Hello -

It's a Friday, so my sister, who's 37, will be seeing a doctor on
Monday.  In the meantime, we'd like to see if there's any light that
could be shed on some symptoms she's experiencing:

at any given time, she doesn't feel normal, in that she feels pressure
on her chest; sporadic rapid heartbeat; general shortness of breath;
while attempting to sleep, she is very frequently awaken by a racing
heart and SEVERE difficulty breathing.  Overall, everything is much
worse when sleeping, which she doesn't really do, because this keeps
her up.  She has chest pain and moderately congested in her nose
(sneezing a bunch).

She feels no "adverse thoughts" or anything that mentally she can
associate with this.  It's almost like a reverse anxiety attack.  The
racing heart and hard breathing cause anxiety.

She has seen a cardiologist who has confirmed no physical problems
with her heart.  Is there perhaps a virus or bacteria or other
physical condition that could cause these symptoms?

A couple of thoughts come to mind - one is asthma, which can cause
severe shortness of breath and tends to be worse at night.  Shortness
of breath from any cause, including asthma, in itself can cause rapid
heartrate.  Asthma can also cause chest pain, and can be associated
with allergies which can cause nasal congestion.  The second thought
is gastroesophagal reflux disease, or GERD.  Although the symptom most
often associated with GERD is heartburn, it can also cause shortness
of breath, rapid heart rate, chest pain/pressure, and other symptoms
wihout the typical heartburn.  It is more common after larger meals
(which for a lot of people is dinner), and is worse with lying flat. 
I had very similar symptoms for a while, and after I started treatment
for GERD, they resolved, and have stayed away even off treatment now
(or when I do get them are easily treated, and because I know what it
is, cause little anxiety).  Of course, without a more thorough
history, exam, and possibly tests, it is not possible to diagnose any
particular cause, but rest assured there are some relatively benign
possible causes.  Good luck with the appointment.

Might it be sleep apnea?

http://www.abed.com/sleepcenter/sleepapnea.html

~ czh ~

If she has seen a cardiologist, did she get any tests? She needs an
echocardiogram, a Holter heart rythm monitoring and pulmonary function
testing. does she take any meds or supplements? Diet pills, caffeine,
and others could be the culprit. Good thing you're going to the doc,
you can't play around with shortness of breath.

The GERD comment seems possible to me.  Would also suggest looking at
Gall Bladder disease.  Late thirties, female is most common.  If she's
overweight and fair skinned she'd be in the number one gall bladder
category (fair/forty/fat/female).  The shortness of breath comes from
gall stones / gall bladder infection being located directly under the
diaphragm.  When it acts up, breathing problems result.  (Had this
problem... was told I was having "panic attacks."  Decent doctor
finally told me I was panicking because I couldn't breathe.)  If it
seems to happen more frequently after fatty and or creamy foods it
would be even more likely.  Also one of the most often misdiagnosed
problems.  Worth considering.

PLEASE HAVE HER THYROID LEVELS CHECKED!!
All of her symptoms point to her having a hyperactive thyroid.  It's
very common to have heart palpitations, especially at rest.
I would bet money that this is what it is.