The new software 'SLDF version 4.0' clearly improved the reliability of assessing the structural parameters of the retinal arterioles. The application delivers reliable measurements of the retinal arteriolar structure in vivo in humans.

Autonomic dysreflexia presents a special situation in high-lesion spinal cord injury, however, intentionally or self-induced autonomic dysreflexia directly before or during competition to increase performance, so called 'boosting', is also being reported. In order to examine the influence of autonomic dysreflexia on plasma catecholamines, cardiocirculatory and metabolic parameters, 6 spinal cord injured wheelchair athletes with high-level lesions underwent wheelchair ergometry without (ST1) and with (ST2) autonomic dysreflexia. At the point of exhaustion significantly higher values for norepinephrine and epinephrine were observed in ST2 than in ST1. During autonomic dysreflexia a significantly higher peak performance (77.5 vs. 72.5 watt), higher peak heart rate (161 vs. 149 x min(-1)), and peak oxygen consumption (1.96 vs. 1.85 l x min(-1)), with comparable peak lactate (7.11 vs. 7.00 mmol x l(-1)) were reached on average. The blood pressure values in ST2 were partially hypertensive and higher than in ST1. In conclusion, autonomic dysreflexia, as a sympathetic spinal reflex, leads to a higher release of catecholamines during exercise. This results in higher peak performance, peak heart rate, peak oxygen consumption, and higher blood pressure values. The peak lactate, as an indicator of the anaerobic lactate metabolism, was unchanged. However, autonomic dysreflexia presents an unpredictable risk, caused predominantly by hypertensive blood pressure values, for high-lesion spinal cord injured persons at rest and more so during exercise; it is seen as a prohibited manipulation by the doping guidelines of the International Paralympic Committee.

Vascular dysfunction due to elevated blood pressure constitutes an early step in the pathogenesis of atherosclerotic disease. A better understanding of the pathophysiology and of clinical correlates of vascular remodeling in retinal arteries and arterioles offers the opportunity for a better risk stratification and treatment. In vivo vascular changes can be best detected by direct imaging techniques. In this review, we summarize the main findings of several recent studies analyzing retinal-arteriolar parameters, such as outer diameter (OD) and lumen diameter (LD), retinal capillary flow (RCF), wall-to-lumen-ratio, and wall cross-sectional area by using scanning laser Doppler flowmetry (SLDF). Blood pressure emerged as an independent determinant of the wall-to-lumen ratio (WLR) of retinal arterioles. Retinal arterioles and small arteries of hypertensive subjects showed eutrophic inward remodeling as indicated by increased WLR, decreased LD and almost unchanged wall cross-sectional area compared to normotensive subjects. These findings are in accordance with those observed in small-resistance vessels analyzed ex vivo. In hypertensive patients, an increased retinal vascular resistance has been documented and basal nitric oxide activity emerged as an independent determinant of early arteriolar remodeling. Thus, SLDF emerged as a noninvasive research tool to assess early vascular changes in the retinal circulation.

No abstract

Abstract-We hypothesized that the increase of retinal capillary blood flow (RCF) to flicker light exposure is impaired in subjects with arterial hypertension. In 146 nondiabetic untreated male subjects with (nϭ50) or without (nϭ96) arterial hypertension, RCF was measured before and after flicker light exposure noninvasively and in vivo using scanning laser Doppler flowmetry. In addition, in a subgroup of 28 subjects, the change of RCF to flicker light exposure was again assessed during parallel infusion of nitric oxide synthase inhibitor N-monomethyl-L-arginine (L-NMMA). The increase of RCF to flicker light exposure was lower in patients with untreated hypertension compared with normotensive subjects when expressed in absolute terms (7.69Ϯ54 versus 27.2Ϯ44 AU; P adjustedϭ0.013) or percent changes (2.95Ϯ14 versus 8.33Ϯ12%; P adjustedϭ0.023). Systolic (␤ϭϪ0.216; Pϭ0.023) but not diastolic blood pressure (␤ϭϪ0.117; Pϭ0.243) or mean arterial pressure (␤ϭϪ0.178; Pϭ0.073) was negatively related to the percent change of RCF to flicker light exposure, independently of other cardiovascular risk factors. In the subgroup of 28 subjects, the increase of RCF to flicker light exposure was similar at baseline and during parallel infusion of L-NMMA when expressed in absolute terms (20.0Ϯ51 versus 22.6Ϯ56 AU; Pϭ0.731) or percent changes (7.12Ϯ16 versus 8.29Ϯ18%; Pϭ0.607). The increase of RCF to flicker light exposure is impaired in arterial hypertension. In the subgroup of the total study cohort, nitric oxide was not a major determinant of the increase of RCF to flicker light exposure. (Hypertension. 2012;60:871-876.)Key Words: retina Ⅲ capillary blood flow Ⅲ vasodilatory properties Ⅲ nitric oxide Ⅲ arterial hypertension A rterial hypertension is a major determinant of morbidity and mortality due to cardiovascular complications. 1 Reduction in systolic and diastolic blood pressure levels was found to reduce and slow the occurrence of cardiovascular events in subjects with arterial hypertension 2 ; however, blood pressure levels per se might be unreliable indicators of cardiovascular risk in the individual subjects. In arterial hypertension, elevated blood pressure levels lead to structural and functional changes of blood vessels and organ damage, such as retinopathy, thickening of carotid arteries, large artery stiffening, left ventricular hypertrophy, and increased urinary albumin excretion, among others. These subclinical parameters represent intermediate end points that frequently precede major cardiovascular events and indicate the need for aggressive medical blood pressure control in context of individual global cardiovascular risk profile. 2Since the famous work by Keith, Wagener, and Barker,3 several studies have demonstrated the prognostic significance of retinal vascular alterations for predicting morbidity and mortality in subjects with arterial hypertension [4][5][6] ; however, owing to improvement in patient management, nowadays, grade 3 and grade 4 hypertensive retinopathy are seldom observed, and grade 1 and 2 hype...