The Measurement of Input Impedance and Apparent Phase Velocity in the Human Aorta

Gabe, I. T.; Karnell, Johan; Porjé, I. G.; Rudewald, B

doi:10.1111/j.1748-1716.1964.tb02944.x

Cited by 58 publications

(17 citation statements)

References 13 publications

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“…3). Modulus and phase of impedance in these subjects were similar to those found by others in man (Gabe et al, 1964;Patel et al, 1965;Mills et al, 1970;Nichols et al, 1977;Pepine et al, 1978;Murgo et al, 1978a;Westerhof et al, 1979). Characteristic impedance (the value of impedance modulus about which fluctuations occur) was approximately 600 dyne sec cm" 3 or with aortic diameter AA 100 BCA ported by others for man.…”

Section: The Arterial Modelsupporting

confidence: 88%

“…Studies of vascular impedance and of pulse wave contour in man generally have been interpreted in terms of peripheral wave reflection (Gabe et al, 1964;Mills et al, 1970;Nichols et al, 1977;Pepine et al, 1978), but there is no agreement as to the intensity of wave reflection or the site or sites of reflection. Recent studies (Murgo et al, 1978a(Murgo et al, , 1978bWesterhof et al, 1979) have been interpreted in terms of one apparent reflecting site in the vicinity of the distal aorta, with variable reflection, ranging from strong to minimal, in different patients and under different conditions.…”

mentioning

confidence: 99%

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Pulsatile flow and pressure in human systemic arteries. Studies in man and in a multibranched model of the human systemic arterial tree.

O’Rourke¹,

Avolio²

1980

Circulation Research

130

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SUMMARY This study seeks to explain mechanisms responsible for the contour of pressure and flow waves and the pattern of vascular impedance in human systemic arteries. Pulsatile pressure and flow were recorded from the ascending aorta of seven patients undergoing open heart surgery and from the ascending aorta and other arteries of 17 patients at diagnostic catheterization. Ascending aortic pressure/flow relationships in the seven surgical patients were expressed as input impedance to the systemic circulation. Pressure and flow wave contour and impedance results were interpreted with the aid of a multibranched model of the systemic arterial tree, whose parameters could be manipulated to simulate different physiological and pathological conditions. Our data and data previously published on pressure and flow waves and their relationship in human subjects could be explained on the basis of two reflecting sites in the systemic circulation-one representing the resultant of all arterial terminations in the upper part of the body, and the other, some 1.5 times further away, the resultant of all arterial terminations in the lower body. The concept of the arterial system as an asymmetric T tube with two discrete ends has been advanced previously to explain the main features of pressure and flow waves and their relationship in different experimental animals. This concept appears equally applicable to human subjects.

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Section: The Arterial Modelsupporting

confidence: 88%

mentioning

confidence: 99%

Pulsatile flow and pressure in human systemic arteries. Studies in man and in a multibranched model of the human systemic arterial tree.

O’Rourke¹,

Avolio²

1980

Circulation Research

130

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“…The contour of the flow pulse was similar in configuration to that obtained from normal subjects in this laboratory (6, 7) and in others (8,9) with the pressure gradient technique. In the three patients with mitral insufficiency the flow was not abnormally small during the last part of ejection as recently described by Elkins, Morrow, Vasco, and and Braunwald (33).…”

Section: Column 5)supporting

confidence: 58%

“…The technique has been experimentally evaluated in both a flow generator (3) and in the dog aorta (4) and found to yield a valid estimate of phasic flow. The technique has been applied sucessfully in this laboratory (5,6) and by other investigators (7)(8)(9) to measure pulsatile blood pressure and flow in the ascending aorta of the intact human subject. The instrumental techniques, manometric accuracy requirements, and calibration procedures used in our laboratory to obtain valid phasic flow and pressure data in man have been previously described in detail and will only be reviewed briefly (10,11).…”

