Automatic Classification of Emotions Based on Cardiac Signals: A Systematic Literature Review.

Emotions play a pivotal role in human cognition, exerting influence across diverse domains of individuals' lives. The widespread adoption of artificial intelligence and machine learning has spurred interest in systems capable of automatically recognizing and classifying emotions and affective states. However, the accurate identification of human emotions remains a formidable challenge, as they are influenced by various factors and accompanied by physiological changes. Numerous solutions have emerged to enable emotion recognition, leveraging the characterization of biological signals, including the utilization of cardiac signals acquired from low-cost and wearable sensors. The objective of this work was to comprehensively investigate the current trends in the field by conducting a Systematic Literature Review (SLR) that focuses specifically on the detection, recognition, and classification of emotions based on cardiac signals, to gain insights into the prevailing techniques employed for signal acquisition, the extracted features, the elicitation process, and the classification methods employed in these studies. A SLR was conducted using four research databases, and articles were assessed concerning the proposed research questions. Twenty seven articles met the selection criteria and were assessed for the feasibility of using cardiac signals, acquired from low-cost and wearable devices, for emotion recognition. Several emotional elicitation methods were found in the literature, including the algorithms applied for automatic classification, as well as the key challenges associated with emotion recognition relying solely on cardiac signals. This study extends the current body of knowledge and enables future research by providing insights into suitable techniques for designing automatic emotion recognition applications. It emphasizes the importance of utilizing low-cost, wearable, and unobtrusive devices to acquire cardiac signals for accurate and accessible emotion recognition.

Advances in Non-Invasive Neuromodulation: Designing Closed-Loop Devices for Respiratory-Controlled Transcutaneous Vagus Nerve Stimulation.

Studies suggest non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) as a potential therapeutic option for various pathological conditions, such as epilepsy and depression. Exhalation-controlled taVNS, which synchronizes stimulation with internal body rhythms, holds promise for enhanced neuromodulation, but there is no closed-loop system in the literature capable of performing such integration in real time. In this context, the objective was to develop real-time signal processing techniques and an integrated closed-loop device with sensors to acquire physiological data. After a conditioning stage, the signal is processed and delivers synchronized electrical stimulation during the patient's expiratory phase. Additional modules were designed for processing, software-controlled selectors, remote and autonomous operation, improved analysis, and graphical visualization. The signal processing method effectively extracted respiratory cycles and successfully attenuated signal noise. Heart rate variability was assessed in real time, using linear statistical evaluation. The prototype feedback stimulator device was physically constructed. Respiratory peak detection achieved an accuracy of 90%, and the real-time processing resulted in a small delay of up to 150 ms in the detection of the expiratory phase. Thus, preliminary results show promising accuracy, indicating the need for additional tests to optimize real-time processing and the application of the prototype in clinical studies.

Maintenance of plasma glucose variability after an acute session of aerobic exercise despite changes in insulin and glucagon-like peptide-1 levels in type 2 diabetes

ABSTRACT Objective: The present study aimed to evaluate glucose variability and hormonal responses during and after an aerobic exercise session performed after breakfast in type 2 diabetes patients treated with metformin. Materials and methods: In this quasi-experimental study individuals underwent clinical and laboratory evaluations and maximal exercise test. After two weeks an aerobic exercise session (30 minutes at 60%-70% of the peak heart rate) was performed. At rest, during and after the exercise session, glucose variability (mean amplitude glucose excursions, glucose coefficient of variation, and glucose standard deviation) and levels of plasma glucose, insulin, glucagon, and glucagon-like-peptide-1 were evaluated. Results: Thirteen patients were enrolled in the study. Plasma glucose increased at 15 minutes during the exercise session (244.6 ± 61.9 mg/dL), and decreased at 60 min after exercise (195.6 ± 50.0 mg/dL). Glucose variability did not show any difference before and after exercise. Insulin levels at 15 min [27.1 µU/mL (14.2-42.1)] and 30 min [26.3 µU/mL (14.6-37.4)] during the exercise were higher than those at fasting [11.2 µU/mL (6.7-14.9)] but decreased 60 minutes after exercise (90 minutes) [16.6 µU/mL (8.7-31.7)]. Glucagon levels did not show any difference. GLP-1 levels increased at 30 min [7.9 pmol/L (7.1-9.2)] during exercise and decreased 60 min after exercise (90 minutes) [7.7 pmol/L (6.8-8.5)]. Conclusion: Subjects with type 2 diabetes presented expected changes in insulin, glucagon and GLP-1 levels after breakfast and a single aerobic exercise session, not accompanied by glycemic variability changes.

