Effect of winter swimming on the cardiovascular system: adaptive mechanisms and potential hazards.

Objective — The aim of this study was to investigate the heart rate variability (HRV) parameters in patients with neurally mediated reflex syncope.Methods — Thirty-three patients (10men, age range 16-50years) who were scheduled to undergo head-upright tilt test (HUTT) with a typical history of vasovagal syncope (VVS) underwent 24-hour Holter monitoring in an attempt to study HRV parameters. Sixteen individuals without syncope and similar baseline characteristics made up the control group.Results — Seventeen of the 33syncopal patients showed HUTT positivity. All the time domain HRV parameters except the mean RR interval were higher in the HUTT (+) syncopal patients than in the negative responders. Although not statistically significant, the positive responders had higher NN50, pNN50, RMSSD and SDNNi values than the control group. HUTT (-) VVS patients had lower SDNN and SDANN values when compared with the control group.The other HRV parameters did not differ significantly between the HUTT (-) patients and the control group.Conclusion — Increased parasympathetic tonus as reflected by significantly higher HRV parameters is associated with a greater frequency of HUTT positivity in patients with syncope and no organic heart disease.

ABSTRACTObjective: To investigate the association between heart rate variability (HRV) parameters with leisure time and commuting physical activities in adolescent boys. Methods: The sample included 1152 male adolescents aged 14 to 19 years. The variation of consecutive heart beats (RR intervals) was assessed and HRV parameters in time (SDNN, RMSSD, pNN50) and frequency domains (LF/HF) were calculated. Leisure time and commuting physical activities were obtained using a questionnaire. A binary logistic regression was performed between HRV parameters and physical activity. Results: Leisure time physical activity was associated with SDNN, RMSSD, pNN50, while LF/HF was not associated. These associations were stronger when adolescents were also physically active for more than six months. Commuting physical activity was not associated with any HRV parameter. Boys who practiced commuting physical activity and were also physically active for more than six months presented a lower chance of having low SDNN and RMSSD. Conclusions: Leisure time physical activity was associated with better HRV and these associations were enhanced when adolescents were physically active for more than six months. Commuting physical activity was not associated with HRV parameters; however, it became associated with better HRV when adolescents were physically active in commuting for more than six months.

Background:Acute ischemic stroke (AIS) induces adverse effects on the cardiovascular system by affecting the autonomic nervous system (ANS).Objectives:This study aimed to determine whether the parameters of heart rate variability (HRV) and heart rate turbulence (HRT) differed in patients with AIS as compared to that in the control group. Furthermore, we aimed to determine the differences in the involvement of the ANS between right and left hemisphere (LH) strokes.Methods:A total of 148 [74 right hemispheres (RH) and 74 left hemispheres] patients with AIS and 80 control subjects were included in the study. The Holter device was used to obtain elcctrocardiogram readings for over 20 h from all patients. Results of HRV and HRT parameters [Tonset (TO) and Tslope (TS)] were acquired through an automatic analysis of the program.Results:All HRV parameters were found to be low in patients with AIS (P < 0.05, for all parameters). TO and TS were disrupted in 99 patients with AIS (66.8%) and in 15 control subjects (18.7%) (HRT–1 and HRT–2 groups, P = <0.001). HRV parameters were detected to be similar in patients, irrespective of the left or right infarct. TO and TS were normal in 31 patients (41.9%) with left hemisphere localization and in only 18 patients (24.3%) with right hemisphere localization.Conclusions:Combined evaluation of HRV and HRT parameters may provide important information regarding the alterations in the ANS in patients with AIS. The utility of HRT in the determination of ANS alterations in patients with AIS should be investigated in larger future prospective studies.

