Effect of Rehabilitation on Recovery of Sympathetic Nervous Activity Measured According to Heart Rate Variability in Frail Elderly Adults

Non-Contact Measurement of Heart Rate Variability in Frail Geriatric Patients: Response to Early Geriatric Rehabilitation and Comparison with Healthy Old Community-Dwelling Individuals - A Pilot Study

INTRODUCTION

Frailty is a central geriatric syndrome characterized by a state of increased physiological vulnerability. As the key components of frailty are difficult to capture in their entirety, easily measurable and reliable surrogate parameters are desirable. Since frailty influences heart rate variability (HRV), HRV may be such a surrogate parameter. HRV is typically acquired by an ECG, which, however, may not be tolerated by all patients; in some, it may even trigger delirium. Therefore, we sought to measure HRV in a non-contact and unobtrusive way through photoplethysmography imaging (PPGI). Using our previously presented HRV estimation algorithm for PPGI, we investigated whether PPGI could reveal (1) HRV differences between frail and non-frail individuals and (2) the influences of early geriatric rehabilitation on HRV.

METHODS

The study involved 10 frail geriatric inpatients undergoing early geriatric rehabilitation and 10 healthy community-dwelling older adults. All participants underwent a comprehensive geriatric assessment. HRV measurements using a PPGI system and a reference ECG were made at the beginning and the end of the rehabilitation. HRV in terms of LF/HF ratio was analysed for both intra-individual changes during the geriatric rehabilitation and differences between frail geriatric patients and healthy community-dwelling individuals.

RESULTS

Across all geriatric patients, the median LF/HF ratio obtained with PPGI was found to be reduced by 0.178 (24.8%) during early geriatric rehabilitation. The assessment at the end of the rehabilitation revealed a simultaneous improvement of the functional state. Moreover, frail geriatric patients had a higher LF/HF ratio than their community-dwelling counterparts. Both observations in PPGI-based HRV were confirmed by the reference. The capability of PPGI to track intra-individual HRV changes was also analysed; a Spearman correlation of ρ = 1.0 between PPGI-based HRV and reference was achieved for 58.8% of the participants.

CONCLUSION

Early geriatric rehabilitation improves the functional state, which is associated with an increased HRV. PPGI is capable of detecting HRV changes/trends in that age group. While the tracking of intra-individual HRV changes is also possible, its reliability needs improvement. Nevertheless, the capabilities demonstrated in our study and the non-contact measurement principle of PPGI emphasize its potential for application in geriatric medicine.

Variation of Autonomic Nervous System Function by Age and Gender in Thai Ischemic Stroke Patients

Background: Ischemic stroke is one of the major causes of disability and mortality. Its effects on the autonomic nervous system (ANS) through nonlinear heart rate variability (HRV) and pulse transit time (PTT) have not been well explored among Thai patients. Objective: This study aims to demonstrate the association between ANS and ischemic stroke through nonlinear HRV and PTT. Methods: In total, 111 patients were enrolled in the study and their short-term HRV and PTT data were collected. Results: Parasympathetic tone was higher in elderly patients (≥60 years). The elderly patients had a higher SD1 but lower SD2 and SD2/SD1 than the younger patients, and a similar pattern was found in the female patients compared to the male patients. These findings were supported by the results of the Poincaré plots. Older and female patients had circular plots and approximately round plots, respectively. Moreover, the parasympathetic nervous system (PNS) response was moderate and positively associated with SD1 (r = 0.47, p < 0.001) and PTT (r = 0.29, p = 0.002), and negatively associated with SD2 and SD2/SD1 (r = −0.47, p < 0.001), after controlling for age and sex. Conclusions: The PNS response was predominant in older and female patients whereas the sympathetic response was lower than in the younger and male patients, which reflected certain characteristics of ANS response to ischemic stroke. Moreover, nonlinear parameters of SD1, SD2, SD2/SD1, and Poincaré plots including PTT are useful and recommended in investigating ANS, particularly in PNS, among ischemic stroke patients.

Role of autonomic nervous activity, as measured by heart rate variability, on the effect of mortality in disabled older adults with low blood pressure in long-term care

AIM

Previous studies have shown the relationship between low blood pressure and high mortality in frail, disabled older adults in long-term care. However, the mechanism of this relationship is still unclear. We hypothesized that autonomic nervous activity decline is involved in the relationship between low blood pressure and high mortality.

METHODS

The present prospective cohort study recruited 61 participants aged ≥75 years. The data from 24-h Holter monitoring and blood pressure recorded by ambulatory blood pressure monitoring were collected. Measured data were divided into three categories: 24-h, daytime and night-time. From power spectral density in the electrocardiogram, low frequency, high frequency and low frequency/high frequency ratio were calculated. The primary end-point was death.

RESULTS

High blood pressure was connected to both high daytime low frequency and high frequency (partial correlation coefficients: 0.42, P < 0.05 and 0.35, P < 0.05, respectively). In addition, the low blood pressure group had higher mortality than the high blood pressure group, and disabled older adults in long-term care and those with elevated daytime systolic and diastolic blood pressure had less risk of mortality compared with those without (systolic: hazard ratio 0.89, 95% confidence interval 0.83-0.96, P = 0.003; diastolic: hazard ratio 0.98, 95% confidence interval 0.79-1.00, P = 0.049). The average blood pressures in the high blood pressure groups were approximately 140/80 mmHg and were connected to low mortality.

CONCLUSIONS

Attenuated autonomic nervous activity might lead to low blood pressure in the daytime and high mortality in disabled older adults in long-term care. Geriatr Gerontol Int 2018; 18: 1153-1158.