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These grafts are often used during the Norwood procedure for patients with hypoplastic left heart syndrome (HLHS). Traditionally, the modified Blalock–Taussig–Thomas shunt is used; however, recently there has been a shift toward using right ventricle-to-pulmonary artery (RV-PA) shunts because of their improved short-term mortality.
Little is known about the occurrence or management of RV-PA shunt perigraft seromas. Here, we present 2 cases of giant mediastinal seroma following RV-PA shunt insertion during the Norwood procedure. The institutional review board or equivalent ethics committee of the Children's Healthcare of Atlanta approved the study protocol and publication of data (STUDY00001460, July 18, 2022). Patient written consent for the publication of the study data was waived by the institutional review board, as it was determined to be research not involving human subjects.
A 3.25-kg full-term neonate with HLHS underwent the Norwood procedure with a 5-mm thin-walled removable ringed RV-PA conduit (cat. no. SRRT05030040L; W. L. Gore & Associates, Inc) on day of life 4. Postoperatively, he steadily was weaned off inotropes, with stable hemodynamics. He required bilateral chest tube placement for pleural effusions. He was noted to have large a mediastinal shadow on radiography of the chest. A computed tomography (CT) scan showed a large hypodense collection in the superior mediastinum (Figure 1), a patent RV-PA shunt and distal anastomosis, no filling defects within the pulmonary arteries (PAs), and mild narrowing of the proximal bilateral branch PAs. The patient was asymptomatic, so we opted to monitor the suspected seroma with serial imaging. He was discharged home on postoperative day 52.
During outpatient follow-up, he was found to have an elevated gradient across the neoaortic arch along with newly depressed ventricular function on echocardiography. CT imaging revealed a size discrepancy between the native and reconstructed aorta (Video 1). We then proceeded with arch revision and seroma evacuation. Intraoperatively, we found a large collection of proteinaceous material surrounding the RV-PA shunt. He again progressed well postoperatively except for some persistent tachypnea. A repeat CT scan showed reaccumulation of the seroma, a widely patent RV-PA shunt and distal anastomosis, and unobstructed central branch PAs (Figure E1). His respiratory status stabilized, so we decided to address the seroma during his stage 2 palliative procedure (bidirectional Glenn) at 4 months of age. Intraoperatively, another well-organized proteinaceous mass was found around the RV-PA conduit. He tolerated the procedure well, recovered fully, and was discharged home after 1 month. A repeat CT scan a few months later showed a persistent anterior mediastinal fluid collection, albeit much smaller than before surgery, and it continued to decrease in size over time on serial imaging.
A 2.32-kg neonate born at 36 weeks with HLHS also underwent the Norwood procedure with the same 5-mm ringed RV-PA conduit as above on day of life 5. Postoperatively, she was weaned off inotropes, with stable hemodynamics. She required chest tube placement for a right pleural effusion associated with respiratory insufficiency. There was concern for mediastinal seroma on radiography of the chest, which was confirmed with CT imaging (Figure 2). The CT also showed a widely patent RV-PA shunt and distal anastomosis, no filling defects within the PAs, and small main and branch PAs (no formal z scores reported) (Video 2, Figure E2). On postoperative day 22, she underwent mediastinal exploration. Intraoperatively, a very large amount of serous fluid and proteinaceous material was noted in the mediastinum and right pleural space. Her postoperative course was complicated by high chest tube output and left pleural effusion requiring chest tube placement. She ultimately recovered and discharged home at 2 months of age. On follow-up CT scans, there was no residual mediastinal seroma or pleural effusions.
Perigraft seromas are suspected to be the result of plasma ultrafiltration through the polytetrafluoroethylene graft, but it is not clear why this happens. Differences in oncotic or hydrostatic pressure may be to blame, and elevated pulmonary vascular resistance could contribute to this. Our patients had either “mild narrowing” or “small” bilateral branch PAs, which is not uncommon in patients with HLHS. The low birth weight and early gestational age of the second patient increased her risk for morbidity and mortality following stage I palliation, but not specifically for elevated pulmonary vascular resistance. We did not identify any other pre- or postoperative variables in either case that might have contributed to seroma formation.
We routinely used 5-mm grafts for these shunts regardless of weight until recently when, for other reasons, we selectively started using 6-mm grafts in certain patients weighing more than 2.5 kg. The cohort remains too small, however, to draw any conclusions about the effect of graft size on seroma formation.
These cases illustrate the rarity of these seromas and may give some insight into how management can be tailored to the patient, as both immediate as well as delayed surgical interventions were employed with favorable initial outcomes in both cases.
Disclosures: The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.