Ventriculo-arterial coupling for predicting cardiac index increase in infants after heart surgery

OBJECTIVES The aim of this study was to test the ability of ventriculo-arterial coupling (VAC) to predict cardiac index (CI) response after milrinone infusion.METHODS This was a retrospective, observational study. We measured arterial blood pressure and echocardiography-derived variables, including CI, systemic vascular resistance index, arterial elastance (Ea) and end-systolic ventricular elastance before and after 18-24 h of milrinone infusion. VAC was calculated as the ratio of Ea to end-systolic elastance. Infants with over 15% increase in the CI were defined as CI responders. Logistical regression was used to evaluate predictors of CI responders.RESULTS We enrolled 92 infants who underwent cardiac surgery and received milrinone infusion, of whom 45 infants were CI responders. High VAC (odds ratio = 5.534, 95% confidence interval 2.339-13.090) and high Ea (odds ratio = 3.035, 95% confidence interval 1.459-6.310) were independently associated with cardiac index responders. Pre-milrinone VAC predicted CI responsiveness with a cut-off value of 1.12 (area under the curve = 0.900, 95% confidence interval 0.819-0.953, P < 0.0001). Furthermore, we observed a decrease in the infant's VAC, Ea and systemic vascular resistance index after milrinone infusion.CONCLUSIONS In infants with congenital heart disease after surgery, a pre-milrinone VAC >1.12 can predict the increase in the CI following milrinone infusion.