Wouldn't that be nice?  I'm afraid the hardware/software you'd need would
be specialized and thus cost a shitload of money.  Even though it wouldn't
take much more technology than the average sound card, e.g.

Dear Mr. Kemph:

First, this is exactly the kind of information your MD would like to
have from you.
However, as a fellow curious do-it-yourself-er, I'm sympathetic to your
interest in the technology.
A Holter monitor is often used to record heartbeats for 24 hours or so
(although the "looping" device mentioned in the previous post sounds
better). Here's an ad for one.
<lR/XMDNQFHLvMCDaXGLruO09CmxqbsLk>
Just a few grand, and you'll probably have to be a doctor to buy it.
EKG machines that record a brief paper strip seem to be a few hundred
dollars on ebay.

What an EKG records is changes in voltage across your chest, generated
by the movement of potassium ions across muscle cell membranes in your
heart muscle. This rush of potassium ions is part of the trigger
mechanism to make each muscle cell begin to contract. Since the cells
trigger each other in a cascade, sort of like a forest of dominoes, you
can deduce the shape, size, rotation, of the heart, and the path,
direction, and speed of the wave of "depolarization" (triggering) as it
moves throught the heart. You basically record the voltage across the
chest in different directions, with a temporal resolution of about a
millisecond, over a range of + to -2 millivolts.
If you can find some standard  PC hardware which would do this, please
let me know, as it would be useful for lots of other projects.

(By the way - I don't recommend performing electrical experiments on
your own chest. External voltages applied across the heart can cause
self-propagating circular or chaotic waves of depolarization known as
"ventricular tachycardia", "ventricular fibrillation" or "sudden
death".)

A popular nurse's reference for adult EKG interpretation is "Rapid
Interpretation of EKG's"
<http://search.barnesandnoble.com/booksearch/isbnInquiry.asp?userid=gF4AeCXAhF&is
bn=0912912065&TXT=Y&itm=1>

The underlying mechanisms are explained in a good Anatomy and
Physiology textbook. The latest edition of the one I used is "Textbook
of Human Physiology" by Guyton and Hall.

Of course, if you're interested in what significance this all has for
your personal health, be aware that the symptom you describe is bread
and butter for an adult doctor. That's what they do.

By the way, you can deduce some information about your heart's
conduction system just by feeling your pulse. Unfortunately, perhaps
due to the ubiquity and superiority of EKG machines in healthcare
facilities, I couldn't find any good references for you. The best I
could find in a brief 'net search was
<http://www.provet.co.uk/equinecardiology/tab72.htm>
You didn't mention whether you are an English horse or not, but I
suppose the information might be valid for other mammals.
It is a three-column database, unfortunately sorted by pathology in the
first column, but has a second column of physical findings which
include pulse rhythms. You'll still need information how to take a
pulse, on the meaning of rhythm signs such as "compensatory pause" and
of the associated findings.