Applicability of heart rate variability for cardiac autonomic assessment in long-term COVID patients: A systematic review.

PURPOSE: To carry out a systematic review to determine the main methods used to study the heart rate variability (HRV) in individuals after the acute phase of COVID-19. METHODS: The study followed the Preferred Items for Reporting for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Web of Science, Scopus and CINAHAL electronic databases were searched from the inception to November 2022. The studies were included if they used HRV assessment based on linear and non-linear methods in long-term COVID-19 patients. Review studies, theses and dissertations, conference abstracts, longitudinal studies, studies conducted on animals and studies that included individuals in the acute phase of the COVID-19 were excluded. The methodological quality of the studies was analyzed using the Joanna Briggs Institute's critical evaluation checklist for cross-sectional analytical studies. RESULTS: HRV was mainly assessed using 24-h Holter monitoring in 41.6% (5/12) of the studies, and 12­lead ECG was used in 33.3% (4/12). Regarding the type of assessment, 66.6% (8/12) of the studies only used linear analysis, where 25% (3/12) used analysis in the time domain, and 41.6% (5/12) used both types. Non-linear methods were combined with the previously cited linear method in 25% (3/12) of the studies. Moreover, 50% (6/12) of the studies demonstrated post-COVID-19 autonomic dysfunction, with an increase in the predominance of cardiac sympathetic modulation. The average score of the evaluation checklist was 6.6, characterized as having reasonable methodological quality. CONCLUSION: 24-h Holter and 12­lead ECG are considered effective tools to assess HRV in post-COVID-19 patients. Furthermore, the findings reveal diverse effects of COVID-19 on the autonomic nervous system's sympathovagal balance, which might be influenced by secondary factors such as disease severity, patients' overall health, evaluation timing, post-infection complications, ventilatory functions, and age.

Impacts of Social Isolation on the Physical and Mental Health of Older Adults During Quarantine: A Systematic Review.

OBJECTIVES: To systematically review articles that reported the impacts of social isolation on the physical and mental health of healthy older adults during the coronavirus disease 2019 (Covid-19) quarantine. METHODS: Electronic search was performed in PubMed, EMBASE, Web of Science, Scopus, and BIREME databases. It included cohort and cross-sectional studies published between January 2020 and January 2022 which evaluated the impacts of social isolation on the physical and mental health of older adults during quarantine. The study was registered in PROSPERO (CRD42021269720). RESULTS: Out of 8,505 studies identified, 17 met the inclusion criteria, with moderate to excellent quality. The majority of the older population perceived changes in their physical and mental health. Impacts differed in cohorts according to sex, age group, income, social participation, exercising before and during confinement, and living alone or with other people. CONCLUSIONS: The long period of social isolation dictated by the COVID-19 pandemic caused changes in most older adults`, reducing levels of physical activity and/or generating depression, anxiety, fear, and mood problems. Follow-up studies are necessary to observe the evolution of these impacts. CLINICAL IMPLICATIONS: Public policies must be developed to promote the emotional and physical health of the older adult population in the post-pandemic period.

Psychometric validation of the short version of the Information Needs in Cardiac Rehabilitation scale through a first global assessment.

AIMS: Tailored education is recommended for cardiac patients, yet little is known about information needs in areas of the world where it is most needed. This study aims to assess (i) the measurement properties of the Information Needs in Cardiac Rehabilitation short version (INCR-S) scale and (ii) patient's information needs globally. METHODS AND RESULTS: In this cross-sectional study, English, simplified Chinese, Portuguese, or Korean versions of the INCR-S were administered to in- or out-patients via Qualtrics (January 2022-November 2023). Members of the International Council of Cardiovascular Prevention and Rehabilitation community facilitated recruitment. Importance and knowledge sufficiency of 36 items were rated. Links to evidence-based lay education were provided where warranted. A total of 1601 patients from 19 middle- and high-income countries across the world participated. Structural validity was supported upon factor analysis, with five subscales extracted: symptom response/medication, heart diseases/diagnostic tests/treatments, exercise and return-to-life roles/programmes to support, risk factors, and healthy eating/psychosocial management. Cronbach's alpha was 0.97. Construct validity was supported through significantly higher knowledge sufficiency ratings for all items and information importance ratings for all subscales in cardiac rehabilitation (CR) enrolees vs. non-enrolees (all P < 0.001). All items were rated as very important-particularly regarding cardiac events, nutrition, exercise benefits, medications, symptom response, risk factor control, and CR-but more so in high-income countries in the Americas and Western Pacific. Knowledge sufficiency ranged from 30.0 to 67.4%, varying by region and income class. Ratings were highest for medications and lowest for support groups, resistance training, and alternative medicine. CONCLUSION: Identification of information needs using the valid and reliable INCR-S can inform educational approaches to optimize patients' health outcomes across the globe.

