<s>
In	O
electrocardiography	B-Application
,	O
during	O
a	O
cardiac	O
cycle	O
,	O
once	O
an	O
action	O
potential	O
is	O
initiated	O
,	O
there	O
is	O
a	O
period	O
of	O
time	O
that	O
a	O
new	O
action	O
potential	O
cannot	O
be	O
initiated	O
.	O
</s>
<s>
This	O
is	O
termed	O
the	O
effective	B-Algorithm
refractory	I-Algorithm
period	I-Algorithm
(	O
ERP	O
)	O
of	O
the	O
tissue	O
.	O
</s>
<s>
For	O
the	O
treatment	O
of	O
atrial	B-Application
fibrillation	I-Application
,	O
it	O
is	O
a	O
problem	O
that	O
the	O
prolongation	O
of	O
the	O
ERP	O
by	O
these	O
agents	O
also	O
affects	O
the	O
ventricles	O
,	O
which	O
can	O
induce	O
other	O
types	O
of	O
arrhythmias	O
.	O
</s>
