Cardiovascular parameters during mental and physical stress in hypertensive patients

Abstract

Stress is a major burden for the society and is one of the leading causes for a number of serious diseases. There exist several invasive and non-invasive methods to quantify the stress and to monitor it. However, mostly the effects of mental or physical stress on cardiovascular parameters in a healthy population have been the focus of many studies. In order to investigate the effects of mental or physical stress on a hypertensive population, various cardiovascular parameters of 48 hypertensive participants with elevated blood pressure or hypertension were monitored in this study. Participants of the study were placed in three different states, a baseline state that occurred twice at the beginning, a stress state that consisted of either a Demtect test or climbing stairs, and a recovery state after the stressful situation. With a hand-held device, electrocardiogram and pulse-photoplethysmogram data were continuously recorded and based on those signals pulse arrival time PAT, heart rate HR, heart rate variability (HRV) data and pulse wave characteristics were calculated and evaluated. Cardiovascular parameters between the different groups of stress modes and blood pressure classes as well as age and sex were statistically evaluated, as well as differences Δ between the beginning and end of the measurement.During both tasks, sympathetic nervous system (SNS) activity increased and parasympathetic nervous system (PNS) activity decreased, resulting in an increase in blood pressure, HR (ΔHR mental 4.45 1/min, physical 35.21 1/min) and ratio of low frequency to high frequency power LF/HF (ΔLF/HF mental 1.13, physical 1.29), and resulting in a decrease in inflection point area IPA (ΔIPA mental −0.18, physical −0.46). The changes in parameters were different for the mental and physical tasks, such that the physical task elicited stronger responses than the mental one. Despite an increase in systolic blood pressure SBP and HR during the mental task, PAT barely fell (ΔPAT mental −9.31 ms, physical −58.13 ms). The standard deviation of normal-to-normal intervals SDNN (ΔSDNN mental 8.26 ms, physical 3.05 ms) increased and the root mean square of successive RR differences RMSSD remained unchanged, indicating that the mental task elicited lighter HRV responses. After the mental task, PNS activity increased and SNS activity remained the same, whereas after the physical task the opposite was observed, here PNS activity remained the same and SNS activity decreased.Hypertensives and subjects with elevated blood pressure showed an increase in LF/HFs (ΔLF/HF 1.40) during both tasks, but also an increase in SDNN (ΔSDNN 10.75 ms). They showed no recovery after the task with an increased RMSSD value, whereas normotensive subjects did (ΔRMSSD 7.31 ms). In addition, hypertensives had generally increased arterial vascular tone, as PAT values were lowest at rest and IPA values did not recover after the task. The correlations between SBP and PAT were significant but not sufficient. The correlation coefficients varied from −0.30 to 0.32, but correlations between HR and PAT in the different phases showed synchronisation in the recovery phase with a correlation coefficient of −0.61. The data showed that the relationship between PAT or the underlying pulse wave velocity with blood pressure is not quite so trivial, but it depends on age, sex and cardiovascular risk factors. Moreover, cardiovascular parameters of hypertensives no longer respond to all stressful situations. An explizitly longer recovery after the mental or physical task in the hypertensive or normotensive participants cannot be stated.This paper presents a study to determine any differences between mental and physical stress in hypertensive and normotensive participants. The results obtained show no increased reactivity to mental stress, neither in normotensive nor in hypertensive participants. A clearly deteriorated recovery can also not be determined in any of the groups. Studies taking into account other stress stimuli would be helpful to confirm these results.