dogs with