Vascular perturbations in the chronic orthostatic intolerance of the postural orthostatic tachycardia syndrome

2000 ◽  
Vol 89 (4) ◽  
pp. 1505-1512 ◽  
Author(s):  
Julian M. Stewart ◽  
Amy Weldon
Keyword(s):  
Blood Flow ◽  
Orthostatic Intolerance ◽  
Venous Pressure ◽  
Fluid Collection ◽  
Lower Extremities ◽  
Postural Orthostatic Tachycardia Syndrome ◽  
Size Change ◽  
Venous Compliance ◽  
Edema Formation ◽  
Calf Blood Flow

Chronic orthostatic intolerance is often related to the postural orthostatic tachycardia syndrome (POTS). POTS is characterized by upright tachycardia. Understanding of its pathophysiology remains incomplete, but edema and acrocyanosis of the lower extremities occur frequently. To determine how arterial and venous vascular properties account for these findings, we compared 13 patients aged 13–18 yr with 10 normal controls. Heart rate and blood pressure were continuously recorded, and strain-gauge plethysmography was used to measure forearm and calf blood flow, venous compliance, and microvascular filtration while the subject was supine and to measure calf blood flow and calf size change during head-up tilt. Resting venous pressure was higher in POTS compared with control (16 vs. 10 mmHg), which gave the appearance of decreased compliance in these patients. The threshold for edema formation decreased in POTS patients compared with controls (8.3 vs. 16.3 mmHg). With tilt, early calf blood flow increased in POTS patients (from 3.4 ± 0.9 to 12.6 ± 2.3 ml · 100 ml−1 · min−1) but did not increase in controls. Calf volume increased twice as much in POTS patients compared with controls over a shorter time of orthostasis. The data suggest that resting venous pressure is higher and the threshold for edema is lower in POTS patients compared with controls. Such findings make the POTS patients particularly vulnerable for edema fluid collection. This may signify a redistribution of blood to the lower extremities even while supine, accounting for tachycardia through vagal withdrawal.

Reflex vascular defects in the orthostatic tachycardia syndrome of adolescents

2001 ◽  
Vol 90 (6) ◽  
pp. 2025-2032 ◽  
Author(s):  
Julian M. Stewart ◽  
Amy Weldon
Keyword(s):  
Blood Flow ◽  
Flow Resistance ◽  
Venous Pressure ◽  
Low Flow ◽  
Postural Orthostatic Tachycardia Syndrome ◽  
Venous Compliance ◽  
Calf Blood Flow ◽  
Normal Resistance ◽  
Head Up Tilt ◽  
Normal Controls

Dependent pooling occurs in postural orthostatic tachycardia syndrome (POTS) related to defective vasoconstriction. Increased venous pressure (Pv) >20 mmHg occurs in some patients (high Pv) but not others (normal Pv). We compared 22 patients, aged 12–18 yr, with 13 normal controls. Continuous blood pressure and strain-gauge plethysmography were used to measure supine forearm and calf blood flow, resistance, venous compliance, and microvascular filtration, and blood flow and swelling during 70° head-up tilt. Supine, high Pv had normal resistance in arms (26 ± 2 mmHg · ml−1 · 100 ml · min) and legs (34 ± 3 mmHg · ml−1 · 100 ml · min) but low leg blood flow (1.5 ± 0.4 ml · 100 ml−1 · min−1). Supine leg Pv (30 ± 2 vs. 13 ± 1 mmHg in control) exceeded the threshold for edema (isovolumetric pressure = 19 ± 3 mmHg). Supine, normal Pv had high blood flow in arms (4.1 ± 0.2 vs. 3.5 ± 0.2 ml · 100 ml−1 · min−1 in control) and legs (3.8 ± 0.4 vs. 2.7 ± 0.3 ml · 100 ml−1 · min−1 in control) with low resistance. With tilt, calf blood flow increased steadily in POTS with high Pv and transiently increased in normal Pv. Calf volume increased in all POTS patients. Arm blood flow increased in normal Pv only with forearm maintained at heart level. These data suggest that there are (at least) two subgroups of POTS characterized by high Pv and low flow or normal Pv and high flow. These may correspond to abnormalities in local or baroreceptor-mediated vasoconstriction, respectively.

