Noninvasive assessment of subclinical atherosclerosis in children and adolescents.

Contains fulltext : 89835thijssen.pdf (publisher's version ) (Closed access)01 maart 201

Importance of measuring the time course of flow-mediated dilatation in humans.

Contains fulltext : 69814thijssen.pdf (publisher's version ) (Closed access)Flow-mediated dilatation (FMD) is widely used to describe conduit artery endothelial function. The traditional approaches to FMD calculation assess diameter change at arbitrary time points after occluding cuff deflation. The aim of this study was to examine the time course of brachial artery FMD after a 5-minute period of forearm ischemia in 12 young, 12 fitness matched older and 12 older untrained subjects. Edge-detection and wall tracking of high resolution B-mode arterial ultrasound images, combined with synchronized Doppler waveform envelope analysis, were used to calculate brachial artery diameter, blood flow, and shear rate continuously across the cardiac cycle after forearm ischemia. FMD was significantly higher in young healthy subjects (7.8+/-3.2%) compared with sedentary older subjects (5.2+/-2.8%, P42%) of true peak diameters fell outside the time frames typically used to assess FMD in the literature. When calculated according to the commonly used approach, ie, 60 s after cuff deflation, FMD was significantly lower compared with true peak FMD in all groups (P<0.001), and no differences were evident between the groups. The time course of FMD differs significantly between young and older subjects. Studies assuming that peak dilation occurs at an arbitrary time point, or within limited time windows, may draw misleading conclusions regarding differences between groups. More sophisticated approaches to measurement of FMD are required if it is to be considered a valid biomarker of vascular disease

Last word on point: counterpoint: exercise training does/does not induce vascular adaptations beyond the active muscle beds.

Contains fulltext : 69528thijssen.pdf (publisher's version ) (Closed access

Exercise and vascular adaptation in asymptomatic humans

Item does not contain fulltextBeneficial effects of exercise training on the vasculature have been consistently reported in subjects with cardiovascular risk factors or disease, whereas studies in apparently healthy subjects have been less uniform. In this review, we examine evidence pertaining to the impact of exercise training on conduit and resistance vessel function and structure in asymptomatic subjects. Studies of arterial function in vivo have mainly focused on the endothelial nitric oxide dilator system, which has generally been shown to improve following training. Some evidence suggests that the magnitude of benefit depends upon the intensity or volume of training and the relative impact of exercise on upregulation of dilator pathways versus effects of inflammation and/or oxidation. Favourable effects of training on autonomic balance, baroreflex function and brainstem modulation of sympathetic control have been reported, but there is also evidence that basal vasoconstrictor tone increases as a result of training such that improvements in intrinsic vasodilator function and arterial remodelling are counterbalanced at rest. Studies of compliance suggest increases in both the arterial and the venous sides of the circulation, particularly in older subjects. In terms of mechanisms, shear stress appears to be a key signal to improvement in vascular function, whilst increases in pulse pressure and associated haemodynamics during bouts of exercise may transduce vascular adaptation, even in vascular beds which are distant from the active muscle. Different exercise modalities are associated with idiosyncratic patterns of blood flow and shear stress, and this may have some impact on the magnitude of exercise training effects on arterial function and remodelling. Other studies support the theory that that there may be different time course effects of training on specific vasodilator and constrictor pathways. A new era of understanding of the direct impacts of exercise and training on the vasculature is evolving, and future studies will benefit greatly from technological advances which allow direct characterization of arterial function and structure