Hemodynamic and neuroendocrine profile of 2 different cardiovascular responses in vasodepressor syncope induced by the head-up tilt test]

BACKGROUND. Syncope in apparently healthy subjects is usually attributed to a vasovagal reaction. However, a vagal cardio-inhibitory component is not always associated with a vasodepressor component in causing syncope: in fact, increases in heart rate, arterial pressure and plasmatic levels of catecholamines frequently precede loss of consciousness. METHODS. Prolonged 60 degrees head-up tilt table test (HUTT) was performed in 50 healthy subjects (27 male, 23 female - mean age 37.2 years) with recurrent syncope of vasodepressor or unknown origin. The upright-tilt test lasted 45 minutes: every minute of HUTT we measured heart rate (HR) and systolic (SBP) and diastolic blood pressure (DBP); at set intervals we took a blood sample to determine epinephrine (EP) and norepinephrine (NEP) levels. RESULTS. In patients with positive HUTT (42%) we observed a vaso-vagal response (10 patients) characterized by a sharp drop in SBP and DBP (> 50% of the basal values) and bradycardia (< 40 bpm) and/or sinus node arrests, and a hyperchronotropic-vasodepressor response (11 patients) characterized by a considerable increase in HR (> 60%) and simultaneous drop in SBP and DBP (> 30% of the basal values), and a large increase in plasmal EP (+881.9%). CONCLUSIONS. According to the Authors, vasovagal response is mainly due to a reflex reaction originating from the cardiac stretch-receptors, whereas hyperchronotropic-vasodepressor response is mainly due to psychic stress and anxiety provoked by prolonged and forced posture during HUTT. The high levels of adrenergic activity and plasmal EP cause the excessive chronotropic response and the vasal effects of the syndrome. Due to the induction of a state of anxiety and its postural effects, HUTT is a useful provocative tool for complete evaluation of young patients with syncope of vasodepressor origin. We treated the patients differently, depending on how they responded to HUTT. Those with a vaso-vagal response were treated with alpha-sympathomimetic agents (ethylephrine or mydodrine) and those with a hyperchronotropic-vasodepressor response received non-selective beta-blockers. None of our patients had syncope recurrences during a mean follow-up of 12.3 months. Only two patients complained of dizziness; in one of them, symptomatology was abolished by an alpha-sympathomimetic beta-blocker association.     

Interferon-alpha differentially rescues CD4 and CD8 T cells from apoptosis in HIV infection

OBJECTIVE: To examine the effects of interferon-alpha (IFN-alpha) on T cell survival and activation in HIV infection. DESIGN: The effects of IFN-alpha on spontaneous apoptosis and CD38 expression among T cell subsets were determined in vitro and studied in relation to CD4 cell counts, plasma HIV RNA levels and the age of the subjects. METHODS: Peripheral blood mononuclear cells from 48 HIV-infected persons and 17 healthy donors were incubated in vitro overnight with or without the addition of IFN-alpha. Percentages of apoptotic cells (positive for annexin V) and CD38 cells were determined among T cell subsets. RESULTS: IFN-alpha inhibited spontaneous apoptosis of CD4 and CD8 T lymphocytes. This protective activity was impaired in CD4 T cells from HIV-infected persons. The reduced protection of IFN-alpha among CD4 cells from HIV-infected persons was not related to the percentages of activated (CD38 or CD45RO+CD38+) cells. Surprisingly, IFN-alpha induced CD38 expression among CD8 T cells from HIV-infected persons, and the magnitude of this effect was directly related to circulating CD4 T cell count. The CD8 T cell subset that expressed CD38 in response to IFN-alpha was defined as CD28 negative, CD62 ligand (CD62L) intermediate/negative. CONCLUSIONS: Heightened expression of IFN-alpha in HIV infection may contribute to the phenotypic activation state that characterizes chronic infection while a diminished responsiveness of CD4 T cells to the protective effect of this cytokine may contribute to differential survival of CD4 and CD8 T cells in HIV disease.