Reproducibility of Impedance Cardiography Hemodynamic Measures in Clinically Stable Heart Failure Patients

Abstract

BACKGROUND AND AIMS. One of the greatest challenges confronting physicians who are managing the care of patients with heart failure is to acquire objective data that signals treatment effectiveness and/or disease progression. The aim of this study was twofold: 1) to determine the extent to which (real time) impedance cardiography measurements obtained with a specific medical device (the BioZ) were reproducible in outpatients with clinically stable heart failure; and 2) to establish "normal" ranges of one week hemodynamic variability in this population of patients. Information of this nature would help clinical cardiologists and primary care practitioners to evaluate the implications of their patient's visit-to-visit hemodynamic variability. METHODS. A one group, prospective, time series design was used. The sample consisted of 62 patients who had clinically stable heart failure and who were being treated in an outpatient heart failure clinic at a university medical center. BioZ hemodynamic measures of cardiac output, contractility, and after load were obtained at five points in time: two, 10, and 60 minutes resting following a 40-50 foot walk on the first day and at two and 10 minutes resting following a 40-50 foot walk on the second day, one week later. RESULTS. Small but significant changes in cardiac output and cardiac index (mainly due to changes in heart rate) were seen during the 60-minute period on week one. Stroke index did not change during this period. In general, reproducibility between measurements taken on the same day and between days was quite good. Establishment of 95% confidence intervals helped define boundaries of variability in this population. Further clinical evaluation of the four patients whose values exceeded the 95% confidence intervals revealed unexpected, potentially relevant changes that could have accounted for their interday variability. Conclusion. The BioZ impedance cardiography measurements are responsive to hemodynamic activity-rest changes and are reproducible at a one week interval in clinically stable heart failure patients being treated in an outpatient clinic. Stroke index is a better measure of patient status than cardiac output or cardiac index. (c)2000 by CHF, Inc.

Effects of Intravenous PD 123319 on Haemodynamic and Arterial Stiffness Indices in Healthy Volunteers

“…The accuracy and reproducibility of this device has been investigated and validated. [16][17][18][19][20] For both arterial stiffness and haemodynamic parameters, baseline recordings were measured at one-minute intervals for a total of 5 minutes. Values were averaged to give a mean baseline result.…”

“…In the previous study, blood pressure was measured using a Finapres (Ohmeda, Eaglewood, Colorado, USA) recorder, which uses digital photoplethysmography to measure beat-to-beat blood pressure from the index finger; readings of mean arterial pressure are calculated from the arterial waveform by in-built software. 19,20 In the present study, an oscillometric sphygmomanometer connected to the BioZ device was used for the measurement of blood pressure parameters. Secondly, the previous study was not placebocontrolled for PD 123319 infusion, which may have resulted in time effects on blood pressure.…”

Transthoracic Bioimpedance and Brain Natriuretic Peptide Assessment for Prognostic Stratification of Outpatients With Chronic Systolic Heart Failure

“…The working hypothesis behind the use of transthoracic bioimpedance, despite some controversial evidence 36 is that when comparing surface and invasive measurements simultaneously, a significant correlation is found between thoracic conductance and pulmonary wedge pressure. 22,24 In fact, thoracic conductance has proven useful in detecting high-risk heart failure patients 25 and in identifying severe diastolic dysfunction. 28 Moreover, the continuous monitoring of intrathoracic impedance with an internal system included in most of the newest ventricular resynchronization devices (CRT or CRT-D) may show impedance changes before the appearance of symptoms and signs of heart failure linked to congestion.…”

Minimally Invasive Determination of Cardiac Output by Transthoracic Bioimpedance, Partial Carbon Dioxide Rebreathing, and Transesophageal Doppler Echocardiography in Beagle Dogs

“…BICO uses a low-amplitude, high-frequency alternating signal to calculate electrical impedance through the chest wall [19]. BICO correlated strongly with TDCO in human patients [1,7,17,18]. The limits of agreement between BICO and TDCO were small in human patients suggesting clinical utility [1,17,18].…”