EFFECTIVE ARTERIAL ELASTANCE AND THE HEMODYNAMIC-EFFECTS OF INTRAAORTIC BALLOON COUNTERPULSATION IN PATIENTS WITH CORONARY HEART-DISEASE

Objectives The goal of the present study was to analyze the effects of different intraaortic balloon counterpulsation (IABC) inflation volum es on effective arterial elastance (Ea) in patients with complicated c oronary heart disease and to determine whether Ea can predict the hemo dynamic response to IABC. Background Ea (the central aortic end-systol ic pressure to stroke volume ratio) incorporates the principal element s of input arterial impedance and has been proved useful to evaluate t he effects of afterload reduction in patients with left ventricular (L V) failure. However, although the hemodynamic action of IABC can be co nsidered as a typical example of ''pure'' afterload reduction, it has never been assessed in terms of changes in Ea. Methods After clinical stabilization, 18 patients treated with IABC for complicated acute myo cardial infarction or unstable angina were enrolled in the study. Syst emic hemodynamics were measured by use of right cardiac thermodilution catheters with IABC off (control) and IABC on at balloon inflation vo lumes of 20 and 40 mi, in randomized sequence. Aortic pressure was rec orded through the central lumen of the IABC catheter to calculate Ea a s the ratio of aortic dicrotic pressure to stroke volume. Results A hi gher control Ea was associated with a lower control IV stroke work and a larger IABC-related hemodynamic improvement (that was maximal with the 40 mi inflation volume). The increase in LV stroke work was closel y related to the decrease in Ea. Accordingly, hemodynamic benefits fro m IABC were less evident in patients with lower control Ea. In conclus ion, effects of IABC were related to both balloon inflation volume and control hemodynamics, reflecting the afterload dependence of a depres sed LV function.