Research in Review

• Pregnancy in postural orthostatic tachycardia syndrome
• Acetylcholinesterase inhibition improves tachycardia in postural tachycardia syndrome
• Splanchnic Hyperemia and Hypervolemia during the Valsalva Maneuver in Postural Tachycardia Syndrome
• Cerebral Autoregulation Is Preserved In Postural Tachycardia Syndrome
• Short-term evolution of vasovagal syncope: Influence on the quality of life
• Orthostatic intolerance and syncope associated with Chiari type I malformation

Pacing Clin Electrophysiol. 2005 Jun;28(6):591-3.

Pregnancy in postural orthostatic tachycardia syndrome.

Glatter KA, Tuteja D, Chiamvimonvat N, Hamdan M, Park JK.

Department of Adult Cardiology, University of California-Davis, 4860 Y Street, Suite 2820, Sacramento, CA 95817, USA. k_glatter@yahoo.com

INTRODUCTION: Postural orthostatic tachycardia syndrome (POTS) is a rare disease characterized by syncope, sinus tachycardia, and orthostasis due to autonomic dysfunction.

METHODS AND RESULTS: Two women aged 26 and 24 years with severe POTS became pregnant. Both women experienced hyperemesis gravidarum with subsequent marked improvement in their POTS symptoms until 6 months gestation, when their syncope and sinus tachycardia caused clinical decompensation. Both patients delivered healthy babies at 37 weeks by elective cesarean section.

CONCLUSION: In long-term follow-up, both women reported improvement in their prepartum symptoms. We describe the first report, to our knowledge, of two successful pregnancy outcomes in severe POTS, including the first report of midodrine use in pregnant women.

PMID: 15955196

Circulation. 2005 May 31;111(21):2734-40. Epub 2005 May 23.

Acetylcholinesterase inhibition improves tachycardia in postural tachycardia syndrome.

Raj SR, Black BK, Biaggioni I, Harris PA, Robertson D.

Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, 1161 21st Ave South, Nashville, TN 37232-2195, USA. satish.raj@vanderbilt.edu

BACKGROUND: Postural tachycardia syndrome (POTS) induces disabling chronic orthostatic intolerance notable for an excessive increase in heart rate that occurs on standing. Many current therapeutic strategies focus on sympatholysis, but the alternative strategy of enhancing cardiovagal tone has not been studied. The objective of this study was to test the hypothesis that acetylcholinesterase inhibitors will attenuate the tachycardia and improve symptom burden in patients with POTS.

METHODS AND RESULTS: Seventeen patients with POTS underwent acute drug trials of pyridostigmine 30 mg orally and placebo, on separate mornings, in a randomized crossover design. Blood pressures, heart rate, and symptoms were assessed while patients were seated and after they had been standing for up to 10 minutes both before the study drug was given and at 2 and 4 hours after study drug. The heart rate was significantly lower at 2 hours after pyridostigmine than after placebo (100+/-16 versus 111+/-14 bpm, P=0.001). Pyridostigmine significantly decreased the standing heart rate from baseline (119+/-16 bpm) at 2 hours (104+/-16 bpm, P<0.001) and 4 hours (100+/-16 bpm, P<0.001) after administration. There was no significant change in blood pressure. The decrease in symptom burden within 4 hours after study drug was significantly greater with pyridostigmine than placebo (-10.4+/-14.0 AU versus 0.6+/-7.5 AU, P<0.025).

CONCLUSIONS: Acute acetylcholinesterase inhibition significantly attenuated tachycardia in POTS. There was also an improvement in symptom burden with this promising therapy.

PMID: 15911704

Am J Physiol Heart Circ Physiol. 2005 Jun 17;

Splanchnic Hyperemia and Hypervolemia during the Valsalva Maneuver in Postural Tachycardia Syndrome.

Stewart JM, Medow MS, Montgomery LD, Glover JL, Millonas MM.

Pediatrics, New York Medical College, Valhalla, New York, USA; Physiology, New York Medical College, Valhalla, New York, USA.

Prior work has 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 years 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 the VM performed supine. Baseline splanchnic blood flow was increased and calculated arterial resistance was decreased in POTS compared to control. Splanchnic resistance decreased and flow increased in POTS while 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 BP overshoot in POTS. Thus, splanchnic hyperemia and hypervolemia are related to excessive phase II BP reduction in POTS despite intense peripheral vasoconstriction. Factors other than autonomic dysfunction may play a role in POTS.