Maintenance of plasma glucose variability after an acute session of aerobic exercise despite changes in insulin and glucagon-like peptide-1 levels in type 2 diabetes.

Objective: The present study aimed to evaluate glucose variability and hormonal responses during and after an aerobic exercise session performed after breakfast in type 2 diabetes patients treated with metformin. Methods: In this quasi-experimental study individuals underwent clinical and laboratory evaluations and maximal exercise test. After two weeks an aerobic exercise session (30 minutes at 60%-70% of the peak heart rate) was performed. At rest, during and after the exercise session, glucose variability (mean amplitude glucose excursions, glucose coefficient of variation, and glucose standard deviation) and levels of plasma glucose, insulin, glucagon, and glucagon-like-peptide-1 were evaluated. Results: Thirteen patients were enrolled in the study. Plasma glucose increased at 15 minutes during the exercise session (244.6 ± 61.9 mg/dL), and decreased at 60 min after exercise (195.6 ± 50.0 mg/dL). Glucose variability did not show any difference before and after exercise. Insulin levels at 15 min [27.1 µU/mL (14.2-42.1)] and 30 min [26.3 µU/mL (14.6-37.4)] during the exercise were higher than those at fasting [11.2 µU/mL (6.7-14.9)] but decreased 60 minutes after exercise (90 minutes) [16.6 µU/mL (8.7-31.7)]. Glucagon levels did not show any difference. GLP-1 levels increased at 30 min [7.9 pmol/L (7.1-9.2)] during exercise and decreased 60 min after exercise (90 minutes) [7.7 pmol/L (6.8-8.5)]. Conclusion: Subjects with type 2 diabetes presented expected changes in insulin, glucagon and GLP-1 levels after breakfast and a single aerobic exercise session, not accompanied by glycemic variability changes.

Parasympathetic modulation withdrawal improves functional capacity in pulmonary arterial hypertension.

In 15 pulmonary arterial hypertension patients, the relation of functional capacity to their peripheral endothelial function and sympathaovagal modulation was studied by carrying out brachial artery ultrasound and electrocardiogram spectral analysis, respectively. The functional capacity was assessed by cardiopulmonary exercise testing and six-minute walking test. The sympathovagal modulation was correlated with the predicted peak oxygen consumption (peak VO2 %; r = 0.692, P < 0.05), peak O2 pulse (mL/beat; r = 0.661, P < 0.05), VE, minute ventilation, VCO2 carbon dioxide production (VE/VCO2 slope; r=-0.806, P < 0.01) and distance walked predicted (%6MWT; r = 0.694, P < 0.05). Moreover, there were negative correlations between parasympathetic modulation with peak VO2 (r = 0.755, P < 0.01), peak VO2% (r=-0.727, P < 0.01) and peak O2 pulse (r = 0.615, P < 0.05), %6MWT (r=-0.834, P < 0.01). Collectively these correlations indicate that parasympathetic withdrawal is crucial for improving functional capacity. This conclusion is supported by both positive and negative correlations of parasympathetic modulation with the functional capacity parameters. The sympathetic modulation predominance, although increases the cardiovascular risk, is probably crucial to facilitate the bronchodilation and the oxygen uptake.

Effect of exercise on glucose variability in healthy subjects: randomized crossover trial.

The aim of this study was to evaluate the acute effect of aerobic (AER) and eccentric (ECC) exercise on glucose variability, correlating it with circulating markers of inflammation and oxidative stress in healthy subjects. Sixteen healthy subjects (32 ± 12 years old) wore a continuous glucose monitoring system for three days. Participants randomly performed single AER and ECC exercise sessions. Glucose variability was evaluated by glucose variance (VAR), glucose coefficient of variation (CV%) and glucose standard deviation (SD). Blood samples were collected to evaluate inflammatory and oxidative stress markers. When compared with the pre-exercise period of 0-6 h, all the indices of glucose variability presented comparable reductions 12-18 h after both exercises (∆AER: VAR= 151.5, ∆CV% = 0.55 and ∆SD = 3.1 and ECC: ∆VAR = 221.2 , ∆CV% = 3.7 and ∆SD = 6.5). Increased interleukin-6 (IL-6) levels after AER (68.5%) and ECC (30.8%) (P<0.001) were observed, with no differences between sessions (P = 0.459). Uric acid levels were increased after exercise sessions (3% in AER and 4% in ECC, P = 0.001). In conclusion, both AER and ECC exercise sessions reduced glucose variability in healthy individuals. Inflammatory cytokines, such as IL-6, and stress oxidative markers might play a role in underlying mechanisms modulating the glucose variability responses to exercise (clinicalTrials.gov NCT02262208).