Patients need information to manage their heart diseases, such as what to do if they have chest pain, what a heart attack is, and how to take their medicine to lower the chances they will have another one, so a study of the information needs of over 1600 heart patients from around the globe was undertaken for the first time. Using the Information Needs in Cardiac Rehabilitation short version (INCR-S) scale­which was shown to be a good measurement tool through the study and hence may improve patient education­patients reported they most wanted information about heart events, heart-healthy eating, exercise benefits, their pills, symptom response, risk factor control, and cardiac rehabilitation­but more so in high-income countries in the Americas and Western Pacific. Knowledge sufficiency ratings for each item ranged from 30.0 to 67.4%, also varying by region and income class; perceived knowledge sufficiency ratings were highest for medications and lowest for support groups, resistance training, and alternative medicine.

Effect of High-Intensity Interval Training on Exercise Capacity, Blood Pressure, and Autonomic Responses in Patients With Hypertension: A Systematic Review and Meta-analysis.

CONTEXT: Despite the well-known positive effects of exercise in hypertensive patients, the best mode of exercise is still under discussion. OBJECTIVE: A systematic review of the literature, synthesizing data on the effects of high-intensity interval training (HIIT) on peak oxygen consumption (VO2 peak), blood pressure (BP), cardiac autonomic modulation, and resting heart rate (HR) in patients with hypertension. DATA SOURCES: MEDLINE (via PubMed), CENTRAL, PEDro database, and SciELO (from the earliest date available to December 31, 2020). STUDY SELECTION: Randomized controlled trials (RCTs) that evaluated the effects of HIIT in hypertensive patients. STUDY DESIGN: Systematic review and meta-analysis. LEVEL OF EVIDENCE: Level 2. DATA EXTRACTION: Mean differences (MDs) with a 95% CI were calculated, and heterogeneity was assessed using the I2 test. RESULTS: Nine RCTs encompassing 569 patients met the eligibility criteria and were included in the systematic review. Five trials compared supervised HIIT with moderate-intensity continuous training (MICT) and a control; 1 trial compared HIIT with MICT, and 3 compared HIIT with a control. In comparison with MICT, HIIT improved VO2 peak MD (3.3 mL.kg-1.min-1; 95% CI, 1.4-5.3; N = 130). In comparison with controls, HIIT improved VO2 peak MD (4.4 mL.kg-1.min-1; 95% CI, 2.5-6.2; N = 162). CONCLUSION: Despite the low quality of the evidence, HIIT is superior to MICT in improving VO2 peak in patients with hypertension. HIIT effectively improved VO2 peak, BP, and resting HR when compared with controls. HIIT appears to be safe only when performed in a supervised manner for stage 1 hypertension patients without associated risk factors.

Heart rate variability as a predictor of mechanical ventilation weaning outcomes.

BACKGROUND: Delays in the mechanical ventilation (MV) weaning process increase mortality. The spontaneous breathing test is the gold standard to assess weaning and extubation success, although it has approximately 85% accuracy. Studies have demonstrated a correlation between decreased heart rate variability (HRV) and weaning failure. OBJECTIVES: To assess the usefulness of HRV as a predictor of MV weaning outcomes. METHODS: Cross-sectional analytical study in adults of both sexes on MV in intensive care unit (ICU) stay. Patients were divided into weaning success and failure groups. Clinical data were collected, and HRV records were obtained with a heart rate monitor. RESULTS: The study included 68 individuals - 91.1% in the weaning success group and 8.9% in the failure group. All HRV indices analyzed in both groups were lower than the reference values. No statistical difference was found in the mean RR interval (RRi), the standard deviation of the NN interval (SDNN), and the square root of the mean squared differences of successive NN intervals (RMSSD) between the groups. The weaning failure group had a significant increase in LF (41 vs. 69.4) and LF/HF ratio (0.685 vs. 2.6) and a significant decrease in HF (58.85 vs. 30.2). CONCLUSIONS: HRV measure with spectral analysis can be a good predictor of MV weaning failure. Integrating this assessment tool in ICU to predict weaning outcomes could provide more precise prognoses and more adequate assistance quality.

