Relationship of cerebral blood flow to aortic-to-pulmonary collateral/shunt flow in single ventricles

Abstract

Objective: Patients with single ventricle can develop aortic-to-pulmonary collaterals (APCs). Along with systemic-to-pulmonary artery shunts, these structures represent a direct pathway from systemic to pulmonary circulations, and may limit cerebral blood flow (CBF). This study investigated the relationship between CBF and APC flow on room air and in hypercarbia, which increases CBF in patients with single ventricle.

Methods: 106 consecutive patients with single ventricle underwent 118 cardiac magnetic resonance (CMR) scans in this cross-sectional study; 34 prior to bidirectional Glenn (BDG) (0.50±0.30 years old), 50 prior to Fontan (3.19±1.03 years old) and 34 3-9 months after Fontan (3.98±1.39 years old). Velocity mapping measured flows in the aorta, cavae and jugular veins. Analysis of variance (ANOVA) and multiple linear regression were used. Significance was p<0.05.

Results: A strong inverse correlation was noted between CBF and APC/shunt both on room air and with hypercarbia whether CBF was indexed to aortic flow or body surface area, independent of age, cardiopulmonary bypass time, Po2 and Pco2 (R=-0.67--0.70 for all patients on room air, p<0.01 and R=-0.49--0.90 in hypercarbia, p<0.01). Correlations were not different between surgical stages. CBF was lower, and APCs/shunt flow was higher prior to BDG than in other stages.

Conclusions: There is a strong inverse relationship between CBF and APC/shunt flow in patients with single ventricle throughout surgical reconstruction on room air and in hypercarbia independent of other factors. We speculate that APC/shunt flow may have a negative impact on cerebral development and neurodevelopmental outcome. Interventions on APC may modify CBF, holding out the prospect for improving neurodevelopmental trajectory.

Trial registration number: NCT02135081.

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Figures

Figure 1

Relationship between CBF and APC flow indexed to aortic output in the entire cohort. Note the inverse correlation between CBF and APC flow on room air whether APC flow calculated by either IVC (A) or DAo flow (B). Ao=aorta; APC, aortic-to-pulmonary collateral; CBF, cerebral blood flow; DAo, descending aorta; IVC, inferior vena cava; Jug, jugular; Pulm, pulmonary; RA, room air.

Figure 2

Relationship between CBF and APC flow indexed to aortic output in the entire cohort. Pre-BDG (A), after BDG (B), after Fontan (C). IVC is used for top figure and DAo is used in bottom figure. Note the inverse correlation between CBF and APC flow at all stages. This remains true whether on room air (solid line, boxes) or in hypercarbia (dashed line, cross-hatch). Ao, aorta; APC, aortic-to-pulmonary collateral; BDG, bidirectional Glenn; CBF, cerebral blood flow; CO2, carbon dioxide; DAo, descending aorta; IVC, inferior vena cava; RA, room air.