Clinical Autonomic Research最新文献

Purpose: Clinical trials have shown that in type 2 diabetes mellitus (T2D) resting office heart rate (HR) values > 70 beats/minute are associated with an increased cardiovascular risk, a worse prognosis and an unfavorable outcome. The present study was aimed at investigating whether the above mentioned treshold HR values reflect a sympathetic overdrive of marked degree.

Methods: In 58 T2D patients (age range: 39-57 years) without signs of autonomic neuropathy and in 52 age-matched healthy controls, we assessed muscle sympathetic nerve activity (MSNA, microneurography) and venous plasma norepinephrine (NE, HPLC), subdividing the study population in different subgroups according to their clinic and 24-h HR values.

Results: In T2D progressively greater clinic and 24-h HR values were accompanied by progressive increases in MSNA and NE. HR cutoff values indicated by clinical trials as associated with an increased cardiovascular risk (> 70 beats/minute) were accompanied by MSNA values significantly higher than those detected in patients with lower HR, this being the case also for NE. In T2D both MSNA and NE were significantly related to clinic (r = 0.93, P < 0.0001 and r = 0.87, P < 0.0001, respectively) and 24-h (r = 0.92, P < 0.0001 and r = 0.84, P < 0.0001, respectively) HR. The MSNA and NE behaviour observed in T2D was not detected in healthy controls.

Conclusions: In T2D clinic HR values allow to detect patients with a greater sympathetic overactivity. Considering the adverse clinical impact of the sympathetic overdrive on prognosis, our data emphasize the need of future studies investigating the potential usefulness of lifestyle and pharmacological interventions exerting sympathomodulatory effects.

Purpose: Hypertension is one of the major causes of cardiovascular morbidity and mortality in the USA and disproportionately affects Black women. Endothelial-derived nitric oxide (eNO) substantially regulates blood pressure in humans, and impaired NO-mediated vasodilation has been reported in the Black population. Previous studies using an NO synthase inhibitor, N^G-monomethyl-L-arginine (L-NMMA) did not fully determine the NO contribution to blood pressure because of baroreflex buffering. Therefore, in the present study we used trimethaphan, a ganglionic blocker, to inhibit baroreflex buffering and study NO modulation of blood pressure in Black women during L-NMMA infusion.

Methods: L-NMMA at doses of 250 μg/kg per minute was infused in combination with trimethaphan at doses of 4 mg/min to eliminate baroreflex mechanisms. Heart rate (HR) was obtained with continuous electrocardiogram monitoring, and continuous blood pressure was measured with the volume clamp method. The increase in systolic blood pressure (SBP) during both infusions was used to estimate the contribution of NO to blood pressure.

Results: Ten Black (age range 30-50 years, body mass index [BMI] 30-45 kg/m²), and nine White women (age range 30-50 years, body mass index 30-45 kg/m²) were enrolled in this study. During autonomic blockade, there was no difference in the decrease in SBP between Black and White women (- 20 ± 16.45 vs. - 24 ± 15.49 mm Hg, respectively; P = 0.659). When autonomic blockade was combined with L-NMMA, Black women had a significant increase in SBP compared to White women (54 ± 13.62 vs. 39 ± 09.64 mm Hg, respectively; P = 0.022, respectively).

Conclusion: Autonomic blood pressure regulation was similar between Black and White women. However, NO contribution to blood pressure was significantly greater in Black women compared to White women.

Registration: ClinicalTrials.gov: NCT01122407.

Direct current stimulation (DCS) is a non-invasive approach to stimulate the nervous system that is now considered a powerful tool for treating neurological diseases such as those affecting cognitive or locomotor functions. DCS, as applied clinically today, is an approach built on early uses in antiquity and knowledge gained over time. Its current use makes use of specific devices and takes into account knowledge of the mechanisms by which this approach modulates functioning of the nervous system at the cellular level. Over the last 20 years, although there are few studies, it has been shown that DCS can also modulate the breathing autonomic function. In this narrative review, after briefly providing the historical perspective and describing the principles and the main cellular and molecular effects, we summarize the currently available data regarding the modulation of ventilation, and propose that DCS could be used to treat autonomic or non-autonomic neurological disorders affecting breathing.

Purpose: Neurogenic orthostatic hypotension (nOH) results from deficient reflexive delivery of norepinephrine to cardiovascular receptors in response to decreased cardiac venous return. Lewy body (LB) forms of nOH are characterized by low ¹⁸F-dopamine-derived radioactivity (a measure of cardiac noradrenergic deficiency), olfactory dysfunction by the University of Pennsylvania Smell Identification Test (UPSIT), and increased deposition of alpha-synuclein (α-syn) in dermal sympathetic noradrenergic nerves by the α-syn-tyrosine hydroxylase (TH) colocalization index. This observational, cross-sectional study explored whether combinations of these biomarkers specifically identify LB forms of nOH.

