Effect of compliance on a time-domain estimate of the characteristic impedance of the pulmonary artery during acute pulmonary hypertension

Fourie, Paula; Coetzee, André

doi:10.1007/bf02441981

Cited by 5 publications

(6 citation statements)

References 15 publications

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“…Moreover, pressure waveform analysis performed in the time domain makes it possible to calculate the timing and extent of wave reflection in systemic and pulmonary circulation with measures such as augmentation index (as shown in Figure 3D), which roughly represents reflected wave summation (⌬P) in the pulmonary circuit and normalizes for the PA pulse pressure. [32][33][34][35][36][37][38][39][40] These values can be obtained easily at the time of right heart catheterization, and future studies will compare both analyses as potential prognostic indicators in patients with pulmonary hypertension and correlate with the previously described concept of capacitance. 41 …”

Section: Time-domain Analysis Of Pa Pressure Waveformsmentioning

confidence: 99%

Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit

2009

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T here is still no answer to William Harvey's rhetorical question. He included the right ventricle (RV), its "pulse," the large pulmonary arteries (PAs), and the lungs in the same sentence, emphasizing the concept of a "unit." Although Harvey realized the importance of the RV and its interactions with the pulmonary circulation, 4 centuries later, the RV is largely understudied. At the same time, there has been significant progress in our understanding of the pathology of pulmonary vascular disease and, over the past few years, an explosion of clinical therapeutic trials for PA hypertension (PAH). 1 This unbalanced approach has generated a number of problems and controversies. For example, it is now becoming apparent that even if experimental therapies improve or reverse PAH pathology, this does not necessarily lead to clinical improvement and prolonged survival unless accompanied by a parallel improvement in RV function. The degree of pulmonary hypertension (ie, PA pressure [PAP]) does not strongly correlate with symptoms or survival, whereas RV mass and size and right atrial pressure reflect functional status and are strong predictors of survival. 2 The 6-minute walk test, used as the primary end point in most PAH clinical trials, correlates better with RV function (ie, cardiac output) than with the degree of pulmonary pressure elevation. However, this test is being heavily criticized because of multiple inherent problems and the fact that it does not provide information on specific components of RV-pulmonary vascular function. 3 Although therapies aiming at reversing pulmonary vascular remodeling might also have a positive effect on the RV (eg, sildenafil, which has been shown to increase RV inotropy 4 and decrease RV hypertrophy, 5 in addition to its effects on the pulmonary circulation), others might have untoward effects on the RV. For example, imatinib, an antiproliferative/proapoptotic agent that shows preliminary promise in reversing pulmonary vascular remodeling, 6 is potentially associated with primary negative (ie, proapoptotic) effects on the myocardium. 7 As our knowledge of RV physiology and biology increases, it is becoming apparent that a comprehensive approach to the RV, the pulmonary circulation, and their interactions will be beneficial in both clinical management of PAH patients and clinical research. The evolution of RV pathology from the normal to a compensated (hypertrophied) and then decompensated state parallels the evolution of pulmonary vascular pathology from a vasodilated highcapacitance state to vasoconstricted arteries and early loss of endothelial cells/capillaries to an end-stage proliferative and obliterative vascular remodeling (Figure 1). Therefore, it is important to study the RV and the PAs comprehensively and simultaneously as a unit. Here, we discuss standard clinical tests (eg, right heart catheterization and echocardiography) and evolving technologies (eg, magnetic resonance [MR] imaging [MRI] and positron emission tomography [PET]) that have the ability to study the ...

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Section: Time-domain Analysis Of Pa Pressure Waveformsmentioning

confidence: 99%

Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit

2009

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“…Moreover, pressure waveform analysis performed in the time-domain makes it possible to calculate the timing and extent of wave reflection in systemic and pulmonary circulation using measures such as augmentation index (as shown in the Figure) which roughly represents reflected wave summation (∆P) in the pulmonary circuit and normalizes for pulmonary arterial pulse pressure. [15][16][17][18][19][20][21][22][23] These values can be easily obtained at the time of right heart catheterization and the future studies will compare both analyses as potential prognostic indicators in patients with pulmonary hypertension. 24 Right ventricular pressure volume loop relations.…”

