Search Results (151)

Sex differences and lifestyle factors such as physical activity play an important role in cardiovascular autonomic regulation. Heart rate variability (HRV) is a widely used marker of cardiac autonomic modulation and cardiovascular health. However, the combined influence of sex and physical activity levels on HRV in young, healthy adults has not been sufficiently explored. Therefore, this study investigated the effects of sex and a physically active lifestyle on HRV in men and women. A cross-sectional study was conducted on a cohort of young, healthy adults aged 18–30 and categorized into four groups based on: physically active men (AM; n = 37), sedentary men (SM; n = 44), and physically active women (AW; n = 31) and sedentary women (SW; n = 40). Regarding the impact of lifestyle, the AM group exhibited 41% higher total variance (VAR-RR) and 34% higher RMSSD (a parasympathetic index) than the SM group. The AW exhibited 74% and 78% higher VAR-RR and RMSSD, respectively, compared to the SW. Furthermore, the physically active groups (AM and AW) displayed a 75% and 50% lower LF/HF ratio, respectively, compared to their sedentary counterparts. Interestingly, the LF/HF ratio was 66% higher, and the RMSSD was 20% lower in the AM group than in the AW group. HRV indices demonstrated large to very large effect sizes. In conclusion, these findings demonstrate significantly advantage in cardiac autonomic modulation among physically active individuals and women. Together, these results reinforce the roles of female sex and an active lifestyle as important protective factors for cardiovascular health. Full article

Background: Heart rate variability (HRV), the physiological variation between consecutive heartbeats and a non-invasive marker of autonomic regulation, is associated with cardiovascular health. This retrospective cross-sectional study investigated the associations of severe obesity, hypertension, and physical activity with 24 h HRV in patients undergoing evaluation for bariatric surgery. Methods: A total of 1048 individuals were classified according to obesity class, hypertension diagnosis, and physical activity level. Results: Severe obesity was associated with lower 24 h HRV indices (p < 0.001) and higher odds ratio of hypertension (OR 2.04 [1.60–2.63]) and antihypertensive medication use (OR 1.98 [1.53–2.58]) compared to class II obesity. Hypertension was associated with lower HRV indices (p < 0.001), higher odds of diabetes (OR 4.20 [2.88–6.12]) and dyslipidemia (OR 2.85 [2.17–3.74]), greater use of related medications (OR 3.53 [2.18–5.70)] and 2.96 [1.99–4.40]), respectively), and lower physical activity (OR 0.64 [0.47–0.87]). Physical activity was associated with higher 24 h HRV indices (p < 0.001) and lower odds of hypertension (OR 0.64 [0.47–0.87]) and antihypertensive medication use (OR 0.70 [0.50–0.97]). Conclusions: Severe obesity and hypertension were associated with reduced 24 h HRV, whereas physical activity was associated with more favorable HRV parameters in adults undergoing evaluation for bariatric surgery, supporting its relevance for cardiovascular health in this population. Full article

Previous studies on healthy controls suggest the added value of thigh-based Electrocardiography (ECG), which collects data using sensors embedded in a toilet seat for unobtrusive signal acquisition. However, further evidence regarding its clinical feasibility is needed; with this work, we investigated three complementary aspects: signal quality, morphological correlation with standard ECG leads, and the system’s potential for heart rate variability (HRV) analysis in patients undergoing aortic valve replacement. This work was divided into two main phases. In the first, 32 healthy volunteers underwent simultaneous ECG recordings using both a standard 12-lead ECG system and the thigh-based system. Signal Quality Index (SQI) analysis revealed that 56.25% of the experimental signals were classified as excellent, and over 62.5% of recordings showed a strong correlation with Lead I of the clinical ECG. These findings extend the state of the art by further characterising the quality and relevance of the captured signals. In the second phase, two patients with severe aortic stenosis were monitored before and after surgical valve replacement. HRV metrics derived from the thigh-based ECG captured distinct autonomic responses: one patient showed significant postoperative improvement in global and parasympathetic modulation (increased SDNN, RMSSD, and Sample Entropy), while the other exhibited reduced variability and complexity, potentially indicating impaired autonomic recovery. These results highlight the feasibility of thigh-based ECG data acquisition for passive, longitudinal cardiac health monitoring in everyday environments and its applicability for pre- and postoperative autonomic assessment. Full article

