Inaccuracy of a continuous arterial pressure waveform monitor when used for congenital cardiac catheterization

Objective To determine the accuracy of a continuous cardiac output monitor (FloTrac sensor) for measuring cardiac index in children with congenital heart disease undergoing cardiac catheterization. Cardiac index is a critical hemodynamic parameter measured during catheterizations in children with congenital heart disease. This has been challenging to measure accurately and many clinicians rely on predictive equations for calculating cardiac index. Design Prospective, nonrandomized trial. Setting Tertiary care congenital heart center. Patients Consecutive participants ≤18 years old undergoing clinically indicated cardiac catheterizations from September 2014 through August 2015. Interventions Oxygen consumption was measured using the Vmax Encore 229 monitor attached to the ventilator circuit. The FloTrac transducer with third generation software was connected to a pigtail catheter in the descending aorta and cardiac index was obtained. Outcome Measures Cardiac index by the Fick equation using measured oxygen consumption was compared to cardiac index from the FloTrac sensor using paired t-test and Bland–Altman analysis. Results 39 participants (median age 5.1 years, 1.5-18.3, 64% female) were studied. Cardiac index by FloTrac was higher than cardiac index by Fick (6.4 ± 3.4 vs 3.7 ± 1.2 L/min/m2, P < .001). Bland–Altman analysis showed a consistent overestimation of cardiac index by FloTrac which worsened as cardiac index increased (mean bias 2.7 L/min/m2, 95% limits of agreement −4.2, 9.5). Conclusions The results of this study show that the FloTrac sensor provides cardiac index measures which are not accurate enough to justify use in children with congenital heart disease undergoing catheterization. Further studies may allow for modifications of the algorithms to obtain more accurate cardiac index in this population.