This sounds to me more like a vascular problem, but lower down, possibly cardiac. You may have a congenital stenosis of a vein or artery that impedes blood flow. Maybe that impediment IS in your brain, but maybe it's in your heart and your heart develops an arrythmia as a result, especially if you are excited and subject to a loss of tone in the Vagus nerve or due to an adrenergic response.

Gastritis can cause a loss of Vagal tone, which can encourage atrial fibrillation or PACs (premature atrial complexes).

It couldn't hurt, if you can afford it, to go to a private clinic for an ECG on a bad day, or get a Kardia Mobile if you don't have/want a smart watch or a smart ring.

I think you'll end up having an MRI, perhaps a nuclear stress test to rule out ischemia. I can't say because I am not a physician, and we don't know each other, but this is something that you can anticipate being asked to undertake.

You will almost certainly be referred to a neurologist if the heart checks out, or even before they decide to take a look at your heart...if at all.