Background/Objective: Cardiac innervation plays a critical role in regulating myocardial function and enabling the heart to adapt to physiological and pathological conditions. Although the general features of sympathetic and parasympathetic innervation of the myocardium are well described, the spatial organisation of nerve fibres within the cardiac muscle remains incompletely characterised. This study aimed to develop and validate the SKUF (Slice–Keep–Unwrap–Fuse) protocol, a multimodal framework for mapping myocardial innervation through the integration of histological data and magnetic resonance imaging (MRI). Methods: The study was performed on the heart of a 7-year-old patient who died from rupture of a cerebral vascular malformation without evidence of cardiovascular disease. Prior to histological processing, post-mortem MRI was performed to provide a precise anatomical reference. The heart was sectioned into sequential transverse rings of 4 mm thickness, yielding 71 paraffin blocks. Histological sections (3 μm) were immunostained with antibodies against UCHL-1 to visualise nerve fibres and scanned using an Aperio AT2 system (20× magnification). Automated image analysis was conducted using the SVSSlide Processor module, which included tissue segmentation, colour-based nerve fibre detection, and sliding-window density mapping. Heatmaps were assembled into ring-based myocardial reconstructions and co-registered with MRI slices using combined rigid and deformable registration, followed by three-dimensional reconstruction of innervation patterns. Results: A higher density of nerve fibres was observed in the right ventricular myocardium compared with the left ventricle, whereas larger nerve trunks were identified in the epicardium of the left ventricle. Quantitative analysis revealed a pronounced longitudinal gradient of innervation, with minimal density in the apical region and progressive increases towards the mid-ventricular segments, where maximal density and spatial organisation of neural structures were observed. The atrioventricular groove exhibited the greatest heterogeneity of innervation due to the presence of large nerve trunks and ganglionated plexuses. Integration of histological maps with MRI enabled three-dimensional visualisation of spatial clusters of nerve fibres. Conclusions: The SKUF protocol provides a robust framework for integrating histological and MRI data to generate three-dimensional maps of myocardial innervation. This approach may facilitate the development of high-resolution anatomical atlases of cardiac innervation and support future studies of neurocardiac mechanisms of arrhythmogenesis and targeted neuromodulation. Full article

Background: Metabolic syndrome (MetS) leads to alterations in cardiac autonomic control that can be detected from electrocardiogram (ECG)-derived markers, particularly when the cardiovascular system is challenged during an oral glucose tolerance test (OGTT). Methods: In this paper, we present an automated framework for MetS identification using RR intervals and heart rate variability (HRV) features extracted from 12-lead ECG recordings acquired during the five OGTT stages in 40 male participants (15 with MetS, 10 controls, and 15 endurance-trained marathon runners). RR intervals were first derived using a multilead Pan-Tompkins approach with fusion-based validation. From these RR series, HRV descriptors were computed from time-domain statistics (RR mean, SDNN, rMSSD, pNN50), spectral indices (VLF, LF, HF, LF/HF), and nonlinear measures (SD1, SD2, SampEn, DFA-${\alpha }_1$). Conventional HRV analysis revealed pronounced physiological differences between groups: MetS subjects exhibited reduced parasympathetic activity, reflected by lower rMSSD and SD1, lower HF power, and higher LF/HF ratios, whereas marathoners showed greater vagal modulation, higher HF power, and increased signal complexity. Healthy controls showed an intermediate autonomic profile. Using RR sequences and HRV descriptors (256 samples per stage), we trained three multimodal classifiers: a CNN-MLP model with a softmax output, a CNN-MLP model with an SVM head, and a CNN + LSTM-MLP + SVM architecture. Results: All models achieved strong discriminative performance, with accuracies ranging from 0.92 to 0.95, F1-macro values from 0.92 to 0.95, and macro-AUC values from 0.96 to 0.97. The CNN-MLP model achieved the best overall performance, whereas the CNN + LSTM-MLP + SVM model showed strong class discrimination, particularly for endurance athletes, while maintaining competitive recall for MetS. Conclusions: These findings support the feasibility of ECG-based autonomic assessment as a complementary non-invasive approach for early metabolic risk detection in clinical and preventive cardiometabolic screening settings. Full article

