<unk>  is a form of tachycardia which has begins and ends in an acute (or paroxysmal) manner.
Paroxysmal tachycardia
Wide complex tachycardia
Narrow complex tachycardia
Junctional tachycardia
Fascicular VT
Paroxysmal AV block
Inappropriate sinus tachycardia
Supraventricular arrhythmias