<s>
A	O
tachycardia-dependent	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
is	O
a	O
defect	O
in	O
the	O
conduction	O
system	O
of	O
the	O
heart	O
,	O
and	O
is	O
distinct	O
from	O
typical	O
bundle	B-Algorithm
branch	I-Algorithm
blocks	I-Algorithm
due	O
to	O
its	O
reliable	O
,	O
reproducible	O
onset	O
related	O
to	O
an	O
increase	O
in	O
the	O
rate	O
of	O
cardiac	O
contraction	O
.	O
</s>
<s>
Tachycardia-dependent	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
can	O
prevent	O
both	O
ventricles	O
from	O
contracting	O
efficiently	O
and	O
can	O
limit	O
the	O
cardiac	O
output	O
of	O
the	O
heart	O
.	O
</s>
<s>
This	O
is	O
referred	O
to	O
as	O
a	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
and	O
is	O
seen	O
clinically	O
as	O
rate-dependent	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
,	O
right	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
or	O
left	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
.	O
</s>
<s>
From	O
here	O
,	O
the	O
signal	O
travels	O
down	O
a	O
signal	O
conducting	O
channel	O
(	O
the	O
bundle	B-Algorithm
of	I-Algorithm
His	I-Algorithm
)	O
where	O
it	O
will	O
diverge	O
into	O
a	O
left	O
and	O
right	O
branch	O
that	O
will	O
control	O
the	O
left	O
and	O
right	O
ventricle	O
,	O
respectively	O
.	O
</s>
<s>
This	O
damage	O
results	O
in	O
the	O
inability	O
of	O
this	O
neural-like	O
tissue	O
to	O
conduct	O
electrical	O
signals	O
and	O
control	O
the	O
heart	O
as	O
efficiently	O
as	O
before	O
,	O
resulting	O
in	O
the	O
cardiac	O
abnormality	O
known	O
as	O
a	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
(	O
BBB	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
certain	O
situations	O
of	O
excessive	O
or	O
reduced	O
heart	O
rate	O
(	O
tachycardia	B-Application
or	O
bradycardia	B-Algorithm
,	O
respectively	O
)	O
can	O
cause	O
a	O
BBB	O
known	O
as	O
a	O
rate-dependent	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
(	O
RDBBB	O
)	O
.	O
</s>
<s>
This	O
manifests	O
in	O
a	O
similar	O
fashion	O
to	O
a	O
regular	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
,	O
but	O
occurs	O
only	O
under	O
conditions	O
that	O
affect	O
contractile	O
rate	O
.	O
</s>
<s>
Tachycardia-dependent	B-Algorithm
bundle	I-Algorithm
branch	I-Algorithm
block	I-Algorithm
(	O
TDBBB	B-Algorithm
)	O
can	O
affect	O
either	O
ventricle	O
in	O
the	O
heart	O
,	O
and	O
occurs	O
when	O
the	O
heart	O
's	O
rate	O
of	O
contraction	O
reaches	O
an	O
elevated	O
level	O
and	O
becomes	O
uncoupled	O
from	O
the	O
heart	O
's	O
refractory	O
period	O
(	O
the	O
time	O
it	O
takes	O
for	O
a	O
cardiac	O
cell	O
to	O
"	O
reset	O
"	O
for	O
future	O
contraction	O
)	O
.	O
</s>
<s>
TDBBB	B-Algorithm
can	O
be	O
diagnosed	O
with	O
use	O
of	O
an	O
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
which	O
will	O
"	O
trace	O
"	O
the	O
electrical	O
activity	O
of	O
the	O
heart	O
,	O
providing	O
an	O
overall	O
view	O
of	O
the	O
hearts	O
electrical	O
system	O
.	O
</s>
<s>
Typically	O
,	O
TDBBB	B-Algorithm
will	O
be	O
evident	O
on	O
an	O
ECG	B-Application
and	O
manifest	O
as	O
a	O
prolongation	O
of	O
the	O
QRS	B-Algorithm
complex	I-Algorithm
(	O
a	O
QRS	B-Algorithm
complex	I-Algorithm
completion	O
time	O
that	O
exceeds	O
120ms	O
)	O
,	O
notching	O
or	O
slurring	O
of	O
the	O
R	B-Algorithm
wave	I-Algorithm
,	O
or	O
the	O
absence	O
of	O
Q	O
waves	O
should	O
the	O
TDBBB	B-Algorithm
affect	O
the	O
left	O
ventricle	O
.	O
</s>
<s>
If	O
an	O
affected	O
individual	O
begins	O
to	O
experience	O
severe	O
TDBBB	B-Algorithm
,	O
then	O
medical	O
intervention	O
is	O
often	O
advised	O
.	O
</s>
<s>
Suggested	O
therapy	O
for	O
the	O
treatment	O
of	O
TDBBB	B-Algorithm
can	O
include	O
the	O
prescription	O
of	O
certain	O
medications	O
or	O
the	O
implantation	O
of	O
a	O
pacemaker	B-Device
device	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
pacemaker	B-Device
would	O
ensure	O
that	O
the	O
heart	O
receives	O
a	O
constant	O
rhythmic	O
electrical	O
input	O
that	O
never	O
changes	O
in	O
frequency	O
.	O
</s>
<s>
While	O
this	O
would	O
effectively	O
eliminate	O
the	O
occurrence	O
of	O
TDBBB	B-Algorithm
,	O
the	O
pacemaker	B-Device
would	O
restrict	O
the	O
patient	O
's	O
heart	O
to	O
a	O
permanent	O
rhythm	O
,	O
eliminating	O
the	O
ability	O
of	O
patients	O
to	O
perform	O
physical	O
activity	O
.	O
</s>
<s>
Future	O
pacemakers	B-Device
that	O
adaptively	O
respond	O
to	O
physiological	O
requirements	O
are	O
being	O
developed	O
in	O
order	O
to	O
negate	O
the	O
limitations	O
observed	O
with	O
their	O
current	O
use	O
.	O
</s>
