160 
CARDIAC MODELS 
r 
3 DAYS 
it 
4 DAYS 
8 DAYS 
Figure 2. — Serial ECG's which demonstrate the initial tachycardia, idioventricular tachycardia, and acute ischemia 
changes. After 48 hours the rhythm is sinus and the Q waves of acute myocardial infarction are present. 
the dogs surviving greater than 48 hours 
(Table II). A statistically significant decrease 
occurred in several parameters at both 24 and 
48 hours after helical wire implant. The cardiac 
output and stroke volume were maximally de- 
creased at 24 hours and in survivors gradually 
improved over the next several days but never 
returned to the control values. The heart rate 
was maximal at 24 hours — usually idioventricu- 
lar tachycardia — and both rate and rhythm re- 
verted to normal by the third day. While the he- 
modynamic changes and infarction weight were 
similar in both left circumflex and anterior de- 
scending artery occlusions the SGOT elevation 
was not as high in the former. However the 
wide range of enzyme values was such that the 
difference was not statistically significant. 