Optimization of Vagal Stimulation Protocol Based on Spontaneous Breathing Rate.

Controlled breathing maneuver is being widely applied for cardiovascular autonomic control evaluation and cardiac vagal activation through reduction of breathing rate (BR). However, this maneuver presented contradictory results depending on the protocol and the chosen BR. These variations may be related to the individual intrinsic profile baseline sympathetic tonus, as described before by others. In this study, we evaluated the effect of controlled breathing maneuver on cardiovascular autonomic control in 26 healthy subjects allocated into two protocols: (1) controlled breathing in three different rates (10, 15, and 20 breaths/min) and (2) controlled breathing in rates normalized by the individual spontaneous breathing rate (SBR) at 100, 80, 70, and 50%. Our results showed autonomic responses favorable to vagal modulation with the lower BR maneuvers. Nevertheless, while this activation was variable using the standard protocol, all participants of the normalized protocol demonstrated an increase of vagal modulation at 80% BR (HFnu 80 = 67.5% vs. 48.2%, p < 0.0001). These results suggest that controlled breathing protocols to induce vagal activation should consider the SBR, being limited to values moderately lower than the baseline.

Impact of treatment with glibenclamide or vildagliptin on glucose variability after aerobic exercise in type 2 diabetes: A randomized controlled trial.

AIMS: To evaluate the glucose variability, oxidative stress, metabolic and cardiovascular responses after an aerobic exercise session in diabetic patients on treatment with metformin plus vildagliptin or glibenclamide. METHODS: Parallel clinical trial including patients with type 2 diabetes treated with metformin plus vildagliptin or glibenclamide for 12 weeks. Glucose variability, oxidative stress, metabolic (plasma glucose, insulin and glucagon-like-peptide-1) and cardiovascular responses were evaluated at rest, during and after a 30 min aerobic exercise session (70% of the peak heart rate). RESULTS: Thirteen patients were included, seven in vildagliptin group (METV) and six in glibenclamide group (METG), baseline glycated hemoglobin (HbA1c) 8.8 ±â€¯0.3%. Treatment reduced HbA1c (1.2% and 1.5% for METV and METG, respectively). The aerobic exercise session did not change glucose variability in both groups. A decrease in glucose during exercise recovery was found, with area under the curve lower in the METG vs. METV (p = 0.04). After the intervention, systolic blood pressure (SBP) decreased in both groups. Patients treated with vildagliptin showed lower SBP variability compared to those treated with glibenclamide. CONCLUSIONS: Besides improvement in glucose control and reduction of SBP obtained by both treatments, lower blood pressure variability was observed in patients receiving vildagliptin. Glucose variability remained unaffected by both interventions and the exercise session.

Exercise training versus T3 and T4 hormones treatment: The differential benefits of thyroid hormones on the parasympathetic drive of infarcted rats.

AIMS: This study aimed to investigate whether beneficial effects of thyroid hormones are comparable to those provided by the aerobic exercise training, to verify its applicability as a therapeutic alternative to reverse the pathological cardiac remodeling post-infarction. MATERIALS AND METHODS: Male rats were divided into SHAM-operated (SHAM), myocardial infarction (MI), MI subjected to exercise training (MIE), and MI who received T3 and T4 treatment (MIH) (n = 8/group). MI, MIE and MIH groups underwent an infarction surgery while SHAM was SHAM-operated. One-week post-surgery, MIE and MIH groups started the exercise training protocol (moderate intensity on treadmill), or the T3 (1.2 µg/100 g/day) and T4 (4.8 µg/100 g/day) hormones treatment by gavage, respectively, meanwhile SHAM and MI had no intervention for 9 weeks. The groups were accompanied until 74 days after surgery, when all animals were anesthetized, left ventricle echocardiography and femoral catheterization were performed, followed by euthanasia and left ventricle collection for morphological, oxidative stress, and intracellular kinases expression analysis. KEY FINDINGS: Thyroid hormones treatment was more effective in cardiac dilation and infarction area reduction, while exercise training provided more protection against fibrosis. Thyroid hormones treatment increased the lipoperoxidation and decreased GSHPx activity as compared to MI group, increased the t-Akt2 expression as compared to SHAM group, and increased the vascular parasympathetic drive. SIGNIFICANCE: Thyroid hormones treatment provided differential benefits on the LV function and autonomic modulation as compared to the exercise training. Nevertheless, the redox unbalance induced by thyroid hormones highlights the importance of more studies targeting the ideal duration of this treatment.

