Aortopulmonary Collateral Flow is Related to Pulmonary Artery Size and Affects Ventricular Dimensions in Patients After the Fontan Procedure

Background: Aortopulmonary collaterals (APCs) are frequently found in patients with a single-ventricle (SV) circulation. The aim of this study was to detect and quantify APC flow using CMR and assess its impact on SV volume and function and to evaluate whether the size of the pulmonary arteries is related to the degree of APC flow.

Methods: 60 patients (mean age 13.3 ± 6.8 y) after the Fontan procedure underwent CMR with ventricular functional anlysis and flow measurements in the inferior vena cava (IVC), superior vena cava (SVC), and ascending aorta (Ao). APC flow was quantified using the systemic flow estimator: (Ao) – (IVC + SVC). Pulmonary artery index was assessed using contrast enhanced MR angiography. The patient cohort was divided into two groups according to the median APC flow: group 1 < and group 2 > 0.495 L/min/m².

Results: Group 1 patients had significant smaller SV enddiastolic (71 ± 16 vs. 87 ± 25 mL/m²; p= 0.004) and endsystolic volumes (29 ± 11 vs. 40 ± 21 mL/m²; p= 0.02) whereas ejection fraction (59 ± 9 vs. 56 ± 13%; p= 0.38) differed not significantly. Consequently, the authors found significant relationships between APC flow and SV enddiastolic and endsystolic volume (r= 0.40, p= 0.002 and r= 0.29, p= 0.03, respectively), but not with SV ejection fraction (r= 0.07, p= 0.57). Pulmonary artery size inversely correlated with APC flow (r=– 0.50, p= 0.002).

Conclusions: APC flow in Fontan patients affected SV dimensions, but was unrelated to SV function. APC flow was related to small pulmonary artery size, suggesting that small pulmonary arteries represent a stimulus for the development of APCs. Further studies are needed to assess the impact of APC flow on pulmonary vascular remodelling and to reveal its prognostic relevance in this patient population.