Tachycardia, << tak uh KAHR dee uh, >> is an unusually fast heartbeat sometimes called palpitation. The disorder is usually organic. There are several types of tachycardia, depending upon the chamber of the heart from which the palpitations originate and how often they occur. For example, paroxysmal atrial tachycardia (PAT) is a rapid heart action that originates in the heart’s atria (upper chambers) and occurs at intervals.
