636 
PHYSIOLOGY 
ATRIAL PACING 
HR/min 
-180 
30 
DLNP/DT sec"^ 
-54 
DP/DT mm hg/sec 
-3733 ^ ^ 
l^-e-Jl^ — — — — ' 
A P mm hff 
-125 ^ 
-88 
LVP mm hff 
LAP mm hg 
-18 ^ 
LVID cm 
-4.5 
,1 ^UJ_L_L„L_-UUU_Uaa.ULLULLLL.LLLLLLU 
Figure 4. — Same as Figure 3 at higher paper speed. Note the high V waves on the left atrial pressure pulse at the 
high pacing rate (panel 4). 
ventricular function curve. Further there is far 
less scatter about the regression line. These data 
show that for any given end-diastolic volume, 
atrial pacing results in more stroke work than 
ventricular pacing. The intersection of lines ( 1 ) 
and (2) is for control data for each period of 
pacing. The finding of a linear relation between 
SW and EDV during ventricular pacing and the 
ease with which control of the ventricle was ob- 
tained led us to investigate the feasibility of 
using ventricular pacing in the genesis of ven- 
tricular function curves. 
In Figure 9 is shown the regression equation 
for atrial pacing (1) and ventricular pacing 
