<s>
An	O
artificial	B-Device
cardiac	I-Device
pacemaker	I-Device
(	O
artificial	B-Device
pacemaker	I-Device
,	O
and	O
sometimes	O
just	O
pacemaker	B-Algorithm
,	O
although	O
the	O
term	O
is	O
also	O
used	O
to	O
refer	O
to	O
the	O
body	O
's	O
natural	O
cardiac	B-Algorithm
pacemaker	I-Algorithm
)	O
is	O
a	O
medical	O
device	O
,	O
nowadays	O
always	O
implanted	O
,	O
that	O
generates	O
electrical	B-Algorithm
pulses	I-Algorithm
delivered	O
by	O
electrodes	O
to	O
the	O
chambers	O
of	O
the	O
heart	O
,	O
either	O
the	O
upper	O
atria	O
or	O
lower	O
ventricles	O
.	O
</s>
<s>
Each	O
pulse	O
causes	O
the	O
targeted	O
chambers	O
to	O
contract	O
and	O
pump	O
blood	O
,	O
thus	O
regulating	O
the	O
function	O
of	O
the	O
electrical	B-Algorithm
conduction	I-Algorithm
system	I-Algorithm
of	I-Algorithm
the	I-Algorithm
heart	I-Algorithm
.	O
</s>
<s>
The	O
primary	O
purpose	O
of	O
a	O
pacemaker	B-Algorithm
is	O
to	O
maintain	O
an	O
adequate	O
heart	O
rate	O
,	O
either	O
because	O
the	O
heart	O
's	O
natural	B-Algorithm
pacemaker	I-Algorithm
is	O
not	O
fast	O
enough	O
,	O
or	O
because	O
there	O
is	O
a	O
block	B-Algorithm
in	O
the	O
heart	O
's	O
electrical	O
conduction	B-Algorithm
system	I-Algorithm
.	O
</s>
<s>
Modern	O
pacemakers	B-Device
are	O
externally	O
programmable	O
and	O
allow	O
a	O
cardiologist	O
,	O
particularly	O
a	O
cardiac	B-Algorithm
electrophysiologist	I-Algorithm
,	O
to	O
select	O
the	O
optimal	O
pacing	O
modes	O
for	O
individual	O
patients	O
.	O
</s>
<s>
Most	O
pacemakers	B-Device
are	O
on	O
demand	O
,	O
in	O
which	O
the	O
stimulation	O
of	O
the	O
heart	O
is	O
based	O
on	O
the	O
dynamic	O
demand	O
of	O
the	O
circulatory	O
system	O
.	O
</s>
<s>
A	O
specific	O
type	O
of	O
pacemaker	B-Algorithm
called	O
an	O
implantable	O
cardioverter-defibrillator	O
combines	O
pacemaker	B-Algorithm
and	O
defibrillator	O
functions	O
in	O
a	O
single	O
implantable	O
device	O
.	O
</s>
<s>
Others	O
,	O
called	O
biventricular	B-Algorithm
pacemakers	I-Algorithm
,	O
have	O
multiple	O
electrodes	O
stimulating	O
different	O
positions	O
within	O
the	O
ventricles	O
(	O
the	O
lower	O
heart	O
chambers	O
)	O
to	O
improve	O
their	O
synchronization	O
.	O
</s>
<s>
This	O
is	O
an	O
old	O
procedure	O
used	O
only	O
as	O
a	O
life-saving	O
means	O
until	O
an	O
electrical	B-Device
pacemaker	I-Device
is	O
brought	O
to	O
the	O
patient	O
.	O
</s>
<s>
Transcutaneous	B-Algorithm
pacing	I-Algorithm
(	O
TCP	O
)	O
,	O
also	O
called	O
external	B-Device
pacing	I-Device
,	O
is	O
recommended	O
for	O
the	O
initial	O
stabilization	O
of	O
hemodynamically	O
significant	O
bradycardias	B-Algorithm
of	O
all	O
types	O
.	O
</s>
<s>
The	O
rescuer	O
selects	O
the	O
pacing	O
rate	O
,	O
and	O
gradually	O
increases	O
the	O
pacing	O
current	O
(	O
measured	O
in	O
mA	O
)	O
until	O
electrical	O
capture	O
(	O
characterized	O
by	O
a	O
wide	O
QRS	B-Algorithm
complex	I-Algorithm
with	O
a	O
tall	O
,	O
broad	O
T	B-Algorithm
wave	I-Algorithm
on	O
the	O
ECG	B-Application
)	O
is	O
achieved	O
,	O
with	O
a	O
corresponding	O
pulse	O
.	O
</s>
<s>
Pacing	O
artifact	O
on	O
the	O
ECG	B-Application
and	O
severe	O
muscle	O
twitching	O
may	O
make	O
this	O
determination	O
difficult	O
.	O
</s>
<s>
External	B-Device
pacing	I-Device
should	O
not	O
be	O
relied	O
upon	O
for	O
an	O
extended	O
period	O
of	O
time	O
.	O
</s>
<s>
It	O
is	O
an	O
emergency	O
procedure	O
that	O
acts	O
as	O
a	O
bridge	O
until	O
transvenous	B-Algorithm
pacing	I-Algorithm
or	O
other	O
therapies	O
can	O
be	O
applied	O
.	O
</s>
<s>
Temporary	O
epicardial	O
pacing	O
is	O
used	O
during	O
open	O
heart	O
surgery	O
should	O
the	O
surgical	O
procedure	O
create	O
atrio-ventricular	O
block	B-Algorithm
.	O
</s>
<s>
Transvenous	B-Algorithm
pacing	I-Algorithm
,	O
when	O
used	O
for	O
temporary	B-Algorithm
pacing	I-Algorithm
,	O
is	O
an	O
alternative	O
to	O
transcutaneous	B-Algorithm
pacing	I-Algorithm
.	O
</s>
<s>
A	O
pacemaker	B-Algorithm
wire	O
is	O
placed	O
into	O
a	O
vein	O
,	O
under	O
sterile	O
conditions	O
,	O
and	O
then	O
passed	O
into	O
either	O
the	O
right	O
atrium	O
or	O
right	O
ventricle	O
.	O
</s>
<s>
The	O
pacing	O
wire	O
is	O
then	O
connected	O
to	O
an	O
external	O
pacemaker	B-Algorithm
outside	O
the	O
body	O
.	O
</s>
<s>
Transvenous	B-Algorithm
pacing	I-Algorithm
is	O
often	O
used	O
as	O
a	O
bridge	O
to	O
permanent	B-Device
pacemaker	I-Device
placement	O
.	O
</s>
<s>
It	O
can	O
be	O
kept	O
in	O
place	O
until	O
a	O
permanent	B-Device
pacemaker	I-Device
is	O
implanted	O
or	O
until	O
there	O
is	O
no	O
longer	O
a	O
need	O
for	O
a	O
pacemaker	B-Algorithm
and	O
then	O
it	O
is	O
removed	O
.	O
</s>
<s>
Permanent	O
pacing	O
with	O
an	O
implantable	O
pacemaker	B-Algorithm
involves	O
transvenous	O
placement	O
of	O
one	O
or	O
more	O
pacing	O
electrodes	O
within	O
a	O
chamber	O
,	O
or	O
chambers	O
,	O
of	O
the	O
heart	O
,	O
while	O
the	O
pacemaker	B-Algorithm
is	O
implanted	O
