<s>
Heart	B-Algorithm
rate	I-Algorithm
turbulence	I-Algorithm
(	O
HRT	O
)	O
is	O
the	O
return	O
to	O
equilibrium	O
of	O
heart	O
rate	O
after	O
a	O
premature	B-Error_Name
ventricular	I-Error_Name
contraction	I-Error_Name
(	O
PVC	B-Error_Name
)	O
.	O
</s>
<s>
The	O
measured	O
values	O
of	O
HRT	O
parameters	O
have	O
been	O
shown	O
to	O
be	O
a	O
statistically	B-General_Concept
significant	I-General_Concept
predictor	O
of	O
the	O
probability	O
of	O
dying	O
from	O
cardiac	O
disease	O
after	O
a	O
patient	O
suffers	O
a	O
myocardial	O
infarction	O
.	O
</s>
<s>
HRT	O
can	O
also	O
be	O
used	O
to	O
predict	O
death	O
in	O
patients	O
with	O
congestive	O
heart	O
failure	O
from	O
a	O
lethal	O
arrhythmia	B-Application
.	O
</s>
<s>
While	O
studying	O
PVC	B-Error_Name
characteristics	O
,	O
Schmidt	O
and	O
his	O
colleagues	O
noticed	O
that	O
heart	O
rate	O
seemed	O
to	O
speed	O
up	O
after	O
a	O
PVC	B-Error_Name
.	O
</s>
<s>
To	O
clarify	O
,	O
they	O
listed	O
the	O
time	O
from	O
one	O
heartbeat	O
's	O
R-wave	B-Algorithm
to	O
the	O
next	O
R-wave	B-Algorithm
(	O
called	O
RR	O
intervals	O
)	O
and	O
synchronized	O
these	O
lists	O
to	O
the	O
time	O
of	O
the	O
PVC	B-Error_Name
beat	O
and	O
averaged	O
the	O
values	O
in	O
the	O
list	O
.	O
</s>
<s>
A	O
plot	O
of	O
this	O
averaged	O
RR	O
interval	O
list	O
(	O
called	O
a	O
PVC	B-Error_Name
tachogram	O
)	O
not	O
only	O
confirmed	O
their	O
observation	O
that	O
heart	O
rate	O
sped	O
up	O
for	O
a	O
few	O
beats	O
after	O
a	O
PVC	B-Error_Name
,	O
but	O
highlighted	O
another	O
less	O
obvious	O
feature	O
,	O
that	O
heart	O
rate	O
then	O
slows	O
down	O
beyond	O
what	O
it	O
was	O
before	O
the	O
PVC	B-Error_Name
,	O
before	O
returning	O
to	O
the	O
original	O
heart	O
rate	O
.	O
</s>
<s>
That	O
is	O
,	O
a	O
PVC	B-Error_Name
interrupts	O
the	O
normal	O
cardiac	O
cycle	O
,	O
so	O
the	O
ventricles	O
of	O
the	O
heart	O
do	O
not	O
have	O
time	O
to	O
fill	O
up	O
to	O
their	O
normal	O
level	O
,	O
before	O
contracting	O
and	O
pumping	O
their	O
contents	O
out	O
.	O
</s>
<s>
The	O
contribution	O
of	O
the	O
compensatory	O
pause	O
,	O
the	O
pause	O
between	O
the	O
PVC	B-Error_Name
and	O
the	O
next	O
normal	O
beat	O
,	O
to	O
HRT	O
is	O
also	O
unknown	O
.	O
</s>
<s>
The	O
reason	O
the	O
size	O
of	O
HRT	O
after	O
a	O
PVC	B-Error_Name
predicts	O
cardiac	O
death	O
is	O
suggested	O
by	O
its	O
mechanism	O
.	O
</s>
