1352537 - Global Strain in the Single Ventricle and Association with Aortopulmonary Collateral Flow

Aortopulmonary collaterals (APC) are a common occurrence in patients with single ventricle (SV) physiology. Increased APC flow has been hypothesized to be associated with poor Fontan outcomes. However, studies have shown that higher APC flow is associated with changes in SV dimensions, with no correlation with SV function. The clinical significance of APC flow in Fontan patients remains unclear. Strain measurements of the single ventricle after the Fontan procedure using feature tracking cine magnetic resonance imaging has been shown to indicate early worsening of cardiac function and predict adverse cardiac events. The aim of our study was to determine the association of SV strain with burden of APC flow.

Methods:

This was a retrospective single center study of Fontan patients who underwent cardiac magnetic resonance imaging (CMR) between 2016 and 2021. Twenty patients (mean age 19.4 ± 6.2 years) who underwent CMR as part of their routine clinical assessment were included. CMR analysis included ventricular function analysis and flow measurements in the ascending aorta (Ao), superior vena cava (SVC) and inferior vena cava (IVC). APC flow was calculated using the equation (Ao flow – (SVC flow +IVC flow)). Global circumferential strain (GCS) and global longitudinal strain (GLS) analysis were performed retrospectively using short-axis and long-axis cine imaging using offline analysis software (CVi⁴², Circle Cardiovascular Imaging Inc., Calgary Canada).

Results:

Patients underwent CMR at 16.3 ± 6.3 years (range 5-30 years) after Fontan operation. Fifty-five percent of patients had a dominant left ventricle. Mean APC flow was 27± 19% of ascending aorta flow, measuring 0.84 ± 0.64 L/min/m2. Average GCS was -16.8 ± 3.3% and average GLS was -16.2 ± 4.5%. There was no correlation between percent APC flow and GCS (r=-0.10, p=0.66) or GLS (r=0.19, p=0.43). There was also no correlation between cardiac index and GCS or GLS. In subgroup analysis comparing left versus right dominant single ventricle, indexed stroke volume, cardiac index, and indexed caval flow were significantly different between the 2 groups (34.4 ± 5.4 vs 42.3 ± 7.1 mL/m2, p=0.03; 2.5 ± 0.8 vs. 3.7 ± 1.1 L/min/m2, p=0.02; 1.7 ± 0.6 vs 2.8 0.8 L/min/m2, p=0.005). However, there was no difference in percent APC flow, GCS, or GLS between the 2 groups.

Conclusion: While APC flow is common in Fontan patients, in this single-institution cohort, there was no correlation between single ventricle strain and APC burden. As strain has been shown to be an indicator of worsening single ventricle function, our study suggests that APC flow does not result in impaired SV function.