<s>
Paroxysmal	B-Algorithm
supraventricular	I-Algorithm
tachycardia	I-Algorithm
(	O
PSVT	B-Algorithm
)	O
is	O
a	O
type	O
of	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
,	O
named	O
for	O
its	O
intermittent	O
episodes	O
of	O
abrupt	O
onset	O
and	O
termination	O
.	O
</s>
<s>
Otherwise	O
symptoms	O
may	O
include	O
palpitations	B-Algorithm
,	O
increased	O
heart	O
rate	O
,	O
feeling	O
lightheaded	O
,	O
sweating	O
,	O
shortness	O
of	O
breath	O
,	O
and	O
chest	O
pain	O
.	O
</s>
<s>
Risk	O
factors	O
include	O
alcohol	O
,	O
caffeine	B-Application
,	O
nicotine	B-Operating_System
,	O
psychological	O
stress	O
,	O
and	O
Wolff-Parkinson-White	O
syndrome	O
,	O
which	O
often	O
is	O
inherited	O
.	O
</s>
<s>
The	O
underlying	O
mechanism	O
typically	O
involves	O
an	O
accessory	B-Algorithm
pathway	I-Algorithm
that	O
results	O
in	O
re-entry	O
.	O
</s>
<s>
Diagnosis	O
is	O
typically	O
by	O
an	O
electrocardiogram	B-Application
(	O
ECG	B-Application
)	O
which	O
shows	O
narrow	B-Algorithm
QRS	I-Algorithm
complexes	I-Algorithm
and	O
a	O
fast	O
heart	O
rhythm	O
typically	O
between	O
150	O
and	O
240	O
beats	O
per	O
minute	O
.	O
</s>
<s>
About	O
2.3	O
per	O
1000	O
people	O
have	O
paroxysmal	B-Algorithm
supraventricular	I-Algorithm
tachycardia	I-Algorithm
.	O
</s>
<s>
An	O
ultrasound	B-Application
of	I-Application
the	I-Application
heart	I-Application
may	O
be	O
done	O
to	O
rule	O
out	O
underlying	O
heart	O
problems	O
.	O
</s>
<s>
Symptoms	O
may	O
include	O
palpitations	B-Algorithm
,	O
feeling	O
faint	O
,	O
sweating	O
,	O
shortness	O
of	O
breath	O
,	O
and	O
chest	O
pain	O
.	O
</s>
<s>
The	O
Valsalva	O
maneuver	O
should	O
be	O
the	O
first	O
vagal	O
maneuver	O
tried	O
and	O
works	O
by	O
increasing	O
intra-thoracic	O
pressure	O
and	O
affecting	O
baroreceptors	B-Algorithm
(	O
pressure	O
sensors	O
)	O
within	O
the	O
arch	O
of	O
the	O
aorta	O
.	O
</s>
<s>
Pressing	O
down	O
gently	O
on	O
the	O
top	O
of	O
closed	O
eyes	O
may	O
also	O
bring	O
heartbeat	O
back	O
to	O
normal	O
rhythm	O
for	O
some	O
people	O
with	O
atrial	O
or	O
supraventricular	B-Algorithm
tachycardia	I-Algorithm
(	O
SVT	O
)	O
.	O
</s>
<s>
If	O
unsuccessful	O
or	O
the	O
PSVT	B-Algorithm
recurs	O
diltiazem	O
or	O
verapamil	O
are	O
recommended	O
.	O
</s>
