Cardiac ischemia model for +Gz using miniature swine and baboons.
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.
Burns
John W
JW
Biosciences and Protection Division, Air Force Research Laboratory Brooks City-Base, TX, USA. john.burns@amedd.army.mil
Kruyer
William B
WB
Celio
Paul V
PV
Deering
Joseph
J
Loecker
Thomas H
TH
Richardson
Londe A
LA
Fanton
John W
JW
Davis
Harold
H
Dick
Edward J
EJ
D000337:Aerospace Medicine; D000818:Animals; D017023:Coronary Angiography; D023921:Coronary Stenosis / Q000473:pathology; D003331:Coronary Vessels / Q000473:pathology; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D018471:Hypergravity; D008055:Lipids / Q000097:blood; D008297:Male; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D048548:Papio cynocephalus; D013552:Swine; D013556:Swine, Miniature; D015899:Tomography, Emission-Computed, Single-Photon
D008055:Lipids