TMBRA - Rider Board

[rick]

Hi Doc,
Ok, here's the facts:47 year old male. 6', 160 LBS. Started racing this Spring season. Max heart rate 182. Resting HR, 47. Been biking, running, hiking, mountaineering for many years. I have a heart rate monitor and use it all the time. Going to the trailhead for a ride about 3 weeks ago, I noticed an irregular beating( thought it was interference from the car). Took my pulse at the trailhead manually,54, but irregular. Didn't really think too much about it. I had done a race two weeks before at 177 avg 196 max for 54 minutes. And another the weekend previous with an avg 172, max 182 for 1hour 30 mins...Go to give blood the next day and was deferred due to irregular HB. My GP did a short EKG and thinks that because my resting HR is low, it gives my heart a chance to throw in an extra beat. Huh?!? It does actually seem like my heart becomes more regular when I'm really cranking.
What do you think?

[The Bike Doc]

rick:

Two things come to mind. One is quite common in a well conditioned individual who has a slow resting heart rate, respiratory variation. Normally the heart rate slows slightly with inhalation and speeds up with exhalation but it is not obvious to most individuals because of their higher resting heart rate. In a well conditioned individual with a slow resting heart rate, this respiratory varriation will be more easily noticed. It can be easily detected by monitoring the pulse during resting and quite breathing. The pulse slows slightly with each inhalation.

The second thing is premature atrial contractions, PACs. These also are common in well conditioned individuals with slow resting heart rates. They are not serious in an of themselves. A rare individual can have an abnormal circuit in the heart that can get triggered by a PAC then a sudden extremely rapid and dangerous heart rate can develop called supraventricular tachycardia SVT. It certainly does not sound like you are experiencing this. If your EKG is good, your doctor's exam of you is good and you are not experiencing a suddening sustained spike in your heart rate, I would not get too concerned.

If you have persisting anxiety about your heart rate or you experience sudden, sustained elevated heart rates, have chest pain, do seek an immediate evaluation by a cardiologist.

Thanks,
_________________
Paul K. Nolan, MD
AKA: The Bike Doc