Characteristics of vascular hydraulic load in patients with heart failure.

Laskey, Warren K.; Kussmaul, William G.; Martin, Jack L.; Kleaveland, J Patrick; Hirshfeld, John W.; Shroff, Sanjeev G.

doi:10.1161/01.cir.72.1.61

Cited by 77 publications

(47 citation statements)

References 47 publications

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“…The values reported from our laboratory are in accord with those from previous studies in both normal subjects and patients with heart failure but are at variance with others. 12 The precise identification of the first minimum in the continuous input impedance spectrum is precluded by the constraints of our method, since the harmonics derived are integral multiples of the fundamental frequency. It is unlikely that the true fmin exactly coincides with the fmin used in this study; therefore, changes in this variable may not truly reflect a shift in the actual minimum of the spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…Eleven of these patients have been previously described. 12 Eleven subjects (10 men, one woman), 22 to 65 years old (mean 43 ± 14) were referred for diagnostic cardiac catheterization and coronary angiography because of chest pain syndromes. All had structurally normal coronary arteries, normal cardiac output, and normal angiographic left ventricular ejection fraction (range 56% to 79%, mean 70 + 8%).…”

Section: Methodsmentioning

confidence: 99%

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Arterial wave reflection in heart failure.

Laskey¹,

Kussmaul²

1987

Circulation

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123

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Arterial wave reflection may adversely influence both left ventricular afterload and ejection performance. Therefore, using multisensor catheter manometers, we derived wave reflection indexes from ascending aortic pressure and velocity recordings in 17 subjects with clinical heart failure secondary to idiopathic dilated cardiomyopathy and 11 control subjects free of detectable cardiovascular disease. Patients were studied at rest as well as during submaximal supine bicycle exercise. Eight of the subjects with cardiomyopathy were also studied during infusion of nitroprusside at rest and on exercise. Reflection indexes decreased on exercise in normal subjects but did not consistently do so in the subjects with heart failure. In both groups the reflected wave on exercise returned earlier during the ejection period. Infusion of nitroprusside at rest in subjects with heart failure had dramatic, and significant, effects on the magnitude and timing of arterial wave reflections. THE PRESENCE of arterial wave reflections may be inferred from characteristic alterations in the pressure pulse as it propagates along the aorta. 1-6 Both the magnitude and timing of the reflected wave(s) are important in assessing their potential physiologic significance. Since a reflected pressure wave adds to the forward wave, a wave returning during systole would increase ventricular afterload. Reflected flow waves, however, subtract from the forward flow pulse. Therefore a wave returning during systole diminishes net forward flow and is disadvantageous to ventricular ejection.Changes in systemic vascular resistance have been shown to result in corresponding changes in the reflection properties of the arterial tree. A decrease in peripheral resistance may decrease wave reflections, whereas an increase in peripheral resistance enhances wave reflections.7-9 However, reflections may diminish in the absence of alterations in peripheral resis- acteristic feature of congestive heart failure.1t We reasoned that physiologic or pharmacologic decreases in systemic vascular resistance might result in corresponding, and hopefully beneficial, changes in the reflection characteristics of the arterial tree. Maneuvers that alter the magnitude of reflected waves may also effect a change in their timing. Thus the overall effect(s) of systemic vasodilation may be difficult to predict. To this end, we compared the magnitude and timing of arterial wave reflections in normal subjects, at rest and on exercise, with those in subjects with congestive heart failure. The effects of nitroprusside in the latter subjects were also analyzed to compare physiologic and pharmacologic arteriolar vasodilation in heart failure. MethodsPatients. Seventeen patients (12 men, five women), 24 to 66 years old (mean 44 + 12) with clinical signs and symptoms of congestive heart failure (NYHA class III to IV) were referred to the cardiac catheterization laboratory for endomyocardial biopsy and to rule out the presence of coronary artery disease. Each patient had a dilated, diff...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Arterial wave reflection in heart failure.

Laskey¹,

Kussmaul²

1987

Circulation

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123

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“…Aerobic exercise is normally associated with a decrease in SVR; an increase in heart rate, stroke volume, cardiac output, and mean arterial pressure; decreased reflection magnitude with earlier arrival of the reflected wave; and decreased pressure augmentation from wave reflections, without changes in Zc. 14,15 In contrast, isometric exercise is associated with an increased heart rate, unchanged or decreased stroke volume with no or little increase in cardiac output, increased SVR, increased mean arterial pressure, increased reflection magnitude with earlier wave reflections, increased Zc, and a marked decreased in TAC 16 ; changes in pulsatile hemodynamics during isometric exercise are not apparent from pulse pressure measurements. Although these are average responses, great interindividual variability in these responses exists.…”

