Vascular remodelling in malignant hypertension

The incidence of malignant hypertension (MH) fails to decline. Improved anti¬ hypertensive agents have reduced mortality, but the economic burden remains high due to complications such as end stage renal failure. Since the condition is initially asymptomatic, little is known about early pathogenesis. However the principal pathology is vascular remodelling of resistance vessels, termed fibrinoid necrosis, which causes ischaemic end-organ injury. Cardiovascular disease is the leading cause of mortality in western society and typically the consequence of atheromatous and/or hypertensive remodelling. As such, attention has focused on understanding the processes that contribute to various forms of vascular remodelling.It is apparent that inflammation plays an important role in modulating, and possibly initiating, some types of large vessel disease including atheroma. Less is known regarding hypertensive remodelling of resistance vessels.Recently a highly controllable and reproducible animal model of MH was developed in the rat. The Inducible Hypertensive Rat (IHR) exploits conditional transgenic technology allowing renin expression to be switched on, and hypertension to develop, following exposure to a dietary inducing agent. The resulting phenotype resembles human MH, where inappropriate activation of the renin angiotensin system is also seen.This study used the IHR to characterise the development of MH with specific reference to the renal vasculature. Histological injury and hypertension were pre-dated 1 by adventitial fibroblast proliferation and inflammatory cell infiltration. In order to determine the role of inflammatory cells the immunosuppressant FK506 was administered pre-emptively, resulting in the total abolition of hypertension and endorgan injury.To allow further investigation of inflammation, the MH phenotype was developed in mice using subcutaneous angiotensin II infusion. When MH was superimposed on a transgenic line susceptible to conditional macrophage depletion, vascular remodelling failed to occur in the mesenteric circulation where depletion was greatest.The effect of volume expansion on the IHR was assessed. Transgenic animals craved saline and the resulting fluid overload overcame cerebral autoregulation resulting in ischaemic stroke without alteration in systemic hypertension or pathology. The onset of stroke was tightly predictable and reproducible. Accordingly, the salineloaded IHR represents a novel and inducible model of ischaemic stroke.In conclusion, this study has identified inflammation as an early and important event in the pathogenesis of MH in two rodent models. Additionally, cerebral autoregulation in the IHR could be overcome by fluid overload resulting in the dissociation of central and systemic pathology

Euclidean Structure from N>=2 Parallel Circles: Theory and Algorithms

International audienceOur problem is that of recovering, in one view, the 2D Euclidean structure, induced by the projections of N parallel circles. This structure is a prerequisite for camera calibration and pose computation. Until now, no general method has been described for N > 2. The main contribution of this work is to state the problem in terms of a system of linear equations to solve.We give a closed-form solution as well as bundle adjustment-like refinements, increasing the technical applicability and numerical stability. Our theoretical approach generalizes and extends all those described in existing works for N = 2 in several respects, as we can treat simultaneously pairs of orthogonal lines and pairs of circles within a unified framework. The proposed algorithm may be easily implemented, using well-known numerical algorithms. Its performance is illustrated by simulations and experiments with real images

Myocardial changes in incident haemodialysis patients over 6-months:an observational cardiac magnetic resonance imaging study

Patients commencing on haemodialysis (HD) have an increased risk of cardiovascular events in the first year after starting HD compared to those patients established on HD longer. Left ventricular (LV) hypertrophy and abnormal myocardial strain predict mortality. There may be changes in the myocardium of incident HD patients over a 6-month period of HD which may explain changes in cardiovascular risk. We used CMR to consider changes in LV mass, myocardial strain and T1 mapping. We examined changes in pre-dialysis highly sensitive troponin T. 33 patients undergoing HD for <12 months were recruited. Participants underwent CMR at baseline and after 6-months of standard care. 6-months of HD was associated with reduction in LV mass index (Baseline: 78.8 g/m2 follow up: 69.9 g/m2, p = <0.001). LV global longitudinal strain also improved (Baseline: −17.9%, follow up: −21.6%, p = <0.001). Change in T1 time was not significant (Baseline septal T1 1277.4 ms, follow up 1271.5 p = 0.504). Highly sensitive troponin T was lower at follow up (Baseline 38.8 pg/L, follow up 30.8 pg/L p = 0.02). In incident HD patients, 6-months of HD was associated with improvements in LV mass, strain and troponin. These findings may reflect improvement in known cardiac tissue abnormalities found in patients over the first year of HD

Vascular function assessed with cardiovascular magnetic resonance predicts survival in patients with advanced chronic kidney disease

<p>Abstract</p> <p>Background</p> <p>Increased arterial stiffness is associated with mortality in patients with chronic kidney disease. Cardiovascular magnetic resonance (CMR) permits assessment of the central arteries to measure aortic function.</p> <p>Methods</p> <p>We studied the relationship between central haemodynamics and outcome using CMR in 144 chronic kidney disease patients with estimated glomerular filtration rate <15 ml/min (110 on dialysis). Aortic distensibilty and volumetric arterial strain were calculated from cross sectional aortic volume and pulse pressure measured during the scan.</p> <p>Results</p> <p>Median follow up after the scan was 24 months. There were no significant differences in aortic distensibilty or aortic volumetric arterial strain between pre-dialysis and dialysis patients. Aortic distensibilty and volumetric arterial strain negatively correlated with age. Aortic distensibilty and volumetric arterial strain were lower in diabetics, patients with ischaemic heart disease and peripheral vascular disease. During follow up there were 20 deaths. Patients who died had lower aortic distensibilty than survivors. In a survival analysis, diabetes, systolic blood pressure and aortic distensibilty were independent predictors of mortality. There were 12 non-fatal cardiovascular events during follow up. Analysing the combined end point of death or a vascular event, diabetes, aortic distensibilty and volumetric arterial strain were predictors of events.</p> <p>Conclusion</p> <p>Deranged vascular function measured with CMR correlates with cardiovascular risk factors and predicts outcome. CMR measures of vascular function are potential targets for interventions to reduce cardiovascular risk.</p