Abstract 13847: Impact of the Unzipping Technique on Pulmonary Artery Structure and Growth

Abstract

Introduction: With the unzipping technique, small diameter stents are implanted to relieve pulmonary artery (PA) stenosis, subsequently dilated, fractured and re-stented with large stents dilatable to adult PA diameters. The unzipping technique is utilized in clinical practice with undefined long term results. This study assessed the impact of unzipping on PA structure and growth. Methods: Twelve piglets with left PA (LPA) stenosis underwent the unzipping sequence at 6, 10 and 18 weeks of age and were compared to normal controls and controls with untreated LPA stenosis. 2D and 3D rotational angiography pre/post interventions and PA histology was performed on all animals. Results: Eleven of twelve animals completed the three catheterizations. One stent (4 mm implant diameter) could not be crossed at the second procedure. Following the interventions, the diameter of the unzipped LPA was similar to the proximal LPA of normal controls (14 mm ± 1.2 vs 14.7 mm ± 1, p = 0.19). The diameter of the distal LPA was larger in normal controls, compared to interventions and controls with untreated LPA stenosis (14.6 mm ± 0.9 vs 11.6 mm ± 1.9, vs 10 mm ± 1.2, p < .01). Diameters of six 1 st order LPA branches were similar between normal controls and interventions, and larger than the branch diameters in the stenosis controls. Right PA (RPA) dimensions were larger in controls with untreated stenosis, compared to normal controls and interventions (17.8 mm ± 1.2 vs 16.2 mm ± .9 vs 16 ± 1.7 mm p<0.05). RPA 1 st order branching diameters were similar for normal controls and interventions. RPA 1 st order branch diameters in stenosis controls were larger for 3 of 6 branches compared to normal controls and 1 of 6 compared to interventions. Histologically, the distal LPA displayed uniform fibrointimal proliferation and smooth muscle hypertrophy in pigs with both interventions and untreated stenosis. Focal RPA fibrointimal proliferation was noted in stenosis and intervention animals. Conclusion: PA growth distal to the unzipped segment is partially compromised, yet 1 st order branch diameters are normal and significantly larger, compared to untreated stenosis. Histological vascular abnormalities are noted bilaterally in stenosis animals which do not normalize following the unzipping technique.