inside	O
the	O
skin	O
under	O
the	O
clavicle	O
.	O
</s>
<s>
After	O
satisfactory	O
lodgement	O
of	O
the	O
electrode	O
is	O
confirmed	O
,	O
the	O
opposite	O
end	O
of	O
the	O
electrode	O
lead	O
is	O
connected	O
to	O
the	O
pacemaker	B-Algorithm
generator	O
.	O
</s>
<s>
There	O
are	O
three	O
basic	O
types	O
of	O
permanent	B-Device
pacemakers	I-Device
,	O
classified	O
according	O
to	O
the	O
number	O
of	O
chambers	O
involved	O
and	O
their	O
basic	O
operating	O
mechanism	O
:	O
</s>
<s>
Single-chamber	O
pacemaker	B-Algorithm
.	O
</s>
<s>
Dual-chamber	O
pacemaker	B-Algorithm
.	O
</s>
<s>
Biventricular	O
pacemaker	B-Algorithm
.	O
</s>
<s>
This	O
pacemaker	B-Algorithm
has	O
three	O
wires	O
placed	O
in	O
three	O
chambers	O
of	O
the	O
heart	O
.	O
</s>
<s>
Rate-responsive	O
pacemaker	B-Algorithm
.	O
</s>
<s>
This	O
pacemaker	B-Algorithm
has	O
sensors	O
that	O
detect	O
changes	O
in	O
the	O
patient	O
's	O
physical	O
activity	O
and	O
automatically	O
adjust	O
the	O
pacing	O
rate	O
to	O
fulfill	O
the	O
body	O
's	O
metabolic	O
needs	O
.	O
</s>
<s>
The	O
pacemaker	B-Algorithm
generator	O
is	O
a	O
hermetically	O
sealed	O
device	O
containing	O
a	O
power	O
source	O
,	O
usually	O
a	O
lithium	B-Device
battery	I-Device
,	O
a	O
sensing	O
amplifier	O
which	O
processes	O
the	O
electrical	O
manifestation	O
of	O
naturally	O
occurring	O
heart	O
beats	O
as	O
sensed	O
by	O
the	O
heart	O
electrodes	O
,	O
the	O
computer	O
logic	O
for	O
the	O
pacemaker	B-Algorithm
and	O
the	O
output	O
circuitry	O
which	O
delivers	O
the	O
pacing	O
impulse	O
to	O
the	O
electrodes	O
.	O
</s>
<s>
The	O
outer	O
casing	O
of	O
pacemakers	B-Device
is	O
so	O
designed	O
that	O
it	O
will	O
rarely	O
be	O
rejected	O
by	O
the	O
body	O
's	O
immune	O
system	O
.	O
</s>
<s>
Leadless	O
pacemakers	B-Device
are	O
devices	O
that	O
are	O
small	O
enough	O
to	O
allow	O
the	O
generator	O
to	O
be	O
placed	O
within	O
the	O
heart	O
,	O
therefore	O
avoiding	O
the	O
need	O
for	O
pacing	O
leads	O
.	O
</s>
<s>
As	O
pacemaker	B-Algorithm
leads	O
can	O
fail	O
over	O
time	O
,	O
a	O
pacing	O
system	O
that	O
avoids	O
these	O
components	O
offers	O
theoretical	O
advantages	O
.	O
</s>
<s>
Leadless	O
pacemakers	B-Device
can	O
be	O
implanted	O
into	O
the	O
heart	O
using	O
a	O
steerable	O
catheter	O
fed	O
into	O
the	O
femoral	O
vein	O
via	O
an	O
incision	O
in	O
the	O
groin	O
.	O
</s>
<s>
Modern	O
pacemakers	B-Device
usually	O
have	O
multiple	O
functions	O
.	O
</s>
<s>
When	O
the	O
pacemaker	B-Algorithm
wire	O
or	O
"	O
lead	O
"	O
does	O
not	O
detect	O
heart	O
electrical	O
activity	O
in	O
the	O
chamber	O
–	O
atrium	O
or	O
ventricle	O
–	O
within	O
a	O
normal	O
beat-to-beat	O
time	O
period	O
–	O
most	O
commonly	O
one	O
second	O
–	O
it	O
will	O
stimulate	O
either	O
the	O
atrium	O
or	O
the	O
ventricle	O
with	O
a	O
short	O
low	O
voltage	O
pulse	O
.	O
</s>
<s>
From	O
this	O
the	O
basic	O
ventricular	O
"	O
on	O
demand	O
"	O
pacing	O
mode	O
is	O
VVI	O
or	O
with	O
automatic	O
rate	O
adjustment	O
for	O
exercise	O
VVIR	O
–	O
this	O
mode	O
is	O
suitable	O
when	O
no	O
synchronization	O
with	O
the	O
atrial	O
beat	O
is	O
required	O
,	O
as	O
in	O
atrial	B-Application
fibrillation	I-Application
.	O
</s>
<s>
The	O
equivalent	O
atrial	O
pacing	O
mode	O
is	O
AAI	O
or	O
AAIR	O
which	O
is	O
the	O
mode	O
of	O
choice	O
when	O
atrioventricular	O
conduction	B-Algorithm
is	O
intact	O
but	O
the	O
sinoatrial	O
node	O
of	O
the	O
natural	B-Algorithm
pacemaker	I-Algorithm
is	O
unreliable	O
–	O
sinus	O
node	O
disease	O
(	O
SND	O
)	O
or	O
sick	B-Algorithm
sinus	I-Algorithm
syndrome	I-Algorithm
.	O
</s>
<s>
Where	O
the	O
problem	O
is	O
atrioventricular	B-Algorithm
block	I-Algorithm
(	O
AVB	O
)	O
the	O
pacemaker	B-Algorithm
is	O
required	O
to	O
detect	O
(	O
sense	O
)	O
the	O
atrial	O
beat	O
and	O
after	O
a	O
normal	O
delay	O
(	O
0.1	O
–	O
0.2	O
seconds	O
)	O
trigger	O
a	O
ventricular	O
beat	O
,	O
unless	O
it	O
has	O
already	O
happened	O
–	O
this	O
is	O
VDD	O
mode	O
and	O
can	O
be	O
achieved	O
with	O
a	O
single	O
pacing	O
lead	O
with	O
electrodes	O
in	O
the	O
right	O
atrium	O
(	O
to	O
sense	O
)	O
and	O
ventricle	O
(	O
to	O
sense	O
and	O
pace	O
)	O
.	O
</s>
<s>
The	O
DDDR	O
mode	O
is	O
most	O
commonly	O
used	O
as	O
it	O
covers	O
all	O
the	O
options	O
though	O
the	O
pacemakers	B-Device
require	O
separate	O
atrial	O
and	O
ventricular	O
leads	O
and	O
are	O
more	O
complex	O
,	O
requiring	O
careful	O
programming	O
of	O
their	O
functions	O
for	O
optimal	O
results	O
.	O
</s>
<s>
Automatic	O
pacemakers	B-Device
are	O
designed	O
to	O
be	O
over-ridden	O
by	O
the	O
heart	O
's	O
natural	O
rate	O
at	O
any	O
moment	O
that	O
it	O
gets	O
back	O
to	O
a	O
non-pathologic	O
normal	O
sinus	O
rhythm	O
and	O
can	O
reinitiate	O
influencing	O
the	O
electric	O
activity	O
in	O
the	O
heart	O
when	O
the	O
pathologic	O
event	O
happens	O
again	O
.	O
</s>
<s>
A	O
"	O
ventricular-demand	O
pacemaker	O
