Time-domain heart rate variability in coronary artery disease patients affected by thyroid dysfunction

Cardiac autonomic neuropathy in Graves' disease: smoking and age as predictive factors

BACKGROUND

Hypermetabolic state in Graves' disease (GD) has a great impact on heart homeostasis, acting directly on the heart muscle and modulating the autonomic nervous system.

AIMS

To characterize Cardiac Autonomic Neuropathy (CAN) as a possible complication in patients with GD.

METHODS

We evaluated euthyroid GD patients and a control group of healthy euthyroid people. CAN was assessed using autonomic tests of cardiovascular reflex and heart rate variability: respiratory, Valsalva, orthostatic and orthostatic hypotension tests, high frequency, low frequency, and very low-frequency bands. Transthoracic echocardiography was performed in GD patients.

RESULTS

60 GD patients and 50 people in control group were assessed. CAN was diagnosed in 20% of GD and 14% in the control group. Among GD, 13.3% presented incipient, and 6.7%, established CAN, while in the control group, it was verified incipient in 8% and established in 6% (p=0.7479). All GD patients with CAN presented an alteration in the deep breathing test. Age and smoking were evidenced as factors associated with the presence of CAN, while higher TRAb values at diagnosis decreased the chance of NAC.

CONCLUSIONS

The prevalence of CAN in euthyroid GD patients was 20%. Changes in the cardiac autonomic nervous system were identified, pointing to the importance of evaluating this complication in these patients. Smoking was a predictive factor for CAN, increasing its relationship with conditions that aggravate GD.

Association of stress and primary hypothyroidism

Background

Hypothyroidism is the result of impaired production and secretion of thyroid hormones. The cardiovascular system is affected by fluctuations in thyroid hormone levels. Stressful events or stressors can affect the hypothalamic-pituitary-thyroid (HPT) axis and psychological and physiological responses. Stress increases thyroid hormone levels while decreasing TSH levels, which exacerbates autoimmune thyroid disease.

Aim

To evaluate the relationship between stress and primary hypothyroidism.

Methods

A total of 77 newly diagnosed hypothyroid patients (TSH >5.0 mIU/L) and 77 healthy adults (TSH 0.5-5.0 mIU/L) were enrolled. During a brief general physical examination, the following values were measured: height, weight, blood pressure, pulse, and pulse rate. A brief systemic examination of the cardiovascular system and lungs was also performed to rule out systemic diseases. Heart rate variability (HRV) processing and analysis were performed using Pro LabChart (PowerLab 8Pro) data analysis software from AD Instrument.

Results

Mean Avg. RR was significantly higher, RM SSD and pRR50 were significantly lower in cases than in controls. Mean HF was significantly lower and LF/HF (frequency range) was significantly higher in cases than in controls. Mean PSS was significantly higher in cases (25.82 ± 2.83) than in controls (22.47 ± 2.10). The majority of cases (54.5%) had a high stress level. The TSH level showed a highly significant correlation with the LF/HF ratio and with the PSS score.

Conclusion

The mean Avg. RR and HF were significantly higher, RM SSD and pRR50 and LF/HF (frequency range) were significantly lower in hypothyroid patients.

Hemodynamic responses to handgrip and metaboreflex activation are exaggerated in individuals with metabolic syndrome independent of resting blood pressure, waist circumference, and fasting blood glucose

Introduction: Prior studies report conflicting evidence regarding exercise pressor and metaboreflex responses in individuals with metabolic syndrome (MetS). Purpose: To test the hypotheses that 1) exercise pressor and metaboreflex responses are exaggerated in MetS and 2) these differences may be explained by elevated resting blood pressure. Methods: Blood pressure and heart rate (HR) were evaluated in 26 participants (13 MetS) during 2 min of handgrip exercise followed by 3 min of post-exercise circulatory occlusion (PECO). Systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP), along with HR and a cumulative blood pressure index (BPI), were compared between groups using independent samples t-tests, and analyses of covariance were used to adjust for differences in resting blood pressure, fasting blood glucose (FBG), and waist circumference (WC). Results: ΔSBP (∼78% and ∼54%), ΔMAP (∼67% and ∼55%), and BPI (∼16% and ∼20%) responses were significantly exaggerated in individuals with MetS during handgrip and PECO, respectively (all p ≤ 0.04). ΔDBP, ΔMAP, and BPI responses during handgrip remained significantly different between groups after independently covarying for resting blood pressure (p < 0.01), and after simultaneously covarying for resting blood pressure, FBG, and WC (p ≤ 0.03). Likewise, peak SBP, DBP, MAP, and BPI responses during PECO remained significantly different between groups after adjusting for resting blood pressure (p ≤ 0.03), with peak SBP, MAP, and BPI response remaining different between groups after adjusting for all three covariates simultaneously (p ≤ 0.04). Conclusion: These data suggest that exercise pressor and metaboreflex responses are significantly exaggerated in MetS independent of differences in resting blood pressure, FBG, or WC.

