Pooling in Chronic Orthostatic Intolerance

Stewart, Julian M.

doi:10.1161/01.cir.0000016348.55378.c4

Cited by 121 publications

(38 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Haemodynamic assessment using head-up tilt with determination of cardiopulmonary volume and systemic vascular resistance differentiated between venous pooling and autonomic insufficiency in these patients (Schutzman et al, 1994). In patients with chronic orthostatic intolerance (postural tachycardia syndrome), blunted arterial vasoconstriction produces passive redistribution of blood within peripheral venous capacitance beds, while venous compliance is similar to that of control subjects (Stewart, 2002). This contrasts with patients with neurocardiogenic syncope (see below), who are characterized by normal peripheral vascular physiology (Stewart & Weldon, 2003).…”

Section: ) Patients With Autonomic Failure and Orthostatic Hypotensionmentioning

confidence: 99%

Squatting test: A posture to study and counteract cardiovascular abnormalities associated with autonomic dysfunction

Philips

Scheen

2011

Autonomic Neuroscience

View full text Add to dashboard Cite

word count = 225 words SUMMARYThe squatting test is an active posture manoeuvre that imposes one of the most potent orthostatic stresses. In normal subjects, the changes in blood pressure and heart rate are transient because of appropriate baroreflex homeostasis and do not provoke symptoms.However, in various pathological conditions, both the increase in blood pressure during squatting and the decrease in blood pressure during standing may be more important and sustained, potentially leading to complaints and adverse events. Squatting has been used to evaluate patients with tetralogy of Fallot, heart transplant, dysautonomia, including diabetic cardiovascular autonomic neuropathy, and individuals prone to vasovagal syncope. Careful analysis of changes in blood pressure and heart rate during the transition from standing to squatting and from squatting to standing allows the early detection of altered vagal and/or sympathetic function. Of note squatting position has been proposed as a therapeutic mean to counteract the fall in blood pressure in patients suffering from dizziness due to dysautonomia and orthostatic hypotension or presenting pre-syncope symptoms, such as soon after exercise.The aims of the present review are to analyse the haemodynamic pattern during a squatting test in various pathological situations and to describe what may be the negative and positive haemodynamic changes associated with this posture. We were especially interested in using the squatting test for the assessment of cardiovascular autonomic neuropathy associated with diabetes mellitus.

show abstract

Section: ) Patients With Autonomic Failure and Orthostatic Hypotensionmentioning

confidence: 99%

Squatting test: A posture to study and counteract cardiovascular abnormalities associated with autonomic dysfunction

Philips

Scheen

2011

Autonomic Neuroscience

View full text Add to dashboard Cite

show abstract

“…9 The microvascular filtration relation (filtration rate versus pressure) was constructed ( Figure 2) for each subject. Normalized volume is expressed in units of (mL volume change/100 mL tissue), normalized filtration rate is expressed in units of (mL/100 mL tissue per minute), and normalized filtration coefficient, K f , the slope in the linear relation shown in Figure 2, is expressed in units of (mL/100 mL tissue per minute per mm Hg).…”

Section: Peripheral Vascular Evaluationmentioning

confidence: 99%

“…Precisely how this occurs is unclear: Prior work has failed to demonstrate increased venous capacitance in POTS 8 or increased venous pressure. 9 Data have demonstrated contributions to limb enlargement from microvascular filtration. 6,10,11 Thus, we hypothesized that orthostatic limb enlargement occurs through enhanced microvascular filtration in POTS.…”

mentioning

confidence: 99%

Microvascular Filtration Is Increased in Postural Tachycardia Syndrome

Stewart

2003

Circulation

Self Cite

View full text Add to dashboard Cite

Background— Postural tachycardia syndrome (POTS) is related to defective peripheral vasoconstriction of dependent extremities with redistributive hypovolemia. Methods and Results— To test whether enhanced microvascular filtration produces leg enlargement, we studied 12 patients 13 to 19 years of age with POTS and defective leg vasoconstriction and 13 age-matched healthy control subjects, with strain-gauge plethysmography used to measure venous pressure (P v ), forearm and calf blood flow, vascular capacitance, and the microvascular filtration coefficient (K f ). Measurements were made while the patient was supine and at steady state during upright tilt to 35°. Supine P v was not different in POTS, but upright leg P v tended to be increased above control. Arm and leg peripheral arterial resistance was decreased in the supine and upright positions in patients with POTS compared with control subjects ( P =0.01, upright legs). Supine K f was not significantly increased in the forearm in patients with POTS but was increased in the calf (9.3±2.2 versus 5.7±2.4 [10 −3 ] mL/100 mL per minute per mm Hg, P =0.04), correlating with calf blood flow (r s =0.84, P =0.002). K f was invariant with orthostasis. The hydraulic contribution to upright filtered flow at 35° tilt, the product of K f and P v , was approximately twice that of control (0.41±0.09 versus 0.19±0.04 mL/100 mL per minute, P =0.04). Conclusions— Increased microvascular filtration accounts for enhanced leg swelling in patients with POTS with increased arterial blood flow.

show abstract

“…We measured venous capacitance using our previously documented techniques. 16 This involved elevating the limb above heart level until no further decrease in volume was obtained and then using 4-minute-long, 10-mm Hg pressure steps to a maximum of 60 mm Hg. At lower pressures, limb size reaches a plateau representing venous filling, whereas at higher pressure, a linear component representing microvascular filtration 17 and a vascular component are superimposed.…”

mentioning

confidence: 99%

“…These are extracted by least-squares methods, 18 and capacitance is calculated from the sum of supine venous volume and vascular increments. 16 …”

mentioning

confidence: 99%

Relation of Postural Vasovagal Syncope to Splanchnic Hypervolemia in Adolescents

Stewart

McLeod²,

Sanyal³

et al. 2004

Circulation

Self Cite

View full text Add to dashboard Cite

Background-The mechanisms of simple faint remain elusive. We propose that postural fainting is related to excessive thoracic hypovolemia and splanchnic hypervolemia during orthostasis compared with healthy subjects. Methods and Results-We studied 34 patients 12 to 22 years old referred for multiple episodes of postural faint and 11 healthy subjects. Subjects were studied in the supine position and during upright tilt to 70°for 30 minutes and subgrouped into Sϩ, historical fainters who fainted during testing (nϭ24); SϪ, historical fainters who did not faint during testing (nϭ10); and control subjects. Supine venous occlusion plethysmography showed no differences between blood flows of the forearm and calf in Sϩ, SϪ, or control. Cardiac index, total peripheral resistance, and blood volume were not different. Using impedance plethysmography, we assessed blood redistribution during upright tilt. This demonstrated decreased thoracic blood volume and increased splanchnic, pelvic, and leg blood volumes for all subjects. However, thoracic blood volume was decreased in Sϩ compared with control volume, correlating well with the maximum upright heart rate. Splanchnic volume was decreased in the Sϩ and SϪ groups, correlating with the change in thoracic blood volume. Pelvic and leg volume changes were similar for all groups and uncorrelated to thoracic blood volume. Conclusions-Enhanced

show abstract

Pooling in Chronic Orthostatic Intolerance

Cited by 121 publications

References 38 publications

Squatting test: A posture to study and counteract cardiovascular abnormalities associated with autonomic dysfunction

Squatting test: A posture to study and counteract cardiovascular abnormalities associated with autonomic dysfunction

Microvascular Filtration Is Increased in Postural Tachycardia Syndrome

Relation of Postural Vasovagal Syncope to Splanchnic Hypervolemia in Adolescents

Contact Info

Product

Resources

About