Effect of continuous postive-pressure ventilation (CPPV) on edema formation in dog lung

1975 ◽  
Vol 39 (4) ◽  
pp. 672-679 ◽  
Author(s):  
P. Caldini ◽  
J. D. Leith ◽  
M. J. Brennan
Keyword(s):  
Blood Flow ◽  
Pulmonary Arterial Pressure ◽  
Venous Pressure ◽  
Arterial Oxygen Tension ◽  
Lung Parenchyma ◽  
Arterial Oxygen ◽  
Morphometric Measurements ◽  
Edema Formation ◽  
Significant Difference ◽  
Pulmonary Arterial

The effect of CPPV on edema formation in lungs perfused at constant blood flow was studied in whole dogs and in isolated dog lungs. In intact animals, subjected to an increase in left atrial pressure relative to pleural pressure of 40 Torr, pulmonary shunts correlate inversely (r = -0.82) with the level of end-expiratory pressure (PEE). CPPV had no significant effect on total extravasation of liquid even though PEE higher than 20 Torr was effective in preventing liquid from accumulating in the airways. In isolated lobes, perfused at constant blood flow and at a venous pressure of zero, accumulation of liquid occurred when PEE was increased above 8–10 Torr. At comparable levels of pulmonary arterial pressure, an increase in PEE resulted in lesser accumulation of liquid than when pulmonary venous pressure was elevated. Morphometric measurements revealed no significant difference in the distribution of accumulated liquid within the lung parenchyma between lobes made edematous either by raising venous pressuure or by raising PEE. It would appear that CPPV, while beneficial in improving arterial oxygen tension in pulmonary edema, does not prevent extravasation of liquid in lungs perfused at constant blood flow. High levels of PEE appear to damage the lung by favoring accumulation of liquid in the extravascular spaces of the lung.

Decreased skeletal muscle pump activity in patients with postural tachycardia syndrome and low peripheral blood flow

2004 ◽  
Vol 286 (3) ◽  
pp. H1216-H1222 ◽  
Author(s):  
Julian M. Stewart ◽  
Marvin S. Medow ◽  
Leslie D. Montgomery ◽  
Kenneth McLeod
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Blood Volume ◽  
Orthostatic Intolerance ◽  
Low Flow ◽  
Peripheral Blood Flow ◽  
Muscle Pump ◽  
Postural Tachycardia ◽  
Calf Blood Flow ◽  
Skeletal Muscle Pump

Standing translocates thoracic blood volume into the dependent body. The skeletal muscle pump participates in preventing orthostatic intolerance by enhancing venous return. We investigated the hypothesis that skeletal muscle pump function is impaired in postural tachycardia (POTS) associated with low calf blood flow (low-flow POTS) and depends in general on muscle blood flow. We compared 12 subjects that have low-flow POTS with 10 controls and 7 patients that have POTS and normal calf blood flow using strain-gauge plethysmography to measure peripheral blood flow, venous capacitance, and calf muscle pump function. Blood volume was estimated by dye dilution. We found that calf circumference was reduced in low-flow POTS (32 ± 1 vs. 39 ± 3 and 43 ± 3 cm) and, compared with controls and POTS patients with normal blood flow, is related to the reduced fraction of calf venous capacity emptied during voluntary muscle contraction (ejection fraction, 0.52 ± 0.07 vs. 0.76 ± 0.07 and 0.80 ± 0.06). We found that blood flow was linearly correlated ( rp = 0.69) with calf circumference (used as a surrogate for muscle mass). Blood volume measurements were 2.2 ± 0.3 in low-flow POTS vs. 2.6 ± 0.5 in controls ( P = 0.17) and 2.4 ± 0.7 in normal-flow POTS patients. Decreased calf blood flow may reduce calf size in POTS and thereby impair the upright ejective ability of the skeletal muscle pump and further contribute to overall reduced blood flow and orthostatic intolerance in these patients.

Changes in microvascular fluid filtration capacity during 120 days of 6° head-down tilt

2001 ◽  
Vol 91 (6) ◽  
pp. 2517-2522 ◽  
Author(s):  
F. Christ ◽  
J. Gamble ◽  
V. Baranov ◽  
A. Kotov ◽  
A. Chouker ◽  
...  
Keyword(s):  
Blood Flow ◽  
Water Permeability ◽  
Strain Gauge ◽  
Venous Pressure ◽  
Venous Congestion ◽  
Edema Formation ◽  
Fluid Filtration ◽  
Fluid Homeostasis ◽  
Strain Gauge Plethysmography ◽  
Filtration Capacity

