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Here's A Few Articls I Came Across Today


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Hello,

I was looking around today, and came across a few articls, I never seen before. I thought I would post them so you could read them if you want! ;)

Amy

Failure of propranolol to prevent tilt-evoked systemic vasodilatation, adrenaline release, and neurocardiogenic syncope Basil A. Eldadah, Sandra L. Pechnik, Courtney S. Holmes, Jeffrey P. Moak, Ahmed M. Saleem and David S. Goldstein

Clinical Neurocardiology Section, NINDS/NIH, BETHESDA, MD 20892-1620, U.S.A.. eldadahb@ninds.nih.gov

In patients with neurocardiogenic syncope, head-up tilt often evokes acute loss of consciousness accompanied by vasodilatation, increased plasma adrenaline, and systemic hypotension. Since hypotension increases adrenaline levels, and adrenaline can produce skeletal muscle vasodilatation by activating b-2 receptors, adrenaline might induce a positive feedback loop precipitating circulatory collapse. We hypothesized that propranolol, a non-selective b-blocker, would prevent adrenaline-induced vasodilatation and thereby prevent syncope. Eight subjects with recurrent neurocardiogenic syncope and previously documented tilt-induced syncope with elevated plasma adrenaline levels participated in this study. Subjects underwent tilt table testing after receiving oral propranolol or placebo in double-blind, randomized, cross-over fashion. Hemodynamic and neurochemical variables were measured using intra-arterial monitoring, impedance cardiography, arterial blood sampling, and tracer kinetics of simultaneously infused [3H]-noradrenaline and [3H]-adrenaline. The occurrence of tilt-induced neurally mediated hypotension and syncope, duration of tilt tolerance, extent of decrease in systemic vascular resistance index (SVRI), and magnitude of plasma adrenaline increases did not differ between the propranolol and placebo treatment phases. SVRI was inversely associated with fractional increase in plasma adrenaline during both phases. One subject did not faint while on propranolol; this subject's response is discussed in the context of central effects of propranolol. In this small but tightly controlled study, propranolol did not prevent tilt-induced vasodilatation, syncope, or elevated plasma adrenaline.

Postural orthostatic tachycardia syndrome: Dental treatment considerations.

Brooks JK, Francis LA.

Department of Diagnostic Sciences and Pathology, Baltimore College of Dental Surgery, Dental School, University of Maryland, Baltimore, MD 21201, USA. Oralpath5@aol.com

BACKGROUND: Postural orthostatic tachycardia syndrome (POTS) is a chronic, relatively common autonomic disorder typically affecting younger females. It is distinguished by a dramatic increase in heart rate on the assumption of an upright posture from the supine position. METHODS: The authors provide an overview of the demographics, clinical assessment, diagnostic features, differential diagnoses, pathogeneses and medical treatment of patients with POTS, with an emphasis on the clinical treatment of the dental patient affected by the syndrome. CONCLUSION: Patients frequently exhibit symptoms of lightheadedness, fatigue, palpitations and syncope. Patients with POTS may have Ehlers-Danlos syndrome, mitral valve prolapse, chronic fatigue syndrome or, rarely, the Brugada syndrome. Despite widespread dissemination of information regarding POTS in the medical literature, scant information on it has appeared in dental publications. PRACTICE IMPLICATIONS: Dentists need to be familiar with the clinical features of POTS and be prepared to treat patients at risk of developing syncope.

PMID: 16637478 [PubMed - in process]

Cerebrovascular blood flow during the near syncopal phase of head-up tilt test: a comparative study in different types of neurally mediated syncope.

Hermosillo AG, Jordan JL, Vallejo M, Kostine A, Marquez MF, Cardenas M.

Department of Electrocardiology, Instituto Nacional de Cardiologia Ignacio Chavez, Juan Badiano #1, Seccion XVI Tlalpan CP 14080, Mexico DF. aghermo@yahoo.com

AIMS: This study analyses the changes in cerebral blood flow (CBF) velocity occurring in the near syncopal phase of head-up tilt test (HUT) to determine whether their appearance during the premonitory symptoms permits the differentiation of the different types of haemodynamic response. METHODS AND RESULTS: Six hundred and nineteen patients aged 35.9 +/- 16.4 with a prior history of syncope (55%) or presyncope (45%) were studied. Head-up tilt test was positive in 585 patients. The test was interrupted before syncope, once hypotension was evident and CBF changed. A vasovagal reaction (VVR) was observed in 245 patients. They had a 59% fall in diastolic CBF velocity, whereas systolic CBF velocity decreased by 12%. Postural orthostatic tachycardia syndrome (POTS) was observed in 82, systolic and diastolic CBF velocity decreased 44 and 60%, respectively. A similar response was observed in 258 patients with the orthostatic intolerance (OI) pattern. No significant changes were observed in the negative group. CONCLUSION: Patients with VVR had changes in CBF velocity, which are different from those presented by patients with POTS and OI pattern. Cerebral blood flow monitoring is useful to increase the yield of HUT and may allow early interruption before syncope occurs, reducing patient discomfort.

PMID: 16627440 [PubMed - in process]

Postural Hypocapnic Hyperventilation is Associated with Enhanced Peripheral Vasoconstriction in Postural Tachycardia Syndrome with Normal Supine Blood Flow.

Stewart JM, Medow MS, Cherniack NS, Natelson BH.

Pediatrics, New York Medical College, Valhalla, New York, United States; Physiology, New York Medical College, Valhalla, New York, United States.

Previous investigations have demonstrated a subset of POTS patients characterized by normal peripheral resistance and blood volume while supine, but thoracic hypovolemia and splanchnic blood pooling while upright secondary to splanchnic hyperemia. Such "normal flow" POTS patients often demonstrate hypocapnia during orthostatic stress. We studied 20 POTS patients aged 14-23 years and compared them to 10 comparably aged healthy volunteers. We measured changes in heart rate, blood pressure, heart rate and blood pressure variability, arm and leg strain gauge occlusion plethysmography (SPG), respiratory impedance plethysmography calibrated against pneumotachography, end tidal carbon dioxide (PETCO2), and impedance plethysmographic (IPG) indices of blood volume and blood flow within the thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations while supine and during upright tilt to 70 degrees . Ten POTS patients demonstrated significant hyperventilation and hypocapnia (POTSHC) while 10 were normocapneic (POTSNCwith minimal increase in postural ventilation comparable to control. While relative splanchnic hypervolemia and hyperemia occurred in both POTS groups compared to controls, marked enhancement in peripheral vasoconstriction occurred only in POTSHC and was related to thoracic blood flow. Variability indices suggested enhanced sympathetic activation in POTSHC compared to other subjects. The data suggest enhanced cardiac and peripheral sympathetic excitation in POTSHC.

PMID: 16565300 [PubMed - as supplied by publisher]

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Thanks for posting those- always good to read up on the newest studies!

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Hey,

That last article regarding hyperventilation...do any of you know if that means hyperventilating when under stress? I have been experiencing panic attacks for the first time in my life over this past year. If a car pulls out in front of me or if it is my turn to talk in a large group......I get a surge that can very quickly send me spiraling. Is that what this article means?

Bri

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