The use of impedance cardiography in heart failure

Hubbard, W.N.; Fish, Douglas; McBrien, Dianne

doi:10.1016/0167-5273(86)90100-2

Cited by 36 publications

(22 citation statements)

References 10 publications

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“…In addition, a high CPO with moderately high systemic vascular resistance (SVR) can be associated with acute hypertension, whereas a low CPO with high SVR is characteristic of pulmonary edema 36. Retrospective studies into the first derivative of the impedance signal suggest that an abnormal impedance increase in early diastole (O wave) may be linked to severe heart failure, myocarditis, or valvular heart disease 31,37,38. The O wave appears most commonly in patients with increased diastolic flow velocity and may be used as an indicator of late-stage heart failure.…”

Section: Current Applications Of Impedance Measurement In Heart Failurementioning

confidence: 99%

Measuring impedance in congestive heart failure: Current options and clinical applications

Tang¹,

Tong²

2009

American Heart Journal

110

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Measurement of impedance is becoming increasingly available in the clinical setting as a tool for assessing hemodynamics and volume status in patients with heart failure. The 2 major categories of impedance assessment are the band electrode method and the implanted device lead method. The exact sources of the impedance signal are complex and can be influenced by physiologic effects such as blood volume, fluid, and positioning. This article provides a critical review of our current understanding and promises of impedance measurements, the techniques that have evolved, as well as the evidence and limitations regarding their clinical applications in the setting of heart failure management.Beginning in the 1940s, there has been recognition that changes in impedance are related to pulsatile blood volume, 1 and the assessment of impedance has been explored in aerospace applications as measures of cardiac output and stroke volume to monitor in-flight physiology. 2,3 Over the past decades, refinement in impedance techniques has led to the development of diagnostic and prognostic tools in cardiovascular medicine. 4,5 With commercial development of diagnostic devices and add-on functionalities in implanted devices that measure impedance, there is increasing interest in the clinical applications of impedance measurements in the management of heart failure. This article reviews our current understanding and promises of impedance measurements, the techniques that have evolved, and the evidence and limitations regarding their clinical applications, with the focus on heart failure management.

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Section: Current Applications Of Impedance Measurement In Heart Failurementioning

confidence: 99%

Measuring impedance in congestive heart failure: Current options and clinical applications

Tang¹,

Tong²

2009

American Heart Journal

110

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“…During volume loading in some experiments, we found an early diastolic peak corresponding to the O‐wave described by Lababidi et al (1970). Hubbard et al (1986) found that this peak was accentuated by passive leg raising and inspiration, and Bour & Kellett (2008) associated it with heart failure, as did Wang & Patterson (1995). We found that larger early diastolic Δ Z peaks were often associated with somewhat larger α values.…”

Section: Discussionmentioning

confidence: 55%

Estimation of left ventricular stroke volume by impedance cardiography: its relation to the aortic reservoir

Wang

Vries

Tyberg

2013

Experimental Physiology

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New Findings r What is the central question of this study?Thoracic impedance has been used to calculate left ventricular stroke volume for decades, while its theoretical basis remains controversial and the parameters generated have not been related satisfactorily to the haemodynamic events. r What is the main finding and what is its importance?We provide mechanistic explanations for the following: (i) why the upstroke of the change in thoracic impedance ( Z) waveform is constantly delayed with respect to that of the central aortic pressure; (ii) why the contour of the Z waveform is 'blunted' compared with that of the central aortic pressure; (iii) what mechanism is related to the 'second bump' of the Z waveform in early diastole (the 'O-wave'); and (iv) the mechanism that is likely to be associated with the decreasing Z waveform in later diastole.Impedance cardiography is a non-invasive technique used to estimate left ventricular (LV) stroke volume (SV) using the change in thoracic impedance ( Z). It remains controversial, partly because impedance cardiographic parameters have not been successfully related to haemodynamic events. We hypothesized that the change in Z may be proportional to the variation in thoracic (primarily aortic) blood volumes. Nine anaesthetized and ventilated dogs were divided into the following two groups: the 'aortic volume group' (n = 5), in which aortic and IVC (inferior vena caval) dimensions were measured ultrasonically; and the 'reservoir volume group', in which aortic and IVC reservoir volumes were calculated using the reservoir-wave model. Measurements were made in control conditions, in the presence of nitroprusside and methoxamine and after volume loading. In both the aortic volume group and the reservoir volume group, the maximal rate of increase in Z [(dZ/dt) max ] strongly correlated with the maximal rate of change in aortic/reservoir blood volume (R 2 = 0.85 and 0.95, respectively), which in turn was proportional to the LV SV. The LV and IVC contributions to Z were small in control conditions (∼5 and 1%, respectively), but the LV contribution increased slightly (to 7%) with administration of methoxamine and after volume loading (to 10%). It is concluded that the change in thoracic impedance ( Z) during the cardiac cycle is proportional to the change in aortic reservoir (i.e. Windkessel) volume, which provides a mechanistic explanation for previously demonstrated good correlations with standard measures of cardiac output.

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“…(Our 'type II' subjects ranged from 32 to 55 years.) Bifurcated waveforms have also been recorded from patients with heart failure [13] and from patients who have undergone 3 h of hemodialysis [4], Patients with complete A-V block, however, did not produce bifurcated waveforms [14,15]. Previously, clinical in vestigators have found greater diagnostic value in the diastolic portion of the ZCG [13,16]; however, the dZ/dt peak may become diagnostically important.…”

Section: Discussionmentioning

confidence: 99%

Bifurcations in the Impedance Cardiograms of Apparently Healthy Men and Women

Frey¹,

Tomaselli²

1989

Am J Noninvas Cardiol

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We have compared data from apparently healthy subjects who produced an impedance cardiogram (ZCG) having a bifurcation in the dZ/dt wave with data from other subjects to determine whether data from the bifurcated waveform should be extrapolated to the general population. Thirty men and 30 women, 21-59 years, participated. The 8 men and 5 women with bifurcations in their ZCGs were shorter, with more ponderous builds and larger chests and abdominal circumferences, and they had lower respiratory flow rates than subjects with normal ZCGs. They also had several differences in cardiovascular function at rest and in response to postural change that were measured independently of the ZCG waveform. Furthermore, the men with bifurcated ZCGs had lesser changes in stroke volume as determined from the ZCG when they changed posture than the men with normal ZCGs. We cannot explain these waveform differences by the physics of impedance or by pathology. The possibility exists that these waveforms indicate something other than 'normal'. Thus, we recommend that cardiovascular data derived from impedance cardiograms with bifurcated dZ/dt waveforms not be extrapolated to the general population until we understand the etiology of the waveform.

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The use of impedance cardiography in heart failure

Cited by 36 publications

References 10 publications

Measuring impedance in congestive heart failure: Current options and clinical applications

Measuring impedance in congestive heart failure: Current options and clinical applications

Estimation of left ventricular stroke volume by impedance cardiography: its relation to the aortic reservoir

Bifurcations in the Impedance Cardiograms of Apparently Healthy Men and Women

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