We used venous congestion strain gauge plethysmography (VCP) to measure the changes in fluid filtration capacity ( K f), isovolumetric venous pressure (Pvi), and blood flow in six volunteers before, on the 118th day (D118) of head-down tilt (HDT), and 2 days after remobilization (Post). We hypothesized that 120 days of HDT cause significant micro- and macrovascular changes. We observed a significant increase in K f from 3.6 ± 0.4 × 10−3 to 5.7 ± 0.9 × 10−3ml · min−1 · 100 ml−1 · mmHg−1 (+51.4%; P < 0.003), which returned to pretilt values (4.0 + 0.4 × 10−3ml · min−1 · 100 ml−1 · mmHg−1) after remobilization. Similarly, Pvi increased from 13.4 ± 2.1 mmHg to 28.9 ± 2.8 mmHg (+105.8%; P < 0.001) at D118 and was not significantly different at Post (12.4 ± 2.6 mmHg). Blood flow decreased significantly from 2.3 ± 0.3 to 1.3 ± 0.2 ml · min−1 · 100 ml tissue−1 at D118 and was found elevated to 3.4 ± 0.7 ml · min−1 · 100 ml tissue−1at Post. We believe that the increased K f is caused by a higher microvascular water permeability. Because this may result in edema formation, it could contribute to the alterations in fluid homeostasis after exposure to microgravity.

Calf blood flow during prolonged tilt in idiopathic dilated cardiomyopathy and after cardiac transplantation

2000 ◽  
Vol 278 (1) ◽  
pp. H239-H248 ◽  
Author(s):  
Søren Galatius ◽  
Henrik Wroblewski ◽  
Vibeke B. Sørensen ◽  
Peter Bie ◽  
Henrik Arendrup ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Right Atrium ◽  
Orthostatic Intolerance ◽  
Muscle Blood Flow ◽  
Severe Congestive Heart Failure ◽  
Idiopathic Dilated Cardiomyopathy ◽  
Skeletal Muscle Blood Flow ◽  
Calf Blood Flow ◽  
Head Up Tilt

In severe congestive heart failure (CHF), abnormal reflex control of calf blood flow during brief head-up tilt that appears to normalize after transplantation (HTX) may be present during prolonged observation also. Therefore, we studied the effect of prolonged (30 min) 50° head-up tilt on calf skeletal muscle blood flow measured by the local133Xe washout method in CHF and after HTX and in patients with the presence vs. absence of native right atrium (+PNA and −PNA, respectively). During brief head-up tilt, skeletal muscle blood flow increased 13 ± 42% in 9 severe CHF patients in contrast to a −28 ± 22% decrease ( P < 0.01) in 11 control subjects, −24 ± 30% decrease in 15 moderate CHF patients ( P < 0.05), −25 ± 14% decrease in 12 patients with recent HTX ( P < 0.01), and −21 ± 24% decrease in 8 patients with distant HTX ( P = 0.06). However, during sustained tilt, blood flow declined to similar levels of that in the other groups in severe CHF. HTX −PNA vs. +PNA showed blunted skeletal muscle vasomotor control ( P < 0.05) and a higher systolic blood pressure (139 ± 14 vs. 125 ± 15 mmHg, P < 0.05) and heart rate (92 ± 10 vs. 83 ± 8 beats/min, P < 0.05). Thus paradox vasodilatation of calf skeletal muscle in severe CHF is present only during brief but not prolonged tilt. This may be one explanation of the rare presence of orthostatic intolerance in CHF and implies only a minor possible role for the abnormality in edema pathogenesis. Removal of all right atrium in HTX has an important hemodynamic impact that may possibly affect later clinical outcome.

Limb venous compliance in patients with idiopathic orthostatic intolerance and postural tachycardia

2002 ◽  
Vol 93 (2) ◽  
pp. 636-644 ◽  
Author(s):  
Roy Freeman ◽  
Vasilios Lirofonis ◽  
William B. Farquhar ◽  
Marcelo Risk
Keyword(s):  
Lower Extremity ◽  
Orthostatic Intolerance ◽  
Lower Extremities ◽  
Population Group ◽  
Venous Compliance ◽  
Postural Tachycardia ◽  
Volume Curve ◽  
Activated State ◽  
Volume Relationship ◽  
Pressure Volume Relationship

