Abstract

Background: Postural orthostatic tachycardia syndrome (POTS) is a debilitating condition without well-established clinical assessment. We evaluate the cardiovascular effect of full lower body compression (FC) in patients with POTS regarding no compression (NC) and healthy control participants (HC). Methods: Data from 10 HC and 10 POTS patients were collected. Beat-to-beat blood pressure (BP) and electrocardiogram were recorded during a 10-minute supine baseline followed by a 10-minute Head-Up Tilt (HUT) test at 80°. The POTS group completed the protocol in two conditions: FC and NC on the same day in a random order. We assessed changes in hemodynamics and systolic blood pressure (SBP) maximum and minimum differences in 30-second windows (SBPR). A univariate linear mixed model evaluated the effect of FC on heart rate (HR) response. Inter- and intra-group differences in mean±SD were assessed using Mann-Whitney U and Wilcoxon rank-sum tests. Results: No significant differences were observed in group demographics and baseline hemodynamics. During HUT, FC-POTS showed higher values regarding NC-POTS in stroke volume (SV: 79±14 ml vs. 63±15 ml; p=0.002), pulse pressure (PP: 43±6 mmHg vs. 34±7 mmHg; p=0.003), SBP (110±8 mmHg vs 100±11 mmHg; p=0.002), resulting in a lower HR (91±17 bpm vs. 110±22 bpm; p=0.002) and SBPR (19±6 mmHg vs. 23±8 mmHg; p=0.001). There were no differences in systemic vascular resistance (SVR) and cardiac output (CO). Compared to HC, FC-POTS still had lower SV (79±14 ml vs. 99±15 ml; p= 0.007) and SVR (964±92 dynes/sec/cm-5 vs. 1136±186 dynes/sec/cm-5; p=0.03), and higher HR (91±17 bpm vs. 61±6 bpm; p=0.001) and CO (6.9±0.6 L/min vs. 5.9 ±0.9 L/min; p=0.04). There were no differences in SBP, PP, and SBPR. Univariate mixed models showed a beneficial interactive effect of FC with SV and PP. The FC-induced increase in SV induces an extra decrease in HR response by 0.10 units per unit of SV (p<0.001), while the additional HR decrease is 0.18 units per unit of PP (p=0.02). Conclusion: FC reduces the exacerbated HR response by buffering the decrease in SV, increasing PP, and decreasing SBPR. FC blunts the drops in SV seen with NC, but it cannot restore it to control levels.