Introduction: Patent foramen ovale (PFO) closure is a widely performed procedure with a success rate exceeding 98%. However, residual right-to-left interatrial shunting can persist in up to 30% of cases (1, 2)^. The occurrence and size of residual shunts are influenced by the anatomical characteristics of the PFO and the dimensions of the implanted closure device (3). We aimed to evaluate the incidence of residual shunting, and its correlation with the size of the Amplatzer occluder device at the University Hospital Centre (UHC) Zagreb.

Patients and Methods: A retrospective analysis was conducted on all patients who underwent PFO closure at the UHC Zagreb to date. The study assessed implantation success rates, device sizing, echocardiographic follow-up methods and frequency, and the detection of residual shunts. Statistical analysis was performed using the Chi-square test and Cramer’s V test.

Results: Between August 2016 and December 2024, a total of 104 PFO closures were attempted, with 100 (96.2%) successfully implanted. Various sizes of Amplatzer occluder devices were used: 65 patients (66%) received smaller devices: 18/25 mm or 25/25 mm, while 33 patients (34%) received larger ones: 25/30 mm, 25/35 mm or 30/30 mm. Size data was unavailable for 2 cases. During the first year of follow-up, residual shunts were assessed in 41 patients (39.4%) using TTE/transesophageal echocardiography (TEE) with color Doppler and in 59 patients (56.7%) using TTE with a bubble test. Residual shunting was detected in 18 patients (18.3%) exclusively with the TTE bubble test, 78% with larger devices. TTE with bubble test beyond one year was performed in 14 (out of 19) patients. A persistent residual shunt was found in 11 patients (10.6%), again in 73% patients with larger devices. A statistically significant difference was observed in the occurrence of residual shunting among different device sizes (Chi-square, p<0.001), with a higher likelihood of residual shunting as device size increased (Cramer’s V = 0.577, p<0.001).

Conclusion: PFO closure outcomes at our center align with data from literature. The findings confirm that larger closure devices are associated with a higher likelihood of residual shunting. TTE with bubble test is superior to Doppler-based methods in detecting residual shunting and therefore important for follow-up assessments.