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 12‑lead 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 12‑lead 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.

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.

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.

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.

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.

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 (F [2.05; 49.17] = 3.31; p < 0.001), FAS (F [2.43; 58.25] = 6.18; p = 0.002) and AF (F [2.56; 61.44] = 5.41; p = 0.004). Participants' FI to engage in HIIE were only significantly correlated with FAS (r = -0.424; p = 0.035) and AF (r =0.431; p = 0.032) responses. FAS responses (βz=-0.455; R2=0.207; p =0.022) and AF responses (βz=0.467; R2=0.218; p=0.019) 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=0.177). 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.

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.

Relação entre capacidade funcional e função diastólica no infarto recente

O infarto do miocárdio (IM) altera a função diastólica (FD) do ventrículo esquerdo (VE) em diferentes graus, o que pode refletir na capacidade funcional (CF). O objetivo deste estudo foi avaliar, após IM recente, a relação entre a FD do VE por meio de ecocardiografia Doppler e a CF estimada por meio da distância percorrida no teste de caminhada de seis minutos (DP6). Cinquenta e seis pacientes com IM não complicado foram selecionados após a alta da unidade coronariana e submetidos aos testes. Foi realizada análise de correlação considerando todos os pacientes e de comparação entre grupos definidos de acordo com a classificação da FD do VE. Foi observada correlação entre a onda a' lateral (referente à diástole tardia) e a DP6 (r=-0,320; p=0,023) e não houve diferença entre a CF dos grupos classificados conforme a FD do VE. As respostas de pressão arterial e frequência cardíaca ao teste foram fisiológicas. A correlação encontrada indica que o comprometimento da diástole precoce amplia o papel da contração atrial na CF, reforçando a necessidade de avaliação desses pacientes ainda no hospital. A resposta fisiológica ao TC6 reforça a viabilidade de sua utilização após IM recente.

Segurança da intervenção fisioterápica precoce após o infarto agudo do miocárdio

INTRODUÇÃO: A fisioterapia na fase I da reabilitação cardiovascular (FTCV) pode ser iniciada de 12 a 24 horas após o infarto agudo do miocárdio (IAM), no entanto, é comum o repouso prolongado no leito em razão do receio de instabilização do paciente. OBJETIVOS: Avaliar as respostas autonômicas e hemodinâmicas de pacientes pós-IAM submetidos ao primeiro dia de protocolo de FTCV fase I, bem como sua segurança. MATERIAIS E MÉTODOS: Foram estudados 51 pacientes com primeiro IAM não complicado, 55 ± 11 anos, 76% homens. Foram submetidos ao primeiro dia do protocolo de FTCV fase I, em média 24 horas pós-IAM. A frequência cardíaca (FC) instantânea e os intervalos R-R do ECG foram captados pelo monitor de FC (Polar®S810i) e a pressão arterial (PA) aferida pelo método auscultatório. A variabilidade da FC foi analisada nos domínios do tempo (RMSSD e RMSM dos iR-R em ms) e da frequência. A densidade espectral de potência foi expressa em unidades absolutas (ms²/Hz) e normalizada (un) para as bandas de baixa (BF) e alta frequência (AF) e pela razão BF/AF. RESULTADOS: O índice RMSSD, a AF e a AFun apresentaram redução na execução dos exercícios em relação ao repouso pré e pós-exercício (p < 0,05), a BFun e a razão BF/AF aumentaram (p < 0,05). A FC e a PA sistólica apresentaram aumento durante a execução dos exercícios em relação ao repouso (p < 0,05). Não foi observado qualquer sinal e/ou sintoma de intolerância ao esforço. CONCLUSÕES: O exercício realizado foi eficaz, pois promoveu alterações hemodinâmicas e na modulação autonômica nesses pacientes, sem ocasionar qualquer intercorrência clínica.