"	O
produces	O
a	O
narrow	O
vertical	O
spike	O
on	O
the	O
ECG	B-Application
,	O
just	O
before	O
a	O
wide	O
QRS	B-Algorithm
.	O
</s>
<s>
The	O
spike	O
of	O
an	O
"	O
atrial-demand	O
pacemaker	O
"	O
appears	O
just	O
before	O
the	O
P	B-Algorithm
wave	I-Algorithm
.	O
</s>
<s>
Comparably	O
,	O
a	O
Triggered	B-Device
Pacemaker	I-Device
is	O
activated	O
immediately	O
after	O
an	O
electrical	O
activity	O
is	O
commenced	O
in	O
the	O
heart	O
tissue	O
by	O
itself	O
.	O
</s>
<s>
A	O
"	O
ventricular	O
triggered	B-Device
pacemaker	I-Device
"	O
produces	O
the	O
impulse	O
just	O
after	O
a	O
pulse	O
is	O
created	O
in	O
the	O
ventricular	O
tissue	O
and	O
it	O
appears	O
as	O
a	O
simultaneous	O
spike	O
with	O
QRS	B-Algorithm
.	O
</s>
<s>
An	O
"	O
atrial	O
triggered	B-Device
pacemaker	I-Device
"	O
is	O
the	O
mode	O
in	O
which	O
an	O
impulse	O
is	O
produced	O
immediately	O
after	O
an	O
electrical	O
event	O
in	O
the	O
atrium	O
.	O
</s>
<s>
It	O
appears	O
as	O
a	O
discharge	O
following	O
the	O
p	B-Algorithm
wave	I-Algorithm
but	O
prior	O
to	O
the	O
QRS	B-Algorithm
which	O
is	O
commonly	O
widened	O
.	O
</s>
<s>
Cardiac	B-Algorithm
resynchronization	I-Algorithm
therapy	I-Algorithm
(	O
CRT	B-Algorithm
)	O
is	O
used	O
for	O
people	O
with	O
heart	O
failure	O
in	O
whom	O
the	O
left	O
and	O
right	O
ventricles	O
do	O
not	O
contract	O
simultaneously	O
(	O
ventricular	B-Algorithm
dyssynchrony	I-Algorithm
)	O
,	O
which	O
occurs	O
in	O
approximately	O
25	O
–	O
50%	O
of	O
heart	O
failure	O
patients	O
.	O
</s>
<s>
To	O
achieve	O
CRT	B-Algorithm
,	O
a	O
biventricular	O
pacemaker	B-Algorithm
(	O
BVP	O
)	O
is	O
used	O
,	O
which	O
can	O
pace	O
both	O
the	O
septal	O
and	O
lateral	O
walls	O
of	O
the	O
left	O
ventricle	O
.	O
</s>
<s>
By	O
pacing	O
both	O
sides	O
of	O
the	O
left	O
ventricle	O
,	O
the	O
pacemaker	B-Algorithm
can	O
resynchronize	O
the	O
ventricular	O
contractions	O
.	O
</s>
<s>
CRT	B-Algorithm
devices	O
have	O
at	O
least	O
two	O
leads	O
,	O
one	O
passing	O
through	O
the	O
vena	O
cava	O
and	O
the	O
right	O
atrium	O
into	O
the	O
right	O
ventricle	O
to	O
stimulate	O
the	O
septum	O
,	O
and	O
another	O
passing	O
through	O
the	O
vena	O
cava	O
and	O
the	O
right	O
atrium	O
and	O
inserted	O
through	O
the	O
coronary	O
sinus	O
to	O
pace	O
the	O
epicardial	O
wall	O
of	O
the	O
left	O
ventricle	O
.	O
</s>
<s>
CRT	B-Algorithm
devices	O
have	O
been	O
shown	O
to	O
reduce	O
mortality	O
and	O
improve	O
quality	O
of	O
life	O
in	O
patients	O
with	O
heart	O
failure	O
symptoms	O
;	O
a	O
LV	O
ejection	O
fraction	O
less	O
than	O
or	O
equal	O
to	O
35%	O
and	O
QRS	B-Algorithm
duration	O
on	O
EKG	B-Application
of	O
120ms	O
or	O
greater	O
.	O
</s>
<s>
Biventricular	O
pacing	O
alone	O
is	O
referred	O
to	O
as	O
CRT-P	O
(	O
for	O
pacing	O
)	O
.	O
</s>
<s>
For	O
selected	O
patients	O
at	O
risk	O
of	O
arrhythmias	B-Application
,	O
CRT	B-Algorithm
can	O
be	O
combined	O
with	O
an	O
implantable	O
cardioverter-defibrillator	O
(	O
ICD	O
)	O
:	O
such	O
devices	O
,	O
known	O
as	O
CRT-D	B-Algorithm
(	O
for	O
defibrillation	O
)	O
,	O
also	O
provide	O
effective	O
protection	O
against	O
life-threatening	O
arrhythmias	B-Application
.	O
</s>
<s>
It	O
has	O
been	O
associated	O
with	O
increased	O
risk	O
of	O
atrial	B-Application
fibrillation	I-Application
,	O
heart	O
failure	O
,	O
weakening	O
of	O
the	O
heart	O
muscle	O
and	O
potentially	O
shorter	O
life	O
expectancy	O
.	O
</s>
<s>
His	B-Algorithm
bundle	I-Algorithm
pacing	I-Algorithm
(	O
HBP	O
)	O
leads	O
to	O
a	O
more	O
natural	O
or	O
perfectly	O
natural	O
ventricular	O
activation	O
and	O
has	O
generated	O
strong	O
research	O
and	O
clinical	O
interest	O
.	O
</s>
<s>
By	O
stimulating	O
the	O
His	B-Algorithm
–	I-Algorithm
Purkinje	I-Algorithm
fiber	O
network	O
directly	O
with	O
a	O
special	O
lead	O
and	O
placement	O
technique	O
,	O
HBP	O
causes	O
a	O
synchronized	O
and	O
therefore	O
more	O
effective	O
ventricular	O
activation	O
and	O
avoids	O
long-term	O
heart	O
muscle	O
disease	O
.	O
</s>
<s>
HBP	O
in	O
some	O
cases	O
can	O
also	O
correct	O
bundle	B-Algorithm
branch	I-Algorithm
block	I-Algorithm
patterns	O
.	O
</s>
<s>
A	O
major	O
step	O
forward	O
in	O
pacemaker	B-Algorithm
function	O
has	O
been	O
to	O
attempt	O
to	O
mimic	O
nature	O
by	O
utilizing	O
various	O
inputs	O
to	O
produce	O
a	O
rate-responsive	O
pacemaker	B-Algorithm
using	O
parameters	O
such	O
as	O
the	O
QT	B-Algorithm
interval	I-Algorithm
,	O
pO2	O
–	O
pCO2	O
(	O
dissolved	O
oxygen	O
or	O
carbon	O
dioxide	O
levels	O
)	O
in	O
the	O
arterial-venous	O
system	O
,	O
physical	O
activity	O
as	O
determined	O
by	O
an	O
accelerometer	O
,	O
body	O
temperature	O
,	O
ATP	O
levels	O
,	O
adrenaline	O
,	O
etc	O
.	O
</s>
<s>
Instead	O
of	O
producing	O
a	O
static	O
,	O
predetermined	O
heart	O
rate	O
,	O
or	O
intermittent	O
control	O
,	O
such	O
a	O
pacemaker	B-Algorithm
,	O
a	O
'	O
Dynamic	O
Pacemaker	B-Algorithm
 '	O
