Table 3

Inappropriate Sinus Tachycardia Versus Postural Orthostatic Tachycardia Syndrome

Inappropriate Sinus TachycardiaPostural Orthostatic Tachycardia Syndrome
DefinitionAbnormally fast sinus rhythm at rest or minimal activity that accelerates beyond expectations and is out of proportion to physiologic necessity not resulting from an explainable underlying causeCondition of orthostatic intolerance leading to abnormal increase in heart rate with change in position
Heart rateResting daytime heart rate exceeds 100 beats/min and average heart rate on 24-h Holter monitor exceeds 90 beats/minPersistent increase in heart rate by more than 30 beats/min or absolute pulse of more than 120 beats/min within 10 min of moving from a supine to upright position in the absence of orthostatic hypotension
DiagnosisDiagnosis of exclusionTilt table