Diagnosis of tachycardia syndromes associated with orthostatic symptoms.

The postural tachycardia syndrome (POTS) is characterized by excessive tachycardia only in upright position without evidence of a cardiac or metabolic disease in combination with orthostatic symptoms like dizziness, lightheadedness or syncope but without relevant falls in blood pressure. The cause is unknown. A specific diagnostic marker has not been found so far. Eighteen patients with typical symptoms of POTS were examined. They underwent standard autonomic function tests with continuous measurement of heart rate (HR) and blood pressure. All fulfilled the inclusion criteria of pathologically increased HR activation during passive tilt or standing over 90 seconds. The upper limits of normal were based on data from 137 healthy volunteers between 18 and 85 years of age. Actively standing up induced more POTS-typical HR increases and lead to more consistent results than passive tilt. HR responses during Valsalva manoeuvre and deep breathing were normal in all except one patient each, indicating that assessment of HR during these tests does not contribute to the diagnosis of POTS. Frequency of symptoms reducing overall well-being and the degree of impairment of life quality by symptoms typical of POTS were measured with a self-assessment scale. The majority of patients reported a permanent reduction of overall well-being and a relevant impairment of life quality due to dizziness, tachycardia, and syncopes. This underlines the importance of considering POTS as a differential diagnosis of orthostatic syndromes and the necessity of treating it adequately.