<s>
Cardiac	B-Algorithm
resynchronisation	I-Algorithm
therapy	I-Algorithm
(	O
CRT	B-Algorithm
or	O
CRT-P	O
)	O
is	O
the	O
insertion	O
of	O
electrodes	O
in	O
the	O
left	O
and	O
right	O
ventricles	O
of	O
the	O
heart	O
,	O
as	O
well	O
as	O
on	O
occasion	O
the	O
right	O
atrium	O
,	O
to	O
treat	O
heart	O
failure	O
by	O
coordinating	O
the	O
function	O
of	O
the	O
left	O
and	O
right	O
ventricles	O
via	O
a	O
pacemaker	B-Device
,	O
a	O
small	O
device	O
inserted	O
into	O
the	O
anterior	O
chest	O
wall	O
.	O
</s>
<s>
CRT	B-Algorithm
is	O
indicated	O
in	O
patients	O
with	O
a	O
low	O
ejection	O
fraction	O
(	O
typically	O
<3	O
5%	O
)	O
indicating	O
heart	O
failure	O
,	O
where	O
electrical	O
activity	O
has	O
been	O
compromised	O
,	O
with	O
prolonged	O
QRS	B-Algorithm
duration	O
to	O
>120	O
ms.	O
</s>
<s>
CRT	B-Algorithm
defibrillators	O
(	O
CRT-D	B-Algorithm
)	O
also	O
incorporate	O
the	O
additional	O
function	O
of	O
an	O
implantable	O
cardioverter-defibrillator	O
(	O
ICD	O
)	O
,	O
to	O
quickly	O
terminate	O
an	O
abnormally	O
fast	O
,	O
life-threatening	O
heart	B-Algorithm
rhythm	I-Algorithm
.	O
</s>
<s>
CRT	B-Algorithm
and	O
CRT-D	B-Algorithm
have	O
become	O
increasingly	O
important	O
therapeutic	O
options	O
for	O
patients	O
with	O
moderate	O
and	O
severe	O
heart	O
failure	O
.	O
</s>
<s>
CRT	B-Algorithm
with	O
pacemaker	B-Device
only	O
is	O
often	O
termed	O
"	O
CRT-P	O
"	O
to	O
help	O
distinguish	O
it	O
from	O
CRT	B-Algorithm
with	O
defibrillator	O
(	O
CRT-D	B-Algorithm
)	O
.	O
</s>
<s>
The	O
key	O
indication	O
for	O
CRT	B-Algorithm
is	O
left	O
bundle	O
branch	O
block	O
(	O
LBBB	O
)	O
of	O
the	O
heart	O
,	O
a	O
cardiac	O
abnormality	O
leading	O
to	O
delayed	O
left	O
ventricular	O
contraction	O
.	O
</s>
<s>
LBBB	O
causes	O
a	O
QRS	B-Algorithm
prolongation	O
of	O
≥120	O
ms	O
on	O
the	O
electrocardiogram	B-Application
,	O
contributing	O
to	O
poor	O
left	O
ventricular	O
coordination	O
and	O
reduced	O
systolic	O
function	O
,	O
thereby	O
reduced	O
ejection	O
fraction	O
(	O
<3	O
5%	O
)	O
.	O
</s>
<s>
Current	O
National	O
Institute	O
for	O
Health	O
and	O
Care	O
Excellence	O
(	O
NICE	O
)	O
guidelines	O
state	O
that	O
CRT-D	B-Algorithm
device	O
placement	O
is	O
inappropriate	O
for	O
class	O
IV	O
heart	O
failure	O
,	O
but	O
placement	O
of	O
CRT-P	O
devices	O
may	O
be	O
appropriate	O
in	O
certain	O
circumstances	O
.	O
</s>
<s>
CRT	B-Algorithm
requires	O
the	O
placement	O
of	O
an	O
electrical	O
device	O
for	O
biventricular	O
pacing	O
,	O
along	O
with	O
placement	O
of	O
(	O
at	O
least	O
)	O
two	O
pacing	O
leads	O
,	O
to	O
facilitate	O
stable	O
left	O
ventricular	O
and	O
right	O
ventricular	B-Device
pacing	I-Device
.	O
</s>
<s>
This	O
is	O
generally	O
performed	O
subsequent	O
to	O
RV	O
lead	O
placement	O
,	O
with	O
the	O
RV	O
lead	O
providing	O
a	O
backup	O
in	O
case	O
of	O
accidental	O
damage	O
to	O
the	O
electric	B-Algorithm
fibers	I-Algorithm
of	I-Algorithm
the	I-Algorithm
heart	I-Algorithm
,	O
causing	O
an	O
asystolic	O
event	O
.	O
</s>
<s>
From	O
here	O
a	O
contrast	B-Algorithm
media	I-Algorithm
is	O
injected	O
,	O
allowing	O
the	O
surgical	O
team	O
to	O
obtain	O
a	O
coronary	O
sinus	O
phlebogram	O
to	O
direct	O
the	O
placement	O
of	O
the	O
lead	O
into	O
the	O
most	O
suitable	O
coronary	O
vein	O
.	O
</s>
<s>
The	O
device	O
,	O
similar	O
to	O
that	O
of	O
a	O
traditional	O
pacemaker	B-Device
,	O
is	O
generally	O
no	O
larger	O
than	O
a	O
pocket	O
watch	O
and	O
has	O
inserts	O
for	O
the	O
electrode	O
leads	O
.	O
</s>
<s>
Several	O
studies	O
have	O
also	O
shown	O
that	O
CRT	B-Algorithm
can	O
decrease	O
mortality	O
,	O
reverse	O
left	O
ventricular	O
remodeling	O
,	O
and	O
improve	O
quality	O
of	O
life	O
,	O
walking	O
distance	O
,	O
and	O
peak	O
oxygen	O
uptake	O
(	O
VO2	O
max	O
)	O
.	O
</s>
<s>
A	O
2013	O
study	O
showed	O
that	O
CRT	B-Algorithm
improved	O
the	O
left	O
ventricular	O
ejection	O
fraction	O
(	O
LVEF	O
)	O
by	O
an	O
average	O
of	O
10.6	O
%	O
12	O
months	O
after	O
placement	O
.	O
</s>
<s>
Several	O
research	O
papers	O
have	O
proposed	O
software	O
platforms	O
for	O
planning	O
and	O
guiding	O
the	O
implantation	O
of	O
CRT	B-Algorithm
devices	O
.	O
</s>
<s>
This	O
research	O
proposes	O
using	O
pre-operative	O
images	O
to	O
characterize	O
tissue	O
and	O
left	O
ventricle	O
activation	O
to	O
identify	O
potential	O
target	O
regions	O
for	O
deploying	O
the	O
CRT	B-Algorithm
leads	O
.	O
</s>