Objective: This study aimed to investigate the acute effects of intermittent high-intensity badminton court exercise on cardiac autonomic modulation in male non-elite badminton players. Methods: This study employed a single-arm, repeated-measures experimental design, recruiting 25 healthy male collegiate badminton players. Participants completed five sets of high-intensity intermittent court tests until exhaustion, followed by calculation of stress index (SI), time-domain (RMSSD and SDNN), and frequency-domain (LF, HF, and LF/HF ratio) parameters at rest using a certified heart rate variability (HRV) analyzer. Repeated-measures ANOVA and effect size (partial η² and Hedges’ g) were used to assess changes and recovery trends of HRV parameters across time points: pre-test, immediate, 15 min, 24 h, and 48 h post-exercise. Results: (1) Stress index: The overall temporal trend showed statistical significance (p < 0.001, partial η² = 0.236, large effect size). Compared to pre-test, immediate and 15 min post-exercise increases were 8.24 (95% CI: 0.63–15.85) and 9.84 (95% CI: 3.07–16.61) respectively, with Hedges’ g values of 0.77 and 0.99 (p < 0.001, large effect sizes). Values returned to pre-test levels at 24 and 48 h with no significant differences (p > 0.05). (2) Time-domain parameters: The overall temporal trend was statistically significant (p < 0.001, partial η² = 0.553 for RMSSD and 0.586 for SDNN, both large effect sizes). Immediate post-exercise decreases in RMSSD and SDNN were 35.44 (95% CI: 21.95, 48.93) and 48.44 (95% CI: 32.49, 64.38) respectively, with Hedges’ g values of 2.31 and 2.78 (p < 0.001, large effect sizes). At 15 min, decreases were 31.64 (17.85, 45.42) and 41.48 (26.23, 56.72) respectively, with Hedges’ g values of 1.99 and 2.25 (p < 0.001, large effect sizes). Values returned to pre-test levels at 24 and 48 h with no significant differences (p > 0.05). (3) Frequency-domain parameters: Compared to pre-test, differences in LF, HF, and LF/HF were not statistically significant at any time point (all p > 0.05). Conclusions: Following high-intensity exercise leading to peripheral fatigue, cardiac autonomic function demonstrates a “suppression–recovery” dynamic pattern: cardiac stress levels increase significantly within 15 min post-exercise, with decreased overall HRV regulatory capacity and strong inhibition of parasympathetic activity; HRV status may return to baseline levels after 24 h. However, the frequency-domain indices of HRV showed no significant changes in response to the acute effects of high-intensity exercise. Full article

Type 2 diabetes mellitus is associated with major cardiovascular complications, including cardiac autonomic neuropathy, which contributes to sympathetic–parasympathetic imbalance and increases susceptibility to arrhythmias and sudden cardiac death. Heart rate variability, assessed through R–R intervals on electrocardiography and 24 h Holter monitoring, represents a sensitive, non-invasive marker of autonomic dysfunction and arrhythmogenic risk. In patients with type 2 diabetes mellitus, chronic hyperglycaemia, oxidative stress, and metabolic inflammation lead to early impairment of the autonomic nervous system, manifested by consistent reductions in SDNN, RMSSD, pNN50, total power, and the high-frequency component, indicating diminished parasympathetic tone and sympathetic predominance. Nonlinear HRV indices demonstrate a loss of complexity and fractal organisation, providing additional prognostic value beyond conventional time- and frequency-domain analyses. Reduced HRV correlates with the severity of cardiac autonomic neuropathy, duration of diabetes, and poor glycaemic control, identifying patients with increased arrhythmogenic vulnerability. HRV analysis enables prediction of arrhythmic risk, facilitating the identification of high-risk individuals and guiding personalised interventions. The integration of HRV assessment into routine clinical practice may improve the early detection of subclinical autonomic neuropathy and optimise cardiovascular risk stratification and management in patients with type 2 diabetes mellitus. Full article

