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Background: Attacks of Hereditary Angioedema due to C1-inhibitor deficiency (C1-INH-HAE)are often triggered by stressful events/hormonal changes. Objective: Our study evaluates the relationship between autonomic nervous system (ANS) and contact/complement system activation. Methods: Twenty-three HAE patients (6 males, mean age 47.5±11.4 years) during remission and 24 healthy controls (8 males, mean age 45.3±10.6 years) were studied. ECG, beat-by-beat blood pressure, respiratory activity were continuously recorded during rest (10’) and 75-degrees-head-up tilt (10’). C1-INH, C4, cleaved high molecular weight kininogen (cHK) were assessed; in 16 patients and 11 controls plasma catecholamines were also evaluated. Spectral analysis of heart rate variability allowed extraction of low-(LF) and high-(HF) frequency components, markers of sympathetic and vagal modulation respectively. Results: HAE patients showed higher mean systolic arterial pressure (SAP) than controls during both rest and tilt. Tilt induced a significant increase in SAP and its variability only in controls. Although sympathetic modulation (LFnu) increased significantly with tilt in both groups, LF/HF ratio, index of sympathovagal balance, increased significantly only in controls. At rest HAE patients showed higher noradrenaline values (301.4±132.9 pg/ml vs 210.5±89.6pg/ml, p = 0.05). Moreover, in patients tilt was associated with a significant increase in cHK, marker of contact system activation (49.5 ± 7.5% after T vs 47.1 ± 7.8% at R, p = 0.01). Conclusions: Our data are consistent with altered ANS modulation in HAE patients, i.e. increased sympathetic activation at rest and blunted response to orthostatic challenge. Tilt test-induced increased HK cleavage suggests a link between stress and bradykinin production. [ABSTRACT FROM AUTHOR]

Background: Syncope is a clinical event characterized by a transient loss of consciousness, estimated to affect 6.2/1000 person-years, resulting in remarkable health care and social costs. Human pathophysiology suggests that heat may promote syncope during standing. We tested the hypothesis that the increase of air temperatures from January to July would be accompanied by an increased rate of syncope resulting in a higher frequency of Emergency Department (ED) visits. We also evaluated the role of maximal temperature variability in affecting ED visits for syncope. Methodology/Principal Findings: We included 770 of 2775 consecutive subjects who were seen for syncope at four EDs between January and July 2004. This period was subdivided into three epochs of similar length: 23 January-31 March, 1 April-31 May and 1 June-31 July. Spectral techniques were used to analyze oscillatory components of day by day maximal temperature and syncope variability and assess their linear relationship. There was no correlation between daily maximum temperatures and number of syncope. ED visits for syncope were lower in June and July when maximal temperature variability declined although the maximal temperatures themselves were higher. Frequency analysis of day by day maximal temperature variability showed a major non-random fluctuation characterized by a ∼23-day period and two minor oscillations with ∼3- and ∼7-day periods. This latter oscillation was correlated with a similar ∼7-day fluctuation in ED visits for syncope. Conclusions/Significance: We conclude that ED visits for syncope were not predicted by daily maximal temperature but were associated with increased temperature variability. A ∼7-day rhythm characterized both maximal temperatures and ED visits for syncope variability suggesting that climate changes may have a significant effect on the mode of syncope occurrence. [ABSTRACT FROM AUTHOR]