,	O
could	O
compensate	O
for	O
both	O
actual	O
respiratory	O
loading	O
and	O
potentially	O
anticipated	O
respiratory	O
loading	O
.	O
</s>
<s>
The	O
first	O
dynamic	O
pacemaker	B-Algorithm
was	O
invented	O
by	O
Anthony	O
Rickards	O
of	O
the	O
National	O
Heart	O
Hospital	O
,	O
London	O
,	O
UK	O
,	O
in	O
1982	O
.	O
</s>
<s>
Many	O
advancements	O
have	O
been	O
made	O
to	O
improve	O
the	O
control	O
of	O
the	O
pacemaker	B-Algorithm
once	O
implanted	O
.	O
</s>
<s>
Many	O
of	O
these	O
have	O
been	O
made	O
possible	O
by	O
the	O
transition	O
to	O
microprocessor	B-Architecture
controlled	O
pacemakers	B-Device
.	O
</s>
<s>
Pacemakers	B-Device
that	O
control	O
not	O
only	O
the	O
ventricles	O
but	O
the	O
atria	O
as	O
well	O
have	O
become	O
common	O
.	O
</s>
<s>
Pacemakers	B-Device
that	O
control	O
both	O
the	O
atria	O
and	O
ventricles	O
are	O
called	O
dual-chamber	O
pacemakers	B-Device
.	O
</s>
<s>
The	O
DAVID	O
trials	O
have	O
shown	O
that	O
unnecessary	O
pacing	O
of	O
the	O
right	O
ventricle	O
can	O
exacerbate	O
heart	O
failure	O
and	O
increases	O
the	O
incidence	O
of	O
atrial	B-Application
fibrillation	I-Application
.	O
</s>
<s>
A	O
pacemaker	B-Algorithm
may	O
be	O
implanted	O
whilst	O
a	O
person	O
is	O
awake	O
using	O
local	O
anesthetic	O
to	O
numb	O
the	O
skin	O
with	O
or	O
without	O
sedation	O
,	O
or	O
asleep	O
using	O
a	O
general	O
anesthetic	O
.	O
</s>
<s>
Pacemakers	B-Device
are	O
generally	O
implanted	O
in	O
the	O
front	O
of	O
the	O
chest	O
in	O
the	O
region	O
of	O
the	O
left	O
or	O
right	O
shoulder	O
.	O
</s>
<s>
An	O
incision	O
is	O
made	O
below	O
the	O
collar	O
bone	O
and	O
a	O
space	O
or	O
pocket	O
is	O
created	O
under	O
the	O
skin	O
to	O
house	O
the	O
pacemaker	B-Algorithm
generator	O
.	O
</s>
<s>
The	O
tips	O
of	O
the	O
leads	O
may	O
be	O
positioned	O
within	O
the	O
right	O
ventricle	O
,	O
the	O
right	O
atrium	O
,	O
or	O
the	O
coronary	O
sinus	O
,	O
depending	O
on	O
the	O
type	O
of	O
pacemaker	B-Algorithm
required	O
.	O
</s>
<s>
Some	O
movements	O
of	O
the	O
shoulder	O
within	O
a	O
few	O
weeks	O
of	O
insertion	O
carry	O
a	O
risk	O
of	O
dislodging	O
the	O
pacemaker	B-Algorithm
leads	O
.	O
</s>
<s>
The	O
batteries	O
within	O
a	O
pacemaker	B-Algorithm
generator	O
typically	O
last	O
5	O
to	O
10	O
years	O
.	O
</s>
<s>
Once	O
the	O
pacemaker	B-Algorithm
is	O
implanted	O
,	O
it	O
is	O
periodically	O
checked	O
to	O
ensure	O
the	O
device	O
is	O
operational	O
and	O
performing	O
appropriately	O
;	O
the	O
device	O
can	O
be	O
checked	O
as	O
often	O
as	O
is	O
deemed	O
necessary	O
.	O
</s>
<s>
Routine	O
pacemaker	B-Algorithm
checks	O
are	O
typically	O
done	O
in-office	O
every	O
six	O
months	O
,	O
though	O
will	O
vary	O
depending	O
upon	O
patient/device	O
status	O
and	O
remote	O
monitoring	O
availability	O
.	O
</s>
<s>
Newer	O
pacemaker	B-Algorithm
models	O
can	O
also	O
be	O
interrogated	O
remotely	O
,	O
with	O
the	O
patient	O
transmitting	O
their	O
pacemaker	B-Algorithm
data	O
using	O
a	O
transmitter	O
at	O
home	O
connected	O
to	O
a	O
cellular	O
telephone	O
network	O
.	O
</s>
<s>
Sensing	O
:	O
the	O
ability	O
of	O
the	O
device	O
to	O
"	O
see	O
"	O
intrinsic	O
cardiac	O
activity	O
(	O
atrial	O
and	O
ventricular	B-Application
depolarization	I-Application
)	O
.	O
</s>
<s>
Percentage	O
of	O
pacing	O
:	O
The	O
percentage	O
of	O
time	O
that	O
the	O
pacemaker	B-Algorithm
has	O
been	O
actively	O
pacing	O
since	O
the	O
previous	O
device	O
interrogation	O
,	O
which	O
shows	O
how	O
dependent	O
the	O
patient	O
is	O
on	O
the	O
device	O
.	O
</s>
<s>
Estimated	O
battery	O
life	O
at	O
current	O
rate	O
:	O
As	O
modern	O
pacemakers	B-Device
are	O
"	O
on-demand	O
"	O
and	O
only	O
pace	O
when	O
necessary	O
,	O
battery	O
lifespan	O
is	O
affected	O
by	O
how	O
much	O
the	O
pacemaker	B-Algorithm
is	O
utilized	O
.	O
</s>
<s>
Any	O
events	O
that	O
were	O
stored	O
since	O
the	O
last	O
follow-up	O
,	O
in	O
particular	O
arrhythmias	B-Application
such	O
as	O
atrial	B-Application
fibrillation	I-Application
.	O
</s>
<s>
Some	O
devices	O
have	O
the	O
availability	O
to	O
display	O
intracardiac	B-Application
electrograms	I-Application
showing	O
the	O
onset	O
of	O
an	O
event	O
as	O
well	O
as	O
the	O
event	O
itself	O
,	O
which	O
helps	O
to	O
diagnose	O
its	O
cause	O
or	O
origin	O
.	O
</s>
<s>
A	O
patient	O
's	O
lifestyle	O
is	O
usually	O
not	O
modified	O
to	O
any	O
great	O
degree	O
after	O
the	O
insertion	O
of	O
a	O
pacemaker	B-Algorithm
.	O
</s>
<s>
There	O
are	O
a	O
few	O
activities	O
that	O
are	O
unwise	O
,	O
such	O
as	O
full-contact	O
sports	O
and	O
exposure	O
of	O
the	O
pacemaker	B-Algorithm
to	O
intense	O
magnetic	O
fields	O
.	O
</s>
<s>
The	O
pacemaker	B-Algorithm
patient	O
may	O
find	O
that	O
some	O
types	O
of	O
everyday	O
actions	O
need	O
to	O
be	O
modified	O
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
shoulder	O
harness	O
of	O
a	O
vehicle	O
seatbelt	O
may	O
be	O