Background/Objectives: Aortic stenosis is associated with autonomic nervous system (ANS) imbalance, while diabetes mellitus is a major contributor to cardiac autonomic neuropathy. Their coexistence may result in more pronounced autonomic dysfunction not fully captured by conventional assessment. This study aimed to compare ANS function in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement (TAVR), according to diabetes status. Methods: This cross-sectional study included 74 patients with severe aortic stenosis referred for TAVR, including 21 patients with diabetes mellitus. Autonomic function was evaluated using non-invasive ECG-based analysis, incorporating short-term and 24 h Holter-derived heart rate variability (HRV), nonlinear Poincaré plot indices, and deceleration and acceleration capacity. Ambulatory blood pressure monitoring and standard clinical and echocardiographic assessment were performed. Results: Patients with diabetes mellitus demonstrated significantly lower long-term HRV parameters and reduced nonlinear Poincaré plot indices compared with non-diabetic patients, indicating altered autonomic modulation. Short-term HRV showed similar trends without statistical significance. Echocardiographic severity of aortic stenosis and left ventricular systolic function were comparable between groups. Conclusions: Autonomic dysfunction appears to be more pronounced in patients with severe aortic stenosis and diabetes mellitus, predominantly affecting parasympathetic modulation. ECG-derived autonomic parameters may offer complementary insight into ANS involvement in this population and warrant further investigation. Full article

The autonomic nervous system (ANS) plays a key role in cardiovascular regulation by maintaining hemodynamic and metabolic homeostasis through balanced sympathetic and parasympathetic activity. While autonomic dysfunction is classically associated with diabetes, neurodegenerative diseases, autoimmune neuropathies, and chronic cardiovascular conditions, growing evidence suggests that disturbances in iron metabolism represent an underrecognized contributor to cardiac autonomic dysregulation. This narrative review summarizes data from 107 studies on ANS disorders, including 49 investigating cardiovascular involvement. Reported abnormalities included reduced heart rate variability and baroreflex sensitivity, prolonged P-wave duration and QT dispersion, and deviations in non-invasive autonomic testing parameters. In iron overload states, these changes appear to be driven primarily by oxidative stress, whereas in iron deficiency they are likely mediated by tissue hypoxia. Importantly, several studies indicate that normalization of iron homeostasis may partially reverse autonomic dysfunction. This potentially reversible component underscores the clinical relevance of screening for and correcting iron imbalance not only to improve hematological status but also to reduce cardiovascular risk. Large-scale, multicenter studies using standardized autonomic assessment protocols are required to clarify prognostic implications and inform evidence-based clinical guidelines. Full article

Background: Frailty is a multifactorial condition that significantly impacts older adults’ health and independence, which can be mitigated through training. This study examined the effects of a 12-week progressive strength training (PST) program on frailty status and short-term autonomic compensatory responses during postural transitions. Methods: Eight older adults (60–79 years) classified as pre-frail or frail according to the frailty index (FI) participated in a 12-week PST program. Time and frequency-domain heart rate variability (HRV) in the supine position, cardiac parasympathetic modulation (CPM) determined from the HR 30:15 ratio (longest RR interval around the 30th heartbeat divided by the shortest RR interval around the 15th heartbeat after standing), and cardiac baroreceptor gain (CBG) assessed as the ratio of heart rate change to systolic blood pressure drop (ΔHR/ΔSBP) at 30, 60, 180, and 420 s after standing were assessed at pre-test, 8 weeks and 12 weeks (autonomic function outcomes). Physical activity levels (PAL), handgrip strength (HGS), and gait speed (GS) were assessed, and orthostatic intolerance (OI) symptoms were self-reported at pre-test, 8 weeks, and 12 weeks. Results: After 12 weeks of PST, FI scores decreased from 0.18 to 0.04 (78% reduction). PAL, HGS, and GS improved by 152%, 13%, and 11%, respectively. Three of eight participants reported OI symptoms at pre-test, with no reported symptoms at week 12. Despite this, PST did not enhance short-term autonomic responses. Conclusions: PST counteracted frailty and improved physical and muscular function but did not enhance indices of short-term autonomic regulation in frail older people. Full article

