Narrow-complex tachycardias can be very confusing to students of basic-level ECG. There are very many rhythms that fall into the broad category of narrow-complex tachycardia. We usually further divide them into sinus tachycardia and other "supraventricular tachycardias". The basic student will want to make this distinction, as well as be able to differentiate atrial fib and atrial flutter from the other SVTs. The more advanced student will want to go into more detail about which mechanism for supraventricular tachycardia is present.