I n t r o d u c t i o n: Stress is an ubiquitous phenomenon in the modern world and one of the major risk factors for cardiovascular disease. Th e aim of our study was to evaluate the effect of various acute stress stimuli on autonomic nervous system (ANS) activity, assessed on the basis of heart rate (HRV) and blood pressure (BPV) variability analysis.
Ma t e r i a l s a n d M e t h o d s: The study included 15 healthy volunteers: 9 women, 6 men aged 20– 30 years (23.3 ± 1.8). ANS activity was assessed by HRV and BPV measurement using Task Force Monitor 3040 (CNSystems, Austria). ECG registration and Blood Pressure (BP) measurement was done 10 minutes at rest, 10 minutes aft er the stress stimulus (sound signal, acoustic startle, frequency 1100 Hz, duration 0.5 sec, at the intensity 95 dB) and 10 minutes aft er the cold pressor test. The cold pressor test (CPT) was done by placing the person’s hand by wrist in ice water (0–4°C) for 120 s.
R e s u l t s: Every kind of stress stimulation (acoustic startle; the CPT) caused changes of HRV indicator values. The time domain HRV analysis parameters (pNN50, RMSSD) decreased aft er acoustic stress and the CPT, but were signifi cantly lower after the CPT. In frequency domain HRV analysis, significant differences were observed only aft er the CPT: (LF-RRI 921.23 ms2 vs. 700.09 ms2; p = 0.009 and HF-RRI 820.75 ms2 vs. 659.52 ms2; p = 0.002). The decrease of LF-RRI and HF-RRI value aft er the CPT was significantly higher than after the acoustic startle (LF-RRI 34% vs. 0.4%, p = 0.022; HF-RRI 19.7% vs. 7% ms2, p = 0.011). The decreased value of the LF and HF components of HRV analysis are indicative of sympathetic activation. Nonlinear analysis of HRV indicated a significant decrease in the Poincare plot SD1 (p = 0.039) and an increase of DFAα2 (p = 0.001) in response to the CPT stress stimulation. Th e systolic BPV parameter LF/HF-sBP increased signifi cantly aft er the CPT (2.84 vs. 3.31; p = 0.019) and was higher than aft er the acoustic startle (3.31 vs. 3.06; p = 0.035). Signifi cantly higher values of diastolic BP (67.17 ± 8.10 vs. 69.65 ± 9.94 mmHg, p = 0.038) and median BP (83.39 ± 8.65 vs. 85.30 ± 10.20 mmHg, p = 0.039) were observed in the CPT group than in the acoustic startle group.
C on c l u s i o n s: Th e Cold Pressor Test has a greater stimulatory eff ect on the sympathetic autonomic system in comparison to the unexpected acoustic startle stress. Regardless of whether the stimulation originates from the central nervous system (acoustic startle) or the peripheral nervous system (CPT), the final response is demonstrated by an increase in the low frequency components of blood pressure variability and a decrease in the low and high frequency components of heart rate variability.