POTS patients exhibited significantly greater muscle sympathetic nerve activity responses to the Valsalva maneuver compared to healthy controls (48 vs 26% of baseline MSNA/mmHg; P=0.03).
Observational
Do patients with POTS have altered muscle sympathetic nerve activity responses to baroreflex stimuli compared to healthy controls?
Patients with POTS exhibit exaggerated muscle sympathetic nerve activity responses to baroreflex challenges, suggesting sympathetic hyperreactivity during orthostatic stress.
Absolute Event Rate: 48% vs 26%
p-value: p=0.03
Postural orthostatic tachycardia syndrome (POTS) is characterized by excessive tachycardia during orthostasis. To test the hypothesis that patients with POTS have decreased sympathetic neural responses to baroreflex stimuli, we measured heart rate (HR) and muscle sympathetic nerve activity (MSNA) responses to three baroreflex stimuli including vasoactive drug boluses (modified Oxford technique), Valsalva maneuver, and head-up tilt (HUT) in POTS patients and healthy control subjects. The MSNA response to the Valsalva maneuver was significantly greater in the POTS group (controls, 26 +/- 7 vs. POTS, 48 +/- 6% of baseline MSNA/mmHg; P = 0.03). POTS patients also had an exaggerated MSNA response to 30 degrees HUT (controls, 123 +/- 24 vs. POTS, 208 +/- 30% of baseline MSNA; P = 0.03) and tended to have an exaggerated response to 45 degrees HUT (controls, 137 +/- 27 vs. POTS, 248 +/- 58% of baseline MSNA; P = 0.10). Sympathetic baroreflex sensitivity calculated during administration of the vasoactive drug boluses also tended to be greater in the POTS patients; however, this did not reach statistical significance (P = 0.15). Baseline MSNA values during supine rest were not different between the groups (controls, 23 +/- 4 vs. POTS, 16 +/- 5 bursts/100 heartbeats; P = 0.30); however, resting HR was significantly higher in the POTS group (controls, 58 +/- 3 vs. POTS, 82 +/- 4 beats/min; P = 0.0001). Our results suggest that POTS patients have exaggerated MSNA responses to baroreflex challenges compared with healthy control subjects, although resting supine MSNA values did not differ between the groups.
Swift et al. (Sat,) conducted a observational in Postural orthostatic tachycardia syndrome (POTS). Baroreflex stimuli (vasoactive drug boluses, Valsalva maneuver, head-up tilt) vs. Healthy control subjects was evaluated on Muscle sympathetic nerve activity (MSNA) response to the Valsalva maneuver (p=0.03). POTS patients exhibited significantly greater muscle sympathetic nerve activity responses to the Valsalva maneuver compared to healthy controls (48 vs 26% of baseline MSNA/mmHg; P=0.03).