Julian Stewart

..CONCLUSIONS: The data suggest that flow-dependent nitric oxide release is reduced in low-flow POTS. This may account for local flow regulation abnormalities...

..The circulatory consequences of reduced cardiac output may help to account for many of the findings of the syndrome...

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..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...

..Thus splanchnic hyperemia and hypervolemia are related to excessive phase II blood pressure reduction in POTS despite intense peripheral vasoconstriction. Factors other than autonomic dysfunction may play a role in POTS...

..Lower body vasoconstriction in high-flow POTS was abnormal, and vasoconstriction in low-flow POTS was sustained at initially elevated supine levels...

..The data suggest that plasma Ang II is increased in low-flow POTS patients with hypovolaemia, which may contribute to local blood flow dysregulation and reduced NO bioavailability...

..Variability indexes suggested enhanced sympathetic activation in POTS(HC) compared with other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTS(HC)...

..We conclude that the exercise pressor reflex is associated with reduced baroreflex cardiovagal regulation and driven by increased cardiac output related to enhanced preload, cardiac contractility, and splanchnic blood mobilization...

..0095-0.021 Hz) do not. The authors investigated whether VLF LDF power is nitric oxide (NO) specific...

..While increased cardiac output and central blood volume characterizes controls, increased peripheral resistance with blunted or eliminated in central blood volume increments characterizes POTS and may contribute to exercise intolerance...

..Patients with low-flow POTS had decreased body mass, but decreased body mass alone cannot account for findings of peripheral vasoconstriction. In conclusion, the findings suggest that reduced body mass relates to increased plasma AngII...

..The data suggest that nNO activity but not NO of endothelial NOS origin is reduced in low-flow POTS...

..53 +/- 2 %CVC(max)). The data suggest that the reduction in cutaneous NO-dependent vasodilation in low-flow POTS is corrected by AT(1)R blockade...

..Data imply impaired catabolism of Ang II through the ACE2 pathway. Vasoconstriction in POTS may result from a reduction in Ang-(1-7) and an increase in Ang II...

..Changes in baseline splanchnic vascular properties may account for variability in thoracic blood volume changes during the Valsalva maneuver...

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..However, persistent orthostatic hypotension and chronic symptoms of orthostatic intolerance indicate postural tachycardia syndrome...

..The volume-pressure relation was unchanged by orthostatic maneuvers. The results suggest that active venoconstriction in the limbs is not important to mild orthostatic response...

..The data suggest that INOH occurs in patients with chronic orthostatic intolerance and orthostatic tachycardia and is related to rapid caudal blood flow when upright because of a vasoconstrictor defect...

..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...

..My colleagues and I tested the hypothesis that pooling results from increased venous compliance in POTS patients...

..POTS may be associated with increased limb blood flow ("high flow") and defective orthostatic vasoconstriction or decreased limb blood flow ("low flow") and potentially with small blood volume...

..v. insertion. There were no differences from the groups that did not receive i.v. insertions. Data suggest, at most, a limited effect of i.v. insertion on autonomic function in adolescents...

..We conclude that peripheral vascular physiology in patients with POTS is abnormal, in contrast with normal peripheral vascular physiology in neurocardiogenic syncope...

..Postural tachycardia syndrome (POTS) is related to defective peripheral vasoconstriction of dependent extremities with redistributive hypovolemia...

..Taken together these data may indicate autonomic impairment in patients with CFS...

..The data demonstrate enhanced thoracic hypovolemia during upright tilt and confirm that POTS is related to inadequate cardiac venous return during orthostasis...

..29 +/- 4 and 28 +/- 4 s; cutaneous time constant = 60 +/- 25 vs. 149 +/- 53 s in controls). Local blood flow regulation in low-flow POTS is impaired...

..The VM depends on vascular as well as autonomic activation, which broadens its utility but complicates its analysis...

..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...

..We hypothesized that chronically increased systemic venous pressures lead to adaptive changes in regional and peripheral vessels to maintain cardiac output, especially when patients are upright...

..Transient leukemia in trisomy 21 mosaicism recapitulates the condition observed in constitutional trisomy 21 at the biological and clinical levels. Infants should be followed for the development of acute leukemia...

..Treatment for recurrent vasovagal syncope includes increased salt and water intake and various drug treatments, most of which are still under investigation...

..Hyperpnea and pulmonary stretch may contribute to the sympathoinhibition that occurs at the time of faint...

..Simple external stimulation of the plantar surface seems to be capable of preventing these cardiovascular stress-based responses...

..Here, we investigate the potential of low-magnitude vibration, applied at the plantar surface, to inhibit the cardiovascular responses of adult women to the orthostatic stress associated with quiet sitting...

..There is appropriate reflex tachycardia. CONCLUSIONS: We conclude that transient orthostatic hypotension is common in many healthy adolescents, especially after prolonged recumbency, and is related to dependent vascular tone...

..Splanchnic emptying in LBNP models regional vascular changes during hemorrhage. Splanchnic filling may limit the ability of the splanchnic bed to respond to thoracic hypovolemia during upright posture...

..ANG II mediates the AT(1)R blunting of local heating, which is not exclusively NO dependent, and is improved by antioxidant supplementation...

..Treatments have resulted in varying degrees of success and are often used in combination with each other...

..Low-dose NLA + SNP duplicates the Keto response. Isoproterenol increased baseline and peak reactive flow. These results suggest that COX inhibition unmasks NO dependence of reactive hyperemia in human cutaneous circulation...

..These may be due to defects in a fundamental signaling molecule called nitric oxide (NO). In the current application we will determine how NO produces POTS in CFS patients and whether drugs that alter NO can improve patient health. ..

..Verifying these hypotheses will improve our ability to diagnose and treat an important cause of vascular pathophysiology in man. ..

..These data will form the basis of future noninvasive prognostic testing and treatment of patients at risk for ECD and can provide a means to follow treatment modalities. ..

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..In the current proposal we will perform sophisticated tests of the circulation and nervous systems to study the causes and mechanisms in these patients and we will test drug treatments. ..