Evaluation of ventricular-arterial coupling by impedance cardiography in healthy volunteers

Abstract

Background: The interplay between cardiac function and the arterial system is currently defined as ventricular-arterial coupling (VAC) and it is an expression of global cardiovascular efficiency. VAC involves a variety of complex interactions between the heart and the vasculature. A basic index of VAC is the ratio of effective arterial elastance (Ea)/ end-systolic elastance (Ees). While this is often done with echocardiography, obtaining Ea/Ees using impedance cardiography is feasible, although this possibility has not been explored so far. Objective: The aim of this study was to compare the Ea/Ees values obtained using echocardiography and impedance cardiography. Approach: Two independent operators estimated Ea/Ees in 91 (41 ± 14 years old, women 51%) untreated apparently healthy individuals using (1) Doppler echocardiography with the single-beat method developed by Chen et al (2001 J. Am. Coll. Cardiol. 38 2028–34); and (2) data provided by impedance cardiography. The differences between Ea/Ees values were compared and correlation between both methods was estimated. Main results: Although Ea and Ees values calculated by impedance cardiography were lower than those estimated by echocardiography (−0.201 ± 0.457 mmHg ml−1 and −0.193 ± 0.413 mmHg ml−1), Ea/Ees ratio values were similar. Thus, there was no significant difference between the mean values of Ea/Ees estimated by impedance cardiography or echocardiography (Ea/Ees impedance cardiography − Ea/Ees echocardiography = −0.015 ± 0.096, p = 0.150). Ea/Ees values calculated by both methods were highly correlated (r = 0.85, p < 0.001), as well as the pre-ejection and left ventricular ejection time (r = 0.83 and r = 0.91, respectively). Significance: In healthy individuals, estimation of Ea/Ees by impedance cardiography yielded similar values to those obtained using echocardiography.