I had a heart attack in 2004. EKG showed no heart muscle damage. I have had nuclear stress test last year(2010) and it showed normal EKG.
Few days ago while I was bicycling early morning (7 AM) in rather warm weather (82 F) after only 4 miles, I felt very uncomfortable and very tired. There was left shoulder pain and all of left hand was very tired for many hours. So around I went o my doc's office and they did an EKG. It showed all was fine except that the P-R interval was 230 mSec. Last year's (2010) EKG was normal but I don't know the exact P-R interval number.
Should I be concerned? Not at all, a little, a lot? Should I slow down my exercises? I routinely push my heart rate to 180-185 bpm for a minute or so but several times in an hour's jog. Stop doing that? It doesn't matter?
Appreciate your comment, particularly if you are a cardiologist and a jogger/runner.
I strongly doubt you will find someone who is both a cardiologist and a runner here (though cardiologists tend to keep in good shape). This is a community, not an "ask a doctor" forum.
Anyway, the fact that you are able to push your heart rate to 185 bpm is itself a sign that your (borderline) 1st degree AV block probably decreases with higher heart rate. A stress test will confirm that. 1st degree AV block (PR above 220 msec) is usually a benign condition, and your PR time is just borderline long. PR time will, as mentioned above, change from moment to moment, it changes with heart rate, adrenaline/stress, electrolytes in the blood, etc. Beta blockers and calcium channel blockers may prolong the PR interval.
I think you should ask your doctor if it's safe for you after a heart attack to push your heart rate to 185 bpm. "Calculated" max heart rate for you is 165 bpm, but this rule has a lot of exceptions. In my family, the maximum heart rate is high, I have a max heart rate of 220, and my mom who is about your age, have a max heart rate of 190. What of course is important, especially after a heart attack, is to make sure that you are in normal sinus rhythm when your heart rate is this high. I assume your stress test did confirm this.
Take care, and I hope a doctor will answer you (it may happen but it's quite uncommon here)
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