Abstract 17490: Impaired Cerebrovascular Oxygen Delivery, Reserve, and Metabolism in Adult Fontan Patients

Abstract

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.