<s>
Trifascicular	B-Algorithm
block	I-Algorithm
is	O
a	O
problem	O
with	O
the	O
electrical	B-Algorithm
conduction	I-Algorithm
of	O
the	O
heart	O
,	O
specifically	O
the	O
three	O
fascicles	O
of	O
the	O
bundle	O
branches	O
that	O
carry	O
electrical	O
signals	O
from	O
the	O
atrioventricular	O
node	O
to	O
the	O
ventricles	O
.	O
</s>
<s>
The	O
most	O
literal	O
meaning	O
of	O
trifascicular	B-Algorithm
block	I-Algorithm
is	O
complete	B-Architecture
heart	I-Architecture
block	I-Architecture
:	O
all	O
three	O
fascicles	O
are	O
blocked	O
.	O
</s>
<s>
A	O
second	O
,	O
and	O
clinically	O
distinct	O
,	O
definition	O
of	O
trifascicular	B-Algorithm
block	I-Algorithm
is	O
a	O
circumstance	O
in	O
which	O
right	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
(	O
RBBB	B-Algorithm
)	O
and	O
left	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
occur	O
in	O
the	O
same	O
patient	O
,	O
but	O
at	O
distinct	O
points	O
in	O
time	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
patient	O
that	O
is	O
found	O
to	O
have	O
a	O
RBBB	B-Algorithm
one	O
day	O
and	O
a	O
LBBB	O
another	O
can	O
be	O
said	O
to	O
have	O
"	O
alternating	O
bundle	B-Algorithm
branch	I-Algorithm
blocks	I-Algorithm
"	O
.	O
</s>
<s>
In	O
this	O
context	O
,	O
because	O
all	O
three	O
fascicles	O
show	O
evidence	O
of	O
block	O
at	O
different	O
points	O
in	O
time	O
,	O
the	O
term	O
trifascicular	B-Algorithm
block	I-Algorithm
is	O
often	O
used	O
.	O
</s>
<s>
Finally	O
,	O
the	O
third	O
meaning	O
of	O
trifascicular	B-Algorithm
block	I-Algorithm
refers	O
to	O
a	O
specific	O
finding	O
on	O
an	O
electrocardiogram	B-Application
in	O
which	O
bifascicular	B-Algorithm
block	I-Algorithm
is	O
observed	O
in	O
a	O
patient	O
with	O
a	O
prolonged	O
PR	O
interval	O
(	O
first	B-Algorithm
degree	I-Algorithm
AV	I-Algorithm
block	I-Algorithm
)	O
.	O
</s>
<s>
The	O
treatment	O
of	O
trifascicular	B-Algorithm
block	I-Algorithm
is	O
highly	O
dependent	O
on	O
which	O
clinical	O
entity	O
(	O
one	O
of	O
the	O
three	O
above	O
)	O
is	O
being	O
described	O
.	O
</s>
<s>
An	O
electrophysiology	B-Algorithm
study	I-Algorithm
of	O
the	O
conduction	B-Algorithm
system	I-Algorithm
can	O
help	O
discern	O
the	O
severity	O
of	O
conduction	B-Algorithm
system	I-Algorithm
disease	O
.	O
</s>
<s>
In	O
an	O
electrophysiology	B-Algorithm
study	I-Algorithm
,	O
trifascicular	B-Algorithm
block	I-Algorithm
due	O
to	O
AV	O
nodal	O
disease	O
is	O
represented	O
by	O
a	O
prolonged	O
AH	O
interval	O
(	O
denoting	O
prolonged	O
time	O
from	O
impulse	O
generation	O
in	O
the	O
atria	O
and	O
conduction	B-Algorithm
to	O
the	O
bundle	B-Algorithm
of	I-Algorithm
His	I-Algorithm
)	O
with	O
a	O
relatively	O
preserved	O
HV	O
interval	O
(	O
denoting	O
normal	O
conduction	B-Algorithm
from	O
the	O
bundle	B-Algorithm
of	I-Algorithm
His	I-Algorithm
to	O
the	O
ventricles	O
)	O
.	O
</s>
<s>
Trifascicular	B-Algorithm
block	I-Algorithm
due	O
to	O
distal	O
conduction	B-Algorithm
system	I-Algorithm
disease	O
is	O
represented	O
by	O
a	O
normal	O
AH	O
interval	O
and	O
a	O
prolonged	O
HV	O
interval	O
.	O
</s>
<s>
An	O
implantable	O
cardiac	O
pacemaker	B-Device
or	O
permanent	B-Device
pacemaker	I-Device
is	O
recommended	O
in	O
the	O
following	O
clinical	O
circumstances	O
.	O
</s>
<s>
Bifascicular	B-Algorithm
block	I-Algorithm
+	O
syncope	O
+	O
alternative	O
causes	O
ruled	O
out	O
(	O
e.g.	O
</s>
