L. N. COTHRAN, E. W. HAWTHORNE AND H. SANDLER 
555 
A P 
LVP 
Figure 2. — A schematic representation of the left ven- 
tricle showing transducer placement (type II). 
(LVC) left ventricular circumference, (Si — S2) sono- 
micrometer for internal diameter, (LVP) left ven- 
tricular pressure, (AP) aortic pressure. 
ular and aortic pressures in the remaining ani- 
mals were obtained through polyvinal catheters 
inserted into the apical dimple and the descend- 
ing aorta. 
After surgery, a recovery period of seven to 
ten days was allowed. Records were obtained on 
each animal while quietly standing in a modified 
Pavlov sling. The five dogs studied by biplane 
cineradiography were lightly tranquilized and 
positioned in sternal recumbency in a fiber glass 
molded cradle and straped in place on the x-ray 
table. All primary variables and their calibra- 
tions were recorded on a multichannel direct 
writing recorder and on analog tape. 
Data Reduction 
The output of the magnetic tape playback 
was amplified, offset where necessary and input 
to the analog to digital converter module of a 
2116B Hewlett Packard digital computer sys- 
tem. Selected samples of the analog signals 
were obtained and processed on command by in- 
structions input through the teletype keyboard. 
Calibration factors were input at the start of 
the data reduction routine so that conversion 
from volts to the appropriate units of dimen- 
sion was complete prior to storage of the prime 
data. Sampling frequency for the data pre- 
sented here was set at one point every 10 milli- 
seconds for each variable digitized for a total of 
200 points per channel. The prime data was 
stored in a buffer array that was dimensioned 
by the source program. The derived data was 
obtained by subjecting the elements of the 
buffer array to the various algorithms provided 
in the source program. A permanent record of 
all data was provided by teletype printout. 
The films obtained during biplane cineo- 
graphic studies were digitized by hand in a 
frame-by- frame fashion. Each frame of the film 
contained in one corner, a trace of the simulta- 
neously recorded analog data and one channel 
of the analog data contained a frame marker 
which corresponded on a one-to-one basis with 
Figure 3. — A schematic representation of the left ven- 
tricle showing transducer placesment (type III). 
(Ci — C3) external diameter coils, (Mi — M2( radi- 
opaque length markers, (LVP) left ventricular pres- 
sure, (AP) aortic pressure. 