Heart rate variability in young, clinically healthy Dachshunds: influence of sex, mitral valve prolapse status, sampling period and time of day

Subclinical hypothyroidism and hyperthyroidism have been recognized as clinical entities with negative effects on the cardiovascular system. Moreover, the effect of treated thyroid dysfunction on parameters associated with the cardiovascular control system has been poorly investigated. In the present study we analyzed time-domain heart rate variability in coronary artery disease (CAD) patients with known thyroid diseases. Twenty-four hour ECG monitoring was performed in 344 patients with coronary artery disease (174 with thyroid dysfunction and 170 without thyroid dysfunction used as a control group), using a 3-channel tape recorder. Time domain parameters of heart rate variability (HRV) were definitely lower both in patients with subclinical hypothyroidism and subclinical hyperthyroidism than in the control group, with statistically significant differences in SDNN, RMSSD, TINN, and mean RR for both subgroups. Furthermore, patients on L-thyroxine treatment and restored euthyroidism had generally higher HRV values than patients with subclinical hypothyroidism, nevertheless SDNN, RMSSD, SDNN index, TINN, and mean RR were significantly lower when compared to those of the control group. Significant differences in HRV were also found between hyperthyroid patients under treatment and control group subjects with respect to RMSSD, TINN, and mean RR values. In conclusion, patients with cardiac disease and known thyroid disease, even when the disease is in the subclinical range or despite treatment, should be regarded as patients at additional risk conveyed by thyroid hormone disturbances.

Introduction and purpose Over the years winter swimming has gained popularity, becoming an eagerly practiced form of physical activity. This review aims to examine its influence on the human organism and explore the mechanisms of adaptation developed by winter swimmers. Materials and methods This work is based on the analysis of the materials obtained from “PubMed” and “Google Scholar” scientific databases using the key words selected based on their relevance to examining the matter in subject, such as: cold adaptation, cold water immersion, ice swimming, hypothermia, winter swimming The state of knowledge Investigated studies indicate that winter swimming influences human organism in various aspects, having a completely different impact depending on previous cold-water exposures, health status and individual adaptation. Winter swimmers tend to develop a wide range of compensatory mechanisms including hormonal, metabolic and immunological changes, improved thermoregulation and enhanced antioxidative protection. In contrast, for unadopted individuals cold water immersions may lead to severe complications including hypothermia and even fatal consequences. Conclusions Winter swimmers develop mechanisms of cold adaptation that enable them to perform and benefit from such activity. However, proper adjustment, following preventive measures and guidelines such as gradual, regular adaptation, warm-up exercises and being aware of individual health status are vital to minimize detrimental effects that concern especially inexperienced individuals.

Objectives: To assess cardiovascular autonomic nervous system function of patients post-brain-injury in the sub-acute phase during a physiotherapy session (PTS).Participants: Fourteen patients post-ischaemic stroke and 11 post-severe traumatic brain injuries.Intervention: Continuous electrocardiogram recording at rest, during active cycling and during routine PTS.Main outcome measure: Heart rate (HR) and Heart rate variability (HRV) parameters included the standard deviation of all R-R intervals (SDNN), the square root of the mean squared differences of successive differences (RMSSD), the Low-frequency (LF) power, High-frequency (HF) power and the LF/HF ratio.Results: The median HR at rest was 76 bpm (interquartile range 61–81). Significant increments were noted during activities; median HR during cycling was 93 bpm, during the most intense activity 91 bpm (p-value < 0.001). A significant decline in HRV parameters’ median values during cycling and PTS was observed only among patients post-stroke.Conclusions: Among patients post-brain injury, HR increased significantly during PTS in different activities and varied positions; therefore, therapists should be aware and monitor HR frequently during training. In addition, HRV values were low at rest and did not respond to activity among patients post-TBI, compared with higher values at rest and some response among patients post-stroke. This may indicate that autonomic impairment post-brain insult is more likely a consequence of central nervous system damage and less likely a result of pre-event cardiovascular illness.