Mesenchymal stem cells from sternum: the type of heart disease, ischemic or valvular, does not influence the cell culture establishment and growth kinetics.

BACKGROUND: In an attempt to increase the therapeutic potential for myocardial regeneration, there is a quest for new cell sources and types for cell therapy protocols. The pathophysiology of heart diseases may affect cellular characteristics and therapeutic results. METHODS: To study the proliferative and differentiation potential of mesenchymal stem cells (MSC), isolated from bone marrow (BM) of sternum, we made a comparative analysis between samples of patients with ischemic (IHD) or non-ischemic valvular (VHD) heart diseases. We included patients with IHD (n = 42) or VHD (n = 20), with average age of 60 years and no differences in cardiovascular risk factors. BM samples were collected (16.4 ± 6 mL) and submitted to centrifugation with Ficoll-Paque, yielding 4.5 ± 1.5 × 107 cells/mL. RESULTS: Morphology, immunophenotype and differentiation ability had proven that the cultivated sternal BM cells had MSC features. The colony forming unit-fibroblast (CFU-F) frequency was similar between groups (p = 0.510), but VHD samples showed positive correlation to plated cells vs. CFU-F number (r = 0.499, p = 0.049). The MSC culture was established in 29% of collected samples, achieved passage 9, without significant difference in expansion kinetics between groups (p > 0.05). Dyslipidemia and the use of statins was associated with culture establishment for IHD patients (p = 0.049 and p = 0.006, respectively). CONCLUSIONS: Together, these results show that the sternum bone can be used as a source for MSC isolation, and that ischemic or valvular diseases do not influence the cellular yield, culture establishment or in vitro growth kinetics.

Improved cardiovascular autonomic modulation in transgenic rats expressing an Ang-(1-7)-producing fusion protein.

Angiotensin-(1-7) counterbalances angiotensin II cardiovascular effects. However, it has yet to be determined how cardiovascular autonomic modulation may be affected by chronic and acute elevation of Ang-(1-7). Hemodynamics and cardiovascular autonomic profile were evaluated in male Sprague-Dawley (SD) rats and transgenic rats (TGR) overexpressing Ang-(1-7) [TGR(A1-7)3292]. Blood pressure (BP) was directly measured while cardiovascular autonomic modulation was evaluated by spectral analysis. TGR received A-779 or vehicle and SD rats received Ang-(1-7) or vehicle and were monitored for 5 h after i.v. administration. In another set of experiments with TGR, A-779 was infused for 7 days using osmotic mini pumps. Although at baseline no differences were observed, acute administration of A-779 in TGR produced a marked long-lasting increase in BP accompanied by increased BP variability (BPV) and sympathetic modulation to the vessels. Likewise, chronic administration of A-779 with osmotic mini pumps in TGR increased heart rate, sympathovagal balance, BPV, and sympathetic modulation to the vessels. Administration of Ang-(1-7) to SD rats increased heart rate variability values in 88% accompanied by 8% of vagal modulation increase and 18% of mean BP reduction. These results show that both acute and chronic alteration in the Ang-(1-7)-Mas receptor axis may lead to important changes in the autonomic control of circulation, impacting either sympathetic and (or) parasympathetic systems.

Bucindolol improves right ventricle function in rats with pulmonary arterial hypertension through the reversal of autonomic imbalance.

