Background: 

Endothelial function and cardiac vagal activity are important factors in cardiovascular regulation. Cardiac vagal activity is strongly influenced by cardiovagal baroreflex sensitivity (BRS). Numerous physiological factors such as ageing, fitness and diurnal rhythm cause parallel changes in endothelial function and baroreflex sensitivity. Besides, existence of disease states – e.g. hypertension, cardiac failure and diabetes mellitus – lead to deterioration of both systems. Whether the alterations occur independently or these systems are linked is currently unknown. Therefore, we aimed to investigate the possible connections between endothelial function and baroreflex sensitivity.

Subjects and methods: 

63 healthy young (21 ± 3 yrs) males were studied. Endothelial function was assessed by brachial artery flow-mediated dilation (FMD). Hyperemic, diastolic shear rate was used to normalize FMD (nFMD). The BRS was quantified by spontaneous sequential (BRSseq) and spectral (LFa) methods. Phenylephrine method was carried out in 13 subjects. Spontaneous measures of BRS were derived from 10 minute long ECG and beat-to-beat blood pressure recordings. Intravenous phenylephrine-induced blood pressure elevation and reflex-reduction of heart rate was used to determine BRSphe.

Results: 

(mean ± SD): FMD – (6.8 ± 2.7 %); nFMD – (36.7 ± 13.5 %/cm/s); BRSseq – (20.1 ± 8.4 ms/mmHg); LFa– (14.5 ± 7.1 ms/mmHg); BRSphe – (24.5 ± 9.8 ms/mmHg). All reported values fell within age-related normal ranges. We found no significant correlation between the endothelial parameters and the BRS indices.

Discussion: 

Since we could not find correlation between these systems, we hypothesize that endothelial function and baroreflex sensitivity undergo independent regulation within physiological and pathophysiological conditions.