Postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS in adults is characterized by a heart rate increase of 30 beats per minute within ten minutes of standing up, accompanied by other symptoms.
Source: Wikipedia — Postural orthostatic tachycardia syndrome (CC BY-SA 4.0)