Exploring cardiac kinetic energy in children with atrial septal defects: A case-control-study

Kinetic energy (KE) of intracardiac blood flow constitutes an important part of the heart's energy expenditure and can be quantified using 4D-flow cardiac magnetic resonance (CMR). Pediatric atrial septal defect (ASD) patients have volume-loaded right ventricles and underfilled left ventricles due to left-to-right shunting, which could make ASD a useful model to study such altered ventricular loading conditions in congenital heart disease to explore related pathophysiological changes to KE. To characterize ventricular KE in children with ASD before and after treatment, we matched patients to controls. We recruited 22 ASD patients (8 males, median/[IQR]: 7.5/[6-9] years) and performed repeat CMR in 16/22 (72.7%) at mean±SD: 7.7±1.7 months following treatment. Left ventricular (LV) and right ventricular (RV) KE was assessed by 4D-flow CMR. Results were compared to 11 controls. Before treatment, RV peak diastolic KE was higher in ASD patients compared to controls (p=0.02) and normalized afterwards (p=0.42) with abolishment of diastolic ASD streaming. Indexed for ventricular volume at the time of peak KE (iKE), RV peak systolic and peak diastolic iKE decreased amongst repeatedly assessed ASD after treatment (both: p<0.01), suggesting altered RV energetics not only attributable to RV volume changes. After treatment, RV iKE was comparable between patients and controls (systolic: p=0.18; diastolic: p=0.87). Within the ASD group, LV peak systolic KE increased with increased LV volumes after treatment (p<0.01) while LV peak diastolic KE did not change (p=0.09). How the different RV and LV peak diastolic KE responses reflect different diastolic ventricular remodeling warrants further investigation.