uncomfortable	O
if	O
it	O
falls	O
across	O
the	O
pacemaker	B-Algorithm
insertion	O
site	O
.	O
</s>
<s>
For	O
some	O
sports	O
and	O
physical	O
activities	O
,	O
special	O
pacemaker	B-Algorithm
protection	O
can	O
be	O
worn	O
to	O
prevent	O
possible	O
injuries	O
,	O
or	O
damage	O
to	O
the	O
pacemaker	B-Algorithm
leads	O
.	O
</s>
<s>
Pacemakers	B-Device
may	O
be	O
affected	O
by	O
magnetic	O
or	O
electromagnetic	O
fields	O
,	O
and	O
ionising	O
and	O
acoustic	O
radiation	O
.	O
</s>
<s>
Some	O
medical	O
procedures	O
,	O
particularly	O
magnetic	O
resonance	O
imaging	O
(	O
MRI	O
)	O
,	O
involve	O
very	O
strong	O
magnetic	O
fields	O
or	O
other	O
conditions	O
that	O
may	O
damage	O
pacemakers	B-Device
.	O
</s>
<s>
However	O
,	O
many	O
modern	O
pacemakers	B-Device
are	O
specified	O
to	O
be	O
MR	O
conditional	O
or	O
MRI	O
conditional	O
,	O
safe	O
to	O
use	O
during	O
MRI	O
subject	O
to	O
certain	O
conditions	O
.	O
</s>
<s>
There	O
are	O
several	O
conditions	O
to	O
use	O
of	O
MR	O
Conditional	O
pacemakers	B-Device
,	O
including	O
certain	O
patients	O
 '	O
qualifications	O
and	O
scan	O
settings	O
.	O
</s>
<s>
the	O
five	O
most	O
commonly	O
used	O
cardiac	B-Device
pacing	I-Device
device	O
manufacturers	O
(	O
covering	O
more	O
than	O
99%	O
of	O
the	O
US	O
market	O
)	O
made	O
FDA-approved	O
MR-conditional	O
pacemakers	B-Device
.	O
</s>
<s>
The	O
use	O
of	O
MRI	O
may	O
be	O
ruled	O
out	O
by	O
the	O
patient	O
having	O
an	O
older	O
,	O
non-MRI	O
Conditional	O
pacemaker	B-Algorithm
,	O
or	O
by	O
having	O
old	O
pacing	O
wires	O
inside	O
the	O
heart	O
,	O
no	O
longer	O
connected	O
to	O
a	O
pacemaker	B-Algorithm
.	O
</s>
<s>
A	O
2008	O
US	O
study	O
found	O
that	O
the	O
magnetic	O
field	O
created	O
by	O
some	O
headphones	O
used	O
with	O
portable	O
music	O
players	O
or	O
cellphones	O
may	O
cause	O
interference	O
if	O
placed	O
very	O
close	O
to	O
some	O
pacemakers	B-Device
.	O
</s>
<s>
Cellphones	O
do	O
not	O
seem	O
to	O
damage	O
pulse	O
generators	O
or	O
affect	O
how	O
the	O
pacemaker	B-Algorithm
works	O
.	O
</s>
<s>
It	O
is	O
recommended	O
that	O
objects	O
containing	O
magnets	O
,	O
or	O
generating	O
a	O
significant	O
magnetic	O
field	O
,	O
should	O
not	O
be	O
in	O
close	O
proximity	O
to	O
a	O
pacemaker	B-Algorithm
.	O
</s>
<s>
Before	O
medical	O
procedures	O
,	O
the	O
patient	O
should	O
inform	O
all	O
medical	O
personnel	O
that	O
they	O
have	O
a	O
pacemaker	B-Algorithm
.	O
</s>
<s>
Having	O
a	O
pacemaker	B-Algorithm
does	O
not	O
imply	O
that	O
a	O
patient	O
requires	O
the	O
use	O
of	O
antibiotics	O
to	O
be	O
administered	O
before	O
procedures	O
such	O
as	O
dental	O
work	O
.	O
</s>
<s>
A	O
panel	O
of	O
the	O
Heart	B-Algorithm
Rhythm	I-Algorithm
Society	O
,	O
a	O
US	O
specialist	O
organization	O
based	O
in	O
Washington	O
,	O
DC	O
,	O
deemed	O
that	O
it	O
was	O
legal	O
and	O
ethical	O
to	O
honor	O
requests	O
by	O
patients	O
,	O
or	O
by	O
those	O
with	O
legal	O
authority	O
to	O
make	O
decisions	O
for	O
patients	O
,	O
to	O
deactivate	O
implanted	O
cardiac	O
devices	O
.	O
</s>
<s>
Lawyers	O
say	O
that	O
the	O
legal	O
situation	O
is	O
similar	O
to	O
removing	O
a	O
feeding	O
tube	O
,	O
though	O
there	O
was	O
no	O
legal	O
precedent	O
involving	O
pacemakers	B-Device
in	O
the	O
United	O
States	O
.	O
</s>
<s>
A	O
patient	O
in	O
many	O
jurisdictions	O
(	O
including	O
the	O
US	O
)	O
is	O
deemed	O
to	O
have	O
a	O
right	O
to	O
refuse	O
or	O
discontinue	O
treatment	O
,	O
including	O
a	O
pacemaker	B-Algorithm
that	O
keeps	O
them	O
alive	O
.	O
</s>
<s>
Security	O
and	O
privacy	O
concerns	O
have	O
been	O
raised	O
with	O
pacemakers	B-Device
that	O
allow	O
wireless	O
communication	O
.	O
</s>
<s>
Unauthorized	O
third	O
parties	O
may	O
be	O
able	O
to	O
read	O
patient	O
records	O
contained	O
in	O
the	O
pacemaker	B-Algorithm
,	O
or	O
reprogram	O
the	O
devices	O
,	O
as	O
has	O
been	O
demonstrated	O
by	O
a	O
team	O
of	O
researchers	O
.	O
</s>
<s>
In	O
response	O
to	O
this	O
threat	O
,	O
Purdue	O
University	O
and	O
Princeton	O
University	O
researchers	O
have	O
developed	O
a	O
prototype	O
firewall	O
device	O
,	O
called	O
MedMon	O
,	O
which	O
is	O
designed	O
to	O
protect	O
wireless	O
medical	O
devices	O
such	O
as	O
pacemakers	B-Device
and	O
insulin	O
pumps	O
from	O
attackers	O
.	O
</s>
<s>
Complications	O
from	O
having	O
surgery	O
to	O
implant	O
a	O
pacemaker	B-Algorithm
are	O
uncommon	O
(	O
each	O
1-3	O
%	O
approximately	O
)	O
,	O
but	O
could	O
include	O
:	O
infection	O
where	O
the	O
pacemaker	B-Algorithm
is	O
implanted	O
or	O
in	O
the	O
bloodstream	O
;	O
allergic	O
reaction	O
to	O
the	O
dye	O
or	O
anesthesia	O
used	O
during	O
the	O
procedure	O
;	O
swelling	O
,	O
bruising	O
or	O
bleeding	O
at	O
the	O
generator	O
site	O
,	O
or	O
around	O
the	O
heart	O
,	O
especially	O
if	O
the	O
patient	O
is	O
taking	O
blood	O
thinners	O
,	O
elderly	O
,	O
of	O
thin	O
frame	O
or	O
otherwise	O
on	O
chronic	O