The objective of this paper was to review the possibility that the QT interval may be a marker of adult human longevity or life expectancy. Following a literature review, data supporting this possibility was assembled and consists of the following. First, in adults, QT interval increases with increasing age. This is analogous to aging-induced hypertension and diabetes mellitus, both of which are associated with shorter longevity. Second, older persons frequently die suddenly regardless of whether or not they have chronic illnesses for which death is expected. Third, longer QTintervals are associated with increased probability of sudden death. Fourth, patients with two conditions associated with accelerated brain aging, namely dementia and Parkinson’s disease, show longer QTcs than age-matched controls. Both of these conditions are associated with sudden cardiac death. Fifth, aging processes may affect the molecular determinants of the QT interval, alter heart composition with increased myocardial fibrosis, or alter the amount of sympathetic and parasympathetic tone, any or all of which can alter myocardial repolarization and the duration of the QTc. Sixth, considering the molecular determinants of the QT interval in the aging heart, which has longer transmembrane action potentials, several factors can account for this change, including changes in late inward Na⁺ current (I_NaL), I_Kr, I_ca, I_to, and K_ATP channels. Transgenic mice overexpressing the Kir6.1 subunit of a K_ATP channel show a prolonged QT interval and reduced longevity, with animals appearing to die suddenly. Seventh, chronic kidney disease, which is associated with a reduced lifespan, is associated with reduced expression of the anti-aging factor Klotho and Klotho-deficient mice have a prolonged QTc and a reduced lifespan. Taken together, there is a cogent case for factors that increase action potential duration in the aging heart, as recognized by increased QTc, to act in concert with other factors to produce fatal arrhythmias leading to sudden cardiac death and shortened longevity. Full article

Heart rate variability (HRV) reflects autonomic nervous system (ANS) activity and provides insight into physiological and emotional regulation. Evaluating HRV during postural and emotional challenges may help characterize autonomic adaptability in healthy individuals. HRV was recorded in 24 young medical residents (17 females, 7 males; mean age 27.04 ± 1.97 years) during four conditions: rest, orthostatic standing, and exposure to positive and negative emotional images. Each session lasted five minutes. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale. Heart rate increased significantly only during standing, consistent with sympathetic activation with postural change. Spectral and normalized HRV parameters (nLF, nlf, LF/HF, and normalized coherence) were lowest at rest and increased during standing and emotional image exposure, particularly in males. Parasympathetic indices showed opposite trends. Emotional image exposure did not produce significant differences between positive and negative valence at the group level; however, sex- and anxiety-related patterns emerged. Females with anxiety showed increased heart rate during positive image exposure, whereas non-anxious females exhibited higher heart rate responses to negative images. Orthostatic challenge elicited the strongest autonomic response, whereas emotional visual stimuli induced subtler, sex- and anxiety-dependent autonomic modulation without overall changes in heart rate. These preliminary observations suggest that anxiety and sex may be associated with differences in cardiac autonomic regulation in young healthy adults. These results should be interpreted cautiously, given the pilot design, the small sample size (N = 24), the imbalance between sexes, the exclusion of the depression subgroup from inferential analyses, and the use of non-validated emotional visual stimuli Full article