Pulmonary arterial hypertension (PAH) is characterised by an elevation in afterload imposed on the right ventricle (RV), leading to hypertrophy and failure. The autonomic nervous system (ANS) plays a key role in the progression to heart failure, and the use of beta-blockers attenuates this process. The aim of this study was to verify the role of bucindolol, aß1-, ß2- and α1-blocker, on the ANS, and its association with RV function in rats with PAH. Male Wistar rats were divided into four groups: control, monocrotaline, control+bucindolol, and monocrotaline+bucindolol. PAH was induced by a single intraperitoneal injection of monocrotaline (60mg/kg). After two weeks, animals were treated for seven days with bucindolol (2mg/kg/day i.p.) or vehicle. At the end of the treatment, animals underwent echocardiographic assessment, catheterisation of the femoral artery and RV, and tissue collection for morphometric and histological evaluation. In the monocrotaline+bucindolol group, there was a decrease in mean pulmonary artery pressure (33%) and pulmonary congestion (21%), when compared to the monocrotaline. Bucindolol treatment also reduced RV pleomorphism, necrosis, fibrosis and infiltration of inflammatory cells. An improvement in RV systolic function was also observed in the monocrotaline+bucindolol group compared to the monocrotaline. In addition, bucindolol promoted a decrease in the cardiac sympathovagal balance (93%) by reducing sympathetic drive (70%) and increasing parasympathetic drive (142%). Bucindolol also reduced blood pressure variability (75%). Our results show that the beneficial effects from bucindolol treatment appeared to be a consequence of the reversal of monocrotaline-induced autonomic imbalance.

Efeitos Agudos da Estimulação Elétrica Funcional e do Treinamento Muscular Inspiratório em Pacientes com Insuficiência Cardíaca: Ensaio Clínico Randomizado Cruzado / Acute Effects of Functional Electrical Stimulation and Inspiratory Muscle Training in Patients With Heart Failure: A Randomized Crossover Clinical Trial

Fundamentos: A insuficiência cardíaca é uma doença multissistêmica que inclui disfunção autonômica. Objetivo: Avaliar os efeitos agudos da Estimulação Elétrica Funcional (EEF) e do Treinamento Muscular Inspiratório (TMI) sobre o controle autonômico, a função endotelial e os níveis de citocinas inflamatórias em pacientes portadores de IC. Métodos: Estudo randomizado cruzado que incluiu 12 pacientes submetidos a três intervenções randomizadas: EEF, TMI, e EEF + TMI, com intervalo de 1 semana entre as sessões. O TMI foi realizado durante 15 minutos, com 30% da pressão inspiratória máxima. A EEF foi realizada nos músculos vasto lateral e vasto medial, a uma frequência de 20Hz durante 30 minutos. O controle autonômico foi medido através de monitorização de pressão batimento por batimento (Finapres); a função endotelial, através da técnica de dilatação mediada por fluxo (DMF); e os níveis de citocinas inflamatórias foram medidos antes e depois de cada sessão. Resultados: O controle autonômico após EEF diminuiu em termos de BF/AF (p=0,01) e BFn.u (p=0,03), e aumentou em termos de RR médio (p=0,005). Observou-se um aumento do RR médio após o TMI (p=0,005) e após EEF+TMI (p=0,02). Não houve diferenças na DMF e na concentração de lactato sérico. Quanto às citocinas, a EEF promoveu uma redução nos níveis de TNF-α (pré versus pós 24 horas, p = 0,05). O TMI resultou em níveis aumentados de IL-10 (pré versus 24 horas pós, p=0,05) e em níveis diminuídos de TNF-α (1 hora pós versus 24 horas pós, p = 0,03). Não houve diferenças quando as duas intervenções foram associadas. Conclusão: EEF, TMI, e EEF + TMI alteraram o controle autonômico, mas não a função endotelial. A EEF e o TMI isoladamente alteraram os níveis de citocinas inflamatórias. Ensaios Clínicos: NCT01325597