Autonomic dysfunction in COVID-19 patients receiving mechanical ventilation: A cross-sectional study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) can damage cardiac tissue by increasing troponin levels and inducing arrhythmias, myocarditis, and acute coronary syndrome. OBJECTIVES: To analyze the impact of COVID-19 on cardiac autonomic control in mechanically ventilated intensive care unit (ICU) patients. DESIGN AND SETTING: This cross-sectional analytical study of ICU patients of both sexes receiving mechanical ventilation was conducted in a tertiary hospital. METHODS: Patients were divided into COVID-19-positive (COVID(+)) and COVID-19-negative (COVID(-)) groups. Clinical data were collected and heart rate variability (HRV) records obtained using a heart rate monitor. RESULTS: The study sample comprised 82 subjects: 36 (44%) in the COVID(-) group (58.3% female; median age, 64.5 years) and 46 (56%) in the COVID(+) group (39.1% females; median age, 57.5 years). The HRV indices were lower than the reference values. An intergroup comparison identified no statistically significant differences in the mean normal-to-normal (NN) interval, standard deviation of the NN interval, or root mean square of successive differences in NN intervals. The COVID(+) group had an increased low frequency (P = 0.05), reduced high frequency (P = 0.045), and increased low frequency/high frequency (LF/HF) ratio (P = 0.048). There was a weak positive correlation between LF/HF and length of stay in the COVID(+) group. CONCLUSION: Patients who received mechanical ventilation had lower overall HRV indices. COVID(+) patients who received mechanical ventilation had lower vagal HRV components. These findings likely indicate clinical applicability, as autonomic control impairments are associated with a greater risk of cardiac death.

Cardiac Autonomic Function and Functional Capacity in Post-COVID-19 Individuals with Systemic Arterial Hypertension.

Individuals diagnosed with systemic arterial hypertension (SAH) are considered risk groups for COVID-19 severity. This study assessed differences in cardiac autonomic function (CAF) and functional capacity (FC) in SAH individuals without COVID-19 infection compared to SAH individuals post-COVID-19. Participants comprised 40 SAH individuals aged 31 to 80 years old, grouped as SAH with COVID-19 (G1; n = 21) and SAH without COVID-19 (G2; n = 19). CAF was assessed via heart rate variability (HRV), measuring R-R intervals during a 10-min supine period. Four HRV indices were analyzed through symbolic analysis: 0V%, 1V%, 2LV%, and 2UV%. FC assessment was performed by a 6-min walk test (6MWT). G1 and G2 showed no significant differences in terms of age, anthropometric parameters, clinical presentation, and medication use. G2 exhibited superior 6MWT performance, covering more distance (522 ± 78 vs. 465 ± 59 m, p < 0.05). Specifically, G2 demonstrated a moderate positive correlation between 6MWT and the 2LV% index (r = 0.58; p < 0.05). Shorter walking distances were observed during 6MWT in SAH individuals post-COVID-19. However, the study did not find impaired cardiac autonomic function in SAH individuals post-COVID-19 compared to those without. This suggests that while COVID-19 impacted FC, CAF remained relatively stable in this population.

Linear and nonlinear analysis of heart rate variability in coronary disease.

OBJECTIVE: Coronary artery disease (CAD) and acute myocardial infarction (AMI) are associated with a reduction of heart rate variability (HRV). The aim of this study was to compare the HRV of CAD patients with and without AMI (CAD-AMI) with health-matched controls by linear (spectral analysis) and nonlinear [Shannon entropy (SE), conditional entropy (CE) and symbolic analysis (SA)] analysis. METHODS: Fifty-eight men were divided into three groups: healthy (n = 19, 57 ± 4 years), CAD (n = 20, 56 ± 10 years) and CAD-AMI (n = 19, 54 ± 12 years). The RR intervals were recorded at rest in the supine position for 10 min with an HR monitor (Polar(®)S810i). A series of 250 beats was selected to analyze variance, spectral analysis, SE, CE [complexity index (CI), normalized CI (NCI)] and SA (0V, 1V, 2LV and 2ULV patterns), as well as 0V (no significant variation) and 2ULV (two significant unlike variations), which reflect sympathetic and vagal modulation, respectively. One-way ANOVA (or the Kruskal-Wallis test when appropriate) and Pearson correlation were used. RESULTS: The CAD group had higher body mass index and weight than the CAD-AMI group, but no differences were found between the healthy and AMI groups. There were no differences between the groups regarding linear and nonlinear analysis. The 0V and 2ULV patterns were significantly correlated with the SE, CI and NCI of the three groups. INTERPRETATION: There was no difference between the groups regarding cardiac autonomic modulation by linear and nonlinear methods, which may be due to beta-blocker use, coronary angioplasty and the exercise capacity of healthy subjects.

