Hi There, Thanks for asking. The description of the situation is very similar to a panic attack. When such a thing happens for the first time, several possibilities should be assessed before the diagnosis is made. As you mentioned, it is sometimes secondary to heart problems (like mitral valve prolaps). Sometimes they are related to endocrine problems. If all of these issues are ruled out, then we should think about primary panic attack. It is a kind of anxiety disorder and fortunately it would be easily controlled with medication. I wish it resolves soon since it is really disturbing.