Normal Leg Venous Capacitance

Home ] Up ] Exercise Intolerance- the Exercise Pressor Reflex in POTS ] Skeletal Muscle Pump ] [ Normal Leg Venous Capacitance ] Postural Neurocognitive ] Splanchnic Pooling in Normal Flow POTS ] Nitric Oxide Dysfunction in Low Flow POTS ] Angiotensin-II in POTS ] Decreased Upright Cerebral Blood Flow and Cerebral Autoregulation in POTS ] Postural Hyperpnea ] Nitric Oxide is Decreased in Angiotensin-II dependent Low flow POTS but increased along with Splanchnic pooling Neuropathic POTS ] Local Vascular Responses in POTS ] Microvascular Filtration in High Flow POTS ] POTS as Thoracic Hypovolemia ]
Orthostatic intolerance is often characterized by “pooling” in the lower extremities comprising acrocyanosis and dependent edema when upright. We tested the hypothesis that pooling results from increased venous compliance in POTS patients. Fifteen patients aged 13-19 years were compared with 11 healthy age matched controls. We divided the POTS group into patients with high venous pressure (>20 mm Hg) and normal venous pressure (Pv) on the basis of resting supine Pv obtained in previous work. Subjects were studied using strain gauge plethysmography to measure blood flow, Pv, and the venous compliance volume-pressure relation while supine and during incremental head-up tilt testing at -10o, 0o, +20o and +35o. Volume-pressure relations of controls, normal Pv, and high Pv POTS patients were not different and were unchanged by orthostasis. Supine leg peripheral resistance (R) was greater than control in high Pv POTS (54±9 vs 30±6 mmHg/ml/100ml/min) and less than control in normal Pv POTS (17±2). On upright tilt, R decreased in high Pv to approximate R in normal Pv. R in controls increased throughout tilt. Leg Pv increased in normal Pv and controls but remained unchanged in the high Pv group. : The findings suggest that pooling in POTS is due to blunted arterial vasoconstriction producing passive redistribution of blood within peripheral venous capacitance beds. Venous compliance in POTS is similar to control.

All volume-pressure data points from all subjects at all angles of tilt are shown. Arm data are shown in the upper panels while leg data are shown in the lower panels. Left hand panels compare control subjects to normal Pv POTS patients. Right hand panels compare control subjects to high Pv POTS patients. The lines represent curvilinear fits to control and POTS group based on supine data alone. There is no difference among compliance relations derived at any angle for any patients.  


Exercise Intolerance- the Exercise Pressor Reflex in POTS
Skeletal Muscle Pump
Normal Leg Venous Capacitance
Postural Neurocognitive
Splanchnic Pooling in Normal Flow POTS
Nitric Oxide Dysfunction in Low Flow POTS
Angiotensin-II in POTS
Decreased Upright Cerebral Blood Flow and Cerebral Autoregulation in POTS
Postural Hyperpnea
Nitric Oxide is Decreased in Angiotensin-II dependent Low flow POTS but increased along with Splanchnic pooling Neuropathic POTS
Local Vascular Responses in POTS
Microvascular Filtration in High Flow POTS
POTS as Thoracic Hypovolemia