<s>
Pacemaker	B-Algorithm
failure	I-Algorithm
is	O
the	O
inability	O
of	O
an	O
implanted	O
artificial	B-Device
pacemaker	I-Device
to	O
perform	O
its	O
intended	O
function	O
of	O
regulating	O
the	O
beating	O
of	O
the	O
heart	O
.	O
</s>
<s>
A	O
pacemaker	B-Device
uses	O
electrical	O
impulses	O
delivered	O
by	O
electrodes	O
in	O
order	O
to	O
contract	O
the	O
heart	O
muscles	O
.	O
</s>
<s>
Failure	O
of	O
a	O
pacemaker	B-Device
is	O
defined	O
by	O
the	O
requirement	O
of	O
repeat	O
surgical	O
pacemaker-related	O
procedures	O
after	O
the	O
initial	O
implantation	O
.	O
</s>
<s>
Most	O
implanted	B-Device
pacemakers	I-Device
are	O
dual	O
chambered	O
and	O
have	O
two	O
leads	O
,	O
causing	O
the	O
implantation	O
time	O
to	O
take	O
longer	O
because	O
of	O
this	O
more	O
complicated	O
pacemaker	B-Device
system	O
.	O
</s>
<s>
These	O
factors	O
can	O
contribute	O
to	O
an	O
increased	O
rate	O
of	O
complications	O
which	O
can	O
lead	O
to	O
pacemaker	B-Algorithm
failure	I-Algorithm
.	O
</s>
<s>
Approximately	O
2.25	O
million	O
pacemakers	B-Device
were	O
implanted	O
in	O
the	O
United	O
States	O
between	O
1990	O
and	O
2002	O
,	O
and	O
of	O
those	O
pacemakers	B-Device
,	O
about	O
8,834	O
were	O
removed	O
from	O
patients	O
because	O
of	O
device	O
malfunction	O
most	O
commonly	O
connected	O
to	O
generator	O
abnormalities	O
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
results	O
of	O
an	O
Oregon	O
study	O
indicated	O
that	O
10%	O
of	O
implanted	B-Device
pacemakers	I-Device
failed	O
within	O
the	O
first	O
month	O
.	O
</s>
<s>
Another	O
study	O
found	O
that	O
more	O
than	O
half	O
of	O
pacemaker	B-Device
complications	O
occurred	O
during	O
the	O
first	O
3	O
months	O
after	O
implantation	O
.	O
</s>
<s>
Causes	O
of	O
pacemaker	B-Algorithm
failure	I-Algorithm
include	O
lead	O
related	O
failure	O
,	O
unit	O
malfunction	O
,	O
problems	O
at	O
the	O
insertion	O
site	O
,	O
failures	O
related	O
to	O
exposure	O
to	O
high	O
voltage	O
electricity	O
or	O
high	O
intensity	O
microwaves	O
,	O
and	O
a	O
miscellaneous	O
category	O
(	O
one	O
patient	O
had	O
ventricular	B-Application
tachycardia	I-Application
when	O
using	O
his	O
electric	O
razor	O
and	O
another	O
patient	O
had	O
persistent	O
pacing	O
of	O
the	O
diaphragm	O
muscle	O
)	O
.	O
</s>
<s>
Pacemaker	B-Device
malfunction	O
has	O
the	O
ability	O
to	O
cause	O
serious	O
injury	O
or	O
death	O
,	O
but	O
if	O
detected	O
early	O
enough	O
,	O
patients	O
can	O
continue	O
with	O
their	O
needed	O
therapy	O
once	O
complications	O
are	O
resolved	O
.	O
</s>
<s>
A	O
Micro-dislodgement	O
is	O
a	O
minimal	O
displacement	O
in	O
the	O
lead	O
that	O
is	O
not	O
visible	O
in	O
a	O
chest	O
X-ray	B-Library
,	O
but	O
has	O
the	O
ability	O
to	O
increase	O
the	O
capture	O
threshold	O
and	O
eventually	O
cause	O
a	O
loss	O
of	O
capture	O
.	O
</s>
<s>
Lead	O
dislodgement	O
can	O
cause	O
sensing	O
failure	O
,	O
which	O
occurs	O
when	O
proper	O
atrial	O
or	O
ventricular	O
sensing	O
is	O
not	O
achieved	O
by	O
the	O
programming	O
of	O
the	O
pacemaker	B-Device
.	O
</s>
<s>
Patients	O
who	O
work	O
with	O
or	O
near	O
such	O
equipment	O
should	O
know	O
that	O
their	O
pacemakers	B-Device
may	O
not	O
work	O
properly	O
in	O
those	O
conditions	O
.	O
</s>
<s>
Cellphones	O
using	O
these	O
new	O
frequencies	O
might	O
make	O
pacemakers	B-Device
less	O
reliable	O
.	O
</s>
<s>
Equipment	O
used	O
by	O
doctors	O
and	O
dentists	O
can	O
affect	O
pacemakers	B-Device
.	O
</s>
<s>
The	O
magnet	O
can	O
interrupt	O
the	O
pacing	O
and	O
inhibit	O
the	O
output	O
of	O
pacemakers	B-Device
.	O
</s>
<s>
If	O
MRI	O
must	O
be	O
done	O
,	O
the	O
pacemaker	B-Device
output	O
in	O
some	O
models	O
can	O
be	O
reprogrammed	O
.	O
</s>
<s>
In	O
February	O
2011	O
,	O
the	O
FDA	O
approved	O
an	O
MRI-safe	O
pacemaker	B-Device
.	O
</s>
<s>
Extracorporeal	O
shock-wave	O
lithotripsy	O
(	O
ESWL	O
)	O
procedure	O
is	O
safe	O
for	O
most	O
pacemaker	B-Device
patients	O
,	O
with	O
some	O
reprogramming	O
of	O
the	O
pacing	O
.	O
</s>
<s>
Patients	O
with	O
certain	O
kinds	O
of	O
pacemakers	B-Device
implanted	O
in	O
the	O
abdomen	O
should	O
avoid	O
ESWL	O
.	O
</s>
<s>
Diagnostic	O
radiation	O
(	O
such	O
as	O
screening	O
X-ray	B-Library
)	O
appears	O
to	O
have	O
no	O
effect	O
on	O
pacemaker	B-Device
pulse	O
generators	O
.	O
</s>
<s>
However	O
,	O
therapeutic	O
radiation	O
(	O
such	O
as	O
for	O
treating	O
cancerous	O
tumors	O
)	O
may	O
damage	O
the	O
pacemaker	B-Device
's	O
circuits	O
.	O
</s>
<s>
The	O
American	O
Heart	O
Association	O
recommends	O
that	O
the	O
pacemaker	B-Device
be	O
shielded	O
as	O
much	O
as	O
possible	O
,	O
and	O
moved	O
if	O
it	O
lies	O
directly	O
in	O
the	O
radiation	O
field	O
.	O
</s>
<s>
These	O
may	O
bypass	O
pacemaker	B-Device
's	O
noise	O
protection	O
and	O
interfere	O
with	O
or	O
permanently	O
damage	O
the	O
pulse	O
generator	O
.	O
</s>