Background: Heart Failure is a multisystem disorder, which includes autonomic dysfunction. Objective: To evaluate the acute effects of Functional Electrical Stimulation (FES) and Inspiratory Muscle Training (IMT) on autonomic control, endothelial function and inflammatory cytokine levels in patients with HF. Methods: Randomized crossover trial including 12 patients undergoing three randomized interventions: FES, IMT, and FES+IMT, with a 1-week interval between sessions. IMT was performed for 15 minutes with 30% of the maximal inspiratory pressure. FES was performed in the vastus lateralis and vastus medialis muscles, at 20Hz for 30 minutes. The autonomic control was measured using beat-to-beat blood pressure monitoring (Finapres); the endothelial function, using the flow-mediated dilation technique (FMD); and inflammatory cytokine levels were assessed before and after the sessions. Results: Autonomic control after FES decreased regarding LF/HF (p=0.01) and LFn.u (p=0.03), and increased regarding mean RR (p=0.005). Increased mean RR was observed after IMT (p=0.005) and after FES+IMT (p=0.02). No differences were found in FMD and blood lactate concentration. As regards the cytokines, FES led to a decrease in TNF-α levels (pre vs. 24 hours post, p = 0.05). IMT resulted in increased IL-10 levels (pre vs. 24 hours post, p=0.05) and decreased TNF-α levels (1 hour post vs. 24 hours post, p = 0.03). No difference was observed when the two interventions were associated. Conclusion: FES, IMT, and FES+IMT changed the autonomic control without changing the endothelial function. FES and IMT separately changed inflammatory cytokine levels. Clinical Trials: NCT01325597

Are glucose levels, glucose variability and autonomic control influenced by inspiratory muscle exercise in patients with type 2 diabetes? Study protocol for a randomized controlled trial.

BACKGROUND: Physical exercise reduces glucose levels and glucose variability in patients with type 2 diabetes. Acute inspiratory muscle exercise has been shown to reduce these parameters in a small group of patients with type 2 diabetes, but these results have yet to be confirmed in a well-designed study. The aim of this study is to investigate the effect of acute inspiratory muscle exercise on glucose levels, glucose variability, and cardiovascular autonomic function in patients with type 2 diabetes. METHODS/DESIGN: This study will use a randomized clinical trial crossover design. A total of 14 subjects will be recruited and randomly allocated to two groups to perform acute inspiratory muscle loading at 2 % of maximal inspiratory pressure (PImax, placebo load) or 60 % of PImax (experimental load). DISCUSSION: Inspiratory muscle training could be a novel exercise modality to be used to decrease glucose levels and glucose variability. TRIAL REGISTRATION: ClinicalTrials.gov NCT02292810 .

Effects of vildagliptin compared with glibenclamide on glucose variability after a submaximal exercise test in patients with type 2 diabetes: study protocol for a randomized controlled trial, DIABEX VILDA.

BACKGROUND: Cardiovascular disease, endothelial dysfunction, and oxidative stress are common complications among patients with type 2 diabetes (T2DM). In addition to the average blood glucose concentration, glycemic variability may be an important factor for the development of chronic diabetes complications. Patients with T2DM are treated with various types of oral glucose-lowering drugs. Exercise is considered to benefit the health of both healthy and unhealthy individuals, which has been confirmed by a number of scientific research studies in which the participants' health improved. Our general aim in this study will be to evaluate glucose variability after submaximal exercise test in patients receiving treatment with either vildagliptin or glibenclamide. The specific aims of this study are to evaluate the oxidative stress, endothelial function, and metabolic and cardiovascular responses to exercise under treatment with vildagliptin or glibenclamide. All these responses are important in patients with T2DM. METHODS/DESIGN: This study is a PROBE (Prospective, Randomized, Open-label, Blinded-Endpoint) design clinical trial. The estimated sample needed is 20 patients with T2DM. In addition to the routine treatment (metformin), patients will receive a second drug orally for 12 weeks: the METV group will receive metformin plus vildagliptin (50 mg twice daily), and the METG group will receive metformin plus glibenclamide (5 to 10 mg twice daily.). Before and after intervention, evaluation of glycemic variability, endothelial function, oxidative stress, and metabolic and cardiovascular response will be performed at rest, during and after a submaximal exercise test (30 minutes, with an intensity based at 10% under the heart rate at the second threshold). DISCUSSION: In addition to drug treatment, exercise is recommended for treatment of glycemic control in patients with T2DM, especially for its beneficial effects on blood glucose and HbA1c. Few studies have determined the effects of the association between exercise and oral glucose-lowering drugs. The study will be conducted to assess the metabolic and cardiovascular responses at rest, and during and after submaximal exercise in patients receiving one of two oral glucose-lowering drugs (vildagliptin or glibenclamide). TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01867502 study release date: May-17-2013.

Efficacy of a low dose of estrogen on antioxidant defenses and heart rate variability.