Methods: Clinical laboratory data were reviewed from patients referred for evaluation at the National Institutes of Health for chronic autonomic failure between 2011 and 2023. The cutoff value for low myocardial ¹⁸F-dopamine-derived radioactivity was 6000 nCi-kg/cc-mCi, for olfactory dysfunction an UPSIT score ≤ 28, and for an increased α-syn-TH colocalization index ≥ 1.57.

Results: A total of 44 patients (31 LB, 13 non-LB nOH) had data for all three biomarkers. Compared to the non-LB group, the LB nOH group had low myocardial ¹⁸F-dopamine-derived radioactivity, low UPSIT scores, and high α-syn-TH colocalization indexes (p < 0.0001 each). Combining the three biomarkers completely separated the groups. Cluster analysis identified two distinct groups (p < 0.0001) independently of the clinical diagnosis, with one cluster corresponding exactly to LB nOH.

Conclusion: LB forms of nOH feature cardiac noradrenergic deficiency, olfactory dysfunction, and increased α-syn-TH colocalization in skin biopsies. Combining the data for these variables efficiently separates LB from non-LB nOH. Independently of the clinical diagnosis, this biomarker triad identifies a pathophysiologically distinct cluster of nOH patients.

Background: The cardiomyopathic and neuropathic phenotype of hereditary transthyretin amyloidosis are well recognized. Cardiovascular autonomic dysfunction is less systematically and objectively assessed.

Methods: Autonomic and clinical features, quantitative cardiovascular autonomic function, and potential autonomic prognostic markers of disease progression were recorded in a cohort of individuals with hereditary transthyretin amyloidosis and in asymptomatic carriers of TTR variants at disease onset (T0) and at the time of the first quantitative autonomic assessment (T1). The severity of peripheral neuropathy and its progression was stratified with the polyneuropathy disability score.

Results: A total of 124 individuals were included (111 with a confirmed diagnosis of hereditary transthyretin amyloidosis, and 13 asymptomatic carriers of TTR variants). Symptoms of autonomic dysfunction were reported by 27% individuals at T0. Disease duration was 4.5 ± 4.0 years [mean ± standard deviation (SD)] at autonomic testing (T1). Symptoms of autonomic dysfunction were reported by 78% individuals at T1. Cardiovascular autonomic failure was detected by functional testing in 75% individuals and in 64% of TTR carriers. Progression rate from polyneuropathy disability stages I/II to III/IV seemed to be shorter for individuals with autonomic symptoms at onset [2.33 ± 0.56 versus 4.00 ± 0.69 years (mean ± SD)].

Conclusions: Cardiovascular autonomic dysfunction occurs early and frequently in individuals with hereditary transthyretin amyloidosis within 4.5 years from disease onset. Cardiovascular autonomic failure can be subclinical in individuals and asymptomatic carriers, and only detected with autonomic function testing, which should be considered a potential biomarker for early diagnosis and disease progression.

Purpose: Central and peripheral chemoreceptors are hypersensitized in patients with heart failure with reduced ejection fraction. Whether this autonomic alteration occurs in patients with heart failure with preserved ejection fraction (HFpEF) remains little known. We test the hypothesis that the central and peripheral chemoreflex control of muscle sympathetic nerve activity (MSNA) is altered in HFpEF.

Methods: Patients aged 55-80 years with symptoms of heart failure, body mass index ≤ 35 kg/m², left ventricular ejection fraction > 50%, left atrial volume index > 34 mL/m², left ventricular early diastolic filling velocity and early diastolic tissue velocity of mitral annulus ratio (E/e' index) ≥ 13, and BNP levels > 35 pg/mL were included in the study (HFpEF, n = 9). Patients without heart failure with preserved ejection fraction (non-HFpEF, n = 9), aged-paired, were also included in the study. Peripheral chemoreceptors stimulation (10% O₂ and 90% N₂, with CO₂ titrated) and central chemoreceptors stimulation (7% CO₂ and 93% O₂) were conducted for 3 min. MSNA was evaluated by microneurography technique, and forearm blood flow (FBF) by venous occlusion plethysmography.

Results: During hypoxia, MSNA responses were greater (p < 0.001) and FBF responses were lower in patients with HFpEF (p = 0.006). Likewise, MSNA responses during hypercapnia were higher (p < 0.001) and forearm vascular conductance (FVC) levels were lower (p = 0.030) in patients with HFpEF.

Conclusions: Peripheral and central chemoreflex controls of MSNA are hypersensitized in patients with HFpEF, which seems to contribute to the increase in MSNA in these patients. In addition, peripheral and central chemoreceptors stimulation in patients with HFpEF causes muscle vasoconstriction.