Effect of the Marine Exercise Retreat Program on Thyroid-Related Hormones in Middle-Aged Euthyroid Women

This study aimed to investigate the effects of a marine exercise retreat program on thyroid-related hormone levels. A total of 62 middle-aged euthyroid women participated in a 6-day marine exercise retreat program. Using thyroid-stimulating hormone (TSH) and free thyroxine (fT4) hormone levels, the participants were divided into high and low-hormone-level groups. Despite decreased TSH and fT4 levels after the program, the factors influencing changes in each group were different. TSH levels were influenced by changes in the normalized low frequency (nLF) of heart rate variability and carbon monoxide (CO) from all the participants, and changes in body fat percentage, nLF, and nitrogen dioxide (NO2) exposure level in the high TSH group. fT4 levels were influenced by changes in body mass index (BMI), NO2 exposure, and particulate matter diameter of 10 µm or less (PM10) exposure in all participants. Changes in BMI and CO exposure influenced the low fT4 group. Lastly, changes in the exercise stress test affected the high fT4 group. Thus, the marine exercise retreat program affected euthyroid thyroid-related hormone levels, and influencing factors differ depending on the initial value of the hormone.

Effect of Hyperthyroidism Treatments on Heart Rate Variability: A Systematic Review and Meta-Analysis

The reversibility of HRV abnormalities in hyperthyroidism remains contradictory. The design of this study involves conducting a systematic review and meta-analysis on the effect of antithyroid treatments on HRV in hyperthyroidism. PubMed, Cochrane, Embase, and Google Scholar were searched until 4 April 2022. Multiple reviewers selected articles reporting HRV parameters in treated and untreated hyperthyroidism. Independent data extraction by multiple observers was stratified by degree of hyperthyroidism for each HRV parameter: RR intervals, SDNN (standard deviation of RR intervals), RMSSD (square root of the mean difference of successive RR intervals), pNN50 (percentage of RR intervals with >50 ms of variation), total power (TP), LFnu (low-frequency normalized unit) and HFnu (high-frequency), VLF (very low-frequency), and LF/HF ratio. We included 11 studies for a total of 471 treated hyperthyroid patients, 495 untreated hyperthyroid patients, and 781 healthy controls. After treatment, there was an increase in RR, SDNN, RMSSD, pNN50, TP, HFnu, and VLF and a decrease in LFnu and LF/HF ratio (p < 0.01). Overt hyperthyroidism showed similar results, in contrast to subclinical hyperthyroidism. Compared with controls, some HRV parameter abnormalities persist in treated hyperthyroid patients (p < 0.05) with lower SDNN, LFnu, and higher HFnu, without significant difference in other parameters. We showed a partial reversibility of HRV abnormalities following treatment of overt hyperthyroidism. The improvement in HRV may translate the clinical cardiovascular benefits of treatments in hyperthyroidism and may help to follow the evolution of the cardiovascular morbidity.

Heart rate variability in hypothyroid patients: A systematic review and meta-analysis

Introduction

Hypothyroidism may be associated with changes in the autonomic regulation of the cardiovascular system, which may have clinical implications.

Objective

To conduct a systematic review and meta-analysis on the impact of hypothyroidism on HRV.

Materials and methods

PubMed, Cochrane, Embase and Google Scholar were searched until 20 August 2021 for articles reporting HRV parameters in untreated hypothyroidism and healthy controls. Random-effects meta-analysis were stratified by degree of hypothyroidism for each HRV parameters: RR intervals (or normal to normal-NN intervals), SDNN (standard deviation of RR intervals), RMSSD (square root of the mean difference of successive RR intervals), pNN50 (percentage of RR intervals with >50ms variation), total power (TP), LFnu (low-frequency normalized unit), HFnu (high-frequency), VLF (very low frequency), and LF/HF ratio.