Background/Objectives: Cardioneuroablation (CNA) is used to treat reflex syncope by parasympathetic denervation of the cardiac conduction system. Respiratory heart rate variability (RespHRV) constitutes an important physiological mechanism that optimizes lung perfusion. The impact of CNA on various components of RespHRV remains unclear. Methods: Eleven subjects (36.8 ± 14.1 years) undergoing CNA for the treatment of cardioinhibitory, vagally mediated syncope were enrolled. For the RespHRV assessment, we used continuous respiratory flow measurement and an electrocardiogram. RespHRV analysis included the following: (a) amplitude, reflecting the overall magnitude of changes in RR interval during the respiratory cycle (RespHRVpv, ms); and (b) efficiency, defined as the percentage of inspirations accompanied by RR shortening (short-RRi inspirations, %), and expirations accompanied by RR prolongation (long-RRi expirations, %). Baroreflex sensitivity (BRS, ms/mmHg) was assessed with a sequential method using a noninvasive hemodynamic monitor. Both RespHRV and BRS were captured 48 h apart, before and after CNA. Results: A significant reduction was observed in RespHRVpv (57 [30–131] vs. 13 [7–16] ms, p = 0.003), short-RRi inspirations (97.0 [77.8–100.0] vs. 36.0 [14.3–63.2] %, p = 0.003), and long-RRi expirations (88.0 [78.1–97.6] vs. 31.1 [21.4–65.8] %, p = 0.008). Moreover, we found a strong relationship between ΔBRS and ΔRespHRVpv (r = 0.77, p = 0.005) following CNA. Conclusions: Our results indicate a substantial role of the cardiac parasympathetic system in RespHRV development, including both its amplitude and efficiency. The marked decrease in key RespHRV measures after CNA highlights the need for further research into its long-term clinical effects. Full article

Background and Objectives: Diabetes mellitus (DM) is a major risk factor for cardiovascular diseases (CVD), including acute myocardial infarction (MI), and is frequently associated with cardiac autonomic neuropathy (CAN). Post-MI autonomic dysfunction contributes to adverse outcomes, but data on prognostic markers in diabetic patients remain limited. This study aimed to (1) compare autonomic nervous system (ANS) function between patients with MI and DM (MI/DM), MI without DM, and DM without MI; (2) assess differences in MI/DM patients based on survival status; and (3) identify prognostic factors for all-cause mortality in diabetic patients following MI. Materials and Methods: This retrospective–prospective study included 375 patients: 93 MI/DM, 229 MI, and 53 DM. MI patients were treated with fibrinolytic or conservative therapy. All participants underwent cardiovascular reflex tests (CARTs) and 24 h Holter ECG with heart rate variability (HRV) analysis; DM patients without MI were tested in an outpatient setting. The primary endpoint was all-cause mortality during a median follow-up of 38 months. Univariable and multivariable Cox regression analyses were performed to determine mortality predictors. Results: Autonomic dysfunction was prevalent in all groups, with MI/DM patients showing the most pronounced impairment, particularly in parasympathetic function. MI/DM patients had significantly lower SDNN values and higher prevalence of definite parasympathetic dysfunction than other groups. In the MI/DM group, abnormal Valsalva maneuver (VM) was more frequent among non-survivors. Multivariable analysis identified abnormal VM and NSTEMI as predictors of overall mortality. Conclusions: Diabetic patients after MI exhibit the most severe autonomic impairment, predominantly parasympathetic, which may contribute to their increased cardiovascular risk. In this high-risk group, abnormal VM and NSTEMI presentations independently predict long-term mortality. Assessment of autonomic function, particularly VM, may provide valuable prognostic information and aid in risk stratification. Full article

Conventional and electronic cigarette (e-cig) users face an increased risk of cardiorespiratory diseases, driven by well-characterized pathways involving inflammation and oxidative stress (OS). Conventional cigarettes contain numerous harmful chemicals, such as nicotine and non-nicotine compounds, which produce reactive oxygen species. Although initially considered a safer alternative, the e-cig still generates toxic aldehydes that are capable of triggering oxidative responses. Heart rate variability (HRV) is an important tool for assessing autonomic function and predicting prognosis. Cardiac autonomic dysfunction, indicated by reduced HRV, has emerged as a critical cardiovascular risk factor associated with several diseases. Clinical and experimental studies show that increased OS is directly associated with heightened sympathetic activity and inversely with parasympathetic modulation. This review demonstrates that exposure to conventional cigarettes smoking and e-cigs adversely affects cardiac autonomic function, detectable by a global reduction in HRV that reflects a shift toward sympathetic dominance and a consequent increase in cardiovascular risk. These changes are associated with increased OS due to nicotine and non-nicotine compounds maintaining sympathovagal imbalance in smokers. Thus, we suggest that autonomic dysfunction, detected by HRV, correlates with oxidative responses and may be used as a modifiable risk factor in longitudinal studies involving both smoking modalities. Full article