LACK OF AGREEMENT BETWEEN MEASUREMENT OF EJECTION FRACTION BY IMPEDANCE CARDIOGRAPHY VERSUS RADIONUCLIDE VENTRICULOGRAPHY

Objective: To determine the limits of agreement between left ventricul ar ejection fraction estimated using systolic time intervals from impe dance cardiography and left ventricular ejection fraction estimated by radionuclide ventriculography. Design: A prospective study for diagno stic tests using radionuclide ventriculography as the criterion standa rd. Setting: A large, military teaching hospital. Patients: Twenty amb ulatory adults scheduled for radionuclide ventriculography. Measuremen ts and Main Results: A regression equation to estimate ejection fracti on from systolic time intervals is available in a widely used impedanc e-based cardiac monitoring device. The estimated ejection fraction is then used in an equation with stroke volume estimated by the same devi ce to calculate an end-diastolic volume. We studied the agreement of t he ejection fraction as estimated by this device with the ejection fra ction estimated by radionuclide ventriculography by obtaining simultan eous estimates of ejection fraction over a broad range of adult patien ts. Twenty ejection fraction pairs were analyzed. The correlation of e jection fraction by impedance cardiography to ejection fraction by rad ionuclide ventriculography was significant (r2 = .55; p < .002). Howev er, the mean difference between the technologies was -8.85%, with a st andard deviation of the differences of 7.15%, resulting in a 95% confi dence range for agreement of -23.2% to +5.5%. Conclusions: The 95% con fidence range defining the limits of agreement between ejection fracti on by impedance cardiography and ejection fraction by radionuclide ven triculography is not clinically acceptable. In the opinion of the auth ors impedance cardiography should not be used in place of radionuclide ventriculography for the assessment of ejection fraction at this time .