Concerns about heart health.?

It doubtful the test missed anything. If you have recurrent SVT it's an AV Node issue and no amount of tests will diagnose that just the recurrent SVT that's doented/picked up by a holter monitor. Frankly it sounds like you have a panic disorder regardless you should consider seeking treatment for that so you won't continue to be debilitated by it and can try to live as normal of a life as possible.