The KONAR-MF™ occluder, with its flexible medium-profile design, has broadened the feasibility of transcatheter closure of muscular ventricular septal defects, particularly in infants.

To assess feasibility, safety, techniques, and outcomes of muscular ventricular septal defect closure using the KONAR-MF™ occluder in a multicentre paediatric cohort.

A retrospective review was conducted at three tertiary paediatric cardiac centres (2018–2024). Patient demographics, ventricular septal defect characteristics, procedural approaches, and follow-up outcomes were analysed. Device implantation was performed via retrograde, antegrade, transseptal, or hybrid approaches under fluoroscopic and echocardiographic guidance.

Fifty patients (54 devices) were included (median age: 48 months [interquartile range 12–96]; weight: 12 kg [interquartile range 7.5–23]), including 14 infants (9 < 7 kg). Indications were failure to thrive (46%), heart failure (28%), recurrent infections (12%), and postoperative residual ventricular septal defect (14%). The mean ventricular septal defect size was 5.8 ± 2 mm. Median fluoroscopy time was 18 minutes (range: 3–71). Residual shunts were present in 18% immediately, reducing to 9% at one week and resolving by three months. Mild, transient tricuspid regurgitation occurred in 14%. Over a median 9-month follow-up (range 1–60), no cases of heart block or haemolysis occurred. One embolisation required surgical retrieval. Pulmonary artery pressure decreased significantly (37 ± 13.4 to 19 ± 3.8 mmHg, p < 0.001).

Transcatheter closure of muscular ventricular septal defects with the KONAR-MF™ occluder is safe, effective, and versatile across paediatric age groups, including infants and postoperative cases. High success rates, minimal complications, and favourable short- to mid-term outcomes support its use in routine practice.