Transcatheter closure of secundum atrial septal defect using Cocoon septal occluder: immediate and long-term results
Authors: Sinha Santosh Kumar , Razi Mahmodullah M. , Sofi Najeeb Ullah , Rohit Manoj Kumar , Pandey Umeshwar , Sharma Awadhesh Kumar , Sachan Mohit , Aggarwal Puneet , Jha Mukesh , Shukla Praveen , Thakur Ramesh , Krishna Vinay , Verma Rakesh Kumar 
Published: August 2022

Abstract
Background
Atrial septal defect (ASD) is one of the common congenital heart defects. Its management has transformed dramatically in the last 4 decades with the transition from surgical to percutaneous transcatheter closure for most secundum-type ASDs. Various devices are available for transcatheter closure of ASD with Amplatzer atrial septal occluder being most commonly used worldwide. Cocoon septal occlude has a nanocoating of platinum using nano-fusion technology over nitinol framework that imparts better radiopacity and excellent biocompatibility and prevents leaching of nickel into circulation, and by smoothening nitinol wire makes this device very soft and smooth. The aim of this study was to evaluate feasibility, effectiveness, safety, and long-term outcome of transcatheter closure of ASD using Cocoon septal occluder (Vascular Innovation, Thailand).

Results
All patients undergoing transcatheter closure of hemodynamically significant ASD between September 2012 and July 2019 in our institute were included into this single-center, prospective study. Exclusion criteria were defect > 40 mm, unsuitable anatomy, Eisenmenger syndrome, and anomalous pulmonary venous return. Three hundred and twenty patients underwent device closure, of which 238 (74%) were female. The mean age was 14.6 years (range 6–29), and the median weight was 30.2 kg (range 10–53 kg). Procedure was performed under fluoroscopy using transthoracic and transesophageal echocardiography in 298 (93.1%) and 22(6.9%) patients, respectively. Balloon-assisted technique was used, when septal defect was ≥ 34 mm, in 9 (2.8%) patients. The mean diameter of defect and device was 21.4 mm (range 12–36 mm) and 26.9 mm (range 14–40 mm), respectively. Aortic rim was absent in 11 (3.4%) patients. Primary success was achieved in 312 (97.5%) patients. Early embolization to right ventricle was noted in 2 (0.6%) patients. In both cases, 40-mm device was attempted for defect of 36 mm with inadequate aortic rim using balloon-assisted technique. One (0.3%) patient developed perforation of right atrium. All were surgically repaired. Three (0.9%) patients developed complete heart block following device deployment requiring device retrieval. Two patients had had moderate residual shunt at 6 months of follow-up. After mean follow-up of 50.92 months (range 12.5–89 months), no erosion, allergic reactions to nickel, or other major complications were reported.

Conclusions
Percutaneous transcatheter closure of ASD by Cocoon septal occluder (up to 36 mm) is safe and feasible with high success rate and without any significant device-related major complications over long-term follow-up. With unique device design and excellent long-term safety, it could be preferred dual-disk occluder for transcatheter closure of atrial septal defect. In most of the patients, ASD device can be safely deployed under transthoracic echocardiographic guidance.