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The aim of the present study was twofold: firstly, to determine cardiac vagal tone in subjects with generalised anxiety disorder directly, using an invasive pharmacological method; and secondly, to test whether the non-invasive method of measuring the amplitude of respiratory sinus arrhythmia (RSA) gives a reliable estimate of cardiac vagal tone in this form of anxiety disorder. Comparison of baseline physiological measures of anxious and control subjects revealed that cardiac vagal tone and heart rate were not different in the two groups of subjects, whereas length of the respiratory cycle and amplitude of respiratory sinus arrhythmia were reduced in the former group. Because of the higher respiratory rates of anxious subjects, the RSA method was found to underestimate cardiac vagal tone in generalised anxiety disorder. [ABSTRACT FROM AUTHOR]

Objectives: Reduced baroreflex sensitivity (BRS) is a frequent complication in end-stage liver disease, but the underlying mechanism is unknown. We investigated the mechanical and neural components of BRS. Increased nitric oxide (NO) production has been reported in end-stage liver failure. Based on earlier experiments, we hypothesised that enhanced endothelial function might affect baroreflex function. Therefore, we explored the relation between endothelial function and the components of BRS., Materials and Methods: We enrolled 24 patients and 23 controls. BRS was determined by the spontaneous sequence method. Mechanical component was characterised by the distensibility coefficient (DC) of common carotid artery. Neural component was estimated as the ratio of integrated BRS and DC. Endothelial function was quantified by flow-mediated dilation (FMD) of the brachial artery., Results: Integrated BRS was reduced in patients [7.00 (5.80-9.25) vs. 11.1 (8.50-14.80) ms/mmHg]. The mechanical component was not different in the two groups, whereas neural component showed significant reduction in patients (3.54 ± 1.20 vs. 4.48 ± 1.43 ms/10 -3 ). FMD was higher in patients (9.81 ± 3.77 vs. 5.59 ± 1.36%). FMD and neural BRS were directly related in controls (r = 0.62), but inversely related in patients (r = -0.49)., Conclusions: Baroreflex impairment in end-stage liver disease might be explained by deterioration of the neural component, while the mechanical component appears to be preserved. Endothelial NO may enhance BRS in health; however, central endothelial overproduction of NO likely contributes to the reduction of neural component of BRS in patients awaiting liver transplantation.

Sudden cardiac death (SCD) is a common late complication in patients with tetralogy of Fallot (ToF). Reduced baroreflex sensitivity (BRS) is an independent predictor of SCD and BRS reduction was reported in ToF. Relationship between BRS and carotid artery distensibility (DC) in healthy subjects was reported by us earlier. We also found that DC was reduced in ToF patients. In the present study we tested the hypothesis that reduced BRS is related to increased carotid artery stiffness. We studied 36 ToF patients (21±11 years) and 60 age-matched healthy control subjects. Intravenous phenylephrine-induced (BRSphe) and spontaneous (BRSseq) BRS indices were derived. DC calculation was based on echo wall-tracking and tonometry. BRS indices were reduced in patients compared with controls (BRSphe 16.8±10.2 vs. 27.3±9.2ms/mmHg; BRSseq 9.3±9.2 vs. 18.3±7.8ms/mmHg). DC was also lower in patients (5.1±1.8 vs. 6.3±2.610(-3)/mmHg). BRS correlated with DC across patients and controls (BRSphe r=0.75 vs. r=0.74; BRSseq r=0.44 vs. r=0.38). Multiple regression analysis indicated that BRS indices are determined independently by DC in ToF patients. We showed that reduced DC may contribute to impaired baroreflex function in ToF patients and could in part explain the elevated risk for SCD postoperatively. Therefore it would be an important future investigation to test carotid artery stiffness and analyze its predictive value for cardiac mortality in ToF. Preventive actions to impede carotid artery stiffening should receive more attention in the clinical management of ToF patients., (Copyright © 2014 Elsevier B.V. All rights reserved.)