Assessment of aortic pressure‐volume relationships with an impedance catheter

Jj, Ferguson; Mj, Miller; Sahagian, P; Jm, Aroesty; Rg, McKay

doi:10.1002/ccd.1810150107

Cited by 19 publications

(4 citation statements)

References 36 publications

(5 reference statements)

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“…Before the availability of this technique, instantaneous aortic dimension measurements could only be obtained in opened-chest or chronically instrumented animals using invasive devices such as sonomicrometers or electromechanical calipers. Recently, investigators were able to obtain measurements of aortic diameter or volume without opening the chest using ultrasonic dimension (40,42) or impedance catheters (16). Transesophageal echocardiography allows measurements of instantaneous lumen area and aortic thickness, variables necessary for the computation of instantaneous aortic wall stress and E inc .…”

Section: Discussionmentioning

confidence: 99%

Smooth muscle relaxation and local hydraulic impedance properties of the aorta

Cholley

Lang

Korcarz

et al. 2001

Journal of Applied Physiology

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Smooth muscle relaxation is expected to yield beneficial effects on hydraulic impedance properties of large vessels. We investigated the effects of intravenous diltiazem infusion on aortic wall stiffness and local hydraulic impedance properties. In seven anesthetized, closed-chest dogs, instantaneous cross-sectional area and pressure of the descending thoracic aorta were measured using transesophageal echocardiography combined with acoustic quantification and a micromanometer, respectively. Data were acquired during a vena caval balloon inflation, both at the control condition and with diltiazem infusion. At the operating point, diltiazem reduced blood pressure in all dogs but did not alter aortic dimensions or wall stiffness. Over the observed pressure range, aortic area-pressure relationships were linear. Whereas diltiazem affected the slope of this relationship variably (no change in 3 dogs, increase in 1 dog, decrease in 3 dogs), the zero-pressure area intercept was significantly increased in every case such that higher area was observed at any given pressure. When comparisons were made at a common level of wall stress, wall stiffness was either increased or unchanged during diltiazem infusion. In contrast, diltiazem decreased wall stiffness in every case when comparisons were made at a common level of aortic midwall radius. Aortic characteristic impedance and pulse wave velocity, components of left ventricular hydraulic load that are determined by aortic elastic and geometric properties, were affected variably. A comparison of wall stiffness at matched wall stress appears inappropriate for assessing changes in smooth muscle tone. Because of the competing effects of changes in vessel diameter and wall stiffness, smooth muscle relaxation is not necessarily accompanied by the expected beneficial changes in local aortic hydraulic impedance. These results can be reconciled by recognizing that components other than vascular smooth muscle (e.g., elastin, collagen) contribute to aortic wall stiffness.

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Section: Discussionmentioning

confidence: 99%

Smooth muscle relaxation and local hydraulic impedance properties of the aorta

Cholley

Lang

Korcarz

et al. 2001

Journal of Applied Physiology

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“…Although others have suggested that a strict linear relationship exists between aortic BP and dimensions, 21 our findings lend credence to more recent literature that describes a hysteretic (loop) relationship between aortic BP and dimensions. [22][23][24] Physiologically, this makes sense because there must be a delay in the volumetric increase (relative to pressure), while the aorta fills with blood ( Figure 4D-4I). Importantly, however, a large proportion of the pressure from the column of blood ejected into the arterial network during systole is dampened within the ascending aorta via the reservoir function (≤37%).…”

Section: Aortic Reservoir and Excess Pressure: A Physiological Paradigmmentioning

confidence: 99%

Aortic Reservoir Pressure Corresponds to Cyclic Changes in Aortic Volume

Schultz

Davies

Hardikar

et al. 2014

ATVB

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C entral (aortic) blood pressure (BP) waveform indices independently predict cardiovascular events and all-cause mortality, 1 but the physiological mechanisms to explain the waveform morphology remain disputed. The well-established wave reflection theory ascribes transmission of discrete forward and backward (incident and reflected) waves as the principal contributory factor underlying the shape of the central BP waveform.2 However, while providing a plausible description of central BP morphology, recent studies have concluded that the influence of discrete reflected waves on central BP may be less than originally conceived, and this is probably because of wave dispersion along the aorta and entrapment of reflected waves in the periphery. 3,4 Indeed, augmentation of central BP may be largely attributable to forward wave propagation (as a result of left ventricular [LV] ejection) and proximal aortic reservoir function. [5][6][7][8][9] Importantly, wave separation theory obscures the pressure buffering role of the highly elastic proximal aorta (ie, the aortic reservoir), and a failure to consider this function may lead to incorrect interpretations of the physiology underlying central BP waveform morphology.The reservoir-excess pressure concept is an alternate method proposed to explain the underlying physiology of the aortic BP waveform. This method has been used invasively to study changes in aortic BP associated with both aging and exercise. 6,8 Moreover, indices derived from this model were recently shown to predict cardiovascular events (fatal and nonfatal) and procedures independent from brachial BP and other conventional cardiovascular risk parameters (eg, age, sex, cholesterol, smoking, diabetes mellitus), including Framingham risk score, in an analysis of the Conduit Artery Function Evaluation study. 10 In accounting for the reservoir function of the aorta, 7,11 the reservoir-excess pressure model is founded on the basis that aortic BP can be separated into © 2014 American Heart Association, Inc.

