72 
CARDIAC MODELS 
Left Ventricular Volumes & Excess Lactate— (10 Dogs) 
After Isoproterenol and in Combination With NE 
baseline 
WM SHOCK 
l.lA — ISO 
ISO & NE 
* N.S. 
(moles/liter) 
Figure 14. — Left ventricular end-diastolic (EDV) and 
end-systolic volumes (ESV) ; ejection fraction (EF) ; 
myocardial excess lactate and pressure rate index 
(PRI, modified tension time index). Note improve- 
ment of EF and excess lactate with combined treat- 
ment. 
CONCLUSIONS 
The total number of dogs to date in whom 
metallic mercury was injected into the coronary 
artery with the intent to produce myocardial in- 
farction and cardiogenic shock was over 100. In 
98% of the animals the circumflex or the ante- 
rior descending coronary artery could easily be 
catheterized with our double catheter technique. 
When the circumflex coronary artery was in- 
jected with mercury 18% developed ventricular 
flbrillation soon after injection. A small number 
of these could be cardioverted and the experi- 
ment could be continued. About 80 % of the ani- 
mals developed hypotension, decrease of cardiac 
output, stroke volume, and dP/dt. In 5% of 
these dogs the hemodynamic changes were mod- 
erate and did not fulfill the criteria of cardiogenic 
shock. Thus 75% of the total mercury injected 
animals developed cardiogenic shock with mod- 
erate hypotension, tachycardia, marked decrease 
of dP/dt, cardiac output, stroke volume, (40- 
50%) and changes in other parameters as de- 
scribed in the results. We can conclude that the 
mercury technique results in a reliable model of 
cardiogenic shock and is useful for various stu- 
dies in the closed chest unanesthetized animal. 
Our results confirm the findings of Lluch et al., 
who also find this model very reliable. 
SUMMARY 
The model allowed us to study afferent vagal 
reflex mechanisms and drug effects in cardi- 
ogenic shock. It helped to elucidate a possible un- 
recognized positive feedback mechanism which 
may be detrimental to the already compromised 
circulatory system in cardiogenic shock. If 
vagal afferent reflexes are overly active in 
shock, then it is not surprising that sym- 
pathetic augmentation is effective. Since the 
organism itself supresses its maximum compen- 
satory capacity by this positive feedback, a com- 
bination of alpha and beta adrenergic stimulating 
drugs may break the vicious cycle by restoring 
this maximum compensatory capacity. How- 
ever, careful analysis of the different circulatory 
and metabolic factors is necessary to eluci- 
date the most effective drug combination for the 
treatment of this delicately balanced condition. 
The mercury model is well suited for the analy- 
sis of these delicate balances and the study of 
combination drug treatment with isoproterenol 
and norepinephrine proved that not only the 
choice of medication but the careful adjustment 
of the dose is an important factor. Based on our 
animal studies we have similarly treated a small 
60 
-2;s -2 ^Ts ^1 ^^^S 0 is i fTs 2 «2.5 
Figure 15. — Relationship of myocardial excess lactate 
to left ventricular stroke work before and during iso- 
proterenol, norepinephrine and combined treatment 
in shock. Note that best effect on these parameters 
occurs with combined treatment. 
