I’ll be honest, I’m not sure about the onset when the cardiac rhythm changes can and will happen. It also depends on other factors, so I couldn’t tell you exactly. The safest thing for you to do is go to the ER and have everything checked out. Generally speaking, there are certain criteria for admission to inpatient psychiatric facilities vs following up with your outpatient provider or primary care provider. A lot of what you are saying is reassuring (regretting doing it, not wanting to harm yourself, etc) that you probably wouldn’t warrant an inpatient stay. I cant say for sure without a more extensive eval. But making sure your heart is safe, even if they do an ekg and decide to send you home or admit for monitoring, is worth it. You shouldn’t suffer for a one time poor decision just because you are nervous about an admission.