Increased central aortic stiffness and left ventricular mass in normotensive young subjects after successful coarctation repair.

BACKGROUND: Hypertension occurs in 20% to 40% of survivors of anatomically successful repair of aortic coarctation (CoA). The aim of the present study was to examine the role of central aortic function in this setting. METHODS: Forty normotensive asymptomatic subjects with successful CoA repair (age 12 +/- 8 years) and 20 age- and sex-matched control subjects underwent detailed magnetic resonance imaging investigation of the thoracic aorta and left ventricle. Aortic distensibility, compliance, and stiffness beta index were calculated in the central (precoarctation) and descending (postcoarctation) aorta. Aortic pulse wave velocity was measured and left ventricular mass was calculated. RESULTS: Compared to control subjects, CoA subjects had markedly decreased central aortic distensibility (2.8 +/- 0.7 vs 4.2 +/- 0.5 mm Hg(-1) x 10(-3), P < .001) and compliance (1.7 +/- 0.3 vs 2.5 +/- 0.6 mm2 mm Hg(-1), P < .001) and increased stiffness beta index (5.2 +/- 1 vs 2.5 +/- 0.6, P < .001). Pulse wave velocity was also significantly increased in the CoA subjects (4.7 +/- 1.3 vs 3.3 +/- 0.6 m/sec, P < .001). Left ventricular mass index was higher in the CoA subjects (84 +/-11 vs 73 +/-10 g/m2, P = .01) and correlated significantly with aortic stiffness beta index (r2 = 0.8, P < .0001). By contrast, descending aortic characteristics were similar in the CoA and control subjects. CONCLUSION: Central aortic stiffness is markedly increased and associated with increased left ventricular mass in normotensive young subjects after successful early repair of CoA.

Statistical content-adapted sampling (SCAS) for 3D Computed Tomography.

In this paper, a framework to create a statistical content-adapted sampling (SCAS) for 3D X-ray Computed Tomography (CT) is introduced. SCAS aims at providing an accurate but light reconstruction volume. Based on decision theory, the 3D reconstruction space is sampled from the raw projection data in three steps to directly fit the sample. To do so, the structural information is first extracted from the projections by edge detection. This information is then merged in the reconstruction space, providing a pointcloud which accurately delineates the 3D interfaces of the specimen. From this pointcloud, a 3D mesh, closely fitting the shape of the studied object, is finally built via constrained Delaunay tetrahedralization. To assess the potential of the proposed SCAS for CT imaging, an iterative reconstruction was performed by classical Ordered Subset Simultaneous Algebraic Reconstruction Technique (OS-SART) - with fitting projection operator. The SCAS was evaluated on both numerical and experimental data. Results show that the use of statistical testing enabled the design of a robust, automated and fast method to build accurate pointclouds from a limited number of projections. The 3D meshes generated from these pointclouds are composed of few cells when compared to the regular voxel representation, leading to a downsize in computational cost and achieving up to 90% of memory footprint reduction. Simulations showed that performed reconstruction on such meshes provide accurate description of the object due to the finer sampling at interfaces.

Angular (Gothic) aortic arch leads to enhanced systolic wave reflection, central aortic stiffness, and increased left ventricular mass late after aortic coarctation repair: evaluation with magnetic resonance flow mapping.

OBJECTIVE: We sought to investigate the mechanism whereby a particular deformity of the aortic arch, an angulated Gothic shape, might lead to hypertension late after anatomically successful repair of aortic coarctation. METHODS: Fifty-five normotensive patients with anatomically successful repair of aortic coarctation and either a Gothic (angulated) or a Romanesque (smooth and rounded) arch were studied with magnetic resonance angiography and flow mapping in both the ascending and descending aortas. Systolic waveforms, central aortic stiffness, and pulse velocity were measured. We hypothesized that arch angulation would result in enhanced systolic wave reflection with loss of energy across the aortic arch, as well as increased central aortic stiffness. RESULTS: Twenty patients were found to have a Gothic, and 35 a Romanesque, arch. Patients with a Gothic arch showed markedly augmented systolic wave reflection (12 +/- 6 vs 5 +/- 0.3 mL, P < .001) and greater loss of systolic wave height in the distal aorta (30% +/- 16% vs 22% +/- 12%, P < .01) compared with that of subjects with a Romanesque arch. Pulse wave velocity was also increased with a Gothic arch (5.6 +/- 1.1 vs 4.1 +/- 1 m/s, P < .0001), as well as left ventricular mass index (85 +/- 15 vs 77 +/- 20 g/m2). Patients with a Romanesque arch had increased aortic stiffness compared with that of control subjects (stiffness beta-index, 3.9 +/- 0.9 vs 2.9 +/- 1; P = .03). CONCLUSIONS: Angulated Gothic aortic arch is associated with increased systolic wave reflection, as well as increased central aortic stiffness and left ventricular mass index. These findings explain (at least in part) the association between this pattern of arch geometry and late hypertension at rest and on exercise in subjects after coarctation repair.

Calculation of left ventricle relative pressure distribution in MRI using acceleration data.

Measurements of pressure variations within the cardiac chambers could provide important information for clinical assessments of cardiovascular function. In this work an MRI method for evaluating spatial distributions of intracardiac relative pressure is presented. We first calculated pressure gradients from MR maps of blood acceleration by applying the NS equation. We then used an original algorithm to compute pressure distribution in a region of interest (ROI) by minimizing the pressure gradient curl so that the result in a given pixel is independent of the integration path. The method was assessed in five healthy volunteers by means of MR 2D maps of the blood acceleration in the left ventricle (LV) during ejection and filling phases. The pressure variations calculated from acceleration mapping fit the known physiological variations better than those based on velocity maps acquired in the same volunteers. Furthermore, the optimization algorithm presented here produced the same results as iterative algorithms proposed by other authors, but in much less time and without requiring adjustable parameters or boundary conditions.