Perceptual Responses and Future Exercise Intentions of Individuals With Systemic Arterial Hypertension.

To analyze the perceptual responses and future intentions (FI) to engage in continuous moderate aerobic exercise (CE) and high-intensity interval exercise (HIIE) of individuals with systemic arterial hypertension (SAH), we had 25 participants with SAH (M age = 48.0, SD = 8.0 years) perform, on different days and in randomized order, 33 minute sessions of CE and 30 minutes of HIIE. Twenty seconds after each 3-minutes of these sessions, we obtained participant responses to Ratings of Perceived Exertion (RPE), the Feeling Scale (FS), the Felt Arousal Scale (FAS), and attentional focus (AF). We assessed their FI to engage in CE and HIIE at the end of each session. We analyzed results using two-way ANOVAs with repeated measures, Spearman correlation coefficients, a simple linear regression, and Wilcoxon test. We found a significant time by session type (CE and HIIE) interaction effect for RPE (p < .001), FAS (p = .002), and AF (p = .004). Participants' FI to engage in HIIE were only significantly correlated with FAS (r = -.424; p = .035) and AF (r = .431; p = .032) responses. FAS responses (ßz = -.455; R2 = .207; p = .022) and AF responses (ßz = .467; R2 = .218; p = .019) predicted FI for engaging in HIIE. There were no significant differences in participants' FI to engage in CE sessions (M = 76.4, SD =22.5%) versus HIIE sessions (M = 71.8, SD = 22.9%; p = .177). Individuals with SAH had more positive perceptions of CE than HIIE, as seen by their greater dissociative AF in the CE sessions. Furthermore, these results supported the application of strategies aimed at manipulating AF in this population, possibly as a tool to increase participants' FI to engage in subsequent physical exercise.

[Regional differences and costs of physical therapy procedures in Brazil's Unified Health System, 1995 to 2008]. / Diferenças regionais e custos dos procedimentos de fisioterapia no Sistema Único de Saúde do Brasil, 1995 a 2008.

OBJECTIVE: Describe the ambulatory physical therapy treatments provided by the Unified Health System (SUS) in Brazil with regard to their geographical distribution, costs, types of procedure, and types of provider. METHODS: Data from the SUS Information Technology Department (DATASUS) were utilized, drawing from the period from 1995 to 2008, which included the quantity and the value of the procedures approved for payment by the Secretariats of Health and the quantity and value of the procedures presented for payment. The treatment coefficients (CoA) were calculated by dividing the number of treatments in a particular year and region by the estimated population of that region in that year. RESULTS: The CoA in Brazil in 2008 was 0.19 and the North and Center-West regions presented the lowest coefficients (0.13 and 0.10, respectively). Between 1995 and 2007 there was an increase in the national treatment coefficient of 33.7%, with the North region showing the largest increase, 143.8%; the Center-West 62.1%, and the Northeast 56.1%. Treatment for motor disorders was the most widely performed procedure (61.8%), and the values of payments approved were lower than those presented by the managers of the services in 2008 (10.4%). Private for-profit establishments provided 44.5% of the physical therapy treatments paid for by the SUS in 2008. Municipal establishments accounted for 26.6% of the treatments, and federal establishments for only 0.9%. Between 1995 and 2007, the quantity of treatments offered by municipal establishments increased 278.7%. CONCLUSIONS: It was observed that the provision of ambulatory physical therapy treatment by the SUS remains small and geographically unequal, although less developed regions showed a larger increase in the CoA. The SUS remunerates inadequately the physical therapy services provided and continues to do so, in large part, by means of agreements with private establishments.

Effect of High-Intensity Interval Training on Aerobic Capacity and Heart Rate Control of Heart Transplant Recipients: a Systematic Review with Meta-Analysis.

