Exercise-induced Tachycardia

[MarathonRunner66]

Hi,

I am 43 years old, 140lbs, 5'9", run 60-70 miles per week. About 3 weeks ago, I suffered from 60-hour diarrhea, which I finally controlled with immodium. I did not run for a few days and then tried a very easy 7.5-mile run. On the last mile or two, I felt extremely exhausted. My heart rate was elevated (about 15-20 bpm higher than normal). I attributed this to the aftermath of the diarrhea. Nevertheless, I stopped running and exercising for about 2 weeks.
2 weeks later, I tried to run very easy again, but stopped after about 2.5 miles. HR was again about 15-20 bpm higher than normal, peaked at about 88% of my maximum heart rate. Everything else felt normal. It certainly did not feel like running at my anaerobic threshold. After the run I felt my pulse, which turned out to be abnormal. For about 2 or 3 minutes after the run, I felt 3 beats, then a break, 3 beats, break, sometimes 2 beats, break. While this was happening, it slowly dropped from 180 to about 120. Although beating normally, the HR stayed at 100-120 bpm for at least an hour. Even though I never checked that before, I do not believe this is normal either.
I went to a cardiologist, but everything turned out normal. The EKG did not show any abnormalities. Blood pressure is low (90/58), resting heart rate slightly elevated (76 vs. 60) and I do sometimes feel a little dizzy after getting up from a chair. He told me I could get slowly back into running, but I do not really feel comfortable. Any suggestions?

Thanks,
Frank

[DREAMGIRL12]

Kudos to you both for staying fit!!  Of course you know that you can be fit and yet have clogged arteries, if it was me I would have my cholesteral numbers checked, do a total lipid panel, if that turns out normal, then just keep an eye on things, but more than one athelete has died because he did not know he had clogged arteries and a chip of the plaque buildup broke loose. Just my ten cents!!!

[runnertom]

      I have had trouble with atrial fibrillation that presents similarly to what your describe, although you don't say how regular your pulse was when it was racing. I would experience my legs "turning into lead" all of a sudden and my pulse running quite high for what I was doing. It used to happen during races when I would get excited when I knew someone was about to catch me or I ran by a group of spectators that I knew. The telltale sign was that my pulse would be very irregular and rapid. Back then, the Afib would go away within minutes and all would be normal. More recently it has persisted for 24 hours or so and I am taking medication to prevent it.

[Cleveland Clinic]

Get an echocardiogram to make sure that your heart function is normal.  Sometimes diarrhea can be a sign of a viral infections that could affect your heart making it weaker.