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

ACE inhibitor use in BDG patients was not associated with reduced systemic to pulmonary collateral flow as a percentage of aortic flow.

• 320 BDG patients were studied in total, with 137 treated with ACEI.
• SPC as a percentage of aortic flow was not different in the ACEI group whether right (RV) or left ventricle (LV) dominant.
• Single-centre retrospective study using cardiac MRI data from 2010 to 2024.
• Patients included were >1 year old and on ACEI for >3 months prior to CMR.

Ejection fraction was lower and end-diastolic volume was higher in BDG patients on ACEI for the entire group and for the RV dominant subgroup.

• This pattern was observed for the entire cohort of 320 BDG patients and specifically in the RV dominant subgroup.
• There was no difference in ventricular dilation or EF on echocardiogram prior to starting drug, suggesting the difference was not due to pre-existing worse function.
• For LV dominant patients, EDV was higher in those on ACEI but there was no difference in EF.
• The finding suggests no improvement of ventricular performance with ACEI use.

SVC flow, used as a proxy for cerebral blood flow, was lower in BDG patients treated with ACEI.

• SVC flow was lower for those on ACEI compared to those not on ACEI.
• In BDG patients, SVC flow reflects cerebral venous return and is used as an indicator of cerebral blood flow.
• This suggests that ACEI use may be associated with decreased cerebral blood flow in this population.

Systemic to pulmonary collateral flow positively correlated with end-diastolic volume.

• A positive correlation between SPC and EDV was identified across the BDG patient cohort.
• This relationship was noted across ventricular dominance types.
• The correlation suggests that higher collateral flow is associated with greater ventricular volume loading.

The two groups (ACEI-treated and non-ACEI-treated) were comparable at baseline with no differences in age, sex, medications other than ACEI, or body surface area.

• 137 of 320 BDG patients were treated with ACEI.
• No difference in age, sex, body surface area, or other medications (except ACEI) was found between the groups.
• There was no difference in ventricular dilation or EF on echocardiogram prior to starting the drug.
• This balance in baseline characteristics supports that observed differences were not due to confounding by indication.

The authors concluded that routine ACEI use in single ventricle patients post BDG should be considered with caution, with age-appropriate and clear indications and measurable therapeutic targets.

• ACEI did not demonstrate the expected benefit of decreasing SPC.
• There was a suggestion of no improvement of ventricular performance.
• Cerebral blood flow appeared decreased based on SVC flow measurements.
• The authors recommend that clear indications along with measurable therapeutic targets should be considered before initiating routine ACEI therapy.