INTRODUCTION: Heart transplantation (HTx) is the gold standard procedure for selected individuals with refractory heart failure. Highintensity interval training (HIIT) is safe and allows patients to exercise in high intensity for longer time when compared to moderateintensity continuous training (MICT). The primary aim of this study was to perform a systematic review and meta-analysis about the effect of HIIT compared to MICT on exercise capacity, peak heart rate, and heart rate reserve in HTx recipients. Secondarily, we pooled data comparing MICT and no exercise training in these patients. METHODS: This systematic review followed the standardization of the Preferred Reporting Items for Systematic Reviews and Metaanalyses statement and the Cochrane Collaboration Handbook. We presented the treatment effects of HIIT on the outcomes of interest as mean difference (MD) and 95% confidence interval (CI). Metaanalysis was performed using the random-effects, generic inverse variance method. RESULTS: HIIT improved peak oxygen consumption (peakVO2) (MD = 2.1; 95% CI 1.1, 3.1; P<0.0001), peak heart rate (MD = 3.4; 95% CI 0.8, 5.9; P=0.009), and heart rate reserve (MD = 4.8; 95% CI -0.05, 9.6; P=0.05) compared to MICT. Improvements on peakVO2 (MD = 3.5; 95% CI 2.3, 4.7; P<0.00001) and peak heart rate (MD = 5.6; 95% CI 1.6, 9.6; P=0.006) were found comparing HIIT and no exercise training. CONCLUSION: Current available evidence suggests that HIIT leads to improvements on peakVO2, peak heart rate, and heart rate reserve compared to MICT in HTx recipients. However, the superiority of HIIT should be tested in isocaloric protocols.

Immediate Effects of Rib Mobilization and Diaphragm Release Techniques on Cardiac Autonomic Control in Patients With Chronic Obstructive Pulmonary Disease: A Pilot Study.

OBJECTIVE: The purpose of this pilot study was to evaluate the feasibility of testing an intervention protocol and measuring the immediate effects of a rib mobilization technique (RMT) and a diaphragm release technique (DRT) on the autonomic nervous system of patients with chronic obstructive pulmonary disease (COPD). METHODS: This was a pilot study of a randomized controlled trial. Fourteen individuals were evaluated. Eligibility criteria were being a sedentary person with a diagnosis of COPD, age between 50 and 72 years, and being clinically stable. Exclusion criteria were heart disease, other respiratory comorbidities, and body mass index above 30kg/m2. Participants first underwent cardiorespiratory evaluation and were then allocated into 2 groups: the RMT + DRT group and the DRT group. Clinical assessments were performed immediately before and after the intervention. Statistical analysis was carried out through a paired-sample Wilcoxon test, and the comparison between groups was performed using the Mann-Whitney test. RESULTS: All randomized participants completed the assessment and intervention protocol. Sample size was estimated at 24 individuals per group. The DRT group decreased resting heart rate by 5 bpm (P = .03) and increased variance (P = .04) and mean R-R interval (P = .03). The RMT + DRT group decreased mean R-R interval (P = .02). CONCLUSION: The design for this study appears to be feasible for evaluating manual-therapy intervention in the nonmusculoskeletal function of patients with COPD. It was possible to determine the sample size for future studies. Preliminary data show that the diaphragm release technique may reduce mean resting heart rate and increase heart-rate variability immediately after the intervention.

Effects of physical exercise on the autonomic nervous system in patients with coronary artery disease: a systematic review.

BACKGROUND: Imbalance in autonomic modulation can occur after a cardiac event, which can lead to deleterious consequences. Exercise has proven to be a therapy which affects this modulation and can be assessed through heart rate variability (HRV). AREAS COVERED: The objective of this systematic review was to investigate the effects of physical exercise on heart rate variability in individuals with coronary artery disease (CAD). The PubMed, PEDro, Scielo, Lilacs and Cochrane databases were systematically searched, for articles which performed supervised exercises in phase II of cardiac rehabilitation in patients with CAD. EXPERT OPINION: Given the differences between studies on interventions and population characteristics, it is difficult to justify similarities or divergences in terms of results. In addition to the variation in sample size, intervention duration, carrying out an additional program at home, and patients with different clinical presentations, it can be inferred that responses to exercise may vary for certain types/clinical profile of individuals with CAD. Thus, it is necessary to carry out more studies with greater methodological rigor, greater standardization of the variables studied and the evaluation forms, in order to increase the veracity of the results and the consequent clinical relevance and therapeutic application.