Section: Introductionmentioning

confidence: 99%

Pressure-flow studies in man during atrial fibrillation

Greenfield¹,

Harley²,

Thompson³

et al. 1968

J. Clin. Invest.

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A B S T R A C T In 13 patients who had atrial fibrillation the ascending aortic pressure-flow relationships were measured by the pressure gradient technique. Both the pressure and flow curves were similar in contour to ones previously obtained by this method. From these recordings, relationships between the phases of systole, the ventricular filling time, and various derived parameters of pressure and flow such as the pulse pressure, stroke volume, peak flow, stroke work, and peak power were evaluated. For stroke volumes greater than 15 cm3 there was little change in the duration of systole in an individual patient. In each patient both the preejection period and the duration of ejection showed a good correlation with stroke volume, peak flow, stroke work, and peak power. When data from all patients were examined, the relationship between stroke volume and duration of ejection was found to be curvilinear and had an overall correlation of r = 0.91. There was marked variation from patient to patient in duration of both the preejection period and systole. Similar correlations between the phases of systole were noted with peak flow, peak power, and stroke work. A positive but mediocre correlation was found between the previous RR interval (an index of ventricular filling time) and the subsequent stroke volume. The correlation, in six patients, between two previous RR intervals and stroke volume was considerably better. The relationship between the pulse pressure and stroke volume was reasonably close except in one patient; however, the group correlation was poor due to differences between individuals.

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“…'5 A second possibility is that this elevated aortic input impedance represents the result of chronic stimulation of the alpha adrenergic nervous system in addition to sodium retention.3 When vessel wall tension is elevated in isolated arterial segments by alpha catecholamine administration, there is an increase in stiffness of this vascular segment. '6 Gabe et al 17 reported an increase in aortic impedance during norepinephrine infusion. The possibility that the impedance increase is secondary to an overdistended aorta operating over a steeper portion of its distensibility relationship (i.e., pressure-diameter) is excluded by the lack of an increased mean distending pressure in the aorta of the heart failure patients compared to the non-heart failure subjects.…”

Section: Discussionmentioning

confidence: 97%

Aortic input impedance in heart failure.

Pepine¹,

Nichols²,

Conti³

1978

Circulation

129

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SUMMARY The input impedance of the systemic circulation was calculated from recordings of pulsatile pressure and flow in the ascending aorta of 20 patients. Ten patients had clinical and hemodynamic evidence of heart failure. The other 10 subjects had no clinical evidence of heart failure and were used as a control group. In the heart failure patients, both input resistance and characteristic impedance (index of aortic distensibility) were significantly increased compared to pressureand age-matched control subjects. Oscillations of impedance moduli, represented by the difference between maximum and minimum moduli, were also significantly increased in the heart failure patients compared with the control subjects. The increased characteristic input impedance in these heart failure patients suggests that the human aorta is stiffer in heart failure, and the larger oscillations in the impedance spectrum indicate an increase in pressure and flow wave reflections. From reflected wave theory in elastic tubes, reflected pressure waves add to the amplitude of incident pressure waves at the entrance of the system, whereas reflected flow waves subtract from the magnitude of the forward flow. Thus, changes in aortic distensibility could have an important influence on the pulsatile function of the failing left ventricle.THE AORTA AND LARGE ARTERIES of the systemic circuit are not rigid pipes, but constitute a distensible elastic buffering chamber. These elastic properties permit a damping mechanism through which pulsatile blood flow waves ejected from the left ventricle are converted to a near-constant blood flow for resistance vessels to distribute to systemic capillaries. Elastic properties of these large vessels can be modified by autonomic nervous effects on vascular smooth muscle cells with only minor changes in vessel dimensions.' Recent studies in our laboratories suggest that age and the presence of atherosclerosis may also be important in modifying the elastic properties of large vessels.2In heart failure, previous studies have emphasized abnormal ventricular and peripheral hemodynamic

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The Measurement of Input Impedance and Apparent Phase Velocity in the Human Aorta

Abstract: GABE, I. T., J. KARNELL, I. G. P O R J~ and B. RUDEWALD. The measurement of input impedance and apparent phase velocity in the human aorta. Acta physiol. scand. 1964. 61. 73-84. Measurement of the input impedance in the

Cited by 58 publications

References 13 publications

Pulsatile flow and pressure in human systemic arteries. Studies in man and in a multibranched model of the human systemic arterial tree.

Pulsatile flow and pressure in human systemic arteries. Studies in man and in a multibranched model of the human systemic arterial tree.

Pressure-flow studies in man during atrial fibrillation

Aortic input impedance in heart failure.

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