Measurements of disordered flows distal to subtotal vascular stenoses in the thoracic aortas of dogs.

Abstract

Instantaneous blood velocity measurements employing a constant temperature hot film anemometer were obtained in the region distal to externally enforced, subtotal vascular stenoses in the descending thoracic aortas of anesthetized dogs. Our objectives were to determine alterations in velocity waveforms and energy spectra as the degree of stenosis was increased. We paid particular attention to distinguishing features of the flow which were characteristic of turbulence. Our results indicate that, for the vessels studied, disturbances in the velocity waveforms occur for very minor localized constrictions. The energy spectra follow certain similarity parameters within a restricted region of the distal velocity field. For severe stenoses relatively high levels of energy exist in frequency ranges which previously have been found to produce poststenotic dilation. The measurements suggest that velocity waveforms and energy spectra provide a very early clue to the existence of localized occlusive vascular disease in larger vessels and that, within a limited region distal to a stenosis, the degree of constriction may be estimated by similarity analysis of the energy spectra.

Doppler power frequency spectrum analysis in the diagnosis of carotid artery disease.

“…We selected to analyze the interval at peak systole because it is a well defined landmark and it also coincides with the earliest onset of flow disturbances, 23 -3 * although the intensity of flow disturbance may increase during the phase of deceleration. 35 * The results presented in this report establish the diagnostic usefulness of the power frequency spectrum analysis (PFSA) approach, which provides two welldefined and practical indices: the maximum frequency contained in the sample signal (f^J and the frequency band width at 50% power level ( f^) .…”

Ultrasound Evaluation of Atherosclerosis

“…3) is found at the location of the stenosis where the stenosis is greater than 40% [9,24]. The blood flow is faster here than in neighboring segments of the artery and on the controlateral side.…”

“…How ever, a reliable diagnosis of less than 40% ste nosis cannot be obtained with a CW Doppler on the basis of the turbulence found in audi ble sounds. Indeed this turbulence may also be found in physiological states when vessel geometry, reduction in arterial compliance, high output states, hemorheological abnor malities and sampling problems may change the normal laminar flow into a disturbed flow pattern [22,24].…”

“…Disturbed flow is present downstream for few diameters of the respective vessel. Such hemodynamic effects can be detected with Doppler methods and the presence of a lesion is indirectly deduced from their occurrence [8,24], The evaluation of flow velocity with ultra sound has allowed demonstration that flow disturbances may occur in normal individu als without stenoses at bifurcations [43]. This finding may be related to the hypothesis that local hemodynamic factors play a role in plaque formation.…”

Differential impact of local stiffening and narrowing on hemodynamics in repaired aortic coarctation: an FSI study

“…The assumption of a constant cardiac output in CoA implies an increased workload on the heart and is justified by the findings reported in [15], stating that the cardiac output and the heart rate barely change after surgically induced stenosis. We, however, believe that, due to the elevated resistance at the coarctation site an early redistribution of flow will take place, manifesting as an increased flow through the subclavian and carotid arteries and a reduction of the descending aortic flow [8].…”