Figure 4.

Spectral Characteristics of patients with postural tachycardia syndrome (POTS) and healthy controls (CON). RRI – R-R intervals. SBP – systolic blood pressure. LF – Low frequency power. HF- high frequency power. RMSSD – root of mean square of successive differences. PNN50 – percentage of normal heart beats with beat to beat differences less than 50 msec. BRS – baroreflex sensitivity by spectral analysis (Spectral BRS), or spontaneous sequence technique (Sequence BRS), or regression analysis of Valsalva response (Valsalva BRS).