This study tested whether a low dose (40% less than the pharmacological dose of 17-ß estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2 mg), and (3) high dose (HE; 0.5 mg) 17-ß estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy.

Capsaicin-induced metabolic and cardiovascular autonomic improvement in an animal model of the metabolic syndrome.

The metabolic syndrome (MetS) is associated with an increased risk of cardiac mortality, as it is characterised by the clustering of multiple cardiovascular risk factors. Studies have shown that capsaicin (red pepper) may be useful as a nutraceutical, ameliorating metabolic profile and cardiovascular function. The aim of the present study was to investigate the cardiovascular and metabolic effects of orally administered capsaicin in rats with the MetS. Neonate spontaneously hypertensive rats were injected with monosodium glutamate and subjected to one of the following three treatments by oral administration for 14 d, between 27 and 30 weeks: low-dose capsaicin (CAP05, n 18, synthetic capsaicin powder diluted in a vehicle (10 % ethyl alcohol) plus 0·5 mg/kg body weight (BW) of capsaicin); high-dose capsaicin (CAP1, n 19, synthetic capsaicin powder diluted in a vehicle (10 % ethyl alcohol) plus 1 mg/kg BW of capsaicin); control (C, n 18, vehicle). Lee's index, lipid/metabolic profile, and cardiovascular parameters with the rats being conscious, including arterial pressure (AP) and heart rate (HR) variability, as well as aortic wall thickness (haematoxylin and eosin staining) and CD68 (cluster of differentiation 68) antibody levels (monocyte/macrophage immunostaining) were evaluated. Weight, Lee's index, and lipid and metabolic parameters, as well as AP and HR and aortic wall thickness, were similar between the groups. Capsaicin determined HR variability improvement (16·0 (sem 9·0), 31·0 (sem 28·2) and 31·3 (sem 19·0) ms2 for the C, CAP05 and CAP1 groups, respectively, P= 0·003), increased vascular sympathetic drive (low-frequency component of systolic AP variability: 3·3 (sem 2·8), 8·2 (sem 7·7) and 12·1 (sem 8·8) mmHg2 for the C, CAP05 and CAP1 groups, respectively, P< 0·001) and increased α-index (spontaneous baroreflex sensitivity). The present data show that capsaicin did not improve lipid and glucose abnormalities in rats with the MetS. However, beneficial cardiovascular effects were observed with this nutraceutical.

Association between endothelial function and autonomic modulation in patients with Chagas disease.

BACKGROUND: Under homeostatic condition, the autonomic nervous system (ANS), through the release of vasoconstrictor neurotransmitters, and the endothelium, through the release of vasodilating substances, interact to maintain blood vessel tone. However, the association between those two systems in patients with Chagas disease in its indeterminate phase (IChD) has not been studied. OBJECTIVE: To assess the association between autonomic modulation parameters and endothelial function in patients with IChD. METHODS: Thirteen patients with IChD (59.2 ± 11.23 years) and no risk factors for cardiovascular disease were assessed for autonomic modulation by using the blood pressure oscillometric method (Finapress) and the heart rate variability technique (HRV) in the frequency domain. Endothelial function was assessed by use of the brachial artery flow-mediated dilation (FMD) method with high-resolution ultrasound images. RESULTS: In the dorsal decubitus position, correlation of FMD was observed with normalized high-frequency (r = 0.78; p = 0.007) and low-frequency spectral components (r = 0.68; p = 0.01), as well as with sympathovagal balance (r = -0.78; p = 0.004). CONCLUSIONS: Our study indicates the existence of a relationship between the changes in autonomic modulation and endothelial function in patients with IChD.

Associação entre função endotelial e a modulação autonômica em pacientes com doença de chagas / Association between endothelial function and autonomic modulation in patients with chagas disease

