In Vivo Evaluation of Fontan Pathway Flow Dynamics by Multidimensional Phase-Velocity Magnetic Resonance Imaging

Abstract

Background-Hemodynamic efficiency of Fontan circulation is believed to be a major determinant of outcome. Prior research on flow dynamics in different modifications of Fontan circulation used in vitro models and computer-based simulation. This study was designed to compare in vivo flow dynamics in the systemic venous pathway between patients with atriopulmonary anastomosis (APA) and those with total cavopulmonary connection (TCPC). Methods and Results-Multidimensional phase-velocity magnetic resonance imaging (PV-MRI) studies were performed on 10 patients who had undergone a modified Fontan operation (5 with TCPC and 5 with APA) and were free of symptoms. The groups were comparable in terms of age and body surface area. The interval since surgery was longer for APA than for TCPC subjects. In each subject, the phase-velocity data sets were used to generate dynamic velocity-vector maps and to calculate quantitative flow indices describing the 3-dimensional blood-flow patterns throughout the cardiac cycle at the widest diameter of the Fontan pathway. Mean flow rate was comparable between groups. Velocity-vector maps showed areas of flow reversal, flow stagnation, and circular flow within APA but not TCPC pathways. Analysis of quantitative flow indices showed that compared with the APA group, flow velocities in the TCPC patients were significantly higher (mean velocity, 14Ϯ6 cm/s versus 5Ϯ3 cm/s; Pϭ0.02), less variable (coefficient of variation, 19Ϯ2% versus 37Ϯ3.5%; PϽ0.0001), and more unidirectional (degree of unidirectionality, 89Ϯ7% versus 71Ϯ12%; Pϭ0.03). APA pathways were significantly more dilated than were TCPC pathways (PϽ0.01) and showed a trend toward larger diameter with increased interval since surgery (R

In vivo flow dynamics of the total cavopulmonary connection from three-dimensional multislice magnetic resonance imaging

“…It was de Leval's landmark in vitro experimental work that first demon strated energy conservation in the TCPC as opposed to the atriopulmonary connection [6]. Subsequently, an in vivo magnetic resonance imaging study has also demon strated improved flow dynamics in the TCPC over the atriopulmonary connection [9]. In a recent study, compu tational modeling of different types of TCPC demon strated that offsetting of the caval connection was efficient [13].…”

Noninvasive quantification of fluid mechanical energy losses in the total cavopulmonary connection with magnetic resonance phase velocity mapping

“…Magnetic resonance (MR) phase velocity mapping (PVM) [22] is currently the only established clinical technique to measure all three spatial components of the velocity vector in every volume element of an imaging slice, showing high in vitro and in vivo accuracy and precision [23][24][25][26][27][28][29][30][31][32][33][34]. The advantage of MR PVM to measure the three-directional blood velocity has enabled the generation of velocity vector maps in vitro and in vivo, showing (qualitatively) the fluid mechanical superiority of the TCPC over other connections and the importance of the presence of caval offset and flaring at the connection site [14,15,[33][34][35][36].…”

Multimodality Noninvasive Imaging for Assessment of Congenital Heart Disease

“…during diastasis. Using multidimensional phase contrast CMR imaging, Be'eri et al 72 demonstrated that blood flow patterns are more organized and uniform in lateral tunnel than in atriopulmonary Fontan pathways and are significantly influenced by pathway diameter. CMR has been shown to be more accurate than lung scintigraphy in quantifying blood flow to each lung in the Fontan circulation.…”