Aortic Junction Research Articles

Effect of reflection from an unmatched junction on the abdominal aortic impedance.

The fluid impedance of the abdominal aorta was measured in anaesthetized dogs before and during the occlusion of the central branch of the aortic/external iliac junction. Aortic impedance increased during the occlusion due to a change in the terminal impedance of the peripheral beds and an increase in reflection from the aortic junction. The higher harmonics of impedance were relatively unaffected by changes in the terminal impedance and hence the increase found for these harmonics may be attributed to reflection from the junction alone. The reflection coefficient calculated from the impedance values of the higher harmonics (> 3rd) agreed well with the theoretical value from the Womersley model of a junction set in an infinite line.

Electron microscope study of myocardial tissue space contents in rat heart.

The tissue space of rat cardiac muscle is continuous with the subendocardial layer and with that of the epicardium. It is bounded by the sarcolemma of myocardial fibres. The spaces between the myocardial fibres are of varying dimensions. The largest areas are probably those associated with the sinoatrial and atrioventricular nodes. The extracellular material of the myocardial tissue space generally is electron-lucent. Native collagen is present as single unit fibrils or in bundles of several unit fibrils. Elastic lamellae are present only at the aortic junction. Fibroblasts are the commonest free cells in the tissue space, and 'myocardial foam cells.' Myelinated and unmyelinated nerve fibres are numerous and are found in close association with the myocardial fibres and the extensive capillary network.

The area ration of normal aortic junctions. Aortic configuration and pulse-wave reflection.

In this investigation the area ratio of the abdominal aortic junction in three species—chicken, dog and man—is measured and compared with the area ratio which theoretically gives minimum reflection of the pressure pulse at this junction. It is shown that in the cockerel and the dog the abdominal aortic junction has an area ratio close to the theoretically expected value. In man, however, it is found that this is true only in infancy and that the junction becomes progressively “mismatched” with age.