Section: Novel Hemodynamic Techniquesmentioning

confidence: 99%

Getting More From Right Heart Catheterization: A Focus on the Right Ventricle

Champion

2008

Advances in Pulmonary Hypertension

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Advances in Pulmonary Hypertension 343The primary challenge in the care of the patient with advanced pulmonary hypertension (PH) is right ventricular dysfunction with concomitant right heart failure, which is the most important cause of mortality in the disease. It is increasingly evident that the interaction of the heart and pulmonary circulation is a very important aspect that is largely understudied and our previous assessment of right ventricular function has been relatively crude. Here, we highlight the future of integrative assessment of ventricular-pulmonary vascular coupling via hemodynamic measures. Current Use of Right Heart CatheterizationCardiac catheterization remains the gold standard for diagnosing pulmonary hypertension, assessing disease severity, and determining prognosis and response to therapy. By directly measuring pressures and indirectly measuring flow, right heart catheterization allows for determination of prognostic markers such as right atrial pressure, cardiac output, and mean pulmonary artery pressure. 1 This procedure has been shown to be safe, with no deaths reported in the NIH registry study. 1 In addition, a recent study reported a procedure-related mortality of 0.055%. 2 Right heart catheterization determines the presence or absence of pulmonary hypertension, may define the underlying etiology, and allows for prognostication. The most critical aspect of right heart catheterization is that it is performed appropriately, and the data are interpreted accurately. Since end-expiratory intrathoracic pressure most closely correlates with atmospheric pressure, it is important that all right ventricular, pulmonary artery, pulmonary wedge, and left ventricular pressures be measured at end-expiration. 3-5 This is especially true in patients in whom there can be significant variation between inspiratory and end-expiratory vascular pressures (obese patients and patients with intrinsic lung disease).After determination of the presence of PH, pulmonary venous pressures should be evaluated by the pulmonary capillary wedge pressure (PCWP). Pulmonary arterial hypertension (PAH) is defined by a PCWP of 15 mmHg or less. 5,6 This value is based on the normal PCWP or left ventricular end diastolic pressure (LVEDP) of less than 8 mmHg and the observation that ~14 mmHg is 2 standard deviations from a normal PCWP. 3 With the exception of patients with severe tricuspid regurgitation, both thermodilution and Fick methods are reliable in patients with PAH for the measurement of cardiac output. 7 Vasodilator challenges with inhaled nitric oxide or intravenous epoprostenol or adenosine are encouraged in all patients at the time of diagnosis and in follow-up studies. 3 Other Testing During Right Heart CatheterizationExercise and fluid challenge Some patients with pulmonary vascular disease are not symptomatic at rest, but have symptoms with exertion. This observation provides a potential for exercise or volume challenge during right heart catheterization to better diagnose early pulmonary vascular disease. In ...

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“…They observed a strong correlation between the two estimates, which lead them to conclude that the time domain estimates of Zc are adequate if no other features of the input impedance spectrum are of interest. These results were contrasted in a study by Fourie & Coetzee (1993), who showed that time and frequency domain approaches yield different estimates of Zc.…”

Section: Introductionmentioning

confidence: 70%

“…Thus it is not possible to analytically prove the equivalence of the two approaches. For this reason the ability of each method, in both domains, to produce quantitatively consistent results on a case by case basis remains an open question (Fourie & Coetzee 1993).…”

Section: Discussionmentioning

confidence: 99%

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Characteristic impedance: frequency or time domain approach?

et al. 2018

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We have used published data measured in different species including humans, dogs, and mice to investigate: (a) the effects of time delay and signal noise in the pressure-flow data, (b) uncertainties about the blood flow conditions, (c) periodicity of the cardiac cycle versus the breathing cycle, on the frequency and time domain estimates of Zc, and (d) if discrepancies observed under different hemodynamic conditions can be eliminated. Main results and Significance: We have shown that the frequency and time domain estimates are not equally sensitive to certain characteristics of hemodynamic signals including phase lag between pressure and flow, signal to noise ratio and the end of systole retrograde flow. The discrepancies between two types of estimates are inherent due to their intrinsically different mathematical expressions and therefore it is impossible to define a criterion to resolve such discrepancies. Considering the interpretation and role of Zc as an important hemodynamic parameter, we suggest that the frequency and time domain estimates should be further assessed as two different hemodynamic parameters in a future study.

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Effect of compliance on a time-domain estimate of the characteristic impedance of the pulmonary artery during acute pulmonary hypertension

Cited by 5 publications

References 15 publications

Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit

Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit

Getting More From Right Heart Catheterization: A Focus on the Right Ventricle

Characteristic impedance: frequency or time domain approach?

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