Diagnosis of tachycardia syndromes associated with orthostatic symptoms

The postural tachycardia syndrome (POTS) is characterized by excessive tach ycardia only in upright position without evidence of a cardiac or metabolic disease in combination with orthostatic symptoms like dizziness, lighthead edness or syncope but without relevant falls in blood pressure. The cause i s unknown. A specific diagnostic marker has not been found so far. Eighteen patients with typical symptoms of POTS were examined. They underwent stand ard 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. T he upper limits of normal were based on data from 137 healthy volunteers be tween 18 and 85 years of age. Actively standing up induced more POTS-typica l HR increases and lead to more consistent results than passive tilt. HR re sponses during Valsalva manoeuvre and deep breathing were normal in all exc ept one patient each, indicating that assessment of HR during these tests d oes not contribute to the diagnosis of POTS. Frequency of symptoms reducing overall well-being and the degree of impairment of life quality by symptom s typical of POTS were measured with a self-assessment scale. The majority of patients reported a permanent reduction of overall wellbeing and a relev ant impairment of life quality due to dizziness, tachycardia, and syncopes. This underlines the importance of considering POTS as a differential diagn osis of orthostatic syndromes and the necessity of treating it adequately.