What is cause of supraventricular tachycardia?

Good question: With no simple answer. There are many triggers like caffeine, nicotine, alcohol, excess thyroid hormone, anxiety, stress, decongestants eg pseudoephedrine, direct stimulants eg cocaine, etc. But you also have to have potential electrical connections in your heart that you're born with or acquire eg from rheumatic fever.

See List: Stmulants Cocaine amphetamines meth caffeine idiopathic aberrant electrical track called WPW syndrome.