P494How does magnetic resonance imaging tricuspid regurgitant fraction compare to qualitative echocardiographic estimation of tricuspid regurgitation in patients with hypoplastic left heart syndrome?

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Purpose: Tricuspid regurgitation (TR) impacts on survival and is a significant problem in hypoplastic left heart syndrome with some patients requiring tricuspid valve repair. TR is usually qualitatively assessed by echocardiography (echo) but can be quantified using magnetic resonance imaging (MRI).Methods: Ethical permission and parental consent was obtained. Children underwent MRI and echo under the same anaesthetic. 2 observers subjectively assessed TR based on colour Doppler imaging from standard echo views. MRI phase contrast neo-aortic flow with volumetric analysis (short axis cine stack) was performed. MRI derived TR fraction (TR%) was calculated from: right ventricular stroke volume - neo-aortic stroke volume/right ventricular stroke volume.Results: 39 patients at different operative stages were included (median age 2 years, range 0.1-13.7). TR was grouped based on subjective echo assessment: none/trivial (38.5%), mild (43.6%), moderate/severe (17.9%). Intraclass coefficient for interuser variability for echo was 0.78 and >0.89 for all MRI parameters. Except for a single case of severe TR there was little concordance between echo and MRI TR% (Fig 1.).Conclusions: MRI quantification of TR (volumetry and phase contrast neo-aortic flow) has poor concordance with echo assessment. Although there is generally good agreement between users in echo assessment, this is view dependent and affected by colour and gain settings. Additionally jet entrainment (meaning high velocity jets may appear important in the large right atrium) and location of the regurgitant jet with respect to the tricuspid valve are likely to play a role. Potential errors in MRI include the additive effect of 2 separate values to derive TR, which may be proportionally more significant in small hearts.

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