Clinical Autonomic Research最新文献

Purpose: Increasing evidence demonstrates that gender-related factors, and not only biological sex, are relevant in the physiological and pathophysiological mechanisms of the cardiovascular system, including the cardiac autonomic regulation. Sex and gender may also affect daytime and night-time cardiac autonomic control. This meta-analysis aimed to provide a comparison between healthy women and men on heart rate variability using 24-h ECG recordings pointing out sex- and gender-related factors.

Methods: A systematic search was conducted to include studies focusing on both sex and gender differences related to heart rate variability indices in the time and frequency domains. Descriptive data were extracted by two independent reviewers. For each index, standardized mean differences with 95% confidence intervals were computed and a pooled estimate using a fixed- or random-effects model was applied.

Results: Twenty-seven studies were included in the meta-analysis. The results showed that only seven studies reported some information about gender-related factors. Concerning sex-related differences, women had a shorter mean RR interval and lower variability of the time domain indices than men. Sex-related differences concerning frequency domain indices were more evident during night-time compared to daytime.

Conclusion: The characterization of gender-related factors in the study of heart rate variability using 24-h ECG recordings is still sporadic and underexplored. The meta-analysis results could not conclusively support a significant increase of high frequency power in women, although women showed a reduced total power and low frequency to high frequency ratio. There is a strong need for considering heart rate variability in relation to gender-related variables.

Purpose: To quantify sweat gland nerve fiber density in adolescents with diabetes. Additionally, to investigate associations between sudomotor innervation, sweat responses, and possible risk factors for sudomotor neuropathy.

Methods: Cross-sectional study where 60 adolescents with type 1 diabetes (duration > 5 years) and 23 control subjects were included. Clinical data, quantitative sudomotor axon reflex test, and skin biopsies were obtained. Skin tissue was immunostained and imaged by confocal microscopy. Quantification of the sweat gland volume and three-dimensional reconstruction of the nerve fibers was performed using a design-unbiased technique.

Results: Adolescents with diabetes had a significant reduction of maximum and mean values of nerve fiber length and nerve fiber density in sweat glands compared to controls (p values < 0.05). No association between nerve fiber density and sweat responses was found (p = 0.21). In cases with reduced sweat gland nerve fiber length, nerve fiber density, and volume, the sweat response was reduced or absent. Height, systolic blood pressure, time in hypoglycemia, and total daily and basal/total insulin dose were positively correlated to sweat response, while low-density lipoprotein, and HbA1c were negatively correlated with sweat response (p values < 0.05). Other microvascular complications and high cholesterol levels increased the relative risk for reduced sweat gland nerve fiber density.

Conclusion: Our findings of reduced sweat gland innervation in a selected group of adolescents add new knowledge about the structural changes that occur in autonomic nerves due to diabetes. Evaluating both the sweat gland innervation and sweat gland volume was important for understanding the association with sweat responses. Further research is needed to understand its clinical relevance.

Purpose: Pediatric patients with autonomic dysfunction and orthostatic intolerance (OI) often present with co-existing symptoms and signs that might or might not directly relate to the autonomic nervous system. Our objective was to identify validated screening instruments to characterize these comorbidities and their impact on youth functioning.

Methods: The Pediatric Assembly of the American Autonomic Society reviewed the current state of practice for identifying symptom comorbidities in youth with OI. The assembly includes physicians, physician-scientists, scientists, advanced practice providers, psychologists, and a statistician with expertise in pediatric disorders of OI. A total of 26 representatives from the various specialties engaged in iterative meetings to: (1) identify and then develop consensus on the symptoms to be assessed, (2) establish committees to review the literature for screening measures by member expertise, and (3) delineate the specific criteria for systematically evaluating the measures and for making measure recommendations by symptom domains.

Results: We review the measures evaluated and recommend one measure per system/concern so that assessment results from unrelated clinical centers are comparable. We have created a repository to apprise investigators of validated, vetted assessment tools to enhance comparisons across cohorts of youth with autonomic dysfunction and OI.

Conclusion: This effort can facilitate collaboration among clinical settings to advance the science and clinical treatment of these youth. This effort is essential to improving management of these vulnerable patients as well as to comparing research findings from different centers.

Purpose: Pure autonomic failure (PAF) is a rare disease characterized by neurogenic orthostatic hypotension (nOH), no known secondary cause, and lack of a neurodegenerative movement or cognitive disorder. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease [LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)] or to the non-LBD synucleinopathy multiple system atrophy (MSA). Since cardiac ¹⁸F-dopamine-derived radioactivity usually is low in LBDs and usually is normal in MSA, we hypothesized that patients with PAF with low cardiac ¹⁸F-dopamine-derived radioactivity would be more likely to phenoconvert to a central LBD than to MSA.

