Heart Rate Variability and Brain Functioning in Hypertensive Patients

Abstract

Objective:Decreased heart rate variability (HRV) reflecting autonomic nervous dysfunction has been associated with increased mortality in cardiovascular diseases. Less is known about the relationship between HRV and hypertension associated cognitive impairment. The study aimed to compare HRV parameters in well-controlled hypertensive patients with and without cognitive dysfunction, as marker of functional brain damage caused by hypertension.Design and method:Data about 226 hypertensive patients were obtained, 53% males, between 37 and 98 years (mean age 66 years ± 10). The mean blood pressure was 135/81 mmHg (±19/11 mmHg) (under hypertensive medication). Cognitive abilities were measured with the multi-domain Montreal Cognitive Assessment questionnaire (MoCA) defining cognitive decline below 24 points. All patients had 24- hour Holter monitoring. Time domain [pNN(50), NN(50) SDNN, rMSSD] and the LF/HF frequency domain HRV parameters were analyzed in patients with normal and impaired cognition, and in different cognitive domains with the IBM SPSS v20 software.Results:Cognitive dysfunction was present in 63.73% of the studied group. Time domain parameters pNN(50), NN(50) and r MSSD were significantly higher in patients with altered cognition (p = 0.002, p = 0.001, p = 0.02). Frequency domain HF was also significantly higher in this group (p = 0.03). Male individuals had significantly higher LF/HF ratio (men 1.08% vs. women 0.97%, p = 0.006). Patients with hypertension grade II had higher LF/HF ratio compared to grade III (1.069 vs. 0.98%, p = 0.01). Analyzes of cognitive domains in the total study group revealed low SDNN, rMSSD values in language, abstraction domains, with statistical significance in the domains of visuospatial-executive (SDNN p = 0.013, rMSSD p = 0.001) and attention (SDNN p = 0.044). Higher LF/HF ratio was found in all cognitive domains, excepting attention, with statistical difference in delayed recall (p = 0.015).Conclusions:Our data suggest a gender difference regarding sympathovagal balance in hypertensive patients with enhanced sympathetic activity in males. Although higher HRV was observed in cognitively impaired well-controlled hypertensive patients, time domain HRV parameters reflecting impaired autonomic nervous function were related to some specific cognitive domains. Future studies are needed to better understand these findings.