Results

We included 17 studies with 11438 patients: 1163 hypothyroid patients and 10275 healthy controls. There was a decrease in SDNN (effect size = -1.27, 95% CI -1.72 to -0.83), RMSSD (-1.66, -2.32 to -1.00), pNN50 (-1.41, -1.98 to -0.84), TP (-1.55, -2.1 to -1.00), HFnu (-1.21, -1.78 to -0.63) with an increase in LFnu (1.14, 0.63 to 1.66) and LF/HF ratio (1.26, 0.71 to 1.81) (p <0.001). HRV alteration increased with severity of hypothyroidism.

Conclusions

Hypothyroidism is associated with a decreased HRV, that may be explained by molecular mechanisms involving catecholamines and by the effect of TSH on HRV. The increased sympathetic and decreased parasympathetic activity may have clinical implications.

Heart Rate Variability in Hyperthyroidism: A Systematic Review and Meta-Analysis

Objective: Cardiovascular effects of thyroid hormones may be measured through heart rate variability (HRV). We sought to determine the impact of hyperthyroidism on HRV. Design: A systematic review and meta-analysis on the impact of hyperthyroidism on HRV. Methods: PubMed, Cochrane, Embase and Google Scholar were searched until 20 August 2021 for articles reporting HRV parameters in untreated hyperthyroidism and healthy controls. Random-effects meta-analysis was stratified by degree of hyperthyroidism for each HRV parameter: RR intervals (or Normal-to-Normal intervals—NN), SDNN (standard deviation of RR intervals), RMSSD (square root of the mean difference of successive RR intervals), pNN50 (percentage of RR intervals with >50 ms of variation), total power (TP), LFnu (low-frequency normalized unit) and HFnu (high-frequency), VLF (very low-frequency), and LF/HF ratio. Results: We included 22 studies with 10,811 patients: 1002 with hyperthyroidism and 9809 healthy controls. There was a decrease in RR (effect size = −4.63, 95% CI −5.7 to −3.56), SDNN (−6.07, −7.42 to −4.71), RMSSD (−1.52, −2.18 to −0.87), pNN50 (−1.36, −1.83 to −0.88), TP (−2.05, −2.87 to −1.24), HFnu (−3.51, −4.76 to −2.26), and VLF power (−2.65, −3.74 to −1.55), and an increase in LFnu (2.66, 1.55 to 3.78) and LF/HF ratio (1.75, 1.02 to 2.48) (p < 0.01). Most parameters had ES that was twice as high in overt compared to subclinical hyperthyroidism. Increased peripheral thyroid hormones and decreased TSH levels were associated with lower RR intervals. Conclusions: Hyperthyroidism is associated with a decreased HRV, which may be explained by the deleterious effect of thyroid hormones and TSH. The increased sympathetic and decreased parasympathetic activity may have clinical implications.

Correlation of heart rate and blood pressure variability as well as hs-CRP with the burden of stable coronary artery disease

BACKGROUND

The aim is to investigate the predictive value of heart rate variability (HRV), blood pressure variability (BPV), and high-sensitivity C-reactive protein (hs-CRP) levels in patients with stable coronary artery disease (SCAD) to assess whether these variables predict the Gensini score.

METHODS

Five hundred and eighty-eight patients with SCAD were enrolled. Normal coronary angiography (102 patients) and healthy physical examination patients (104 patients) were enrolled as control group for HRV. Dynamic electrocardiogram, ambulatory blood pressure, and hs-CRP were measured in SCHD, and Gensini scores were calculated. The relationship between the level of Gensini scores and HRV, BPV and hs-CRP in SCAD was analyzed. We assessed the predictive value of non-invasive markers for the degree of coronary artery disease in SCAD.

