Comparison of New Impedance Cardiography versus Ventricular Angiography in Measuring Hemodynamic Variables

Abstract

Background: Hemodynamic variables provide crucial information to a critical care clinician. Non-invasive, safe, easily reproducible continuous hemodynamic monitoring is helpful in diagnosing and guiding treatment in critically ill patients. This study determined the correlation and agreement of measuring stroke volume (SV) and left ventricular ejection fraction (LVEF) using new generation impedance cardiography (ICG) and ventricular angiography (Cath). Methods: Biplanar left ventriculograms were done to calculate SV and LVEF among patients who underwent cardiac catheterization from October 2004 to December 2004. ICG was performed to obtain concurrent SV and LVEF. Thirty-six comparative measurements were obtained. Pearson's r correlation coefficients and Bland-Altman comparisons were calculated. Results: Thirty-six patients (30 acute coronary syndromes, 3 congestive heart failure and 3 valvular heart disease; mean New York Heart Association Class 2+/-1) were examined using the 2 methods. The average age of the patients was 53+/-15 years. The correlation coefficient between the values of SV(subscript ICG) and SV(subscript cath) was r=0.50 (p＜0.01; n=36; bias=-1ml; standard deviation = 19.6 ml). The correlation coefficient between the values of EF(subscript ICG) and EF(subscript cath) was r = 0.67(p＜0.01; n=36; bias=-2.5%; standard deviation=12.3%). The limits of agreement between SV(subscript ICG) and SV(subscript cath) were-40.2 ml to 38.2 ml; the limits of agreement between EF(subscript ICG) and EF(subscript cath) were-27.1% to 22.1%. Conclusions: In our study, the limits of agreement between the new generation ICG and the left ventricular angiogram were wide. We concluded that the new generation ICG should not replace the standard methodology at a single time point.