Use of Implantable Telemetry Systems for Study of Cardiovascular Phenomena

Recent advances in bioinstrumentation and microelectronics have led to the development of single- and multichannel telemetry units. These units are presently being used to transmit all variables necessary for characterizing cardiovascular function from the body surface or from transmitters implanted completely within the body. Continuous transmission of the electrocardiogram has been obtained in implanted Rhesus monkeys for periods up to one year; multichannel units, using intermittent sampling of data, have operated for a similar period in dogs and chimpanzees. Reliable power sources for long-term implantations are still lacking, and continued improvement and miniaturization of transducer design are still needed.

Preliminary observations of cardiovascular function have been made in four chimpanzees using multichannel implantable units. Measurements of right- and left-sided pressures were periodically made in these animals over a four-month period, including continuous observations for selected 24-hour periods. Pressures recorded with animals in an awake, unanesthetized, unrestrained state were much lower than pressures reported for restrained animals in similar situations. Diurnal variations of pressure tended to occur, but were not as clearcut as those reported to occur for humans. The ability to implant a transmitter chronically and receive useful multichannel information in the chimpanzee encourages the future use of such implant devices as part of the control system for an artificial heart or directly for use in man.