P2A158: Echocardiographically-derived Fontan Fenestration Gradient Is Not Correlated with Catheter-based Measurement

Background: Patients born with single ventricle physiology typically undergo palliation in three stages culminating in the Fontan procedure, which allows for lower body venous return to passively flow to the pulmonary circulation via a conduit. A fenestration in the Fontan conduit placed at the time of surgery provides a route for partial decompression of systemic venous pressure into the functional left atrium, and allows for a theoretical non-invasive calculation of the transpulmonary gradient (TPG) by Doppler ultrasound. Our objective was to determine the correlation between non-invasive and catheter-based measurements of TPG in patients with fenestrated Fontans.

Methods: We performed a single center retrospective cohort study of 34 patients with fenestrated Fontans completed between 2000-2020. The primary predictor variable was the echocardiographyically calculated TPG, and the primary outcome was catheter-based measurement of TPG in the same patient. Demographics and clinic information, including cardiac diagnosis and timing of surgical interventions, were collected from patient records. Both systemic right and left ventricular patients were included in the study. We excluded patients if echocardiograms were not completed within 6 months before or after cardiac catheterization. Linear regression was used to evaluate correlation.

Results: The slope of the relationship between echocardiographically-calculated TPG and catheter-based measurement was 0.2379, and R2 = 0.02 (p = 0.20).

Conclusion: TPG assessed by Doppler ultrasound is poorly correlated with cather-based measurements. Attention is needed when using this noninvasive measurement as a reliable measurement of transpulmonary gradient in Fontan patients. Larger studies are needed to further assess accuracy.