Section: Resting Versus Provoked Loadmentioning

confidence: 95%

Noninvasive Evaluation of Left Ventricular Afterload

2010

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Abstract-The mechanical load imposed by the systemic circulation to the left ventricle is an important determinant of normal and abnormal cardiovascular function. Left ventricular afterload is determined by complex time-varying phenomena, which affect pressure and flow patterns generated by the pumping ventricle. Left ventricular afterload is best described in terms of pressure-flow relations, allowing for quantification of various components of load using simplified biomechanical models of the circulation, with great potential for mechanistic understanding of the role of central hemodynamics in cardiovascular disease and the effects of therapeutic interventions. In the second part of this tutorial, we review analytic methods used to characterize left ventricular afterload, including analyses of central arterial pressure-flow relations and windkessel modeling (pressure-volume relations). Conceptual descriptions of various models and methods are emphasized over mathematical ones. Our review is aimed at helping researchers and clinicians obtain and interpret results from analyses of left ventricular afterload in clinical and epidemiological settings. (Hypertension. 2010;56:563-570.)Key Words: afterload Ⅲ noninvasive Ⅲ input impedance Ⅲ arterial load T he mechanical load imposed by the systemic circulation to the left ventricle (LV) is an important determinant of normal and abnormal cardiovascular function. With the availability of noninvasive methods to accurately measure central pressure and flow, as well as computational tools for their analysis, there is great potential for their application in order to gain further mechanistic understanding of the role of central hemodynamics in cardiovascular disease. In the first part of this tutorial, we reviewed noninvasive methods to measure aortic pressure and flow, introduced basic concepts of analyses of pressure/flow relations in the time and frequency domains based on simple models of wave conduction and reflection, and briefly discussed wave reflections in the arterial tree. In this article, we review modeling of the arterial system as a windkessel, techniques for analyses of human arterial pressure-flow relations and considerations for interpreting hemodynamic indices in the context of research studies and individual hemodynamic assessments. The Arterial WindkesselIn addition to considering the arterial tree as a system of tubes with wave travel and reflection (or as a transmission line network), one might address it in terms of "windkessel" model components. Frank proposed the original windkessel model as a resistance and compliance (C) pair (2-element windkessel), meant to represent small vessel resistance and large artery compliance, respectively. 1 In the arterial system, total resistance to flow originates predominantly from small arteries, whereas most of the summed compliance is provided by large arteries. This is not a perfect distinction, because large arteries impose some resistance and smaller vessels provide some compliance, whereas the model only measu...

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“…19,20 This notion is in keeping with our findings, where reflected wave components in the aorta seemed relatively unaffected by exercise-induced peripheral vasodilation, despite large increases in the magnitude of the incident pressure wave. Interestingly, Laskey et al 24 also found a reduction in the first harmonic of the reflection coefficient (suggesting diminished reflected wave magnitude) on initiation of exercise in healthy subjects. Adding to this observation, this current study found a strong and negative association between the change in magnitude of reflection and change in central systolic BP with exercise.…”

Section: Exercise Hemodynamics: Forward and Reflected Waves In The Aortamentioning

confidence: 97%

Exercise Central (Aortic) Blood Pressure Is Predominantly Driven by Forward Traveling Waves, Not Wave Reflection

et al. 2013

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A hypertensive response to exercise independently predicts cardiovascular events and mortality.1 However, the physiological mechanisms contributing to elevation in blood pressure (BP) with exercise are poorly understood. Previous studies have focussed on changes to brachial BP during exercise, but little attention has been directed toward understanding central (aortic) BP (the pressure to which organs such as the heart are exposed). Because of variations in pulse pressure amplification, central systolic BP is usually lower than brachial systolic BP and may differ greatly between individuals with the same brachial systolic BP.2-5 Moreover, central to peripheral pressure amplification may be magnified during exercise, 6,7 and we have also reported that individuals with increased cardiovascular risk because of hypercholesterolemia have significantly raised central systolic BP and augmentation index, but not brachial systolic BP, during light to moderate exercise. 8 Thus, risk related to BP may be better assessed by central BP during light to moderate intensity exercise, rather than resting brachial BP. However, despite these observations, little is known of the contributing central hemodynamics.At rest, with each heart beat a pressure wave generated by the left ventricle is propagated along the arteries and is reflected back toward the heart at sites of impedance mismatch. Return of this reflected pressure wave is proposed to be the sole contributor to augmentation (increase) in central BP.3 However, more recently it has been proposed that aortic pressure can be regarded as the sum of a reservoir pressure and an excess pressure, composed of discernibly discrete forward and backward propagating waves.9,10 Moreover, recent work has proposed that such discrete reflected waves make only a minor contribution to augmentation of the central BP under resting conditions.11 Whether the rise in central systolic BP with exercise can be attributed to increases in discrete forward or reflected waves, or the reservoir, has not been determined in humans. Given the large increase in systemic vasodilation that Abstract-Exercise hypertension independently predicts cardiovascular mortality, although little is known about exercise central hemodynamics. This study aimed to determine the contribution of arterial wave travel and aortic reservoir characteristics to central blood pressure (BP) during exercise. We hypothesized that exercise central BP would be principally related to forward wave travel and aortic reservoir function. After routine diagnostic coronary angiography, invasive pressure and flow velocity were recorded in the ascending aorta via sensor-tipped intra-arterial wires in 10 participants (age, 55±10 years; 70% men) free of coronary artery disease with normal left ventricular function. Measures were recorded at baseline and during supine cycle ergometry. Using wave intensity analysis, dominant wave types throughout the cardiac cycle were identified (forward and backward, compression, and decompression), and aortic reservoi...

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Characteristics of vascular hydraulic load in patients with heart failure.

Cited by 77 publications

References 47 publications

Arterial wave reflection in heart failure.

Arterial wave reflection in heart failure.

Noninvasive Evaluation of Left Ventricular Afterload

Exercise Central (Aortic) Blood Pressure Is Predominantly Driven by Forward Traveling Waves, Not Wave Reflection

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