Venous denervation and increased venous pooling may contribute to symptoms of orthostatic intolerance. We examined venous compliance in the calf and forearm in 11 orthostatic-intolerant patients and 15 age-matched controls over a range of pressures, during basal conditions and sympathetic excitation. Occlusion cuffs placed around the upper arm and thigh were inflated to 60 mmHg and deflated to 10 mmHg over 1 min. Limb volume was measured continuously with a mercury-in-Silastic strain gauge. Compliance was calculated as the numerical derivative of the pressure-volume curve. The pressure-volume relationship in the upper and lower extremities in the basal and sympathetically activated state was significantly lower in the orthostatic-intolerant patients (all P < 0.05). Sympathoexcitation lowered the pressure-volume relationship in the lower extremity in patients ( P < 0.001) and controls ( P < 0.01). Venous compliance was significantly less in patients in the lower extremity in the basal state over a range of pressures ( P < 0.05). Venous compliance was less in patients compared with controls in the upper ( P < 0.005) and lower extremities ( P < 0.01) in the sympathetically activated state, but there were no differences at individual pressure levels. Sympathetic activation did not change venous compliance in the upper and lower extremity in patients and controls. Patients with orthostatic intolerance have reduced venous compliance in the lower extremity. Reduced compliance may limit the dynamic response to orthostatic change and thereby contribute to symptoms of orthostatic intolerance in this population group.

Effects of methysergide administration on edema formation at the site of scald

1995 ◽  
Vol 78 (1) ◽  
pp. 191-197 ◽  
Author(s):  
J. J. Ferrara ◽  
E. W. Franklin ◽  
E. U. Choe ◽  
H. L. Lippton ◽  
A. L. Hyman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Concentration Ratio ◽  
Protein Concentration ◽  
Venous Pressure ◽  
Lymph Flow ◽  
Plasma Protein Concentration ◽  
Edema Formation ◽  
Femoral Blood Flow ◽  
S 100 ◽  
Femoral Blood

Femoral blood flow (Qa), hind paw lymph flow (Qlym), and lymph-to-plasma protein concentration ratio (Clym/Cp) were monitored before and 4 h after 1) 5-s 100 degrees C paw scald, 2) methysergide (1 mg/kg iv) 20 min before scald, 3) methysergide 30 min after scald, and 4) methysergide only. Before experimentation, hind paw venous pressure was elevated and maintained until steady-state Qa, Qlym, and minimal Clym/Cp levels were reached. The reflection coefficient (sigma d) was determined as 1 - minimal Clym/Cp; the filtration coefficient (Kf) was calculated. Methysergide alone caused no changes. Increases in Qa, Qlym, Clym/Cp, and Kf were identified in all scald groups. Compared with scald only animals, pre- and postscald methysergide blunted the increases in Qa, Qlym, Kf, and paw weight gain without an effect on sigma d. These data demonstrate that methysergide reduces edema formation at the site of scald, perhaps by modulating the burn-induced vasodilator response and/or by limiting the burn-induced increase in microvascular surface area.

Vascular adaptation to 4 wk of deconditioning by unilateral lower limb suspension

2005 ◽  
Vol 288 (4) ◽  
pp. H1747-H1755 ◽  
Author(s):  
Michiel W. P. Bleeker ◽  
Patricia C. E. De Groot ◽  
Fleur Poelkens ◽  
Gerard A. Rongen ◽  
Paul Smits ◽  
...  
Keyword(s):  
Blood Flow ◽  
Femoral Artery ◽  
Superficial Femoral Artery ◽  
Lower Limb ◽  
Venous Pressure ◽  
Venous Occlusion ◽  
Calf Blood Flow ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Echo Doppler Ultrasound

Physical inactivity or deconditioning is an independent risk factor for atherosclerosis and cardiovascular disease. In contrast to exercise, the vascular changes that occur as a result of deconditioning have not been characterized. We used 4 wk of unilateral lower limb suspension (ULLS) to study arterial and venous adaptations to deconditioning. In contrast to previous studies, this model is not confounded by denervation or microgravity. Seven healthy subjects participated in the study. Arterial and venous characteristics of the legs were assessed by echo Doppler ultrasound and venous occlusion plethysmography. The diameter of the common and superficial femoral artery decreased by 12% after 4 wk of ULLS. Baseline calf blood flow, as measured by plethysmography, decreased from 2.1 ± 0.2 to 1.6 ± 0.2 ml·min−1·dl tissue−1. Both arterial diameter and calf blood flow returned to baseline values after 4 wk of recovery. There was no indication of a decrease in flow-mediated dilation of the superficial femoral artery after ULLS deconditioning. This means that functional adaptations to inactivity are not simply the inverse of adaptations to exercise. The venous pressure-volume curve is shifted downward after ULLS, without any effect on compliance. In conclusion, deconditioning by 4 wk of ULLS causes significant changes in both the arterial and the venous system.

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