Table 1.
Time of event, systolic blood pressure, mean cerebral blood velocity, and heart rate
| POTS-↓CO2 < 30 Torr (n = 26) |
POTS-nlCO2 ≥ 30 Torr (n = 28) |
Control (n = 34) |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Event | Time | SBP | mCBv | ETCO2 | HR | Time | SBP | mCBv | ETCO2 | HR | Time | SBP | mCBv | ETCO2 | HR |
| Baseline | 116 ± 3 | 76 ± 3 | 36 ± 1*# | 83 ± 4* | 115 ± 4 | 76 ± 2 | 41 ± 1 | 75 ± 3 | 115 ± 4 | 77 ± 2 | 40 ± 2 | 72 ± 2 | |||
| Stand | 0 | 124 ± 3* | 64 ± 3*# | 35 ± 2 | 94 ± 4*# | 0 | 123 ± 3* | 85 ± 2 | 39 ± 2 | 80 ± 3 | 0 | 116 ± 3 | 80 ± 2 | 39 ± 2 | 82 ± 4 |
| CBFv nadir | 9 ± 1 | 83 ± 4 | 48 ± 3*# | 27 ± 2*# | 116 ± 3* | 10 ± 1 | 86 ± 5 | 61 ± 3 | 37 ± 1 | 106 ± 5 | 9 ± 3 | 84 ± 7 | 60 ± 2 | 36 ± 2 | 105 ± 4 |
| BP nadir | 12 ± 1 | 73 ± 2* | 52 ± 3*# | 30 ± 2*# | 117 ± 3* | 12 ± 1 | 73 ± 3* | 64 ± 3 | 37 ± 1 | 112 ± 7 | 10 ± 1 | 82 ± 3 | 61 ± 3 | 37 ± 2 | 106 ± 4 |
| HR peak | 14 ± 2 | 123 ± 7 | 70 ± 5 | 28 ± 1*# | 131 ± 3* | 19 ± 2 | 118 ± 6 | 82 ± 4 | 36 ± 1 | 127 ± 3* | 15 ± 1 | 111 ± 5 | 78 ± 3 | 35 ± 2 | 116 ± 4 |
| CBv recovery | 18 ± 1 | 88 ± 5* | 72 ± 4*# | 27 ± 2*# | 127 ± 4*# | 19 ± 1 | 95 ± 5* | 88 ± 4 | 36 ± 1 | 113 ± 5 | 16 ± 1 | 121 ± 7 | 88 ± 4 | 35 ± 2 | 100 ± 5 |
| BP recovery | 21 ± 2 | 150 ± 6* | 62 ± 5* | 28 ± 2*# | 110 ± 3* | 27 ± 3 | 148 ± 6 | 74 ± 4 | 37 ± 1 | 102 ± 4 | 21 ± 1 | 139 ± 7 | 76 ± 4 | 36 ± 2 | 91 ± 6 |
| HR recovery | 42 ± 8* | 140 ± 6*# | 63 ± 4*# | 28 ± 2*# | 105 ± 4*# | 39 ± 6* | 134 ± 7 | 71 ± 4 | 37 ± 1 | 87 ± 4 | 25 ± 1 | 122 ± 6 | 72 ± 4 | 37 ± 2 | 78 ± 3 |
| Steady state | 85 ± 12* | 135 ± 5*# | 55 ± 4*# | 26 ± 2*# | 115 ± 5* | 101 ± 13* | 120 ± 4 | 68 ± 4 | 37 ± 1 | 105 ± 4* | 55 ± 12 | 122 ± 4 | 72 ± 4 | 37 ± 2 | 90 ± 3 |
| End stand | 300 ± 12 | 136 ± 6*# | 56 ± 4*# | 26 ± 2*# | 116 ± 5* | 300 ± 6 | 121 ± 3 | 67 ± 5 | 35 ± 1 | 107 ± 4* | 300 ± 10 | 120 ± 3 | 71 ± 4 | 37 ± 2 | 89 ± 4 |
All values = means ± SD. Comparisons of study groups on baseline spectral analysis of heart rate and blood pressure variability were conducted using independent t tests for all postural tachycardia syndrome (POTS) vs. controls and for each POTS subgroup vs. controls. Similarly, independent t tests were used for comparing each POTS subgroup. For these univariable tests, there was no adjustment for multiple comparisons. P values are unadjusted for multiple comparisons. BP, blood pressure; CBv, cerebral blood velocity; CBFv, cerebral blood flow velocity; ETCO2, end-tidal CO2; HR, heart rate; mCBv, mean cerebral blood velocity; POTS-↓CO2, postural tachycardia syndrome with low carbon dioxide; POTS-nlCO2, postural tachycardia syndrome with normal upright carbon dioxide; SBP, systolic blood pressure.
P < 0.05 compared with controls; #P < 0.05 compared with baseline.