Orthostatic intolerance

A chronic disorder of dysautonomia, characterized by palpitation, shortness of breath, labored breathing, and subjective complaints of effort and discomfort provoked by physical exertion or upright posture, often accompanied by dizziness, tremulousness, sweating, and insomnia. The heart rate increases by at least 30 beats per minute when moving from a recumbent to a standing position (or ≥40 bpm in individuals 12-19 years of age), without orthostatic hypotension. Historically described as soldier's heart, irritable heart, effort syndrome, or Da Costa syndrome. Anxiety is a frequently associated feature rather than the underlying cause.