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“…The values for this stiffness index for the descending and ascending aorta varied greatly, yielding inconsistent results. Other authors also encountered major problems in fitting the exponential model to their pressure-area data and concluded that a linear model fitted better to their data (7,12). Lacombe et al (13), on the other hand, concluded that an exponential model applied better to their data than a linear model.…”

Section: Discussionmentioning

confidence: 99%

Echocardiographic assessment of aortic elastic properties with automated border detection in an ICU: in vivo application of the arctangent Langewouters model

Heerman

Segers

Roosens

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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We studied whether combined pressure and transesophageal ultrasound monitoring is feasible in the intensive care unit (ICU) setting for global cardiovascular hemodynamic monitoring [systemic vascular resistance (SVR) and total arterial compliance (C PPM)] and direct estimation of local ascending and descending aortic mechanical properties, i.e., distensibility and compliance coefficients (DC and CC). Pressurearea data were fitted to the arctangent Langewouters model, with aortic cross-sectional area obtained via automated border detection. Data were measured in 19 subjects at baseline, during infusion of sodium nitroprusside (SNP), and after washout. SNP infusion lowered SVR from 1.15 Ϯ 0.40 to 0.80 Ϯ 0.32 mmHg ⅐ ml Ϫ1 ⅐ s (P Ͻ 0.05), whereas C PPM increased from 0.87 Ϯ 0.46 to 1.02 Ϯ 0.42 ml/mmHg (P Ͻ 0.05). DC and CC increased from 0.0018 Ϯ 0.0007 to 0.0025 Ϯ 0.0009 l/mmHg (P Ͻ 0.05) and from 0.0066 Ϯ 0.0028 to 0.0083 Ϯ 0.0026 cm 2 /mmHg (P Ͻ 0.05), respectively, at the descending, but not ascending, aorta. The Langewouters model fitted the descending aorta data reasonably well. Assessment of local mechanical properties of the human ascending aorta in a clinical setting by automated border detection remains technically challenging.afterload; large artery function; nitroprusside; coronary artery bypass grafting; intensive care unit LEFT VENTRICULAR SYSTOLIC function and cardiac output are determined by left ventricular preload, contractility, afterload, and heart rate (HR). Therefore, assessment of cardiovascular hemodynamic function should include these determinants. Transesophageal echocardiography is increasingly being used for patient monitoring in the operating room and intensive care unit (ICU). Interestingly, these patients often have a pressure catheter in the aorta for pressure monitoring. The simultaneous availability of ultrasound imaging modalities and intra-arterial pressure potentially allows for the online and in situ assessment of most determinants of cardiovascular function.The main determinants of arterial afterload are systemic vascular resistance (SVR) and total arterial compliance, reflecting the steady and main pulsatile component of arterial load, respectively (18,21,24). Both are derived from aortic pressure and flow; therefore, they can be monitored in the clinical setting as described above.In addition to the aforementioned global afterload parameters, transesophageal echocardiography in conjunction with arterial pressure monitoring has the potential to assess local mechanical characteristics of central vessels via the construction and analysis of pressure-area or pressure-diameter curves (3, 4). It is well established that large artery elastic dysfunction is an important cardiovascular risk factor (1, 28). Reduced arterial compliance leads to an increased systolic pressure and pulse pressure (PP) and, consequently, an increased load to the heart. Because Ͼ60% of the total arterial compliance resides in the ascending and thoracic aorta, determining the regional compliance of the thorac...

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Assessment of aortic pressure‐volume relationships with an impedance catheter

Cited by 19 publications

References 36 publications

Smooth muscle relaxation and local hydraulic impedance properties of the aorta

Smooth muscle relaxation and local hydraulic impedance properties of the aorta

Aortic Reservoir Pressure Corresponds to Cyclic Changes in Aortic Volume

Echocardiographic assessment of aortic elastic properties with automated border detection in an ICU: in vivo application of the arctangent Langewouters model

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