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Impedance cardiography fails to measure accurately left ventricular ejection fraction
D S Miles1, R W Gotshall, J D Quinones
1Department of Physiology and Biophysics, School of Medicine, Wright State University, Dayton, OH 45401-0927.
Insights
Impedance cardiography (IC) is not a reliable method for measuring left ventricular ejection fraction (LVEF). This study found low correlations between IC-derived LVEF and radionuclide angiocardiography, indicating it should not be used for clinical diagnosis.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Imaging
Background:
- Left ventricular ejection fraction (LVEF) is a critical indicator of cardiac function.
- Radionuclide angiocardiography (RNA) is a standard method for LVEF assessment.
- Impedance cardiography (IC) offers a non-invasive alternative for hemodynamic monitoring.
Purpose of the Study:
- To evaluate the accuracy of impedance cardiography (IC) for measuring left ventricular ejection fraction (LVEF).
- To compare LVEF measurements obtained via IC with those from radionuclide angiocardiography (RNA).
Main Methods:
- LVEF was measured using impedance cardiography (ZEF) and RNA (MEF) in healthy controls and patients.
- Correlation analysis was performed between ZEF and MEF.
- Comparison included assessment of correlation with regional wall motion.
Main Results:
- In healthy controls, ZEF and MEF showed comparable averages.
- In patients, average ZEF and MEF were similar, but correlations were unacceptably low.
- RNA-derived LVEF correlated well with regional wall motion, while ZEF did not.
Conclusions:
- The proposed impedance cardiography technique for LVEF measurement is unreliable.
- IC-derived LVEF measurements lack clinical validity compared to RNA.
- This method should not be used for making clinical diagnoses.
Abstract:
The purpose of this study was to describe the technique proposed to measure left ventricular ejection fraction (LVEF) with the impedance cardiogram and to compare these values with those measured by radionuclide angiocardiography. Characteristics (mean +/- SE) of the healthy control group were: age, 32 +/- 3 yr; weight, 75 +/- 6 kg; and height, 177 +/- 3 cm. Characteristics of the patient population of 46 men and 49 women were: age, 63 +/- 1 yr; weight 74 +/- 2 kg; and height, 170 +/- 1 cm. LVEF was measured by impedance (ZEF) and multiple-gated scans (MEF) while in the supine position. The control group ZEF averaged 72% (range 67% to 78%) and the MEF averaged 71% (range 65% to 77%). There were no differences between the average ZEF (56 +/- 1%) and MEF (53 +/- 2%) in the patients. Correlations, however, between ZEF and MEF were unacceptably low for the several clinical populations within this group (-0.17 to 0.16). Furthermore, MEF correlated well with regional wall motion (r = .84) while ZEF did not (r = .00). Subdividing the patients according to heart function as determined by regional wall motion failed to improve the correlation between MEF and ZEF. The use of a previously published regression equation to predict LVEF from the systolic time interval ratio of pre-ejection period/left ventricular ejection time derived from the impedance cardiogram also proved ineffective. These data suggest that the previously proposed analysis of the impedance cardiogram to measure LVEF should not be used to make a clinical diagnosis.