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      Automated Impedance Cardiography for Detecting Ischemic Left Ventricular Dysfunction during Exercise Testing

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          Automated impedance cardiography (ICG) is an attractive method for noninvasive hemodynamic evaluation. The objective of our study was to evaluate the feasibility and diagnostic value automated ICG in patients with suspected coronary artery disease (CAD). We measured stroke index (SI) and cardiac index (CI) in 65 patients with suspected CAD at rest and during bicycle exercise testing. All patients underwent subsequent cardiac catheterization including coronary angiography (CA). Depending on the results of CA, patients were divided into three groups, patients without significant CAD (group 0), single vessel disease (group 1) or multivessel disease (group 2–3). In a subset of 20 patients, automated ICG was compared to measurements of CI by the thermodilution (TD) method. Results: There were no significant differences in SI and CI at baseline between the three groups. At 75- and 100-watt exercise, patients in group 2–3 showed significantly lower mean values of SI and CI as compared to patients of group 0 and group 1 (all p < 0.05), indicating exercise-induced ischaemic left ventricular (LV) dysfunction. Three patients had to be excluded because of inappropriate quality of the ICG signals during exercise. Comparison of automated ICG with TD measurements of CI showed good correlations between both methods at rest (r = 0.73) and during exercise (r = 0.89–0.91). Conclusions: We conclude that hemodynamic monitoring by automated ICG is both feasible and practical during exercise testing. Automated ICG can provide reliable and valuable additional diagnostic information on LV function during exercise which is helpful for selecting those patients for angiography who are likely to benefit from coronary interventions.

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          Accurate, Noninvasive Continuous Monitoring of Cardiac Output by Whole-Body Electrical Bioimpedance

          Cardiac output (CO) is measured but sparingly due to limitations in its measurement technique (ie, right-heart catheterization). Yet, in recent years it has been suggested that CO may be of value in the diagnosis, risk stratification, and treatment titration of cardiac patients, especially those with congestive heart failure (CHF). We examine the use of a new noninvasive, continuous whole-body bioimpedance system (NICaS; NI Medical; Hod-Hasharon, Israel) for measuring CO. The aim of the present study was to test the validity of this noninvasive cardiac output system/monitor (NICO) in a cohort of cardiac patients.
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            Measurements of cardiac output during constant exercises: comparison of two non-invasive techniques.

            We compared cardiac output (CO) determined simultaneously by electrical impedance cardiography method (CO (ICG)) and by the CO (2) rebreathing technique (CO (2REB)) during three different steady-state exercises (target heart rate of 120, 140, and 160 min (-1)) in 8 healthy fit young men. The mean difference correlation coefficient obtained between the values of CO (ICG) and CO (2REB) was 0.85 and the mean difference (CO (ICG)-CO (2REB)) was 0.06 l/min (0.12 %). At 120 min (-1), CO (ICG) was lower than CO (2REB) but the tendency was reversed at 140 and 160 min (-1) where CO (ICG) was higher than CO (2REB). This evolution may be explained by the difficulty of using CO (2) rebreathing technique at the highest steady-state exercises and by the progressive acidemia due to exercise. The present results suggest that electrical impedance cardiography method provides acceptable evaluation of CO and may favourably replace the CO (2) rebreathing technique during mild (or moderate) to high steady-state exercises.
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              Cardiac output measured by impedance cardiography during maximal exercise tests.

              The overall accuracy of cardiac output measurements made by impedance cardiography during maximum exercise was studied in man. Initially, the systematic error of the technique was assessed over the range 3.5 to 18 litre . min-1 by comparing with simultaneous measurements of cardiac output made using the direct Fick method. No systemic error was demonstrated in 40 estimations made in 20 subjects. The random error was assessed in 4 subjects in a steady state at rest and during exercise at 80 and 130 W and found to be less than 5% in each subject. The reproducibility of maximum exercise response was assessed in six healthy male subjects (age 26.2 +/- 4.4 years, +/- SEM) who underwent maximum exercise tests twice, 1 week apart, on a bicycle ergometer. Simultaneous recordings of cardiac output and oxygen uptake (VO2) at rest and during each 3 min stage of exercise were made. Highly significant correlations were obtained in the stroke volume (r = 0.84, p less than 0.001), cardiac output (r = 0.98, p less than 0.001) and VO2 (r = 0.98, p less than 0.001) between the two tests. Average maximum cardiac output was 27.0 +/- 1.2 litre . min-1 (+/- SEM) and maximum VO2 was 4.4 +/- 0.2 litre . min-1 (+/- SEM). These results show that measurements of cardiac output were reproducible over one week. Impedance cardiography is non-invasive technique which is as accurate as invasive methods and can be used for maximal exercise testing.

                Author and article information

                Kidney Blood Press Res
                Kidney and Blood Pressure Research
                S. Karger AG
                April 2005
                13 April 2005
                : 28
                : 2
                : 77-84
                aI. Medical Clinic, University Hospital Mannheim, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, and bRehabilitationsklinik Heidelberg Koenigsstuhl, Heidelberg, Germany
                83695 Kidney Blood Press Res 2005;28:77–84
                © 2005 S. Karger AG, Basel

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                Figures: 2, Tables: 4, References: 24, Pages: 8
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