Figure 3.

ANS (left) and HRV (right) responses from predosing (test N) to postdosing (test N + 1), where midodrine was introduced immediately after test N. Each data point represents a parameter response to a 5-minute seated to a 5-minute standing postural change. Each pair of points shows the change in the postural response from a pair of consecutive tests, “test N” to a follow-up “test N + 1” where midodrine was introduced immediately after test N. Test N + 1 is approximately 3 months after dosing. (Left) Sympathetic (LFa) and parasympathetic (RFa) measures, sympathovagal balance (SB = LFa/RFa), systolic BP, and mean HR. (Right) Normalized low- and high-frequency parameters (LFnu and HFnu, respectively), total spectral power (TSP), and range HR. See text for details.