When i saw the title, i immediately knew what this was. I used to refer to these as "stomach jolts". It feels like electric spasms or sensations that go off in the gut, you feel like a minor drop (almost like a small rollercoaster drop if you know what I mean) followed by heart palpitations and possible arrthymias within a second or so. This is leaky gut period.
I dealt with this over a year and did not know what the hell it was and referring to it as "Anxiety" will totally screw you over by doctors, integrative or not. It definitely gives you anxiety and you feel like fainting and just vfeel like you cannot take any stress. It is related to the adrenals but the cause is damage to the gut, AKA leaky gut. I am know able to know this very distinctly because much of my symptoms have been managed quite stably and noticed most recently that anything i take that irritates my leaky gut, such as antifungals at burn a hole in my gut (SF722 AKA undecylenic acid, caprylic acid, oregano oil, digestive enzymes, etc.) irritate and increase the inflammation in the gut and it causes these spasms along with the adrenals kicking in full force.
If you think about it, the GI tract is a very very big thing for the adrenals to quell (in terms of inflammation) as it starts from the tongue down to the rectum and it is said to have its own nervous system along with production of pretty much everything that our body needs, such as neurotransmitters, hormones, etc. Mine went from unbearable and not being able to ride in a car because of constant heart palpitations, or being able to watch Toy Story (wtf right?) to being much better and only reacting to stress. Still is there and to me, it means my leaky gut needs work. Antifungals that dont aggravate my LG are hard to come by but it is the first step to healing.