Tachycardia, as the name suggests, means that the heart beats fast. How many beats per minute constitute a fast heartbeat or tachycardia? Clinically, it is generally considered that a heartbeat exceeding 100 beats/min can be termed as tachycardia. There are various types of tachycardia, such as sinus tachycardia, supraventricular tachycardia, or ventricular tachycardia. There are also atrial tachycardia and junctional tachycardia. The origin of tachycardia varies, and its clinical significance is completely different. Therefore, it is essential to identify the nature of the tachycardia in order to treat it effectively. How to confirm the diagnosis? In this case, it is best to obtain an electrocardiogram during an episode. If the electrocardiogram at the moment of occurrence is not available, it is recommended to wear a 24-hour Holter monitor to determine the cause further. Only after identifying the cause can targeted treatment be administered.