Magnetic Resonance Imaging Assessment Of Fenestration Flow Following The Fontan Procedure
Husnu Firal Altin, Timothy Slesnick, Kirk Kanter, Sassan Hashemi, *Bahaaldin Alsoufi
Emory University School of Medicine, Atlanta, GA
Routine fenestration at time of Fontan is controversial and conceivable benefits (improved cardiac output, decreased drainage, etc.) are counterbalanced by potential drawbacks (cyanosis, emboli, etc.). We aim to evaluate the hemodynamics across the fenestration using Magnetic Resonance Imaging (MRI) in patients who have undergone various forms of the Fontan procedure.
Retrospective review of all patients who have undergone MRI studies following Fontan at our institution between 2013 and 2016 was performed. A comprehensive set of anatomic and hemodynamic measurements were estimated with the current study focusing on fenestration size, shunt fraction (Qp/Qs), percentage of inferior vena cava flow shunting across the fenestration (Fen/IVC flow), percentage of contribution of fenestration to aortic flow (Fen/Asc AO flow).
Our patient cohort was composed of 79 patients who had MRI at a mean interval 69 months following Fontan. Among those patients, 47 (59%) had evidence of persistent fenestration flow while the remaining 32 (41%) had spontaneous (n=22, 28%) or percutaneous (n=10, 13%) closure of their fenestration.
Overall, mean fenestration size was 3.4 mm and mean Oxygen saturation was 93%. The mean Fen/IVC flow varied between 20% and 38% with the ratio decreasing with longer interval following Fontan in association with decreased fenestration size. Nonetheless, the fenestration seemed to contribute to systemic output with Fen/Asc AO flow varying between 9% and 14% in various forms of Fontan. The mean Qp/Qs ranged between 0.64 and 0.73, with higher ratio, related to increased pulmonary blood flow, associated with longer follow up interval.
A significant percentage of IVC flow is directed across the fenestration into the systemic atrium away from pulmonary arteries, contributing to overall systemic flow. The ability to perform those calculations, coupled with other hemodynamic assessments in future studies, might allow us to determine patients who would benefit from selective fenestration.
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