steroid	O
use	O
.	O
</s>
<s>
A	O
possible	O
complication	O
of	O
dual-chamber	O
artificial	B-Device
pacemakers	I-Device
is	O
'	O
pacemaker-mediated	O
tachycardia	O
 '	O
(	O
PMT	O
)	O
,	O
a	O
form	O
of	O
reentrant	O
tachycardia	O
.	O
</s>
<s>
In	O
PMT	O
,	O
the	O
artificial	B-Device
pacemaker	I-Device
forms	O
the	O
anterograde	O
(	O
atrium	O
to	O
ventricle	O
)	O
limb	O
of	O
the	O
circuit	O
and	O
the	O
atrioventricular	O
(	O
AV	O
)	O
node	O
forms	O
the	O
retrograde	O
limb	O
(	O
ventricle	O
to	O
atrium	O
)	O
of	O
the	O
circuit	O
.	O
</s>
<s>
Treatment	O
of	O
PMT	O
typically	O
involves	O
reprogramming	O
the	O
pacemaker	B-Algorithm
.	O
</s>
<s>
Another	O
possible	O
complication	O
is	O
"	O
pacemaker-tracked	O
tachycardia	O
,	O
"	O
where	O
a	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
such	O
as	O
atrial	B-Application
fibrillation	I-Application
or	O
atrial	O
flutter	O
is	O
tracked	O
by	O
the	O
pacemaker	B-Algorithm
and	O
produces	O
beats	O
from	O
a	O
ventricular	O
lead	O
.	O
</s>
<s>
This	O
is	O
becoming	O
exceedingly	O
rare	O
as	O
newer	O
devices	O
are	O
often	O
programmed	O
to	O
recognize	O
supraventricular	B-Algorithm
tachycardias	I-Algorithm
and	O
switch	O
to	O
non-tracking	O
modes	O
.	O
</s>
<s>
Sometimes	O
the	O
leads	O
,	O
which	O
are	O
small	O
diameter	O
wires	O
from	O
the	O
pacemaker	B-Algorithm
to	O
the	O
implantation	O
site	O
in	O
the	O
heart	O
muscle	O
,	O
will	O
need	O
to	O
be	O
removed	O
.	O
</s>
<s>
Changes	O
to	O
the	O
programming	O
of	O
the	O
pacemaker	B-Algorithm
may	O
overcome	O
lead	O
degradation	O
to	O
some	O
extent	O
.	O
</s>
<s>
However	O
,	O
a	O
patient	O
who	O
has	O
several	O
pacemaker	B-Algorithm
replacements	O
over	O
a	O
decade	O
or	O
two	O
in	O
which	O
the	O
leads	O
were	O
reused	O
may	O
require	O
lead	O
replacement	O
surgery	O
.	O
</s>
<s>
Leads	O
can	O
normally	O
be	O
disconnected	O
from	O
the	O
pacemaker	B-Algorithm
easily	O
,	O
which	O
is	O
why	O
device	O
replacement	O
usually	O
entails	O
simple	O
surgery	O
to	O
access	O
the	O
device	O
and	O
replace	O
it	O
by	O
simply	O
unhooking	O
the	O
leads	O
from	O
the	O
device	O
to	O
replace	O
and	O
hooking	O
the	O
leads	O
to	O
the	O
new	O
device	O
.	O
</s>
<s>
The	O
free	O
end	O
of	O
a	O
pacemaker	B-Algorithm
lead	O
is	O
actually	O
implanted	O
into	O
the	O
heart	O
muscle	O
with	O
a	O
miniature	O
screw	O
or	O
anchored	O
with	O
small	O
plastic	O
hooks	O
called	O
tines	O
.	O
</s>
<s>
Pacemaker	B-Algorithm
lead	O
malposition	O
in	O
various	O
locations	O
has	O
been	O
described	O
in	O
the	O
literature	O
.	O
</s>
<s>
Another	O
possible	O
complication	O
called	O
twiddler	O
's	O
syndrome	O
occurs	O
when	O
a	O
patient	O
manipulates	O
the	O
pacemaker	B-Algorithm
and	O
causes	O
the	O
leads	O
to	O
be	O
removed	O
from	O
their	O
intended	O
location	O
and	O
causes	O
possible	O
stimulation	O
of	O
other	O
nerves	O
.	O
</s>
<s>
Overall	O
life	O
expectancy	O
with	O
pacemakers	B-Device
is	O
excellent	O
,	O
and	O
mostly	O
depends	O
upon	O
underlying	O
diseases	O
,	O
presence	O
of	O
atrial	B-Application
fibrillation	I-Application
,	O
age	O
and	O
sex	O
at	O
the	O
time	O
of	O
first	O
implantation	O
.	O
</s>
<s>
Sometimes	O
devices	O
resembling	O
pacemakers	B-Device
,	O
called	O
implantable	O
cardioverter-defibrillators	O
(	O
ICDs	O
)	O
are	O
implanted	O
.	O
</s>
<s>
An	O
ICD	O
has	O
the	O
ability	O
to	O
treat	O
many	O
types	O
of	O
heart	B-Algorithm
rhythm	I-Algorithm
disturbances	O
by	O
means	O
of	O
pacing	O
,	O
cardioversion	O
,	O
or	O
defibrillation	O
.	O
</s>
<s>
Some	O
ICD	O
devices	O
can	O
distinguish	O
between	O
ventricular	O
fibrillation	O
and	O
ventricular	B-Application
tachycardia	I-Application
(	O
VT	O
)	O
,	O
and	O
may	O
try	O
to	O
pace	O
the	O
heart	O
faster	O
than	O
its	O
intrinsic	O
rate	O
in	O
the	O
case	O
of	O
VT	O
,	O
to	O
try	O
to	O
break	O
the	O
tachycardia	O
before	O
it	O
progresses	O
to	O
ventricular	O
fibrillation	O
.	O
</s>
<s>
ATP	O
is	O
only	O
effective	O
if	O
the	O
underlying	O
rhythm	O
is	O
ventricular	B-Application
tachycardia	I-Application
,	O
and	O
is	O
never	O
effective	O
if	O
the	O
rhythm	O
is	O
ventricular	O
fibrillation	O
.	O
</s>
<s>
In	O
1889	O
,	O
John	O
Alexander	O
MacWilliam	O
reported	O
in	O
the	O
British	O
Medical	O
Journal	O
(	O
BMJ	O
)	O
of	O
his	O
experiments	O
in	O
which	O
application	O
of	O
an	O
electrical	O
impulse	O
to	O
the	O
human	O
heart	O
in	O
asystole	O
caused	O
a	O
ventricular	O
contraction	O
and	O
that	O
a	O
heart	B-Algorithm
rhythm	I-Algorithm
of	O
60	O
–	O
70	O
beats	O
per	O
minute	O
could	O
be	O
evoked	O
by	O
impulses	O
applied	O
at	O
spacings	O
equal	O
to	O
60	O
–	O
70/minute	O
.	O
</s>
<s>
"	O
The	O
pacemaker	B-Algorithm
rate	O
was	O
variable	O
from	O
about	O
80	O
to	O
120	O
pulses	O
per	O
minute	O
,	O
and	O
likewise	O
the	O
voltage	O
variable	O
from	O
1.5	O
to	O
120	O
volts	O
"	O
.	O
</s>
<s>
Hyman	O
himself	O
referred	O
to	O
