Worth worrying about?

[RT273]

I've been ridding a fitness kick the past few weeks and I've been doing pretty well. I started paying a lot more attention to my heart cause of it though (I get palpitations pretty frequently, just not enough for treatment), and I've noticed a third heart sound (ie s3). I haven't been worrying about it, but it's starting to get more prominent and I'm starting to have some symptoms; I was bored last night and felt kind of weird, so I listened to my heart for awhile and it was like it would sort of catch on the s3 and then take off, went from like 60 to 120 and stayed that way for 3-4 minutes at a time, then sort of beat with the s3 a few times before doing it again. I'm kind of a cardio-nerd (if that makes sense), so I know a bunch about the heart, but I can't think of anything that would cause this without being a serious condition with other prominent symptoms. Any ideas?

Oh, also, I'm 18 m, good health. Work out daily, do cardio at ~70% for half an hour then do sprints, get my hr way up during those (190-210, it's redline training which I know can be dangerous but I've researched it). 5'11", 185 lbs. I've gotten PVCs while exercising, but never during or after cardio. Thanks for the help!

[Wisconsin2007]

I just read a little today about a gallop rhythm, and that it can be found more commonly in younger people like yourself.

As for the racing HR for a few minutes, that doesn't sound like a gallop rhythm.  Sounds like SVT or VT, though those can happen in younger, healthy people, too.

Sorry I can't offer more - not a cardio nerd, I guess.  :)

[RT273]

Anyone? Anyone?