I lied at MEPS. Will they go back and look through my medical records?

Not only do I agree with LTC Jason Mackay, I would further point out this question should be addressed to an attorney (hopefully a JAG or former JAG) who is bound by attorney client privilege from telling anyone (not that you just told everyone). I would not seek cardiac advice over the internet, I believe that legal advice over the internet is worth even less than what you pay for it (nada!).

Don't say anything. Most kids have murmurs it's not uncommon let a doctor tell you if you still have one. If you do just say I had no idea

If you hadn't posted this, nobody would have known or cared. Seriously. Now that you have, congrats, you opened pandoras box, and may be rejected. If, by some miracle, nobody in the chain at MEPS sees this, it could still bite you in the rear and you might be separated later under fraudulent enlistment.

Unfortunately From Commander in Chief all the way down to PVT “no body cares” from your local school board to the senate, from your local police to the top justice, integrity, loyalty, honor are just words. But you as a nobody recruit will be held to a higher standard of integrity and honor if the situation and person catching your issue determine that making an example of you will float their skirt. Coming on RP and admitting you purposely withheld medical information is evidence that can be used to deny you enlistment and or a security clearance. So your heart murmur is irrelevant as cause for denying enlistment.

Lol

I agree with ZaGara. This is something you need to come clean about before you are sworn in to your recruiter. If it's a none issue as you claim by your doctor, then MEPS may clear you. But if they clear you and later CID finds out, you can be dishonorably discharged or worse.

Plus if for some reason you are placed into a combat situation and your heart fails do to it and you get men killed, would you be willing to live with that if you survive the encounter?

I understand the drive to serve, but if you are not medically able to, it is best to step aside.

Do yourself a favor and DELETE THIS THREAD!!!!
you will be fine as long as the wrong person doesn't read this, if they do you will be barred from enlistment at the very least. If they wanted to make an example out of you they could prosecute you.
Lying to Get Into the Military is a Felony
The Manual for Courts-martial (MCM) lists the maximum punishment for a violation of this article as: dishonorable discharge, reduction to the lowest enlisted rank, forfeiture of all pay and allowances, and confinement at hard labor for two years.

They most likely won’t. It will become an issue if you get in and it becomes an issue, which at that point, if they know you knew about it prior, they can take UCMJ action and discharge you.

You lied so it will catch up to you. Why would think that you can lie and get away with that?
That makes me what else you lied about...

What's done is done, nothing you can do about it now. If the doctors at MEPS didn't find any heart murmur, then you're good, if they do, you go home. Most likely will only get a lecture if you do still have one.