Burns JW, Kruyer WB, Celio PV, Deering J, Loecker TH, Richardson LA, Fanton JW, Davis H, Dick EJ Jr. Cardiac ischemia model for +Gz using miniature swine and baboons. Aviat Space Environ Med 2008; 79:374–83.
Background:
Military
aircrew with minimal coronary artery disease (MCAD) may be restricted from flying high-performance aircraft due to possible ischemia during high +Gz. An animal model is presented to provide ischemia data for a more informed decision.
Methods:
There were 18 swine
that were placed on a high cholesterol/high fat diet for up to 57 wk. Five control swine were maintained on a standard swine diet. Also, nine male baboons had a constrictor placed around the left anterior descending coronary artery. Two baboons were sham-operated controls. The unanesthetized
swine and baboons were infused with Tc-99m at the end of +Gz exposure and scanned for myocardial perfusion.
Results:
Five swine died unexpectedly before +Gz exposure with moderate-to-severe CAD. Dysrhythmias during +Gz were seen
equally in both the control and experimental swine and in the baboons before and after stenosis, with or without propranolol. During +Gz, ECG ST-T wave changes suggesting ischemia were observed in the cholesterol swine but not the control swine, and in the baboons before and
after stenosis, with or without propranolol. There was a positive relationship between a normal/abnormal ECG and a normal/abnormal myocardial perfusion scan in the swine and a weak relationship in the baboon before stenosis, but somewhat better after stenosis. Coronary histopathology showed
normal vessels from the control swine and stenoses ranging from 0–95% from the cholesterol swine. Baboon stenosis averaged 37.6 ± 15.0%.
Conclusions:
In the swine and the baboon extended high levels of +Gz were associated with evidence of myocardial
ischemia.