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Hypertension. 2019 May;73(5):1087-1096. doi: 10.1161/HYPERTENSIONAHA.118.11803.

Vagal and Sympathetic Function in Neuropathic Postural Tachycardia Syndrome.

Author information

1
From the Department of Medicine F & J. Recanati Autonomic Dysfunction Center, Tel Aviv "Sourasky" Medical Center and Sackler Faculty of Medicine, University of Tel Aviv, Israel (G.J.).
2
US Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville (L.D.).
3
Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center (K.S., S.R.R., D.R., I.B., A.D.), Vanderbilt University School of Medicine, Nashville, TN.
4
Department of Medicine, Tokyo Women's Medical University, Medical Center East, Japan (K.S.).
5
Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD (R.J.B.).
6
Department of Neurology (D.R.), Vanderbilt University School of Medicine, Nashville, TN.
7
Department of Biomedical Engineering (A.D.), Vanderbilt University School of Medicine, Nashville, TN.

Abstract

The diagnosis of neuropathic postural tachycardia syndrome (POTS) requires research techniques not available clinically. We hypothesized that these patients will have impaired vagal and sympathetic cardiovascular control that can be characterized with clinical autonomic tests. We included 12 POTS patients with possible neuropathic subtype because of normal plasma norepinephrine and no increase in upright blood pressure. We compared them to 10 healthy subjects. We assessed hemodynamics, heart rate and blood pressure variability, baroreflex sensitivity, raw and integrated muscle sympathetic nerve activity, and blood volume. To understand the vagal/sympathetic control, we dissected the phase 2 of Valsalva maneuver (VM) into early (VM2e) and late (VM2l). POTS' upright heart rate increased 43±3 bpm. Patients had normal plasma volume but reduced red blood cell volume (1.29 L versus predicted normal values 1.58 L; P=0.02). Vagal indices of heart rate variability, HFRRI (430±130 versus 1680±900; P=0.04), PNN50, and root mean squared of successive differences were lower in POTS. Patients showed a decrease in vagal baroreflex sensitivity (VM2e; P=0.04). In POTS, integrated muscle sympathetic nerve activity was lower at rest (12±1.5 versus 20±2 burst/min; P=0.004) and raw muscle sympathetic nerve activity spike analysis showed blunted responses during VM2e, despite a greater drop in systolic blood pressure (34±5 in POTS and 14±6 mm Hg in controls; P=0.01). This cohort of POTS patients enriched for possible neuropathic subtype had lower resting muscle sympathetic nerve activity, impaired vagal cardiac control, and exaggerated drop in blood pressure in response to VM and a delay in the sympathetic cardiovascular responsiveness during hypotensive challenge.

KEYWORDS:

Valsalva maneuver; baroreflex; blood pressure; heart rate; tachycardia

PMID:
30879357
PMCID:
PMC6592426
[Available on 2020-05-01]
DOI:
10.1161/HYPERTENSIONAHA.118.11803

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