Splanchnic hyperemia and hypervolemia during Valsalva maneuver in postural tachycardia syndrome

Abstract

Prior work demonstrated dependence of the change in blood pressure during the Valsalva maneuver (VM) on the extent of thoracic hypovolemia and splanchnic hypervolemia. Thoracic hypovolemia and splanchnic hypervolemia characterize certain patients with postural tachycardia syndrome (POTS) during orthostatic stress. These patients also experience abnormal phase II hypotension and phase IV hypertension during VM. We hypothesize that reduced splanchnic arterial resistance explains aberrant VM results in these patients. We studied 17 POTS patients aged 15-23 yr with normal resting peripheral blood flow by strain gauge plethysmography and 10 comparably aged healthy volunteers. All had normal blood volumes by dye dilution. We assessed changes in estimated thoracic, splanchnic, pelvic-thigh, and lower leg blood volume and blood flow by impedance plethysmography throughout VM performed in the supine position. Baseline splanchnic blood flow was increased and calculated arterial resistance was decreased in POTS compared with control subjects. Splanchnic resistance decreased and flow increased in POTS subjects, whereas splanchnic resistance increased and flow decreased in control subjects during stage II of VM. This was associated with increased splanchnic blood volume, decreased thoracic blood volume, increased heart rate, and decreased blood pressure in POTS. Pelvic and leg resistances were increased above control and remained so during stage IV of VM, accounting for the increased blood pressure overshoot in POTS. 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.vasoconstriction; splanchnic arterial resistance; mesenteric artery; autonomic dysfunction; orthostatic intolerance IN PREVIOUS WORK WE DEMONSTRATED (31) the dependence of decrease in blood pressure on degree of thoracic hypovolemia during phase II of the Valsalva maneuver in healthy volunteers. We later showed that splanchnic hypervolemia during the Valsalva maneuver determines the magnitude of decrease in thoracic blood volume during early phase II of the maneuver (31). This, in turn, governs pressure recovery during late phase II (31).Prior work has shown that postural tachycardia syndrome (POTS), characterized by excessive tachycardia when upright in association with symptoms of orthostatic intolerance, is linked to thoracic hypovolemia (31). In POTS, thoracic hypovolemia may be produced by absolute hypovolemia, as observed in a variant of POTS with low peripheral blood flow (15), or may be produced by an excessive redistribution of blood volume away from the thoracic compartment, as observed in other variants (33). One such subset of POTS patients with redistributive thoracic hypovolemia, we designated "normal-flow POTS." This variant is characterized by normovolemia, normal cardiac output, and normal peripheral blood flow while resting supine. During orthostasis, however, there is thoracic ...

Postural hypocapnic hyperventilation is associated with enhanced peripheral vasoconstriction in postural tachycardia syndrome with normal supine blood flow

“…However, indirect measures of arm and leg peripheral vasoconstriction are at least consistent with the claim of sympathoexcitation, as are observed heart rate and BP variability data. Prior published work indicates exaggerated vasoconstriction in comparable normal-flow POTS patients during phase II of the Valsalva maneuver (34).…”

“…Methods have recently been validated in our laboratory for the detection of leg, thoracic, and splanchnic blood flow (33,34). Pulsatile changes in electrical resistance for each segment were employed to compute the time derivative ‫ץ‬R/‫ץ‬t, which we used to obtain the blood flow responses of each body segment during tilt.…”

“…These patients are characterized by blood volume, cardiac output, and peripheral resistance similar to healthy control subjects but in whom splanchnic blood flow is increased and peripheral blood flow is decreased during upright tilt (33) and during phase II of the Valsalva maneuver (34).…”

Pathophysiology, Diagnosis, and Treatment of Orthostatic Hypotension and Vasovagal Syncope

“…In addition, a recent clinical trial by Stewart et al suggested that splanchnic hyperemia during tilt table testing might correlate with the rapid decrease in BP after a Valsalva maneuver in a subset of patients with POTS. 58 A second type of POTS referred to as the "␤-hypersensitivity" form is believed to be due to an inadequate feedback process that arises from above the level of the baroreflex. 59 Thus far, treatment of POTS remains largely supportive and palliative, although recent studies have shown some success with acetylcholinesterase inhibition 60 and selective serotonin reuptake inhibitors.…”

Anaesthesia for caesarean section in a patient with Ehlers-Danlos syndrome associated with postural orthostatic tachycardia syndrome

“…They may develop significant hypotension in phase II of the manoeuvre and the overshoot in phase IV is also exaggerated. 18 A recent case report of a successful vaginal delivery used continuous low-dose epidural infusion and invasive blood pressure monitoring along with a forceps-assisted delivery to diminish the Valsalva manoeuvres made by the mother. 6 This mother had previously had a near cardiac arrest during normal vaginal delivery of her first baby before her condition was recognised.…”