RESULTS

HRV was negatively correlated with coronary lesions Gensini scores, and BPV was positively correlated with them. The correlation coefficients of SDNN, PNN50, SDANN, RMSSD, and TRIA in HRV are -0.327, -0.489, -0.153 -0.206, -0.292, respectively (P<0.01); while 24hSBPV, 24hDBPV, dSBPV, dDBPV, nSBPV and nSBPdrinBPV were 0.286, 0.233, 0.141, 0.139, 0.218, 0.113, respectively (P<0.01). hs-CRP was positively correlated with the Gensini scores of coronary lesions (0.325, P<0.01), HRV decreased (PNN50<14.97, TRIA<160.86) and BPV increased (24hSBPV>20%, nSBPV>20%) combined with hs-CRP positive (hs-CR >3.0 mg/L) performance can effectively predict coronary lesions in SCAD.

CONCLUSIONS

HRV, BPV and hs-CRP are all significantly associated with coronary lesions. And these variables can predict the Gensini score in SCAD.

Thyroid disorders in Brazil: the contribution of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Thyroid disorders are common diseases, both in Brazil and worldwide. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study that investigates cardiovascular diseases, diabetes, and associated factors, including non-classical cardiovascular risk factors such as thyroid function. Thyroid function was classified according to thyrotropin stimulating hormone (TSH), free thyroxine (FT4), and use of medication to treat thyroid disorders, after excluding participants who reported use of any medication that could alter the results of the TSH and FT4 tests. All analyses included in this review are cross-sectional using baseline data (2008 to 2010). The results showed an association of subclinical thyroid disorders with biomarkers of subclinical atherosclerosis, measured by carotid intima-media thickness and coronary artery calcium, insulin resistance, metabolic syndrome, and some psychiatric disorders. No association was found with the biomarker of inflammation high-sensitivity C-reactive protein, or changes in pulse wave velocity or heart rate variability.

Heart rate variability in hyperthyroidism on sub Saharan African patients: a case-control study

Objective

We aimed to determine heart rate variability in freshly diagnosed untreated hyperthyroidism patients. We enrolled 10 patients (9 females) and 10 matched controls for sex and age. Each eligible patient underwent five different tests according to Ewing battery tests for cardiac autonomic dysfunction assessment. HRV was assessed during each maneuver and on 24 h using a continuous electrocardiogram with automatic estimation of SDNN, RMSSD, LF HF and HF/LH ratio. Results of tests were compared between hyperthyroidism patients and matched controls using the non-parametric test of Mann–Whitney.

Results

Heart rate was significantly higher in patients with thyrotoxicosis (82.91 ± 10.99 vs 67.04 ± 6.80; 0.006) compared to their controls. On time-domain analysis, there was a trend towards reduction in SDNN (39.52 vs. 63.75; p = 0.2) as well as the RMSSD (30.44 vs 64.03; p = 0.09) in patients with hyperthyroidism. The frequency-domain analysis showed non-significant higher values for the LF (43.87 vs 38.85 ± 12.85; p = 0.8) and lower for the HF (32.54 vs 43.39; p = 0.3). Test’s results were mostly impaired in hyperthyroid patients and all patients presented abnormal results for parasympathetic activity. Untreated and recently diagnosed hyperthyroidism is associated to an altered parasympathetic activity in sub Saharan African patients.

Relationship between heart rate variability and subclinical thyroid disorders of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

The association between subclinical thyroid dysfunctions and autonomic modulation changes has been described by many studies with conflicting results. We aimed to analyze the association between subclinical hyperthyroidism (SCHyper), subclinical hypothyroidism (SCHypo), and heart rate variability (HRV) using the baseline from ELSA-Brasil. SCHyper and SCHypo were classified by use of medication to treat thyroid disorders, thyrotropin levels respectively above and under the reference range, and normal free thyroxine levels. For HRV, the participants underwent 10 min in supine position and the R-R intervals of the final 5 min were selected for analysis. We first used linear regression models to report crude data and then, multivariate adjustment for sociodemographic (age, sex, and race) and cardiovascular risk factors (hypertension, dyslipidemia, diabetes, smoking, body mass index, use of alcohol, and leisure physical activity) using the euthyroid group as reference. From 9270 subjects (median age, 50; interquartile range: 44–56), 8623 (93.0%) were classified as euthyroid, 136 (1.5%) as SCHyper, and 511 (5.5%) as SCHypo. Compared to euthyroid subjects, SCHyper participants presented significantly higher heart rate (68.8 vs 66.5 for euthyroidism, P=0.007) and shorter R-R intervals (871.4 vs 901.6, P=0.007). Although SCHyper was associated with lower standard deviation of NN interval (SDNN) (β: –0.070; 95% confidence interval (95%CI): –0.014 to –0.009) and low-frequency (LF) (β: –0.242, 95%CI: –0.426 to –0.058) compared to the euthyroid group, these differences lost significance after multivariate adjustment for confounders. No significant differences were found for HRV in SCHypo. No association was found between HRV and SCHyper or SCHypo compared to euthyroid subjects in this sample of apparently healthy subjects.

