Heart Rate Variability for the Early Detection of Cardiac Autonomic Dysfunction in Type 1 Diabetes

Recent advances in facilitating the translation of bioelectronic medicine therapies

Bioelectronic medicine is a growing field which involves directly interfacing with the vagus, sacral, enteric, and other autonomic nerves to treat conditions. Therapies based on bioelectronic medicine could address previously intractable diseases and provide an alternative to pharmaceuticals. However, translating a bioelectronic medicine therapy to the clinic requires overcoming several challenges, including titrating stimulation parameters to an individual's physiology, selectively stimulating target nerves without inducing off-target activation or block, and improving accessibility to clinically approved devices. This review describes recent progress towards solving these problems, including advances in mapping and characterizing the human autonomic nervous system, new sensor technology and signal processing techniques to enable closed-loop therapies, new methods for selectively stimulating autonomic nerves without inducing off-target effects, and efforts to develop open-source implantable devices. Recent commercial successes in bringing bioelectronic medicine therapies to the clinic are highlighted showing how addressing these challenges can lead to novel therapies.

Orthostatic test shows higher systolic blood pressure and sympathetic response in uncomplicated type 1 diabetes patients with normal V̇O2max vs. healthy controls

PURPOSE

Cardiovascular autonomic neuropathy remains underdiagnosed in type 1 diabetes mellitus, posing a risk for severe complications, particularly in patients with lowered V̇O2max, compared to controls. This study aimed to determine whether heart rate variability during cardiovascular autonomic reflex tests reveals early signs of cardiovascular autonomic neuropathy in patients with uncomplicated type 1 diabetes mellitus and normal cardiovascular fitness, compared to healthy controls.

METHODS

A type 1 diabetes mellitus group (n = 14) with no other diagnosed diseases (diabetes duration 15 ± 7 years) and a control group (n = 31) underwent deep breathing test, passive orthostatic test, and cardiopulmonary exercise test. Participants were assessed for heart rate variability, heart rate, blood pressure, and V̇O2max (mL/min/kg).

RESULTS

Participant characteristics, including V̇O2max (mL/min/kg), showed no significant differences. The type 1 diabetes mellitus group had higher systolic blood pressure during the supine phase of the orthostatic test than healthy controls (131.6 ± 14.7 mmHg vs. 122.4 ± 10.8 mmHg, p = 0.022). After 5 mins in the upright position, systolic blood pressure (132.2 ± 20.6 mmHg vs. 118.7 ± 11.7 mmHg, p = 0.036), heart rate (85 (76; 89) bpm vs. 75 (72; 83) bpm, p = 0.013), and the root mean square of successive RR interval differences (20.22 (11.22; 27.42) vs. 27.11 (19.90; 35.52), p = 0.033) were significantly different compared to controls.

CONCLUSION

Patients with uncomplicated type 1 diabetes mellitus, despite having normal cardiorespiratory fitness, exhibited higher systolic pressure and greater sympathetic activation in orthostatic tests, suggesting subclinically altered cardiovascular autonomic function.

Lipid profile, inflammatory biomarkers, endothelial dysfunction, and heart rate variability in adolescents with type 1 diabetes. A case-control study among UAE population

Background

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by the chronic inflammation and cause of endothelial dysfunction (ED). Heart rate variability (HRV) is a marker of sympathetic and parasympathetic autonomic nervous system dysfunction. We investigated the association of lipid profile, inflammatory biomarkers, endothelial dysfunction, and heart rate variability in adolescents with T1DM among UAE population.

Method

In this case-control study we recruited 126 adolescents (13-22 years) from Abu Dhabi, UAE (United Arab Emirates). Demographic, anthropometric, blood and urine samples were collected after an overnight fasting. HRV measurements were determined per Task Force recommendations. Independent t-test or Mann-Whitney U test and Pearson's Chi-squared test were used to compare groups. Adjusted conditional logistic regression model was used to identify the determinants independently associated with T1DM.

Results

The mean ages in control (n = 47) and patient (n = 79) groups were 17.5 ± 4.6 and 18.6 ± 4.8 years, respectively. A family history of diabetes and waist and hip circumferences significantly differed between the groups (p = 0.030 and 0.010). The patients with T1DM exhibited significantly higher levels of atherogenic markers than control. Endothelial dysfunction biomarkers such as levels of sICAM-1 (p < 0.001), adiponectin (p < 0.001) and 25-hydroxyvitamin D (p < 0.001) were significantly different in the control group compared with those in the T1DM group. There was a significant difference in SDNN intervals, NN50, pNN50, and SD1/SD2 among the two groups. In adjusted analysis, total cholesterol (adjusted Odds Ratio (aOR): 2.78, 95 % CI:1.37-5.64; p = 0.005), LDL (2.66, 95%CI:1.19-5.92; p = 0.017), and triglycerides (5.51, 95%CI:1.57-19.41; p = 0.008) were significantly associated with developing T1DM. The HRV indicators were significantly associated with decrease odds of T1DM after controlling for SBP, BMI, and family history of DM.

Conclusion

In this study, adolescents with T1DM showed a significant association with lipid profile, ED, and HRV compared with controls. Thus, an early attention to diabetes control is required to reduce the risk of cardiac autonomic neuropathy leading to various cardiovascular diseases.

Impaired Cardiovagal Activity as a Link Between Hyperglycemia and Arterial Stiffness in Adults With Type 2 Diabetes Mellitus Among an Eastern Indian Population: A Cross-sectional Study

OBJECTIVES

Cardiac autonomic neuropathy (CAN) is one of the most common yet overlooked complications of type 2 diabetes mellitus (T2DM). Individuals with T2DM with CAN have a 5-fold higher rate of cardiovascular morbidity and mortality. The presence of CAN in T2DM could potentially lead to arterial stiffness. However, only sparse data are available suggesting any association between autonomic dysfunction and arterial stiffness in T2DM.

METHODS

We recruited 80 people with T2DM and 74 healthy controls for our study. Heart rate variability (HRV) testing was performed to assess autonomic function. Assessment of arterial stiffness was done by measuring the brachial pulse wave velocity (baPWV) and augmentation index (AI).

RESULTS

The time-domain parameters were significantly decreased (p<0.001) and frequency-domain parameters, such as total power and high-frequency band expressed as a normalized unit, were found to be significantly reduced in people with T2DM (p<0.001). Both baPWV and AI were significantly higher in people with T2DM compared with healthy controls (p<0.001). We observed a moderate correlation between standard deviation of normal to normal interval (SDNN) and baPWV (r=-0.437, p=0.002) and AI (r=-0.403, p=0.002). A multiple linear regression model showed an association between SDNN and arterial stiffness parameters, such as baPWV and AI, which were statistically significant (p<0.05) in a fully adjusted model that included the conventional risk factors for atherosclerosis.

CONCLUSIONS

Impaired cardiovagal activity is an independent risk factor for the development of arterial stiffness. Incorporation of HRV testing into the diabetes management protocol would have potential benefits for identifying individuals at high risk of developing cardiovascular events. Hence, preventive measures can be taken as early as possible to improve patient outcomes.

Is fat-to-lean mass ratio a better predictor of heart variability than body mass index?

BACKGROUND

Body mass index (BMI) may not accurately predict cardiometabolic risk due to confounders like age, gender, relatively high lean mass, and the "thin-fat phenotype" prevalent in south Asian populations. Fat-to-lean mass ratio (FTLM), which assesses the balance between fat and lean body mass, may provide a more complete assessment of cardiometabolic health.

MATERIALS AND METHODS

This cross-sectional analytical study investigated the relationship between FTLM ratio, BMI, and heart rate variability (HRV) in apparently healthy male adults. 88 participants recruited through convenience sampling underwent anthropometric assessments, bioimpedance body composition analysis, and HRV testing. Pearson's or Spearman's correlation and linear regression analyses were performed where appropriate to assess the relationship between FTLM ratio, BMI, and HRV.

RESULTS

Both BMI and FTLM showed significant positive correlation with normalized LF power and LF-HF ratio and a negative correlation with normalized HF power, RMSSD, and pNN50. However, FTLM ratio showed a stronger association with HRV parameters than BMI and could explain a greater percentage of the variability in LF-HF ratio (32% compared to 18.4%, P < 0.001).

CONCLUSION

Assessment of both fat and lean mass, expressed as a ratio, is a better index of quantifying adiposity and predicting the influence of altered body composition on cardiometabolic health.

Changes in beat-to-beat blood pressure and pulse rate variability following stroke

Associations between cerebrovascular disease and impaired autonomic function and cerebrovascular reactivity have led to increased interest in variability of heart rate (HRV) and blood pressure (BPV) following stroke. In this study, beat-to-beat pulse rate variability (PRV) and BPV were measured in clinically stable stroke patients (6 ischemic, 2 hemorrhagic) at least one year after their last cerebrovascular event. Beat-to-beat blood pressure (BP) measurements were collected from subjects while resting in the sitting position for one hour. Compared with healthy controls, stroke patients exhibited significantly greater time-domain (standard deviation, coefficient of variation, average real variability) and normalized high-frequency BPV (all p < 0.05). Stroke patients also exhibited lower LF:HF ratios than control subjects (p = 0.003). No significant differences were observed in PRV between the two groups, suggesting that BPV may be a more sensitive biomarker of cerebrovascular function in long-term post-stroke patients. Given a paucity of existing literature investigating beat-to-beat BPV in clinically stable post-stroke patients long (> 1 year) after their cerebrovascular events, this pilot study can help inform future studies investigating the mechanisms and effects of BPV in stroke. Elucidating this physiology may facilitate long-term patient monitoring and pharmacological management to mitigate the risk for recurrent stroke.

Adynamic response to cold pain reflects dysautonomia in type 1 diabetes and polyneuropathy

Cardiac autonomic neuropathy (CAN), widely assessed by heart rate variability (HRV), is a common complication of long-term diabetes. We hypothesized that HRV dynamics during tonic cold pain in individuals with type 1 diabetes mellitus (T1DM) could potentially demask CAN. Forty-eight individuals with long-term T1DM and distal symmetrical polyneuropathy and 21 healthy controls were included. HRV measures were retrieved from 24-h electrocardiograms. Moreover, ultra-short-term HRV recordings were used to assess the dynamic response to the immersion of the hand into 2 °C cold water for 120 s. Compared to healthy, the T1DM group had expectedly lower 24-h HRV measures for most components (p < 0.01), indicating dysautonomia. In the T1DM group, exposure to cold pain caused diminished sympathetic (p < 0.001) and adynamic parasympathetic (p < 0.01) HRV responses. Furthermore, compared to healthy, cold pain exposure caused lower parasympathetic (RMSSD: 4% vs. 20%; p = 0.002) and sympathetic responses (LF: 11% vs. 73%; p = 0.044) in the T1MD group. QRISK3-scores are negatively correlated with HRV measures in 24-h and ultra-short-term recordings. In T1DM, an attenuated sympathovagal response was shown as convincingly adynamic parasympathetic responses and diminished sympathetic adaptability, causing chronometric heart rhythm and rigid neurocardiac regulation threatening homeostasis. The findings associate with an increased risk of cardiovascular disease, emphasizing clinical relevance.