Table 3.
Cardiorespiratory and Sympathetic Changes During Head-Up Tilt
| Control Subjects (n = 11) |
Patients With POTS (n = 25) |
P Value | |
|---|---|---|---|
| Peripheral hemodynamics | |||
| Δ Heart rate, beats/min | 12 ± 10 | 21 ± 9 | 0.022 |
| Δ Stroke volume, mL | −19 ± 10 | −26 ± 7 | 0.019 |
| Δ Cardiac output, L/min | −0.5 ± 0.5 | −0.8 ± 0.7 | 0.29 |
| Δ Mean arterial pressure, mm Hg | 10 ± 8 | 9 ± 10 | 0.74 |
| Δ Systemic vascular resistance, dynes/cm5 | 439 ± 412 | 425 ± 382 | 0.92 |
| Δ Pulse pressure, mm Hg | 0.6 ± 5.0 | −4.3 ± 5.6 | 0.016 |
| Δ Arterial pulsatility index | −0.06 ± 0.06 | −0.1 ± 0.04 | 0.026 |
| Cerebral hemodynamics | |||
| Δ MCAvmean, cm/s | −1.3 ± 3.6 | 0.7 ± 5.7 | 0.31 |
| Δ MCAvpeak, cm/s | −4.5 ± 5.1 | −4.1 ± 8.0 | 0.88 |
| Δ MCAvmin, cm/s | 0.3 ± 4.1 | 3.1 ± 5.0 | 0.13 |
| Δ MCAv pulsatility index | −0.05 ± 0.07 | −0.1 ± 0.05 | 0.022 |
| Sympathetic | (n = 5) | (n = 9) | |
| Δ Burst frequency, bursts/min | 20 ± 5 | 20 ± 11 | 0.87 |
| Δ Burst amplitude, % of peak | 32 ± 9 | 37 ± 14 | 0.43 |
| Δ Total MSNA, AU/min | 1,782 ± 576 | 2,162 ± 1,813 | 0.66 |
| End-tidal gases | |||
| Δ End tidal CO2, mm Hg | 0.01 ± 2.4 | −0.1 ± 0.3 | 0.35 |
| Δ End tidal O2, mm Hg | 0.2 ± 1.3 | 0.1 ± 1.2 | 0.76 |
Values are mean ± SD. P values in bold denote statistical significance.
Abbreviations as in Table 2.