Balloon dilation of the para-device space to alleviate severe flow restriction in an oversized pulmonary flow restrictor: a case report

Abstract

Background: Manually modified microvascular plugs (MVPs) to pulmonary flow restrictors (PFRs) are innovative devices for managing pulmonary overcirculation percutaneously, though achieving optimal restriction while maintaining device stability can be challenging.

Case presentation: We describe a full-term newborn with a double outlet right ventricle and a large malaligned subaortic ventricular septal defect, complicated by pulmonary overcirculation. At 24 days of life (2.4 kg, 50 cm), bilateral MVP-based PFRs were implanted, with an MVP-7Q placed in the right pulmonary artery (4.1 mm diameter) and an MVP-5Q in the left (3.8 mm diameter), after fenestrating the MVPs by removing one triangle with a surgical scalpel. Immediate severe flow restriction to the right lung was managed with dilation of the para-right PFR space using 2 mm and then 3 mm semi-compliant coronary balloons, increasing oxygen saturation from 60 to 87%. By the end of the procedure, the Qp: Qs ratio decreased from 2.3:1.0 to 1.1:1.0. At 12 weeks, the patient weighed 4.8 kg, with oxygen saturation at 92% and Doppler gradients of 70 mmHg on the left and 45 mmHg on the right. Nine months post-intervention, the patient underwent biventricular repair and PFR removal at 7.9 kg. A fibrotic endothelial reaction with wall thinning on the right required autologous patch repair. A two-week follow-up ultrasound showed no stenosis.

Conclusions: Para-device space dilation with semi-compliant coronary balloons effectively relieves severe flow restriction in oversized PFRs, restoring flow while preserving device integrity. However, long-standing oversized PFRs cause intimal damage, necessitating patch repair, despite excellent surgical outcomes.