Postural Orthostatic Tachycardia Syndrome

A patient with POTS may look well while lying down and become lightheaded, shaky, breathless, cognitively slowed or markedly tachycardic after standing. The experienced nurse notices the relationship between posture and symptoms before assuming that the fast pulse represents a primary cardiac disorder. Standing normally shifts blood into the legs and abdomen. In POTS, venous return and effective circulating volume do not adapt adequately, so the sinus node accelerates in an attempt to preserve cardiac output. The diagnosis depends on the pattern, not on tachycardia alone: orthostatic symptoms must be chronic, the heart-rate rise must meet the age-specific threshold, and orthostatic hypotension and reversible causes must be absent.