Impact of type of intervention for aortic valve replacement on heart rate variability

Heart rate variability (HRV) parameters are an important indicator of cardiovascular health. While it has been well established that aerobic exercise improves HRV, the effects of resistance training on HRV remain less explored. To compare the impact of a resistance training routine on HRV parameters in physically active young adults. This observational study included 24 participants, 12 who underwent resistance training and a control group of 12 who underwent moderate-intensity exercise. HRV was assessed during a 15-minute resting period in the supine position with a Polar RS800CX heart rate monitor. The analysis encompassed time-domain metrics (root mean square of successive differences between adjacent normal R-R intervals [RMSSD] and the standard deviation of normal-to-normal R-R intervals [SDNN]), frequency-domain metrics (high-frequency and low-frequency indices, both expressed in normalized units, and the low-frequency/ high-frequency ratio), and non-linear metrics (SD of the Poincaré plot width [SD1] and the SD of the Poincaré plot length [SD2]). HRV parameters were processed in Kubios HRV. Statistical analysis included unpaired t-tests, with significance set at p < 0.05. The resistance-trained group demonstrated significantly higher RMSSD (75.3 [SD, 28.5] ms) and SDNN (65.8 [SD, 23.1] ms) values than the untrained group (RMSSD: 37.5 [SD, 19.6] ms; SDNN: 40.2 [SD, 14.2] ms; p < 0.01). SD1 and SD2 were also significantly higher in the resistance training group than the control group, reflecting greater parasympathetic activity. Long-term resistance training was associated with improved parasympathetic modulation, indicating potential cardiovascular benefits and enhanced autonomic function.

Recent studies have linked low heart rate variability (HRV) with COVID-19, indicating that this parameter can be a marker of the onset of the disease and its severity and a predictor of mortality in infected people. Given the large number of wearable devices that capture physiological signals of the human body easily and noninvasively, several studies have used this equipment to measure the HRV of individuals and related these measures to COVID-19. The objective of this study was to assess the utility of HRV measurements obtained from wearable devices as predictive indicators of COVID-19, as well as the onset and worsening of symptoms in affected individuals. A systematic review was conducted searching the following databases up to the end of January 2023: Embase, PubMed, Web of Science, Scopus, and IEEE Xplore. Studies had to include (1) measures of HRV in patients with COVID-19 and (2) measurements involving the use of wearable devices. We also conducted a meta-analysis of these measures to reduce possible biases and increase the statistical power of the primary research. The main finding was the association between low HRV and the onset and worsening of COVID-19 symptoms. In some cases, it was possible to predict the onset of COVID-19 before a positive clinical test. The meta-analysis of studies reported that a reduction in HRV parameters is associated with COVID-19. Individuals with COVID-19 presented a reduction in the SD of the normal-to-normal interbeat intervals and root mean square of the successive differences compared with healthy individuals. The decrease in the SD of the normal-to-normal interbeat intervals was 3.25 ms (95% CI -5.34 to -1.16 ms), and the decrease in the root mean square of the successive differences was 1.24 ms (95% CI -3.71 to 1.23 ms). Wearable devices that measure changes in HRV, such as smartwatches, rings, and bracelets, provide information that allows for the identification of COVID-19 during the presymptomatic period as well as its worsening through an indirect and noninvasive self-diagnosis.

To compare heart rate variability (HRV) parameters in newly diagnosed and untreated temporal lobe epilepsy (TLE) between the interictal, preictal, ictal, and postictal states. HRV parameters were extracted from single-lead electrocardiography data collected during video-electroencephalography (EEG) recordings from 14 patients with newly diagnosed TLE in a resting, awake, and supine state. HRV parameters in the time and frequency domains included low frequency (LF), high frequency (HF), standard deviation of all consecutive R wave intervals (SDNN), and square root of the mean of the sum of the squares of differences between adjacent R wave intervals (RMSSD). Cardiovagal index (CVI), cardiosympathetic index (CSI), and approximate entropy (ApEn) were also studied. Frequency domain analysis showed significantly higher preictal, ictal, and postictal LF/HF ratio compared to the interictal state. Similarly, the LF component increased progressively and was significantly higher during the ictal state compared to interictal and preictal states. RR interval values were lower in the ictal state compared to basal and preictal states and in the postictal state compared to the preictal state. Interictal RMSSD was significantly higher compared to all other states, and ictal SDNN was significantly higher compared to all other states. Ictal CSI was significantly higher compared to preictal and interictal states, whereas preictal CVI was lower than in basal and ictal states. In addition, ictal ApEn was significantly lower than interictal and preictal ApEn. Interictal CVI was lower in left TLE compared to right TLE. In addition, in left TLE, ictal CVI was higher than interictal CVI, whereas in right TLE, CVI was lower in the preictal state compared to all other states. Our data suggest an ictal sympathetic overdrive with partial recovery in the postictal state. Higher sympathetic tone and vagal tone imbalance may induce early autonomic dysfunction and increase cardiovascular risk in patients affected by TLE.

