I have episodes of a cold flash that starts in my feet and works upward. Tightness in my chest, sweaty, clammy, feels like I m going to pass out, but I dont. My heart either feels like its going to race, or stop. Usually lasts 1-3 minutes. Random occurs, have seen cardio, numerous holters (but cant catch an episode), but also have thyroid issues (which are controlled at the moment.) Caffeine causes palpitations and rapid heartrates. My brother and maternal aunt have very similar episodes. Currently on a beta blocker , and synthroid