Serum Sirolimus Levels After Implantation of Third Generation Drug Eluting Cobalt Chromium Coronary Stent in Ductus Arteriosus in Neonates with Duct-Dependent Pulmonary Circulation

Abstract

Ductal stenting (DS) palliates duct-dependent lesions using coronary stents. Sirolimus-eluting stents have replaced bare-metal stents in coronary interventions. Concerns exist about sirolimus levels in neonates. Therapeutic immunosuppressive sirolimus level is 5-15 ng/ml. After neonatal DS, drug levels were assessed at 24 h, 7 days and monthly thereafter till they were undetectable. Clinical course, ductal patency till their final corrective surgery was analyzed. The exact quantity of sirolimus in each stent was known. Twelve neonates with median age of 5.5 days received sirolimus-eluting stents, one stent in nine and two in the rest. The lesions were pulmonary atresia intact ventricular septum(PAIVS) in four, univentricular lesions with pulmonary atresia in four, biventricular lesions with pulmonary atresia in three and right ventricular rhabdomyoma in one neonate. If single stents up to 22 mm length, 24-h drug levels were less than 5 ng/ml. Even though 24-h levels were above 5 ng/ml in patients with single longer stent or two stents, it reduced to very low levels by seventh day. Two hospital deaths included rhabdomyoma with complete heart block and post-valvotomy cardiac failure for PAIVS. Stent patency after valvotomy for PAIVS exceeded three years. Patency was retained for 8-27 months till their elective corrective surgery in others. Sirolimus levels were acceptable at 24 h in all neonates receiving single stent under 22 mm length. In patients needing two stents, drug levels were in immunosuppressive range at 24 h but reduced rapidly within 7 days. The palliation provided by sirolimus-eluting DS was sufficiently long to provide clinical benefit.

Keywords: Drug eluting stents; Ductal stenting; Neonates; Pulmonary atresia; Sirolimus; Stent patency.