Objectives: The aim of the study is to investigate the effect of winter swimming on cardiovascular function in the middle-aged and elderly men. Methods: Thirty cases were included in the control group and seventy cases were in the winter swimming group. The control group and swimming group were 60–69 years of age in the elderly. The winter swimming group was followed for 1 year and the control group carried out an index test the same year. Four items of blood lipid, electrocardiogram, and cardiac function parameters were selected as index. Results: The high-density lipoprotein cholesterol of the winter swimming group was significantly higher than that of the control group (P 0.05); the comparison of serum cytokines were weak but in a positive direction. Conclusions: Long-term insist to winter swimming can make the heart to adapt to the morphological changes, improve cardiac function, improve myocardial blood supply, improve blood lipid metabolism, and reduce the risk of Arsenic (AS).

Objective of the study – to investigate the impact of anxiety and depression caused by military actions on heart rate variability parameters and the characteristics of heart rhythm disturbances in patients with myocarditis.Material and methods. The study involved 60 patients with acute myocarditis who were divided into three groups based on the results of the HADS (Hospital Anxiety and Depression Scale) questionnaire. Group 1 included 20 patients with predominant anxiety (HADS-A ≥8; HADS-D &lt;8). Group 2 consisted of 20 patients with predominant depression (HADS-A &lt;8; HADS-D ≥8). Group 3 comprised 18 patients exhibiting both pronounced anxiety and depression (HADS-A ≥8; HADS-D ≥8). The control group included 20 patients with myocarditis without significant signs of anxiety or depression (HADS-A &lt;8; HADS-D &lt;8). All patients underwent Holter ECG monitoring to assess the number of ventricular and supraventricular extrasystoles, episodes of non-sustained ventricular tachycardia, and heart rate variability (HRV) parameters: SDNN, RMSSD, and the LF/HF ratio.Results. In patients of group 1, the values of SDNN, RMSSD, HF power, and the LF/HF ratio were significantly lower (by 11.2%, 9.8%, 11.8%, and 9.4%, respectively; p &lt; 0.05) compared to the control group. In patients of group 2, a reduction in SDNN by an average of 11.9%, RMSSD by 15.4%, HF by 10.1%, and LF/HF by 12.2% (p &lt; 0.05) was observed compared to the control group. When comparing HRV parameters between groups 1 and 2, no significant differences were found except for RMSSD, which was 10.3% lower in group 2 (p &lt; 0.05). In group 3, SDNN, RMSSD, HF, and the LF/HF ratio were significantly lower both compared to the control group and to patients in groups 1 and 2. In group 1, supraventricular arrhythmias predominated, while the number of ventricular extrasystoles was comparable to that of the control group. Patients in group 2 demonstrated a significantly higher number of ventricular extrasystoles compared to groups 1 and the control group. In group 3, the frequency of ventricular rhythm disturbances, particularly episodes of non-sustained ventricular tachycardia, was the highest. Additionally, patients in this group more frequently presented with AV block and bundle branch blocks — in 51.6% and 55.1% of cases, respectively.Conclusions. In patients with symptoms of anxiety, supraventricular arrhythmias were more frequently recorded against the background of predominant sympathetic regulation of the autonomic nervous system. In those with depressive symptoms, a significantly higher number of ventricular extrasystoles and episodes of non-sustained ventricular tachycardia were observed, along with a marked decrease in time and spectral parameters of heart rate variability. The combination of anxiety and depression was associated with the most pronounced disturbances in autonomic regulation and significantly more frequent ventricular arrhythmias, both in comparison with the control group and with patients exhibiting isolated symptoms of anxiety or depression.

