Introduction:
Patients with univentricular hearts undergo a three-stage surgical palliation, culminating in total caval-pulmonary connection (Fontan procedure), maximizing delivery of oxygenated blood to the systemic circulation. Prior brain research in this population has highlighted genetic predisposition, in-utero oxygen delivery, surgical insults, and pre-Fontan cyanosis as possible mechanisms of brain injury, but none have examined the impact of the Fontan repair on brain hemodynamics.
Study Purpose:
To determine the sufficiency of brain O
2
delivery, cerebrovascular reserve (CVR), brain O
2
extraction fraction (OEF), and cerebral metabolic rate of O
2
(CMRO
2
) in adult Fontan patients, compared to permeability-surface area (PS) of blood brain barrier (BBB) integrity to water, and endothelin levels.
Hypothesis:
We hypothesized that brain O
2
delivery, CVR, PS, and CMRO
2
would be decreased in Fontan patients, proportional to endothelin levels, an established surrogate for low cardiac output.
Methods:
We have enrolled 35 Fontan patients (age 20.8 ± 2.5 years, 21M) and 24 control subjects (age 23.4 ± 4.8 years, 9M) to undergo brain MRI, excluding all subjects with known stroke, seizure, or genetic abnormalities. We collected total cerebral blood flow (CBF), OEF, CVR, and PS using 3T MRI.
Results:
Table 1 summarizes differences in O
2
delivery, CBF, OEF, CMRO
2
, CVR, PS, and endothelin levels in the study cohort. O
2
delivery, CBF, CVR, and CMRO
2
were decreased in Fontan patients; OEF and PS were not different. Endothelin was increased but uncorrelated with the brain metrics. CMRO
2
was correlated with PS (r
2
= 0.19, p<0.001).
Conclusion:
Adult survivors of Fontan palliation have decreased brain O
2
delivery and reserve, without compensatory OEF increases, leading to lower CMRO
2
. Decreased CMRO
2
was associated with decreased PS, but not endothelin, suggesting microvascular dysfunction rather than low cardiac output as the fundamental etiology.