At the er for chest pain hospital monitor says couplet pvcs amd sv rhythm. What does sv rhythm mean? And are couplet pvcs dangerous?

Not necessarily. SV="supraventricular rhythm" which is normal. PVCs are "extra beats" that sometimes lead to the feeling of a thump or irregular heart beat. By themselves, extra PVCs or couplets of PVCs are not dangerous. Some people get them when they drink caffeine or smoke cigarettes. They aren't an indicator of a heart attack, but if they happen during a heart attack, they can be a sign of impending problem.