Effect of propranolol on heart rate variability in hyperthyroidism

Objectives

We aimed to determine the effect of propanolol on heart rate variability (HRV) in hyperthyroidism before antithyroid treatment. This was a before and after study, on ten patients presenting overt hyperthyroidism naïve to treatment. In each patient, a resting electrocardiogram was done followed by estimation of cardiac autonomic dysfunction during five maneuvers (Ewing battery tests). Long term HRV measurement was done using 24 h ambulatory electrocardiographic recording. This automatically provided estimation of HRV using SDNN and RMSSD index, LF, HF, and HF/LF ratio. After baseline investigations, 40 mg of propanolol was given twice a day for 3 days and same parameters were measured after 72 h of treatment.

Results

Our patients were aged 40 ± 10 years. Propanolol significantly reduced RR and HR interval (669 ms vs 763 ms and 91 vs 79 bpm; p < 0.01). QT and PR space were significantly extended (360 vs 384 ms and 133 vs 172 ms; p = 0.01). It increases QRS complex and blood pressure response to sustained handgrip but failed to modify previously decreased heart response to deep breathing. HRV parameters such as SDNN, RMSSD, LF, HF and sympathovagal balance estimate by HF/LF ratio remained unchanged. Although a significant reduction in heart excitability, propanolol failed to restore a good sympathovagal balance in hyperthyroidism.

Trial registration NCT03393728 “Retrospectively registered”

Oscillating blood pressure therapeutic target in type 2 diabetes patients with hypertension

There is controversy regarding the J-shaped curve associating low blood pressure (BP) with increased cardiovascular events and mortality in hypertensive treated patients. This has partially motivated the revision of several hypertension treatment guidelines to raise the threshold for the definition and initiation of pharmacological treatment of hypertension in diabetes patients from 130/80 to 140/90 mmHg. However, there are increasing evidence that the increase cardiovascular risk caused by lower BP is not due to hypertensive treatment itself, rather to co-morbidities, especially in patients with diabetes. Much more, lower BP than currently recommended might be associated with significantly lower risk of cardiovascular events in diabetes patients. In this paper, we revisit the issue of ideal therapeutic BP target in diabetes patients with hypertension.

Cardiac autonomic function and vascular profile in subclinical hypothyroidism: Increased beat-to-beat QT variability

BACKGROUND

Patients with subclinical hypothyroidism (SH) may have higher incidence of coronary heart disease and autonomic dysfunction.

DESIGN OF THE STUDY

Prospective case control study.

AIM AND OBJECTIVES

To evaluate beat-to-beat QT variability and vascular stiffness in patients with SH compared to normal controls.

MATERIALS AND METHODS

We compared linear and nonlinear measures of cardiac repolarization liability using beat-to-beat QT intervals derived from the surface electrocardiogram during supine posture and vascular indices including pulse wave velocity and ankle-brachial index (ABI) during supine posture between female patients with SH and age- and sex-matched normal controls. Spectral analysis was done at very low frequency (LF) (0.003-0.04 Hz), Low frequency (LF) (0.04-0.15 Hz), and high frequency (HF) (0.15-0.4 Hz). The HF represents vagal regulation (parasympathetic) and LF represents both parasympathetic and sympathetic regulation.

RESULTS

We recruited 58 women with a mean age of 31.83 ± 8.9 years and 49 controls with mean age of 32.4 ± 9.9 years (P = NS). QT variability index (QTvi) was higher in cases compared to controls (P = 0.01). The ratio of LF/HF of R-R interval which is an index of sympathovagal tone was significantly more in cases compared to controls (P = 0.02). The difference in the left minus the right ABI was significant between cases and controls (P = 0.03).

CONCLUSIONS

The cases had lower parasympathetic activity as compared to controls, and there was a predominance of sympathetic activity in cases. QTvi may be an important noninvasive tool in this group of patients to study the risk of cardiovascular mortality.