PMID: 15964926

J Appl Physiol. 2005 Apr 28;

Cerebral Autoregulation Is Preserved In Postural Tachycardia Syndrome (POTS).

Schondorf R, Benoit J, Stein R.

Department of Neurology, SMBD Jewish Generla Hospital, McGill University, Montreal, QC, Canada.

To test whether cerebral autoregulation is impaired in patients with postural tachycardia syndrome (POTS) we evaluated 17 healthy control subjects and 27 patients with POTS. Blood pressure (BP), heart rate, and cerebral blood velocity (CBV) (transcranial Doppler) were recorded at rest and during 80 degrees head-up tilt (HUT). Static cerebral autoregulation as assessed from the change in cerebrovascular resistance during HUT was the same in POTS and in controls. The properties of dynamic cerebral autoregulation were inferred from transfer gain, coherence and phase of the relationship between BP and CBV estimated from filtered data segments (0.02-0.8Hz). Dynamic cerebral autoregulation of patients with POTS did not differ from that of controls. The patients' dynamic cerebral autoregulation did not change over the course of HUT despite increased tachycardia suggestive of worsening orthostatic stress. Inflation of MAST pants substantially reduced the tachycardia of patients with POTS without affecting cerebral autoregulation. Symptoms of orthostatic intolerance were reduced in half the patients following MAST pants inflation. We conclude that cerebral perfusion and autoregulation in many patients with POTS does not differ from that of normal control subjects.

PMID: 15860686

Int J Cardiol. 2005 Jul 10;102(2):315-9.

Short-term evolution of vasovagal syncope: Influence on the quality of life.

Baron-Esquivias G, Gomez S, Aguilera A, Campos A, Romero N, Cayuela A, Valle JI, Redondo M, Pedrote A, Burgos J, Martinez A, Errazquin F.

Cardiology Department, Hospital Universitario Virgen del Rocio, Seville, Spain.

To evaluate the short-term evolution and changes in the quality of life (QoL) of patients suffering from vasovagal syncope (VVS) by the application of the Short Form 36 questionnaire (SF-36) that was prospectively administrated to all consecutive patients with syncope and abnormal response to head-up tilt test. We included 167 patients (55.7% women, median age 42 years old). During a 6-month follow-up, recurrence was observed in 33 patients (19.8%). The mean recurrence-free time was 6.2+/-0.34 months. Among those patients with and without relapses, there were only differences in the previous number of syncopes (6 vs. 3, p=0.0051). Of them, 19 (11%) only presented 1 syncopal relapse and 14 (8.2%) presented more than 1. There were differences in the time until the first relapse [4 months (2.3-5.4) vs. 1.6 months (0.8-3.3), p=0.002] and an inverse correlation between the time until the appearance of recurrences and their number (r(2) Spearman=-0.54, p=0.002). In just 6 months, those patients who had recurrence had a worse QoL than those who did not, in 7 dimensions of the SF-36 questionnaire. In the short-term, one in every five patients with VVS had at least 1 relapse, and if it is very early, it can recur in up to 8% of them. The QoL of these patients is correlated with the appearance of relapses.

PMID: 15982503

J Neurol Neurosurg Psychiatry. 2005 Jul;76(7):1034-6.

Orthostatic intolerance and syncope associated with Chiari type I malformation.

Prilipko O, Dehdashti AR, Zaim S, Seeck M.

Presurgical Epilepsy Evaluation Unit, Program of Functional Neurology and Neurosurgery, University of Lausanne, Switzerland.

The Chiari type I malformation (CM1) is characterized by herniation of cerebellar tonsils to at least 3-5 mm below the plane of foramen magnum and can present with a wide variety of clinical symptoms, frequently including occipital headaches, secondary to bulbar and/or medullary distress. Rarely, syncopal episodes have also been described and attributed to either compression of the midbrain ascending reticular system, or vascular compromise (vertebrobasilar artery compression, hypotension). We report the first case of a CM1 patient with frequently recurring syncope due to postural orthostatic tachycardia syndrome (POTS), a form of orthostatic intolerance, whose symptoms resolved completely after surgical intervention. It is important to stress that it is not clear whether the described association of POTS and CM1 in our patient is a fortuitous finding in an isolated case or a reflection of a more systematic association between the two pathologies.

PMID: 15965223

Research abstracts obtained from PubMed

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