Systemic Sirolimus to Prevent In-Stent Stenosis in Pediatric Pulmonary Vein Stenosis.

Evaluate the efficacy of systemic sirolimus (rapamycin) in preventing in-stent stenosis (ISS) in pediatric intraluminal pulmonary vein stenosis (PVS). Report the adverse events related to sirolimus therapy. There is a high incidence of ISS following stent implantation in PVS. The use of sirolimus in preventing ISS has not been reported. Retrospective review of all patients who received sirolimus (8 week course) for treatment of ISS for PVS between January 2013 and June 2018. Forty stents (37 bare metal, 3 drug-eluting) in 20 patients were treated with sirolimus; 20 at the time of implantation (primary prevention [1P]) and 20 following documented ISS requiring transcatheter reintervention (secondary prevention [2P]). Treated patients were young (median 2 y/o [0.7-5.7]) and most had PVS associated with congenital heart disease (75%, 15/20; 4/15 with TAPVC). In the 1P group, 85% (17/20) of stents were without significant (< 50%) ISS at median of 102 days (range 56-527); the growth rate of ISS in this group was 7.5 ± 7.1%/month. In the 2P group, most stents had a slower growth rate of ISS after sirolimus therapy compared to pre-treatment (median 3.7 [- 0.2 to 13.1] vs. 10.4 [1.3 to 19.5] %/month; p < 0.001). One patient developed pneumonia on drug while concurrently taking another immunosuppressive agent. No other serious adverse events were related to sirolimus therapy. Systemic sirolimus slows the growth rate of ISS following stent implantation in PVS compared to pre-treatment rates and was administered safely in a small number of pediatric patients with complex heart disease.