Increases in oxygen saturation following discharge from Fontan palliation – an indicator of resolution of pulmonary arteriovenous malformations? Van Galder H, Schaal AM, Feng M, Pan AY, Frommelt MA, Ginde S, Spearman AD. Cardiol Young. 2021 Mar 11:1-7. doi: 10.1017/S1047951121000913. PMID: 33691814
Take Home Points:
- Pulmonary arteriovenous malformations in single ventricle congenital heart disease are poorly understood.
- Pulmonary arteriovenous malformations are variably diagnosed prior to Fontan palliation; however, all study groups had increased oxygen saturations after Fontan discharge, potentially indicating resolution of pulmonary arteriovenous malformations in all groups.
- The prevalence of pulmonary arteriovenous malformations pre-Fontan is likely underestimated.
Commentary from Dr. Manoj Gupta (New York, USA), chief section editor of Pediatric & Fetal Cardiology Journal Watch
Introduction:
In single ventricle patients, intrapulmonary shunting through pulmonary arteriovenous malformations may develop, worsen, or regress after Fontan palliation and can variably impact oxygen saturation. The prevalence of pulmonary arteriovenous malformations in single ventricle CHD is variably reported – ranging from 15 to 100% depending on the specific cohort, diagnostic criteria, and follow-up duration.
The primary objective of this study was to determine whether pulmonary arteriovenous malformations are diagnosed more frequently before Fontan palliation in patients with heterotaxy syndrome compared to matched non-heterotaxy patients. Secondarily the authors sought to compare oxygen saturation changes after Fontan discharge as a clinical marker of resolution of pulmonary arteriovenous malformations.
Diagnosis of pulmonary arteriovenous malformations pre-Fontan was obtained by contrast echocardiogram using agitated saline (“bubble study”) or during cardiac catheterization. Severity of shunting was classified as negative (no bubbles entering the single ventricle), mild (occasional or few bubbles filling of the single ventricle), moderate (moderate filling of the single ventricle), or severe (complete opacification of the single ventricle)
Results
A total of 124 patients with single ventricle CHD and previous Fontan palliation were included in this study with 62 heterotaxy patients and 62 non-heterotaxy hypoplastic left heart syndrome controls. Of the 62 heterotaxy patients, 14 (22.6%) had an interrupted inferior cava vein.
Patients with heterotaxy and interrupted inferior cava vein were more likely to have a documented diagnosis of pulmonary arteriovenous malformations in their medical record prior to Fontan palliation (85.7%) compared to patients with heterotaxy and intact inferior caval vein (20.8%) and non-heterotaxy control (24.2%) (p < 0.01). Using a linear mixed model, there was no difference in Pre-Fontan oxygen saturations among the three groups (heterotaxy: intact inferior caval vein 82.0 (78.0, 85.0)%, interrupted inferior caval vein 80.5 (77.0, 85.0)%; non-heterotaxy control 82.0 (79.0, 85.0)%
At Fontan discharge, the non-heterotaxy control group (90.0 (86.0, 94.0)%) increased their oxygen saturations more than both heterotaxy sub-groups (intact inferior caval vein 87.0 (83.0, 92.0)%, p < 0.01; interrupted inferior caval vein 84.0 (82.0, 86.0)%, p < 0.01), but there was no difference in oxygen saturation between the two heterotaxy sub-groups (p = 0.18).
At 3, 6, and 12 months post-Fontan, there was no difference in oxygen saturation among the three groups at each time point.
Discussion
In this study, patients with heterotaxy syndrome and non-heterotaxy hypoplastic left heart syndrome had variable diagnostic rates of pulmonary arteriovenous malformations pre-Fontan, yet all study groups had increases in oxygen saturation after Fontan discharge. This data indicate that pulmonary arteriovenous malformations are present prior to Fontan palliation and resolve after Fontan palliation for patients with and without heterotaxy syndrome. The specific patient factors that increase susceptibility to pulmonary arteriovenous malformations remain unknown. Despite a lack of consensus on the prevalence and optimal diagnostic criteria for pulmonary arteriovenous malformations, studies have repeatedly used increased oxygen saturations after Fontan discharge as a surrogate for resolution of pulmonary arteriovenous malformations.
In conclusion, our data indicate that pulmonary arteriovenous malformations are variably diagnosed prior to Fontan palliation. It remains unclear, though, if there are true differences in susceptibility to pulmonary arteriovenous malformations because patients with and without heterotaxy syndrome have increases in oxygen saturations throughout the first year after Fontan discharge. A quantitative, systematic approach to diagnosis and follow-up pulmonary arteriovenous malformations is needed to better understand pulmonary microvascular remodeling in single ventricle CHD.
