Capability of a new paediatric oesophageal Doppler monitor to detect changes in cardiac output during testing of external pacemakers after cardiac surgery

Background: The Cardio QP™ oesophageal Doppler monitor measures the velocity time integral of the blood flow in the descending aorta. Based on system integrated normograms of the aortic cross-sectional area of a paediatric population, the cardiac output is calculated and displayed. Objective: Evaluation of the capability of the Cardio QP™ to detect changes in cardiac output during desynchronizing ventricular pacing (VVI) in children after cardiac surgery. Patients: Eleven children (6 female, 5 male) with epicardial pacemaker electrodes admitted to the paediatric intensive care unit (PICU) after corrective surgery for congenital heart defects. Mean age: 6.3 (2.1-15.0) months, mean body weight: 5.3 (3.5-7.8) kg. Interventions: After baseline measurements of cardiac output (base I), we performed 3 steps, each lasting 5 min: (1) ventricular pacing (VVI), (2) baseline (base II) recording, (3) atrial pacing (AOO). We measured the effects on haemodynamic parameters and blood gases as well as on the measured cardiac output. Results: Ventricular pacing, with atrio-ventricular dyssynchrony, led to a significant drop in blood pressure and central venous saturation. Cardiac output parameters showed a decrease in stroke volume (SV) from 4.9±2.2 to 4.2±2.1 ml (P = 0.005) and cardiac index (CI) (2.6±1.1-2.1±0.8 ml/min/m ²) (P = 0.009) during ventricular pacing. Cardiac index and haemodynamic parameters during atrial stimulation did not show significant changes from baseline. Conclusion: The Cardio QP™ seems to be capable of detecting slight changes in cardiac output.