Methods: We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about ¹⁸F-dopamine positron emission tomography (PET).

Results: Nineteen patients (15 with low ¹⁸F-dopamine-derived radioactivity, 4 with normal radioactivity) met the above criteria and had follow-up data. Nine (47%) phenoconverted to a central synucleinopathy over a mean of 6.6 years (range 1.5-18.8 years). All 6 patients with low cardiac ¹⁸F-dopamine-derived radioactivity who phenoconverted during follow-up developed a central LBD, whereas none of 4 patients with consistently normal ¹⁸F-dopamine PET phenoconverted to a central LBD (p = 0.0048), 3 evolving to probable MSA and 1 upon autopsy having neither a LBD nor MSA.

Conclusion: Cardiac ¹⁸F-dopamine PET can predict the type of phenoconversion of PAF. This capability could refine eligibility criteria for entry into disease-modification trials aimed at preventing evolution of PAF to symptomatic central LBDs.

Purpose: This systematic review aimed to summarize how oral contraceptives (OC) affect resting autonomic function and the autonomic response to a variety of physiological stressors.

Methods: A search strategy was created to retrieve citations investigating physiological responses comparing OC users to non-users (NOC) in response to autonomic reflex activation.

Results: A total of 6148 citations were identified across databases from inception to June 2, 2022, and 3870 citations were screened at the abstract level after deduplication. Then, 133 texts were assessed at full-text level, and only 40 studies met eligibility requirements. Included citations were grouped by the aspect of autonomic function assessed, including autonomic reflex (i.e., baroreflex, chemoreflex, mechanoreflex, metaboreflex, and venoarterial reflex), or indicators (i.e., heart rate variability, pulse wave velocity, and sympathetic electrodermal activity), and physiological stressors that may alter autonomic function (i.e., auditory, exercise, mental or orthostatic stress, altitude, cold pressor test, sweat test, and vasodilatory infusions).

Conclusion: OC influence the physiological responses to chemoreflex, mechanoreflex, and metaboreflex activation. In terms of autonomic indices and physiological stressors, there are more inconsistencies within the OC literature, which may be due to estrogen dosage within the OC formulation (i.e., heart rate variability) or the intensity of the stressor (exercise intensity/duration or orthostatic stress). Further research is required to elucidate the effects of OC on these aspects of autonomic function because of the relatively small amount of available research. Furthermore, researchers should more clearly define or stratify OC use by duration, dose, and/or hormone cycling to further elucidate the effects of OC.

Purposes: Habitual coffee drinking is ubiquitous and generally considered to be safe despite its transient hypertensive effect. Our purpose was to determine the role of the sympathetic nervous system in the hypertensive response.

Methods: In a single-centre crossover study, medical caregivers were studied after consumption of standard coffee (espresso), water and decaffeinated coffee (decaff) given in random order at least 1 month apart. Plasma caffeine levels, mean arterial pressure, heart rate, total peripheral resistance and muscle sympathetic activity were recorded. Baroreflex activity was assessed using burst incidence and RR interval changes to spontaneous blood pressure fluctuations.

Results: A total of 16 subjects (mean [± standard error] age 34.4 ± 2 years; 44% female) were recruited to the study. Three agents were studied in ten subjects, and two agents were studied in six subjects. Over a 120-min period following the consumption of standard coffee, mean (± SE) plasma caffeine levels increased from 2.4 ± 0.8 to 21.0 ± 4 µmol/L and arterial pressure increased to 103 ± 1 mmHg compared to water (101 ± 1 mmHg; p = 0.066) and decaff (100 ± 1 mmHg; p = 0.016). Peripheral resistance in the same period following coffee increased to 120 ± 4% of the baseline level compared to water (107 ± 4; p = 0.01) and decaff (109 ± 4; p = 0.02). Heart rate was lower after both coffee and decaff consumption: 62 ± 1 bpm compared to water (64 bpm; p = 0.01 and p = 0.02, respectively). Cardio-vagal baroreflex activity remained stable after coffee, but sympathetic activity decreased, with burst frequency of 96 ± 3% versus water (106 ± 3%; p = 0.04) and decaff (112 ± 3%; p = 0.001) despite a fall in baroreflex activity from - 2.2 ± 0.1 to - 1.8 ± 0.1 bursts/100 beats/mmHg, compared to water (p = 0.009) and decaff (p = 0.004).

Conclusion: The hypertensive response to coffee is secondary to peripheral vasoconstriction but this is not mediated by increased sympathetic nerve activity. These results may explain why habitual coffee drinking is safe.