What Causes Palpitations While Playing Soccer?

Hello, I experienced palpitations or rapid thumping in my chest today when playing soccer. It lasted for about a minute, while I layed down and tried to relax. The thumping was extremely fast, faster than I have ever experienced. I do exercise regularly, but have not played soccer in awhile- perhaps I over exerted myself? My medical history includes a patent foramen ovale but was checked out with an EKG and was told it was nothing to worry about. I am a 22 year old, otherwise healthy male. I am living in rural China now, so getting a Doctor's advice is difficult.