Which treatment works the best and fastest for tachycardia?

?cause. It depends on the type & cause. An ekg will determine the type of tachycardia. If it's occurs with normal conduction, treatment is directed at reducing factors like fever, pain, infection, anxiety, dehydration, etc. If it is an abnormal tachycardia originating in the atria or ventricles, treatment varies depending on the specifics.