A validation study of a smartphone application for heart rate variability assessment in asymptomatic adults.

BACKGROUND: Assessment of heart rate variability (HRV) is an effective non-invasive tool to obtain data on cardiac autonomic modulation and may be assessed by a range of devices, including mobile applications. Objective: This study aimed to validate a smartphone application by comparing the R-R intervals (RRi) obtained by the app with a classic electrocardiogram (ECG)-derived reference condition Methods: Fifteen asymptomatic adults (24.9±3.4 years) underwent an orthostatic challenge during which RRi were simultaneously recorded by a freeware smartphone application and by an ECG recorder. Pearson correlation coefficients (r) and coefficients of determination (r 2) were calculated to determine the degree of association between the two electronic devices. Two-way repeated measures analysis of variance and Bland-Altman analysis were used to calculate the measurement consistency and agreement, respectively, between the two methods. Effect size was also used to estimate the magnitude of the differences. RESULTS: The number of RRi from asymptomatic adults recorded by the ECG and by the free smartphone application was similar at rest in supine position (13,149 vs. 13,157; P = 0.432) and during orthostatic challenge (10,666 vs. 10,664 P = 0.532). RRi in milliseconds from both devices presented a near perfect correlation in the supine position (r = 0.999; Confidence Interval [CI] at 95%: 0.999-0.999; P < 0.0001) and during orthostatic challenge (r = 0.988; 95% CI: 0.988-0.989; P < 0.0001). A negative bias of -0.526 milliseconds (95% limits of agreement [LoA] from -4.319 to 3.266 milliseconds) was observed in supine position between ECG and the smartphone application. On the other hand, a positive bias of 0.077 milliseconds (95% LoA from -10.090 to 10.240 milliseconds) during the orthostatic challenge was observed. CONCLUSIONS: Our results cross-validated a freeware smartphone application with the ECG-derived reference condition for asymptomatic adults at rest in the supine position and during orthostatic challenge.

Can RR intervals editing and selection techniques interfere with the analysis of heart rate variability?

BACKGROUND: Oscillation between successive sinus beats or RR intervals, termed heart rate variability, is an important marker of autonomic function of the heart. However, its analysis may be influenced by the database recorded based on the occurrence of interference. OBJECTIVE: To evaluate if the techniques of identification and editing of artifacts, as well as the selection methods of RR intervals, can interfere with heart rate variability analysis. METHODS: The RR intervals of 56 subjects (30 aortic stenosis patients, 14 physically active individuals, 12 amateur athletes) were recorded for 10min using a heart rate monitor. Values with differences greater than 20%, higher than three standard deviations or outside of the normal curve (95% confidence interval) were considered artifacts. These points were corrected through data replacement, adjacent, linear and polynomial interpolation, or excluded. Then, the 256 highest stability points and the last 5min of recordings were chosen. The software programs, Kubios HRV and GraphPAD, were used to calculate and to analyze the indices of heart rate variability, respectively. RESULTS: Strong agreement was observed among the identification algorithms; there was no difference between the correction techniques (p=0.95); and the selection methods exhibited different sections (p<0.01) with a direct influence on approximated entropy (p<0.05). CONCLUSION: With short-term recordings, selection methods may interfere with the non-linear heart rate variability analysis. The confidence interval, the replacement by the average of previous data and the selection of 256 of the highest stability points of the signal seem to be the most adequate procedures to treat the data with prior to analysis.

Autonomic dysfunction in COVID-19 patients receiving mechanical ventilation: A cross-sectional study

