Abstract 10432: Simultaneous Recording of Skin Sympathetic Nerve Activity and Blood Pressure in Ambulatory Outpatients with Postural Orthostatic Tachycardia Syndrome

Abstract

Introduction: neuECG is a method to simultaneously record ECG and skin sympathetic nerve activity (SKNA). Postural orthostatic tachycardia syndrome (POTS) is known to be associated with increased cardiac sympathetic norepinephrine release. Hypothesis: Average SKNA correlates positively with heart rate (HR) and blood pressure (BP) in POTS patients. Methods: We used Bittium Faros 180 Holter Monitor (sampling rate 1,000 Hz) to record neuECG and SpaceLab OnTrak arterial BP monitor (ABPM) to record BP simultaneously over 24-hr in 20 POTS patients (19 women, 38±12 years old). The Faros signals were high pass filtered at 300 Hz to display the SKNA. The same original signals were bandpass filtered 0.05-150 Hz to display ECG. BP was measured every 30-min when awake (7AM to 9 PM) and hourly at night (9 PM to 7 AM). Results: Fig 1 shows an example of typical recording from a 38-year-old woman. Panel A shows average SKNA (aSKNA) 1-min prior to HR and BP measurement. The overall successful ABPM measurement was 90% with average BP of 126/75 mmHg. B shows bursts of SKNA in daytime (red dot in A), but no bursts at night (blue dot in A). C shows a positive correlation between HR, systolic BP (SBP) diastolic BP (DBP) and mean BP (MBP) with aSKNA. For all patients studied, 16 of 20 showed positive correlation between MBP and aSKNA (r=0.559±0.152, p<0.05 for all) and 15 of 20 showed positive correlation between HR and aSKNA (r=0.511±0.175, p<0.05 for all). The nocturnal aSKNA averaged 0.919±0.059 μV (N=17) and 1.060±0.215 (N=3) (p<0.001) in patients with and without nocturnal dip, respectively. However, the overall 24-hr aSKNA (1.036±0.120 vs 1.044±0.095, μV) was not different between these two groups. Conclusions: aSKNA positively correlated with BP and HR in ambulatory outpatients with POTS. High aSKNA at night was associated with nocturnal non-dipping of BP.