Is supraventricular tachycardia an emergency?

Sometimes: It often is well tolerated and can be treated with medications. Individuals can also terminate it at times with certain maneuvers, like a valsalva (bearing down for 10-20 secs or so). Other times svt can be associated with chest pain, lightheadedness and low blood pressure requiring prompt conversion to reguler rhythm wit either medications or electrical cardioversion.

Can be: Depends on how long it is since the event started and is it paroxysmal or persistant , is it causing symptoms of chest pain , low bp, passing out feeling etc. If symptomatic it can be an emergency you must seek medical attention either way.