What caused this tachycardia?

[Sylvaneer]

Facts:

I'm a 28 year old male in excellent shape, exercise regularly, resting heart rate around 50BPM, low blood pressufe, low body fat %, low blood cholesterol (and normal everything else on a blood test done 7 months ago), don't smoke, never had any major medical issues.  I do live an incredibly stressful life with fairly frequent anxiety from a demanding job.

I was participating in a charity bike ride that was 66 total miles.  A distance I am comfortable riding and have done so many times before.  On a warm low humidity day (maybe low 80s at that time of day).  I wear a Garmin chest strap heart monitor at all times when exercising.  I was putting out a moderate effort with an average heart rate of about 135BPM which is well below my typical hard effort training.

About 40 miles in we roll to a rest stop, I hop off the bike and a few seconds later while I am standing there my heart rate begins to steadily increase (I feel it in my chest).  I look at the bike computer that displays the HR monitor data and watch the numbers climb in 10-20 seconds from about 160BPM when I rolled into the rest stop to 215BPM.  I check my pulse to make sure the monitor isn't malfunctioning and my heart was definitely beating that fast.  The beats were weaker than my normal heart beat.  It stays at that level about 1 minute before gradually slowing to 180 still with the weak beats, then it instantly jumps back to a normal HR around 120BPM and is beating with the same strength it normally does.

All this happened while I was just standing there monitoring the situation.  The total event lasted about 2 minutes.  There were no other symptoms and other than the rapid heart rate (and being scared) I felt fine.

I was fairly well hydrated, having drank 2 full bottles over the 2 hours period (about 48 ounces), one was sport drink, one was plain water.  Also ate 2 bananas, an orange, and a protein bar during the same time period.  And I was not feeling sweaty, dehydrated, or overheated during the ride.

After resting for a while, and taking in more fluids I continued the ride.  The remaining 26 miles I rode at a high intensity, greater than the previous 2 hours of effort, without issue.

I saw my Doctor, who then referred me to a cardiologist.  Neither knows what happened.  But both hear a heart murmur which I have never had before (at least as of 7 months ago at my last annual checkup).  We can't say for certain if it is related to the tachycardia event or not yet.

I'm scheduled for an echo, stress test, and a follow up with a second cardiologist.

Any idea what the heck happened?

Thanks for your time.

[Sylvaneer]

Thanks for your thoughts.

I figured it could be a plethora of things and it is probably nothing to worry about, but not knowing what it was is driving me nuts.  They do have an ECAT monitor hooked up to me for the next 30 days.

More than anything, not being able to exercise (cardiologist's orders until all tests are done) is killing me.  The echo is the first test, if that comes back OK I might cheat and go for a light jog.

[cindy707]

Sorry this happened to you when you are so cautious about taking such great care of your body.  Sounds like the docs are at least super pro active with this situation but i would definately ask them to put you on a 30 day holter monitor to see what they can catch.  This could be just about anything Sylvaneer....since the heart basically pumps off of electrical activity you could have just had a short random run of the correct pattern it follows running amok on you, could be you had a short run of atrial fib...i mean the list is endless, could be something so simple as that you weren't hydrating well enough for your output that day and sport drinks are very tempting but stats still show plain old water is still the best and i know that dehydration will cause runs like this along w. stress, all types fo things...i personally think that the only way to know is to get thru your appts. and see what they pop up with...but definately consider the holter...heart murmurs are super super common and its estimated that over 40% of the whole population has one but who knows...docs want to make sure that nothing is hiding itself behind the murmur......good lock to you wish i could have been more helpful but hopefully someone else will weigh in that may have gone through this....