Methods: I n t he s tudy, t he m edical r ecords o f 4 0 p atients (22 males, 18 females) who underwent Fontan operation between August 1993 and August 2020 were retrospectively reviewed. The patients were followed up for at least six months.

Results: The Fontan operation was performed at a median age of 6.5 years (range, 3 to 22 years), and the mean follow-up time was 4.1±3.8 years (range, 0.5 to 17 years). The most frequently occurring defect was tricuspid atresia (45.0%). Fifteen (37.5%) patients experienced 24 late adverse events. Late complications and severe side effects, in order of frequency, were arrhythmia in eight (53.3%) patients, hypoxia in five (33.3%) patients, and ventricular dysfunction in three (20%) patients. While protein-losing enteropathy and mortality were each observed in two (13.3%) patients, Fontan failure, thromboembolic event, pulmonary arteriovenous fistulae, and ascites were each observed in one (6.6%) patient. When possible risk factors for late complications were examined, a statistical significance was not found.

Conclusion: Life expectancy and quality of life of patients with Fontan circulation have increased with advances in surgical technique and increased management success. However, complications are not uncommon after the Fontan operation, and late events remain a significant problem. The results of our study indicate that in mid-term follow-up of patients who underwent Fontan surgery at our institution, although not statistically significant, those who underwent fenestration and those operated at a later age tended to experience more severe events and late complications.