Accession Number:

ADA202923

Title:

Automatic Cardiac Pacing Technique for Electrophysiologic Investigations: Measurement of Myocardial Excitability in the Dog during Exposure to +Gz

Descriptive Note:

Final rept. 1985-1987

Corporate Author:

NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA AIR VEHICLE AND CREW SYSTEMS TECHNOLOGY DEPT

Personal Author(s):

Report Date:

1987-12-01

Pagination or Media Count:

47.0

Abstract:

The objective of this effort was to quantify changes in the excitability of the heart muscle during exposure to various G acceleration profiles. Dogs were catheterized with cardiac pacing electrodes which were inserted into the ventricle of the heart. The exteriorized end of the catheter was protected by a cloth and tape collar allowing the animals to reside in ordinary cages with experimentation taking place for at least 3-4 weeks. A microcomputer-controlled pacemaker was designed, built, and programmed to pace the heart with a basic rhythm established with periodic suprathreshold pulses S1, and a test stimulus S2 inserted at a frequency typically every tenth beat chosen by the investigation. Other parameters which can be varied by the investigator include pulse amplitudes, durations and S1-S2 delay. The automated equipment described, has been used to collect experimental data on dogs undergoing Gz forces on the NAVAIRDEVCEN animal centrifuge. The threshold of stimulation levels are plotted as a function of Gz. We have demonstrated a system in which an animal with a chronic pacing catheter and a computer-based instrument have been combined to provide a useful model in which cardiac threshold of excitability changes can be observed in response to stressors such as Gz. Keywords Multi-application technology animal subjects, Cardiac excitability, Cardiac arrhythmia, Acceleration physiology, ExposurePhysiology.

Subject Categories:

  • Stress Physiology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE