Finger volume pulse waveforms facilitate reliable assessment of heart rate variability, but not blood pressure variability or baroreflex function

Effects of Blood Flow Restriction Resistance Training on Autonomic and Endothelial Function in Persons with Parkinson's Disease

Background

Autonomic dysfunction precedes endothelial dysfunction in Parkinson's disease (PD) and causes blood pressure and circulation abnormalities that are highly disruptive to one's quality of life. While exercise interventions have proven helpful for motor symptoms of PD, improving associated non-motor symptoms is limited. Low-intensity resistance training with blood flow restriction (LIRT-BFR) improves autonomic dysfunction in non-PD patients and high-intensity resistance training (HIRT) is recommended for motor symptom improvements for people with PD (PwPD).

Objective

To determine the effects of LIRT-BFR and HIRT on homocysteine and autonomic and endothelial function in PwPD and to determine the hemodynamic loads during LIRT-BFR and HIRT in PwPD using a novel exercise protocol.

Methods

Thirty-eight PwPD were assigned LIRT-BFR, HIRT or to a control (CNTRL) group. The LIRT-BFR and HIRT groups exercised three days per week for four weeks. The LIRT-BFR protocol used 60% limb occlusion pressure (LOP) and performed three sets of 20 repetitions at 20% of the one-repetition maximum (1RM). The HIRT group performed three sets of eight repetitions at 80% 1RM. The CNTRL group was asked to continue their normal daily routines.

Results

LIRT-BFR significantly improved orthostatic hypotension (p = 0.026), homocysteine levels (p < 0.001), peripheral circulation (p = 0.003), supine blood pressure (p = 0.028) and heart rate variability (p = 0.041); LIRT-BFR improved homocysteine levels (p < 0.018), peripheral circulation (p = 0.005), supine blood pressure (p = 0.007) and heart rate variability (p = 0.047) more than HIRT; and hemodynamic loads for LIRT-BFR and HIRT were similar.

Conclusions

LIRT-BFR may be more effective than HIRT for autonomic and endothelial function improvements in PwPD and hemodynamic loads may be lessened in LIRT-BFR protocols using single-joint exercises with intermittent blood flow restriction. Further research is needed to determine if non-motor symptoms improve over time and if results are sustainable.

Reliability of carotid-femoral arterial waveforms for the derivation of ultra-short term heart rate variability in injured British servicemen: An inter-rater reliability study

In this study, the comparative precision of carotid versus femoral arterial waveforms to measure ultra-short term heart rate variability (HRVUST) following traumatic injury was investigated for the first time. This was an inter-rater reliability study of 50 British servicemen (aged 23-44 years) with non-acute combat-related traumatic injury (CRTI). Paired continuous arterial waveform data for HRVUST analysis, were simultaneously sampled at the carotid and femoral arterial sites (14-16 seconds) during pulse wave velocity (PWV) measurement. HRVUST was reported as the root mean square of the successive differences (RMSSD). Following the determination of the superior sampling site (carotid versus femoral), the blinded inter-rater agreement in RMSSD for the preferred site was quantified using the Intra-class Correlation Coefficient (ICC) and the Bland-Altman plot. The mean age of participants was 34.06±4.88 years. The femoral site was superior to the carotid site with a significantly higher number of reliable signals obtained (Fisher's Exact test; p<0.001). The inter-rater agreement in femoral-derived RMSSD was excellent [ICC 0.99 (95%CI: 0.994-0.997)] with a moderate level of agreement (mean difference [bias]: 0.55; 95% CI: -0.13-1.24 ms). In this study, we demonstrated that the femoral artery is a more reliable site than the carotid artery for HRVUST measurement and post-trauma risk stratification following CRTI.

Bromocriptine quick-release as adjunct therapy in youth and adults with type 1 diabetes: A randomized, placebo-controlled crossover study

AIM

To evaluate the potential for glycaemic, renal and vascular benefits of bromocriptine quick release (BCQR) in adolescents and adults with type 1 diabetes.

MATERIALS AND METHODS

Forty adolescents and 40 adults with type 1 diabetes aged 12-60 years old were enrolled in a double-blind, placebo-controlled, random order crossover study of 4 weeks of treatment in the morning with BCQR (titrated weekly from 0.8 mg to 1.6 mg to 3.2 mg, minimum dose 1.6 mg). Study assessments after each phase included blood pressure (BP), lipids, peripheral arterial stiffness and autonomic function, mixed meal tolerance test, continuous glucose monitoring (CGM), creatinine, estimated glomerular filtration rate, estimated insulin sensitivity, insulin dose and indirect calorimetry.

RESULTS

Adolescents displayed baseline hyperglycaemia, insulin resistance, metabolic dysfunction and increased renal filtration compared with adults. In both age groups, continuous glucose monitoring measures, estimated insulin sensitivity and insulin dose did not differ with BCQR treatment. In adolescents, BCQR decreased systolic BP, diastolic BP and triangular index and increased serum creatinine. In adults, systolic BP, mean arterial pressure, systemic vascular resistance, and mixed meal tolerance test glucose and glucagon-like peptide 1 areas under the curve were lower, and the orthostatic drop in systolic BP was greater with BCQR.

CONCLUSIONS

Greater hyperglycaemia, insulin resistance, metabolic dysfunction and renal hyperfiltration in adolescents argues for increased attention during this high-risk age period. Although BCQR had little impact on glycaemia or insulin sensitivity, initial vascular and renal responses suggest potential benefits of BCQR in adolescents and adults with type 1 diabetes requiring further study.

Short-term aerobic training improves heart rate variability in men living with HIV: a pre-post pilot study

BACKGROUND

Heart rate variability (HRV) a feasible predictor of prognosis in cardiovascular outcomes shown to be reduced in people living with HIV (PLWH).

OBJECTIVE

This study sought to understand the effects of short-term aerobic training (AT) on the resting HRV and endothelial function in this population.

METHODS

PLWH performed 24 sessions of AT protocol. The protocol consists of 40 min of treadmill (60 to 80% of the VO_2max), 3 times per week, for 8 weeks. HRV (standard deviation of all normal RR intervals - SDNN; root mean square of the successive differences - rMSSD; low frequency - LF; high frequency - HF; LF:HF ratio) and endothelial function parameters were evaluated by EndoPAT system pre and post intervention.

RESULTS

7 men, the median age of the sample was 49 years (range, 38-68 years), completed the protocol. AT improved resting HRV parameters: SDNN (p = 0.02, power analysis (PA) 0.54), rMSSD (p = 0.02, PA = 0.99), LF (p = 0.02, PA = 0.85). HF, LF:HF ratio and endothelial function parameters showed no changes.

CONCLUSIONS

The results suggest the short-term AT may improve HRV in men living with HIV.

A Walking Intervention to Increase Weekly Steps in Dialysis Patients: A Pilot Randomized Controlled Trial

RATIONALE & OBJECTIVE

Patients receiving dialysis report very low physical activity. We implemented a pilot trial to assess the feasibility of a pedometer-based intervention to gather preliminary evidence about its impact on physical activity, symptoms, and surrogates of cardiovascular risk.

STUDY DESIGN

Pilot randomized controlled trial.

SETTING & PARTICIPANTS

60 dialysis patients from San Francisco dialysis clinics.

INTERVENTION

Participants were randomly assigned 1:1 to receiving pedometers with weekly step goals or usual care for 3 months.

OUTCOMES

The primary outcome was step counts, measured using pedometers. Secondary outcomes included physical performance using the Short Physical Performance Battery, the Physical Function and Vitality scales of the 36-Item Short Form Health Survey, the Dialysis Symptoms Index, and the Center for Epidemiologic Studies-Depression Scale, with endothelial function as a secondary and heart rate variability as an exploratory surrogate measure of cardiovascular risk. Targeted enrollment was 50% and targeted completion was 85%.

RESULTS

49% of approached patients were enrolled, and 92% completed the study. After 3 months, patients randomly assigned to the intervention (n=30) increased their average daily steps by 2,256 (95% CI, 978-3,537) more than the 30 controls (P<0.001). Heart rate variability (standard deviation of N-N intervals) increased by 14.94 (95% CI, 0.31-33.56) millisecondsin the intervention group as compared with controls (P = 0.05). There were no statistically significant differences across intervention groups in symptoms, physical performance, or endothelial function. Participants in the intervention group reverted to baseline steps during the postintervention follow-up.

LIMITATIONS

The Northern California study setting may limit generalizability. Walking does not capture the full spectrum of physical activity.

CONCLUSIONS

A short-term pedometer-based intervention led to increased step counts in dialysis patients, but the increase was not sustained. Pedometer-based interventions are feasible for dialysis patients, but future studies are needed to address whether more prolonged interventions can improve physical function or symptoms.

FUNDING

Supported by grants from the American Kidney Fund, National Institutes of Health-National Institute of Diabetes and Digestive and Kidney Diseases, and International Society of Nephrology.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study identifier NCT02623348.

Non-contact measurement of heart response reflected in human eye

This study aims to develop a non-contact measurement technique for cardiac response that uses an infrared image of the patient's pupil. The pupil contraction rhythm is related to the autonomic balance and major organs (such as the heart) via a neural pathway. In this study, the response of the heart was determined by analyzing the pupillary rhythm based on the harmonic frequencies between them. Seventy undergraduate volunteers of both genders, (35 females and 35 males), with ages ranging between 20 and 30years (mean: 24.52±0.64years) were asked to conduct a simple conversation, perform slight movements, and experience sound stimuli to evoke arousal, relaxation, happiness, sadness, or a neutral mood in this experiment. Electrocardiograms and pupil images were measured and analyzed, and the harmonic frequencies were identified to determine the relational response. The cardiac time (heart rate (HR), beats per minute (BPM), the standard deviation of the normal-to-normal (NN) intervals (SDNN), the mean squared differences in the successive N-N intervals (rMSSD), and the percentage difference between adjacent normal interbeat (R-R) intervals>50 (pNN50)) and frequency (very low frequency (VLF), low frequency (LF), high frequency (HF), VLF/HF, and LF/HF) parameters were also observed with regard to the effects of the movement, conversation, and physiological state. The cardiac response was stable, showing less significance than the effects of the three conditions. Therefore, multi-cardiac measurements were successfully obtained from a simple, low-cost, non-invasive, and non-contact data acquisition method in this study.

Beneficial Effects of Magnesium Treatment on Heart Rate Variability and Cardiac Ventricular Function in Diabetic Rats

BACKGROUND

Diabetes mellitus induces life-threatening cardiovascular complications such as cardiac autonomic neuropathy and ventricular dysfunction and is associated with hypomagnesemia. In this study, we investigated the short-term effects of magnesium (Mg²⁺) treatment on streptozotocin (STZ)-induced diabetic cardiac complications.

METHODS

Adult Wistar rats were treated once with STZ (50 mg/kg, intraperitoneally [ip]) or vehicle (citrate) and then daily for 7 days with MgSO₄ (270 mg/kg, ip) or saline. On the eighth day, in vivo tail-pulse plethysmography was recorded for heart rate variability (HRV) analysis, and ex vivo Langendorff-based left ventricular (LV) pressure-volume parameters were measured using an intraventricular balloon. Measurements of plasma lipid and Mg²⁺ levels as well as blood glucose and cardiac tissue Mg²⁺ levels were also performed.

RESULTS

Treatment with Mg²⁺ prevented diabetes-induced alterations in the standard deviation of the averages of normal-to-normal (NN) intervals (SDANN), root mean square differences of successive NN intervals (RMSSD), heart rate, and low-frequency (LF) power-high-frequency (HF) power ratio. In addition, Mg²⁺ restored orthostatic stress-induced changes in SDANN, RMSSD, and LF-HF ratio in diabetic rats. In isolated hearts, Mg²⁺ reversed the diabetes-induced decrease in LV end-diastolic elastance and the right shift of end-diastolic equilibrium volume intercept, without altering LV-developed pressure or end-systolic elastance. However, Mg²⁺ did not prevent the elevation in blood glucose, total cholesterol, and triglycerides or the decrease in high-density lipoprotein cholesterol in diabetes. Plasma- or cardiac tissue Mg²⁺ was not different among the treatment groups.

CONCLUSION

These results suggest that Mg²⁺ treatment may attenuate diabetes-induced reduction in HRV and improve LV diastolic distensibility, without preventing hyperglycemia and dyslipidemia. Thus, Mg²⁺ may have a modulatory role in the early stages of diabetic cardiovascular complications.

Correlations Between Cardiovascular Autonomic Control Indices During the Two-hour Immobilization Test in Healthy Subjects

Objective:

The aim of the present study was to assess the features of dynamics of cardiovascular autonomic indices and correlations between them during the two-hour immobilization test in healthy subjects.

Methods:

Photoplethysmogram (PPG) and electrocardiogram were recorded simultaneously during the two-hour immobilization test in 14 healthy subjects (5 men and 9 women) aged 29±5 years (mean±SD). Dynamics of heart rate variability (HRV) power spectrum in high-frequency and low-frequency ranges (in ms2 and percents of total spectral power), mean heart rate (HR), and index S of synchronization between 0.1-Hz rhythms in PPG and HR were analyzed.

Results:

Individual dynamics of all studied cardiovascular autonomic indices during the two-hour immobilization test was unique in each healthy subject. Two groups of healthy subjects were identified basing on individual features of autonomic control. The group with initial low level of index S maintained the low level of S during the two-hour immobilization test. The group with initial high index S maintained the high level of S only during the first 100 minutes of test. During the last 20 minutes of test, index S was similar in both groups. Many cardiovascular autonomic indices correlate between themselves for an individual subject, but they do not correlate between the subjects. Multiple regression analysis in each subject has shown a high correlation between mean HR and all other studied autonomic parameters in 57% of subjects (multiple R>0.9, P<0.05). For 204 records analyzed without taking into account the individual features of subjects, the above mentioned correlation was smaller (multiple R=0.45, P<0.001). Index S was found out to be the most independent one among the autonomic indices.

Conclusion:

Cardiovascular autonomic control is characterized by a pronounced variability among healthy subjects and stability in time in each subject. We have not found any regularity in variation of cardiovascular autonomic indices, which is common for the entire group of healthy subjects during the two-hour immobilization test. Mean HR is a summary index of efficiency of heart autonomic control. Index S is the most independent cardiovascular autonomic parameter.