his	O
invention	O
as	O
an	O
"	O
artificial	B-Device
pacemaker	I-Device
"	O
,	O
the	O
term	O
continuing	O
in	O
use	O
to	O
this	O
day	O
.	O
</s>
<s>
For	O
example	O
,	O
"	O
Hyman	O
did	O
not	O
publish	O
data	O
on	O
the	O
use	O
of	O
his	O
pacemaker	B-Algorithm
in	O
humans	O
because	O
of	O
adverse	O
publicity	O
,	O
both	O
among	O
his	O
fellow	O
physicians	O
,	O
and	O
due	O
to	O
newspaper	O
reporting	O
at	O
the	O
time	O
.	O
</s>
<s>
In	O
1950	O
,	O
Canadian	O
electrical	O
engineer	O
John	O
Hopps	O
designed	O
and	O
built	O
the	O
first	O
external	O
pacemaker	B-Algorithm
based	O
upon	O
observations	O
by	O
cardio-thoracic	O
surgeons	O
Wilfred	O
Gordon	O
Bigelow	O
and	O
John	O
Callaghan	O
at	O
Toronto	O
General	O
Hospital	O
.	O
</s>
<s>
A	O
substantial	O
external	O
device	O
using	O
vacuum	O
tube	O
technology	O
to	O
provide	O
transcutaneous	B-Algorithm
pacing	I-Algorithm
,	O
it	O
was	O
somewhat	O
crude	O
and	O
painful	O
to	O
the	O
patient	O
in	O
use	O
and	O
,	O
being	O
powered	O
from	O
an	O
AC	O
wall	O
socket	O
,	O
carried	O
a	O
potential	O
hazard	O
of	O
electrocution	O
of	O
the	O
patient	O
and	O
inducing	O
ventricular	O
fibrillation	O
.	O
</s>
<s>
A	O
number	O
of	O
innovators	O
,	O
including	O
Paul	O
Zoll	O
,	O
made	O
smaller	O
but	O
still	O
bulky	O
transcutaneous	B-Algorithm
pacing	I-Algorithm
devices	O
from	O
1952	O
using	O
a	O
large	O
rechargeable	O
battery	O
as	O
the	O
power	O
supply	O
.	O
</s>
<s>
These	O
studies	O
demonstrated	O
the	O
restoration	O
of	O
heart	O
rate	O
,	O
cardiac	O
output	O
and	O
mean	O
aortic	O
pressures	O
in	O
animal	O
subjects	O
with	O
complete	O
heart	B-Algorithm
block	I-Algorithm
through	O
the	O
use	O
of	O
a	O
myocardial	O
electrode	O
.	O
</s>
<s>
In	O
1958	O
Colombian	O
doctor	O
Alberto	O
Vejarano	O
Laverde	O
and	O
Colombian	O
electrical	O
engineer	O
Jorge	O
Reynolds	O
Pombo	O
constructed	O
an	O
external	O
pacemaker	B-Algorithm
,	O
similar	O
to	O
those	O
of	O
Hopps	O
and	O
Zoll	O
,	O
weighing	O
45kg	O
and	O
powered	O
by	O
a	O
12	O
volt	O
car	O
lead	B-Device
–	I-Device
acid	I-Device
battery	I-Device
,	O
but	O
connected	O
to	O
electrodes	O
attached	O
to	O
the	O
heart	O
.	O
</s>
<s>
The	O
development	O
of	O
the	O
silicon	O
transistor	B-Application
and	O
its	O
first	O
commercial	O
availability	O
in	O
1956	O
was	O
the	O
pivotal	O
event	O
that	O
led	O
to	O
the	O
rapid	O
development	O
of	O
practical	O
cardiac	O
pacemaking	O
.	O
</s>
<s>
In	O
1958	O
,	O
engineer	O
Earl	O
Bakken	O
of	O
Minneapolis	O
,	O
Minnesota	O
,	O
produced	O
the	O
first	O
wearable	O
external	O
pacemaker	B-Algorithm
for	O
a	O
patient	O
of	O
C	O
.	O
Walton	O
Lillehei	O
.	O
</s>
<s>
This	O
transistorized	O
pacemaker	B-Algorithm
,	O
housed	O
in	O
a	O
small	O
plastic	O
box	O
,	O
had	O
controls	O
to	O
permit	O
adjustment	O
of	O
pacing	O
heart	O
rate	O
and	O
output	O
voltage	O
and	O
was	O
connected	O
to	O
electrode	O
leads	O
which	O
passed	O
through	O
the	O
skin	O
of	O
the	O
patient	O
to	O
terminate	O
in	O
electrodes	O
attached	O
to	O
the	O
surface	O
of	O
the	O
myocardium	O
of	O
the	O
heart	O
.	O
</s>
<s>
Nolan	O
designed	O
and	O
created	O
the	O
first	O
blocking	O
oscillator	O
and	O
transistor-powered	O
pacemaker	B-Algorithm
.	O
</s>
<s>
This	O
pacemaker	B-Algorithm
was	O
worn	O
on	O
a	O
belt	O
and	O
powered	O
by	O
a	O
rechargeable	O
sealed	O
battery	O
,	O
enabling	O
users	O
to	O
live	O
a	O
more-normal	O
life	O
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
patients	O
to	O
receive	O
this	O
Lucas	O
pacemaker	B-Algorithm
device	O
was	O
a	O
woman	O
in	O
her	O
early	O
30s	O
.	O
</s>
<s>
The	O
first	O
clinical	O
implantation	O
into	O
a	O
human	O
of	O
a	O
fully	O
implantable	O
pacemaker	B-Algorithm
was	O
on	O
October	O
8	O
,	O
1958	O
,	O
at	O
the	O
Karolinska	O
Institute	O
in	O
Solna	O
,	O
Sweden	O
,	O
using	O
a	O
pacemaker	B-Algorithm
designed	O
by	O
inventor	O
Rune	O
Elmqvist	O
and	O
surgeon	O
Åke	O
Senning	O
(	O
in	O
collaboration	O
with	O
Elema-Schönander	O
AB	O
,	O
later	O
Siemens-Elema	O
AB	O
)	O
,	O
connected	O
to	O
electrodes	O
attached	O
to	O
the	O
myocardium	O
of	O
the	O
heart	O
by	O
thoracotomy	O
.	O
</s>
<s>
The	O
world	O
's	O
first	O
implantable	O
pacemaker	B-Algorithm
patient	O
,	O
Arne	O
Larsson	O
,	O
went	O
on	O
to	O
receive	O
26	O
different	O
pacemakers	B-Device
during	O
his	O
lifetime	O
.	O
</s>
<s>
In	O
1959	O
,	O
temporary	O
transvenous	B-Algorithm
pacing	I-Algorithm
was	O
first	O
demonstrated	O
by	O
Seymour	O
Furman	O
and	O
John	O
Schwedel	O
,	O
whereby	O
the	O
catheter	O
electrode	O
was	O
inserted	O
via	O
the	O
patient	O
's	O
basilic	O
vein	O
.	O
</s>
<s>
This	O
pacemaker	B-Algorithm
,	O
the	O
first	O
implanted	O
in	O
the	O
Americas	O
,	O
lasted	O
until	O
the	O
patient	O
died	O
of	O
other	O
ailments	O
,	O
nine	O
months	O
later	O
.	O
</s>
<s>
Implantable	O
pacemakers	B-Device
constructed	O
by	O
engineer	O
Wilson	O
Greatbatch	O
entered	O
