JACOB I. HIRSCH, FRITZ STREULI AND FRED GORSTEIN 
31 
2. The effect of pairing the intracoronary 
electrode against a single precordial electrode 
versus 6 external electrodes arranged around 
the circumference of the chest. 
3. Varying the total energy delivered. 
4. Observation on the strenth and duration 
of the electric current using v^^eak currents of 
less than 1 milliampere for 5 minutes or more 
versus intense currents delivered in pulses of 11 
milliseconds each. 
Pathophysiologic Consequences 
The effect of thrombotic occlusion of a branch 
of the coronary artery system upon 5 variables 
are cited. 
The first is the electrocardiographic, in vi^hich 
changes in pattern and in rhythm v^ere moni- 
tored. In 5 of the so-called chronic experiments, 
the electrocardiogram was recorded continu- 
ously on magnetic tape for 24 hours following 
delivery of electric current into the coronary ar- 
tery. 
The second group is the serum enzymes in- 
cluding creatine phosphokinase (CPK), glu- 
tamic oxaloacetic transaminase (GOT), and 
lactic dehydrogenase (LDH), which were meas- 
ured at intervals in 37 dogs. In 25 of these, A-V 
differences were measured between arterial 
blood and coronary sinus blood. 
The third is A-V differences in serum lactate 
concentration between arterial and coronary 
sinus blood, which were determined in 7 experi- 
ments. In 5 of these myocardial infarction oc- 
curred, and in 2 it did not occur. In all of the 
lactate studies, serum samples were drawn 70 
minutes and 15 minutes prior to initiation of 
electric current, and 60, 90, 120 and 150 min- 
utes following the beginning of electric current. 
The fourth group of sequelae of coronary oc- 
clusion and myocardial infarction comprises 
changes in hemodynamics. Heart rate (HR), 
cardiac output (CO), ejection fraction (EF), 
maximum isovolumic pressure (MIP), maxi- 
mum rate of pressure rise (dp/dt), aortic pres- 
sure (AP) and left ventricular pressure (LVP) 
were measured. In addition, stroke volume 
(SV), end-diastolic volume (EDV), left ventri- 
cular circumference (LVC) and contractility 
index (ConI) were calculated.-"* Cardiac output, 
stroke volume, end-diastolic volume and ejec- 
tion fraction were determined by means of the 
dye dilution method using a Lexington Analog 
Computer and Cardiogreen dye. 
The fifth group of observations made follow- 
ing myocardial infarction consists of the patho- 
logic changes which occurred in the coronary 
artery and in the myocardium. Following sacri- 
fice, hearts were fixed in 10 percent formalin. 
Fifty-nine of these were prepared for histologi- 
cal examination in addition to gross examina- 
tion. The coronary arteries and veins were 
examined in all cases. The myocardium was ex- 
amined in all cases except those in which death 
occurred very early in the experiment. Examina- 
tion of the coronary arteries and veins included 
tissue blocks proximal to, at, and distal to the 
site of occlusion. In the chronic experiments, 
the fixed hearts were sliced in parallel coronal 
sections 1 cm thick. The surfaces of these sec- 
tions were photographed and then traced, and 
the infarction mapped using gross and histo- 
logic findings. 
RESULTS 
General Techniques 
Depending upon the degree to which the 
Sones catheter was wedged within the coronary 
artery, the rate of clearance of injected Hy- 
paque was either very rapid, slowed to varying 
degrees or completely arrested. We have found 
that for intimal damage and thrombus forma- 
tion to occur, the rate of Hypaque clearance 
must have been reduced to a significant de- 
gree. In each experiment, therefore, this was 
achieved. When a substantial reduction in blood 
flow occurred, the electrocardiogram always 
manifested repolarization abnormalities due to 
the resulting myocardial ischemia.* If the flow 
was completely arrested a current of injury was 
observed after about 3 minutes. These changes 
were distinct from the transient, direct effect 
upon repolarization caused by the Hypaque it- 
self. 
Traumatic Interventions 
A comparison of changing the polarity of the 
intracoronary electrode from anode to cathode 
demonstrated that both were effective in pro- 
ducing arterial lesions and thromboses. The 
slightly greater effectiveness of anodal current 
