Search

The influence of abdominal aortic stenosis on the uptake of the protein-binding trypan blue dye and 131 I human serum albumin (HSA) has been studied. The major change was a region of high uptake proximal to the stenosis, returning to normal by the level of the renal arteries. There was reduced uptake distal to the stenosis, apart from occasional small areas of high uptake probably due to turbulence. The increase in uptake immediately proximal to the stenosis was dependent on the severity and duration of the stenosis. Removal of the stenosis immediately before the injection of dye and 131 I-HSA still resulted in elevated uptake in the proximal region. Some haemodynamic modifications resulting from a stenosis are described. It is suggested that the most satisfactory haemodynamic explanation of the observed uptake change is a proximal increase in oscillatory pressure/strain. The relevance of these findings to atherosclerotic development at and above arterial junctions is discussed.

SUMMARY Insufficiency of the mitral valve was produced surgically in 7 young male beagles. Clinical, radiological, haemodynamic, electrocardiographical and serum biochemical parameters were measured during the pre- and postoperative periods. Following post-mortem examination, lungs were examined histologically. Individual dogs were observed post-operatively for periods ranging from 1 to 20 weeks and on clinical, radiological and haemodynamic assessment could be divided into two groups. Group I showed marked passive pulmonary hypertension and an unusual pattern of exercise intolerance. Group II resembled clinical cases of mild left heart failure with compensation. Each group showed a definite sequence of cardiomegaly. A consistent feature was localized dilatation of the main pulmonary artery. Lung histology revealed mainly vascular congestion, with a relatively high incidence of inflammatory change.

The construction of bifurcation grafts is such that the flow velocity in the branches is twice that in the parent vessel. This sudden increase in velocity leads to turbulence generation at comparatively low aortic velocities, ie., ∼35 cm sec −1 . The physiological consequences of turbulence are discussed.

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.

An increase in aortic distensibility was observed in cockerels fed an atherogenic crushed-egg diet. The abnormal distensibility was correlated with the severity of the atherosclerotic lesions, using an atherosclerotic index that ranged from 1 to 100. It was found that distensibility increased up to index values of ∼ 40. For index values > 60 distensibility decreased progressively to below normal values due to increasing calcification and fibrosis. The area ratio of the aortic/sciatic junction was lowered as a result of these distensibility changes and the haemodynamic consequences of this decrease are discussed. A similar decrease in the area ratio of the aortic/iliac bifurcation was observed in man.