use	O
in	O
humans	O
from	O
April	O
1960	O
following	O
extensive	O
animal	O
testing	O
.	O
</s>
<s>
The	O
Greatbatch	O
innovation	O
varied	O
from	O
the	O
earlier	O
Swedish	O
devices	O
in	O
using	O
primary	O
cells	O
(	O
a	O
mercury	B-Algorithm
battery	I-Algorithm
)	O
as	O
the	O
energy	O
source	O
.	O
</s>
<s>
The	O
first	O
use	O
of	O
transvenous	B-Algorithm
pacing	I-Algorithm
in	O
conjunction	O
with	O
an	O
implanted	B-Device
pacemaker	I-Device
was	O
by	O
Parsonnet	O
in	O
the	O
United	O
States	O
,	O
Lagergren	O
in	O
Sweden	O
and	O
Jean-Jacques	O
Welti	O
in	O
France	O
in	O
1962	O
–	O
63	O
.	O
</s>
<s>
Cardiothoracic	O
surgeon	O
Leon	O
Abrams	O
and	O
medical	O
engineer	O
Ray	O
Lightwood	O
developed	O
and	O
implanted	O
the	O
first	O
patient-controlled	O
variable-rate	O
heart	B-Device
pacemaker	I-Device
in	O
1960	O
at	O
Birmingham	O
University	O
.	O
</s>
<s>
The	O
preceding	O
implantable	O
devices	O
all	O
suffered	O
from	O
the	O
unreliability	O
and	O
short	O
lifetime	O
of	O
the	O
available	O
primary	O
cell	O
technology	O
,	O
mainly	O
the	O
mercury	B-Algorithm
battery	I-Algorithm
.	O
</s>
<s>
In	O
the	O
late	O
1960s	O
,	O
several	O
companies	O
,	O
including	O
ARCO	O
in	O
the	O
US	O
,	O
developed	O
isotope-powered	B-Application
pacemakers	B-Device
,	O
but	O
this	O
development	O
was	O
overtaken	O
by	O
the	O
development	O
in	O
1971	O
of	O
the	O
lithium	O
iodide	O
cell	O
by	O
Wilson	O
Greatbatch	O
.	O
</s>
<s>
Lithium-iodide	O
or	O
lithium	O
anode	O
cells	O
became	O
the	O
standard	O
for	O
pacemaker	B-Algorithm
designs	O
.	O
</s>
<s>
This	O
phenomenon	O
was	O
overcome	O
by	O
encasing	O
the	O
pacemaker	B-Algorithm
generator	O
in	O
a	O
hermetically	O
sealed	O
metal	O
case	O
,	O
initially	O
by	O
Telectronics	O
of	O
Australia	O
in	O
1969	O
,	O
followed	O
by	O
Cardiac	B-Algorithm
Pacemakers	I-Algorithm
,	I-Algorithm
Inc	I-Algorithm
.	I-Algorithm
of	O
St.	O
Paul	O
,	O
Minnesota	O
in	O
1972	O
.	O
</s>
<s>
On	O
July	O
9	O
,	O
1974	O
,	O
Manuel	O
A	O
.	O
Villafaña	O
and	O
Anthony	O
Adducci	O
,	O
the	O
founders	O
of	O
Cardiac	B-Algorithm
Pacemakers	I-Algorithm
,	I-Algorithm
Inc	I-Algorithm
.	I-Algorithm
(	O
Guidant	O
)	O
,	O
manufactured	O
the	O
world	O
's	O
first	O
pacemaker	B-Algorithm
with	O
a	O
lithium	O
anode	O
and	O
a	O
lithium-iodide	O
electrolyte	O
solid-state	O
battery	O
.	O
</s>
<s>
Lithium-iodide	O
or	O
lithium	O
anode	O
cells	O
increased	O
the	O
life	O
of	O
pacemakers	B-Device
from	O
one	O
year	O
to	O
as	O
long	O
as	O
eleven	O
years	O
,	O
and	O
has	O
become	O
the	O
standard	O
for	O
pacemaker	B-Algorithm
designs	O
.	O
</s>
<s>
They	O
began	O
designing	O
and	O
testing	O
their	O
implantable	O
cardiac	B-Algorithm
pacemaker	I-Algorithm
powered	O
by	O
a	O
new	O
longer-life	O
lithium	B-Device
battery	I-Device
in	O
1971	O
.	O
</s>
<s>
The	O
first	O
patient	O
to	O
receive	O
a	O
CPI	O
pacemaker	B-Algorithm
emerged	O
from	O
surgery	O
in	O
June	O
1973	O
.	O
</s>
<s>
The	O
devices	O
are	O
roughly	O
the	O
size	O
and	O
shape	O
of	O
a	O
pill	O
,	O
much	O
smaller	O
than	O
the	O
size	O
of	O
a	O
traditional	O
pacemaker	B-Algorithm
.	O
</s>
<s>
In	O
November	O
2014	O
,	O
Bill	O
Pike	O
of	O
Fairbanks	O
,	O
Alaska	O
,	O
received	O
a	O
Medtronic	O
Micra	O
pacemaker	B-Algorithm
in	O
Providence	O
St	O
Vincent	O
Hospital	O
in	O
Portland	O
,	O
Oregon	O
.	O
</s>
<s>
Also	O
in	O
2014	O
,	O
St.	O
Jude	O
Medical	O
Inc	O
.	O
announced	O
the	O
first	O
enrollments	O
in	O
the	O
company	O
's	O
leadless	O
Pacemaker	B-Algorithm
Observational	O
Study	O
evaluating	O
the	O
Nanostim	O
leadless	O
pacing	B-Device
technology	I-Device
.	O
</s>
<s>
The	O
Nanostim	O
pacemaker	B-Algorithm
received	O
European	O
CE	O
marking	O
in	O
2013	O
.	O
</s>
<s>
While	O
the	O
St	O
Jude	O
Nanostim	O
and	O
the	O
Medtronic	O
Micra	O
are	O
single-chamber	O
pacemakers	B-Device
,	O
it	O
was	O
anticipated	O
that	O
leadless	O
dual-chamber	O
pacing	O
for	O
patients	O
with	O
atrioventricular	B-Algorithm
block	I-Algorithm
would	O
become	O
possible	O
with	O
further	O
development	O
.	O
</s>
<s>
Worldwide	O
each	O
year	O
,	O
in	O
a	O
simple	O
procedure	O
to	O
avoid	O
explosions	O
,	O
thousands	O
of	O
pacemakers	B-Device
are	O
removed	O
from	O
bodies	O
to	O
be	O
cremated	O
.	O
</s>
<s>
Pacemakers	B-Device
with	O
significant	O
remaining	O
battery	O
life	O
are	O
potentially	O
life-saving	O
devices	O
for	O
people	O
in	O
low	O
-	O
and	O
middle-income	O
countries	O
(	O
LMICs	O
)	O
.	O
</s>
<s>
Ever	O
since	O
the	O
1970s	O
,	O
multiple	O
studies	O
worldwide	O
have	O
reported	O
on	O
the	O
safety	O
and	O
efficacy	O
of	O
pacemaker	B-Algorithm
reuse	O
.	O
</s>
<s>
,	O
widely	O
acceptable	O
standards	O
for	O
safe	O
pacemaker	B-Algorithm
and	O
ICD	O
reuse	O
had	O
not	O
been	O
developed	O
,	O
and	O
there	O
continued	O
to	O
be	O
legal	O
and	O
regulatory	O
barriers	O
to	O
widespread	O
adoption	O
of	O
medical	O
device	O
reuse	O
.	O
</s>
