JohnDThompson: I am, in fact, taking the Beta-blocker Carvedilol for cardiac arrythemia (irregular heartbeat).

I appreciate your concern regarding this issue, but it’s an area with which I am quite familiar, unfortunately. Carvedilol has a wide range of unpleasant side-effects that I’ve learned to live with for the last 40 years in order to ensure that my fluttering heart doesn’t result in a stroke.

For example, the meds are at least partly responsible for sleep disorders such as apnea, insomnia and nightmares. I won’t go into how I deal with those except to say that I dread bedtimes the way most people dread visits to the dentist.

Sleep disturbances aside, Carvedilol lowers my body’s plasma glucose and stimulates hepatic glycogen breakdowns, leading to potentially deadly hypoglycemia (very low blood sugar). The drug’s natural tendency to do that is exaggerated by physical activity (such as bike riding) without appropriate carb fuels (digested food, in other words). For me as a (former) diabetic, each bike outing is a balancing act of trying to ingest enough food into my egg-size stomach without either throwing it up or gong into low blood sugar shock. If I make myself sick by over-eating or eating the wrong things (solid meat, for example), I’ll spend from two to six hours in the bathroom and not be able to ride anywhere. If I don’t eat enough and fail to refuel while riding and/or immediately afterward, I could end up in the hospital or the morgue.

It’s an unpleasant game I play with my body every day, but it’s a game I believe is absolutely necessary in order to maintain my muscle tone, fitness and weight (currently 175 – about 7 pounds above my maintenance weight).

Dehydration is a potential side effect of Carvedilol but is much less likely than with other B-blockers. It is definitely not a problem for me. On the other hand, there is no doubt Carvedilol causes edema (fluid accumulation) in my legs, and biking lessens that somewhat.

As I mentioned earlier, my doctors believe Carvedilol might be responsible in part for my low heart rate, but although dosages have been changed and tweaked over the last couple of years, there’s been no significant change in my HR, no matter whether I’m bike riding or spending all my waking hours behind my computer.

Dudelsack: My docs (including my cardiologist) are very much aware of my low HR. They’ve had me do the treadmill/ekg routine several times and tell me that my treadmill-HR is just slightly below normal, but my at-rest HR, while a little alarming, appears to be normal for me currently.

I really appreciate everyone's thoughtful comments.