Heart rate variability (HRV) has been used to measure autonomic nervous system (ANS) activity noninvasively. The purpose of this study was to identify the most suitable HRV parameters for ANS activity in response to brief rectal distension (RD) in patients with Irritable Bowel Syndrome (IBS). IBS patients participated in a five-session study. During each visit, an ECG was recorded for 15 min for baseline values and during rectal distension. For rectal distension, a balloon was inflated in the rectum and the pressure was increased in steps of 5 mmHg for 30 s; each distension was followed by a 30 s rest period when the balloon was fully deflated (0 mmHg) until either the maximum tolerance of each patient was reached or up to 60 mmHg. The time-domain, frequency-domain and nonlinear HRV parameters were calculated to assess the ANS activity. The values of each HRV parameter were compared between baseline and RD for each of the five visits as well as for all five visits combined. The sensitivity and robustness/reproducibility of each HRV parameter were also assessed. The parameters included the Sympathetic Index (SI); Root Mean Square of Successive Differences (RMSSD); High-Frequency Power (HF); Low-Frequency Power (LF); Normalized HF Power (HFn); Normalized LF Power (LFn); LF/HF; Respiratory Sinus Arrhythmia (RSA); the Poincare Plot's SD1, SD2 and their ratio; and the pNN50, SDSD, SDNN and SDNN Index. Data from 17 patients were analyzed and compared between baseline and FD and among five sessions. The SI was found to be the most sensitive and robust HRV parameter in detecting the ANS response to RD. Out of nine parasympathetic parameters, only the SDNN and SDNN Index were sensitive enough to detect the parasympathetic modulation to RD during the first visit. The frequency-domain parameters did not show any change in response to RD. It was also observed that the repetitive RD in IBS patients resulted in a decreased autonomic response due to habituation because the amount of change in the HRV parameters was the highest during the first visit but diminished during subsequent visits. In conclusion, the SI and SDNN/SDNN Index are most sensitive at assessing the autonomic response to rectal distention. The autonomic response to rectal distention diminishes in repetitive sessions, demonstrating the necessity of randomization for repetitive tests.

The aim of this work was a synchronous study of cardiovascular and respiratory indicators with a search for their relationship among residents of different latitudes and in high-latitude Arctic expeditions. The effect of place of residence on cardiorespiratory system parameters was studied in 113 men - workers of industrial enterprises (Sochi, Moscow, North). Adaptation to short-term Arctic expeditions was assessed in men (43 people in total, aged 35-60 years); 15 Moscow residents of the same age served as a control. The dynamics of adaptive processes in Arctic expeditions was assessed based on the results of testing before and after the start of the expeditions, on SP-41 - monthly. Two two-minute recordings were made on the spiroarterioacardiorrhythmograph (SACR) device: with voluntary breathing and with controlled breathing at a frequency of 6 cycles per minute. The amplitude-temporal values of the average respiratory cycle were assessed, as well as the statistical parameters of heart rate variability (HRV) SDNN and RMSSD. It has been shown that residents of the North, in contrast to both southerners and Muscovites, are characterized by a shorter inspiration. In the HRV indices, northerners showed lower SDNN values compared to Sochi residents, with a similar trend (p = 0.065) for the RMSSD value. Only northerners had correlations between the respiratory and HRV indices. We did not detect any dynamics of the assessed indices of the cardiorespiratory system in short-term (up to 4 weeks) Arctic expeditions, neither with any of the breathing patterns used, nor with double or triple testing. In monitoring at SP-41, it was found that 2-3 days after the start of the expedition, under controlled breathing conditions, the RMSSD index was reduced. A month after the start of wintering, a decrease in the tidal volume in the controlled breathing test (at the trend level, p = 0.078) and a decrease in the SDNN and RMSSD indices were recorded. In high-latitude expeditions, a decrease in autonomic regulation indicators is observed against the background of a reduction in volumetric, but not time-related indicators of the respiratory cycle, which is revealed only when breathing at a frequency of 6 cycles per minute.