Clinical Variables Associated with Pre-Fontan Aortopulmonary Collateral Burden

Abstract

Aortopulmonary collaterals (APCs) develop universally, but to varying degrees, in patients with single ventricle congenital heart disease (CHD). Despite their ubiquitous presence, APCs remain poorly understood. We sought to evaluate the association between APC burden and common non-invasive clinical variables. We conducted a single center, retrospective study of patients with single ventricle CHD and previous Glenn palliation who underwent pre-Fontan cardiac magnetic resonance (CMR) imaging from 3/2018 to 3/2021. CMR was used to quantify APC flow, which was normalized to aortic (APC/Q_Ao) and pulmonary vein (APC/Q_PV) blood flow. Univariate, multivariable, and classification and regression tree (CART) analyses were done to investigate the potential relationship between CMR-quantified APC burden and clinical variables. A total of 29 patients were included, all of whom had increased APC flow (APC/Q_Ao: 26.9, [22.0, 39.1]%; APC/Q_PV: 39.4 [33.3, 46.9]%), but to varying degrees (APC/Q_Ao: range 11.9-44.4%; APC/Q_PV: range 17.7-60.0%). Pulmonary artery size (Nakata index, at pre-Fontan CMR) was the only variable associated with APC flow on multivariable analysis (APC/Q_Ao: p = 0.020, R² = 0.19; APC/Q_PV: p = 0.0006, R² = 0.36) and was the most important variable associated with APC burden identified by CART analysis (size inversely related to APC flow). APC flow is universally increased but highly variable in patients with single ventricle CHD and Glenn circulation. Small branch pulmonary artery size is a key factor associated with increased APC burden; however, the pathogenesis of APCs is likely multifactorial. Further research is needed to better understand APC pathogenesis, including predisposing and mitigating factors.

Keywords: Aortopulmonary collaterals; Fontan; Glenn; Single ventricle.

Fig. 1

Scatter plots with median line showing increased and highly variable aortopulmonary collateral (APC) flow quantified during pre-Fontan cardiac magnetic resonance (CMR) imaging. APC flow is shown relative to aortic blood flow ( Q_Ao; quantified by ascending aorta flow) and relative to pulmonary vein blood flow ( Q_PV; quantified by the sum of pulmonary vein flow). Groups above (n = 14) and below (n = 15) the median were identical with both calculations

Fig. 2

Pulmonary artery size is inversely related to the magnitude of aortopulmonary collateral (APC) blood flow. XY plots with linear regression and 95% confidence intervals show the relationship between indexed pulmonary artery size and A APC flow relative to aortic blood flow (Q_Ao) and B APC flow relative to pulmonary blood flow (Q_PV). Branch pulmonary arteries and APC flow were measured during pre-Fontan cardiac magnetic resonance imaging (CMR). n = 29

Fig. 3

Aortopulmonary collateral (APC) flow is increased to the left lung. Scatter plots with median and interquartile ranges show that individual lung APC flow relative to the individual lung’s total pulmonary blood flow (APC-R/Q_PV-R or APC-L/Q_PV-L) is increased in the left lung compared to the right lung in both the A whole cohort (n = 27) and B patients with a history of right-sided BT shunt (n = 12). Scatter plot also shows that C the cross-sectional area of the right pulmonary artery (RPA) is larger than the left pulmonary area (LPA) (n = 29), which is consistent with pulmonary artery size inverse relationship with APC flow