FUNDAMENTO: Em condição homeostática, o Sistema Nervoso Autônomo (SNA), pela liberação de neurotransmissores vasoconstritores, e o endotélio, pela liberação de substâncias vasodilatadoras, atuam em sintonia para manter o tônus vascular. Todavia, a associação entre esses dois sistemas em portadores da doença de Chagas na forma indeterminada (DChI) ainda não foi estudada. OBJETIVO: Verificar a associação entre parâmetros referentes à modulação autonômica e à função endotelial em portadores da DChI. MÉTODOS: Treze pacientes com DChI (59,2 ± 11,23 anos) sem fatores de risco para doença cardiovascular foram avaliados para modulação autonômica pelo método oscilométrico da pressão arterial (Finapress) e a análise dos registros mediante a técnica da Variabilidade da Frequência Cardíaca (VFC) no domínio da frequência. A função endotelial foi avaliada pelo método de dilatação mediada pelo fluxo da artéria braquial (DMF), usando imagens de ultrassom de alta resolução. RESULTADOS: Na posição em decúbito dorsal foi observada correlação entre os componentes espectrais de alta (HF) (r = 0,78 p = 0,007) e baixa (LF) frequências normalizadas (r = 0,68 p = 0,01), bem como com o balanço simpatovagal (LF/HF) (r= -0,78 p = 0,004) com a DMF. CONCLUSÃO: Nosso estudo aponta a existência de uma relação entre as alterações na modulação autonômica e na função endotelial em pacientes com Doença de Chagas na forma indeterminada.

BACKGROUND: Under homeostatic condition, the autonomic nervous system (ANS), through the release of vasoconstrictor neurotransmitters, and the endothelium, through the release of vasodilating substances, interact to maintain blood vessel tone. However, the association between those two systems in patients with Chagas disease in its indeterminate phase (IChD) has not been studied. OBJECTIVE: To assess the association between autonomic modulation parameters and endothelial function in patients with IChD. METHODS: Thirteen patients with IChD (59.2 ± 11.23 years) and no risk factors for cardiovascular disease were assessed for autonomic modulation by using the blood pressure oscillometric method (Finapress) and the heart rate variability technique (HRV) in the frequency domain. Endothelial function was assessed by use of the brachial artery flow-mediated dilation (FMD) method with high-resolution ultrasound images. RESULTS: In the dorsal decubitus position, correlation of FMD was observed with normalized high-frequency (r = 0.78; p = 0.007) and low-frequency spectral components (r = 0.68; p = 0.01), as well as with sympathovagal balance (r = -0.78; p = 0.004). CONCLUSIONS: Our study indicates the existence of a relationship between the changes in autonomic modulation and endothelial function in patients with IChD.

Inspiratory muscle training reduces blood pressure and sympathetic activity in hypertensive patients: a randomized controlled trial.

BACKGROUND: Autonomic imbalance, characterized by sympathetic hyperactivity and diminished vagal tone, is a known mechanism for essential hypertension. Inspiratory muscle training (IMT) demonstrates beneficial outcomes in a number of cardiovascular populations, which may potentially extend to patients with hypertension. The aim of this study was to further elucidate the effects of IMT on blood pressure and autonomic cardiovascular control in patients with essential hypertension. METHODS: Thirteen patients with hypertension were randomly assigned to an eight-week IMT program (6 patients) or to a placebo-IMT (P-IMT, 7 patients) protocol. We recorded RR interval for posterior analysis of heart rate variability and blood pressure, by ambulatory blood pressure monitoring (ABPM), before and after the program. RESULTS: There was a significant increase in inspiratory muscle strength in the IMT group (82.7 ± 28.8 vs 121.5 ± 21.8 cmH2O, P<0.001), which was not demonstrated by P-IMT (93.3 ± 25.3 vs 106.1 ± 25.3 cmH2O, P>0.05). There was also a reduction in 24-hour measurement of systolic (133.2 ± 9.9 vs 125.2 ± 13.0 mm Hg, P=0.02) and diastolic (80.7 ± 12.3 vs 75.2 ± 1.0 mm Hg, P=0.02) blood pressure, as well as in daytime systolic (136.8 ± 12.2 vs 127.6 ± 14.2 mm Hg, P=0.008) and diastolic (83.3 ± 13.1 vs. 77.2 ± 12.2 mm Hg, P =0.01) blood pressure in the IMT group. In relation to autonomic cardiovascular control, we found increased parasympathetic modulation (HF: 75.5 ± 14.6 vs. 84.74 ± 7.55 n.u, P=0.028) and reduced sympathetic modulation (LF: 34.67 ± 20.38 vs. 12.81 ± 6.68 n.u; P=0.005). Moreover, there was reduction of cardiac sympathetic discharge (fLF) in IMT group (P=0.01). CONCLUSIONS: IMT demonstrates beneficial effects on systolic and diastolic blood pressure as well as autonomic cardiovascular control in hypertensive patients.