Wentzel, AMalan, Lvon Kanel, RSmith, WMalan, N.T2024-06-092024-06-092019-07-05Wentzel A, Malan L, von Kanel R, Smith W, Malan NT. Heart rate variability, the dynamic nature of the retinal microvasculature and cardiac stress: Providing insight into the brain-retina-heart link: The SABPA study. Eye (Lond). 2019 Jul 5. doi: 10.1038/s41433-019-0515-yhttps://doi.org/10.1038/s41433-019-0515-yhttps://pubmed.ncbi.nlm.nih.gov/31278382/https://hdl.handle.net/11288/596355Background and aims: Decreased heart-rate-variability (HRV) indicates increased sympathetic nervous system (SNS) activity and modulation with a shift in the sympatho-vagal balance towards SNS predominance. Increased SNS activity may precede volume-loading hypertension, contribute to increases in cardiac troponin T (cTnT), endothelial dysfunction and small vessel disease. Therefore, we investigated the retinal vasculature, HRV during flicker-light-induced-provocation (FLIP) and systemic cTnT, a marker of cardiac stress, to provide further evidence in support of the brain-retina-heart link. Methods: Cross-sectional observations were obtained from a bi-ethnic cohort (N = 264), aged 23-68 years. Fasting serum samples for cTnT were obtained. Retinal vascular calibres were quantified from mydriatic eye fundus images and dynamic retinal vessel calibre responses were determined during FLIP. Time-and frequency domain parameters of HRV were calculated during FLIP for each participant. Results: Africans had wider venules and attenuated time domain parameters during FLIP. In Africans, inverse associations emerged between arteriolar dilation and both cTnT and root-mean squared of the standard deviations of successive RR-intervals (rMSSD) (p = 0.030), and between arteriolar constriction and both low-frequency expressed in normalised units (LFnu) (p = 0.003) and high-frequency expressed in normalised units (p = 0.021). Wider venules inversely associated with standard deviation of the NN intervals (SDNN) as well as LFnu (p = 0.009) in Africans. An opposite profile was observed in Caucasians with both time-and frequency domain parameters of HRV in relation to retinal vessel structure and function. Conclusion: FLIP elicited increased SNS activity and modulation in this bi-ethnic cohort. In Africans, decreased HRV during FLIP accompanied arteriolar and venular responses and elevated systemic levels of cTnT, implying that the SNS exerted a significant effect on the smooth muscle tone of the retinal vasculature. Disrupted retinal autoregulation may imply general autonomic nervous system dysfunction; exemplifying central control by the brain on all systemic regulatory functions, across different vascular beds.enAttribution 3.0 United Stateshttp://creativecommons.org/licenses/by/3.0/us/Heart rateRetinal microvasculatureHypertensionCardiologyArticleEye (Lond)