ABSTRACT BACKGROUND: Coronavirus disease 2019 (COVID-19) can damage cardiac tissue by increasing troponin levels and inducing arrhythmias, myocarditis, and acute coronary syndrome. OBJECTIVES: To analyze the impact of COVID-19 on cardiac autonomic control in mechanically ventilated intensive care unit (ICU) patients. DESIGN AND SETTING: This cross-sectional analytical study of ICU patients of both sexes receiving mechanical ventilation was conducted in a tertiary hospital. METHODS: Patients were divided into COVID-19-positive (COVID(+)) and COVID-19-negative (COVID(-)) groups. Clinical data were collected and heart rate variability (HRV) records obtained using a heart rate monitor. RESULTS: The study sample comprised 82 subjects: 36 (44%) in the COVID(-) group (58.3% female; median age, 64.5 years) and 46 (56%) in the COVID(+) group (39.1% females; median age, 57.5 years). The HRV indices were lower than the reference values. An intergroup comparison identified no statistically significant differences in the mean normal-to-normal (NN) interval, standard deviation of the NN interval, or root mean square of successive differences in NN intervals. The COVID(+) group had an increased low frequency (P = 0.05), reduced high frequency (P = 0.045), and increased low frequency/high frequency (LF/HF) ratio (P = 0.048). There was a weak positive correlation between LF/HF and length of stay in the COVID(+) group. CONCLUSION: Patients who received mechanical ventilation had lower overall HRV indices. COVID(+) patients who received mechanical ventilation had lower vagal HRV components. These findings likely indicate clinical applicability, as autonomic control impairments are associated with a greater risk of cardiac death.

Effect of high-intensity interval training on aerobic capacity and heart rate control of heart transplant recipients: a systematic review with meta-analysis

Abstract Introduction: Heart transplantation (HTx) is the gold standard procedure for selected individuals with refractory heart failure. High-intensity interval training (HIIT) is safe and allows patients to exercise in high intensity for longer time when compared to moderate-intensity continuous training (MICT). The primary aim of this study was to perform a systematic review and meta-analysis about the effect of HIIT compared to MICT on exercise capacity, peak heart rate, and heart rate reserve in HTx recipients. Secondarily, we pooled data comparing MICT and no exercise training in these patients. Methods: This systematic review followed the standardization of the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement and the Cochrane Collaboration Handbook. We presented the treatment effects of HIIT on the outcomes of interest as mean difference (MD) and 95% confidence interval (CI). Meta-analysis was performed using the random-effects, generic inverse variance method. Results: HIIT improved peak oxygen consumption (peakVO2) (MD = 2.1; 95% CI 1.1, 3.1; P<0.0001), peak heart rate (MD = 3.4; 95% CI 0.8, 5.9; P=0.009), and heart rate reserve (MD = 4.8; 95% CI -0.05, 9.6; P=0.05) compared to MICT. Improvements on peakVO2 (MD = 3.5; 95% CI 2.3, 4.7; P<0.00001) and peak heart rate (MD = 5.6; 95% CI 1.6, 9.6; P=0.006) were found comparing HIIT and no exercise training. Conclusion: Current available evidence suggests that HIIT leads to improvements on peakVO2, peak heart rate, and heart rate reserve compared to MICT in HTx recipients. However, the superiority of HIIT should be tested in isocaloric protocols.

Respiratory sinus arrhythmia in Chagas disease.

We applied the respiratory sinus arrhythmia (RSA) quantification algorithm to 24-hour ECG recordings of Chagas disease (ChD) patients with (G1, n=148) and without left ventricular dysfunction (LVD) (G2, n=33), and in control subjects (G0, n=28). Both ChD groups displayed a reduced RSA index; G1=299 (144-812); G2=335 (162-667), p=0.011, which was correlated with vagal indexes of heart rate variability analysis. RSA index is a marker of vagal modulation in ChD patients.

Relationship between inspiratory muscle capacity and peak exercise tolerance in patients post-myocardial infarction.

OBJECTIVE: The study objective was to evaluate inspiratory muscle endurance in patients post-myocardial infarction without respiratory muscle weakness and its correlation with peak exercise capacity. METHODS: Ten patients who recently had a myocardial infarction (recent infarction group [RIG]), 9 patients who less recently had a myocardial infarction (less recent infarction group [LIG]), and 12 healthy subjects (control group [CG]) underwent a cardiopulmonary exercise test and respiratory endurance protocol. Analysis of variance with post hoc Dunn comparisons was used to contrast performances on all tests, and Pearson's correlation was used to determine associations between variables. RESULTS: The RIG presented lower maximal incremental pressure and oxygen consumption than the CG (P < .01). There was a positive correlation between peak oxygen uptake and both maximal inspiratory pressure (.68, P < .001) and maximal incremental pressure (.65, P < .001) in the RIG. CONCLUSION: The RIG showed lower maximal incremental pressure, which is related to peak exercise capacity. This novel relationship in functional capacity can indicate the need to improve muscle endurance in these patients even in the absence of inspiratory muscle weakness.