Effects of ACE inhibitor and afterload reduction in single ventricles following bidirectional Glenn

Background Patients with single ventricles after bidirectional Glenn (BDG) are placed on ACE inhibitors (ACEIs) to reduce afterload and to decrease systemic to pulmonary collateral flow (SPC). The objective is to determine if ACEI use in BDG patients improves SPC and ventricular function. Methods Single-centre retrospective study of BDG patients who underwent cardiac magnetic resonance (CMR) from 2010 to 2024. Demographics, medication, ventricular function and flow data were collected. Patients included were >1 year old and on ACEI for >3 months prior to CMR. Results A total of 320 BDG patients were studied, 137 were treated with ACEI with no difference in age, sex, medications (except for ACEI) or body surface area. SPC as a percentage of aortic flow was not different in the ACEI group, whether right (RV) or left ventricle (LV) dominant. Ejection fraction (EF) was lower and end- diastolic volume (EDV) was higher in BDG on ACEI for the entire group and for RV dominant. Although LV EDV was higher with those on ACEI, there was no difference in EF. There was no difference in ventricular dilation or EF on echocardiogram prior to starting drug. SPC positively correlated with EDV. SVC flow was lower for those on ACEI. Conclusions BDG patients treated with ACEI did not demonstrate decreased SPC. There was a suggestion of no improvement of ventricular performance. Cerebral blood flow is decreased in BDG on ACEI using SVC flow. Findings suggest that routine ACEI use in single ventricle patients post BDG should be considered with caution and age-appropriate and clear indications along with measurable therapeutic targets should be considered.