Abstract Body (Do not enter title and authors here): Background
Postural orthostatic tachycardia syndrome (POTS) is a prevalent cardiovascular disorder after COVID-19 infection. Although POTS is characterized by the presence of sinus tachycardia, other hemodynamic disturbances including blood pressure (BP) regulation, remain largely unexplored.

Aims
We investigated BP changes using 24-hour ambulatory-BP-monitoring in patients with new-onset POTS after COVID-19 compared with pre-pandemic healthy controls.

Methods
We performed a case-control study in 100 verified COVID-19 patients with new-onset POTS (mean age 40.0±12.9 years, 85% women) diagnosed by positive head-up tilt-testing versus 100 healthy controls (mean age 45.0±14.6 years, 70% women) from a population-based cohort with negative active standing test, no history of syncope, orthostatic intolerance, or endocrine disease. We analyzed 24-hour Systolic BP (SBP) and hypotensive SBP episodes (<80, <90, and <100mmHg).

Results
Study characteristics are illustrated in the Table. Post-COVID-19 POTS patients had significantly higher nighttime-SBP, but not daytime-SBP, and more daytime SBP hypotensive episodes (<80, <90, and <100 mmHg, Figure) compared with controls. Non-dipper (34% vs 19%, p<0.001) and reverse dipper patterns (9% vs 0 %, <0.001) were more frequent in post-COVID-19 POTS. In the logistic regression, post-COVID-19 POTS was associated with significantly higher mean 24h SBP (odds ratio (OR) 1.08, 95%CI 1.04-1.11, p<0.001) and nighttime SBP (OR 1.07, 95%CI 1.04-1.10, p<0.001), independently of age and sex.

Conclusions
Post-COVID-19 POTS patients demonstrate higher mean 24h and nighttime systolic BP, and show signs of disrupted BP regulation compared with healthy controls. They also have more daytime hypotensive episodes. Future studies are needed to assess if post-COVID-19 POTS patients may benefit from tailored BP therapy.