From: brit@wagner.Physics.McGill.CA (Dave Britton)
Newsgroups: rec.running
Subject: Summary: Irregular heart beat (LONG)
Date: 30 Aug 92 02:44:12 GMT
Organization: McGill University

My original post has generated quite a large response, both
posted and e-mailed. I did not keep the vast majority of
the responses but most of them had the basic message
"Yes, I get that too. I had it checked out, and it was
nothing to worry about"
There were a couple of more serious responses which I will
include below after a copy of my original post. I am no
longer concerned about my present bout of irregular
heart beats becasue it coincides with increased training
which fits the discriptions of many other posters. ALSO,
I had an echo-cardiogram a couple of years ago and there
is nothing fundamentally wrong with my heart (though it
refused to do a single irregular beat for the ECG or for
an EEG at that point). However, as with all these things,
consult a Doctor if you are in doubt. Many people confirm
that giving up caffeine is benificial... the effect is
probably present in many people but you only start to
notice it when you get down to a 40-odd pulse.
Dave.

In <1992Aug25.231448.14729@sifon.cc.mcgill.ca>  
brit@wagner.Physics.McGill.CA (Dave Britton) writes:

>This reminded me of a question I meant to post: My resting pulse rate
>is also in the low 40's (clocked as low as 39 but normally around 44).
>However, I regularly get irregularities in the beat, but only when it
>is beating slow. These irregularities are like an extra beat or a
>beat that is way out of time. Happens once or twice in 5 minuites
>a couple of times an hour but only sometimes (usually notice it
>in the evenings). I avoid caffeine which I have noticed makes 
>this effect worse. The more I run, the slower my heart beat gets
>and the more I notice this effect. Anyone have any comments?
>(don't suggest I quit running :)

From: elman@crl.ucsd.edu (Jeff Elman)
One common source of PVC's and PAC's is over-training, particularly in
endurance sports.  The heart normally expands with increased training.
This is normal and appropriate.  But if the stretching occurs too
quickly, it can irritate parts of the heart.  Most of the heart has
pace-making capability which is normally suppressed; irritation can
cause these other regions to trigger premature contractions.  (These
are often either masked or supressed during intense exercise, so you
may only notice the problem at rest.)  Eliminating caffeine, cutting
back on the level of training, and re-building at a slower pace will
frequently solve the problem.

However, as several people have pointed out, there are many different
things which can cause an irregular heartbeat.  It can be chronic and
totally benign in some people. In others it can be indicative of a
serious problem.  Get it checked, preferably by a cardiologist who's
knowledgeable about sports medicine.

From: hmiller@lucpul.it.luc.edu (Hugh Miller)
    Get it checked out.  I have a similar problem.  After 6 sedentary
years (I ran XC, rowed crew in U.) I took up running again: 30 mins/day,
6 days a week, at a target HR of 156.  Soon I had a chronic arrhythmia,
a skipped beat every fourth beat.  (At the time my morning rising pulse
was 68).  A quick-'n'-dirty EKG revealed a lot of PAC's (premature
atrial contractions), but also what looked like PVC's (p. ventricular
c.'s), which are much more serious.
    Had an echocardiogram, treadmill stress test, and a 24-hour Holter
monitor done.  Echo showed mild MVP (mitral valve prolapse), a common
condition in tall skinny folks with pectus excavatus (hollow chests!).
Especially common with athletes' large, floppy hearts.  The PVC's turned
out, on very close examination of the Holter monitor record, to be all
PAC's with associated right bundle branch block, again a common syndrome
with endurance athletes.
    BTW, at high heart rates all pulse irregularities disappeared!
    I knocked off training entirely, drank beer for 2 weeks, and started
over, running only 20 mins. every other day.  Every 4 weeks I added 5
minutes to the total time.  I'm up to 60 mins. every other day.  Morning
rising HR is now 50 (my all-time low was 36, rowing crew), and skipped
beats are a rarity, usually occurring only in the couple of hours after
a run.
    So I turned out OK.  But you may not have the same problem.  I
encourage you to get tested, pronto monto.  PVC's are potentially
serious bidness.

From: Bill Innanen <wgi@aplcomm.jhuapl.edu>
Sounds to me like PVCs (premature ventricular contractions).  

NOTE:  I'm not a doctor!  Don't take anything I say too seriously!

I noticed the same thing several years back.  I would have periods of
several minutes upt to several hours, once, when my heart would really get
syncopated with "extra" beats thrown in here and there.  I _immediately_
hauled myself into my quack (im my mid-40s I can't ignore such things).   
He
diagnosed it as PVCs.  He said (to me, in my case) that it was harmless
unless it upset me to the point that the upset caused problems.  There are
drugs that will suppress them, but once you start you can count on taking
them for the rest of your life.  Otherwise I could give up caffeine.  It
turns out that he (the quack) had the same thing.  He'd given up caffeine
and the problem went away.  So I gave up caffeine (tea, coffee, colas,
etc.) and the problem went away.

Two years ago I went in for my first (baseline, no problems) stress test
with the cardiologist.  Treadmill, all wired up, the whole bit.  He kept
upping the speed and slope on the 'mill and my heart rate only reluctantly
rose.  (Actually, it wasn't very stressful. :-))  But at one point his
technician jumped quickly to hit the start switch on the strip chart
recorder.  She had spotted some PVCs while I was exercising!  I hadn't
noticed them!  But the only excitement was to get them on paper.  The
cardiologist was just as unimpressed and unworried as my personal quack.

bottom line:  Not to worry.  Drop all caffeine.  And they do happen
even when you don't notice them, like while running.