Outcome of Fontan Patients After Reaching Adolescence: The Impact of Hypoplastic Left Heart Syndrome

<b>Background/Objectives</b>: Data on the long-term outcomes of hypoplastic left heart syndrome (HLHS) patients compared to other single-ventricle patients reaching adolescence after Fontan surgery is limited. This study analyzes the outcomes of HLHS patients compared to non-HLHS patients following total cavopulmonary connection (TCPC) from the same era at a large single center. <b>Methods</b>: This study included patients aged ≥ 12 years at the last follow-up who underwent TCPC surgery between 05/2001 and 12/2009, with follow-up data available from 05/2012 to 01/2024. The primary endpoint (Fontan-specific major adverse cardiovascular events, MACEs) included all-cause death, cardiac transplantation or listing, heart failure hospitalizations, ventricular arrhythmias, third-degree AV block, or resuscitation. <b>Results</b>: A total of 130 patients were included, with 39 (30.0%) having HLHS. Among non-HLHS patients, 18 (13.8%) had a systemic right ventricle, and 73 (56.2%) had a systemic left ventricle. The mean age at the last follow-up was 18.6 ± 3.2 years, with no significant age difference between groups (<i>p</i> = 0.195). HLHS patients experienced significantly more MACEs (<i>p</i> = 0.019), had reduced ventricular function (<i>p</i> = 0.009), and exhibited higher NT-proBNP levels (<i>p</i> = 0.004) compared to non-HLHS patients. <b>Conclusions</b>: While long-term outcomes for adolescents with TCPC are generally encouraging, HLHS patients are at higher risk of adverse cardiovascular events. These findings highlight the need for targeted follow-up and interventions to improve long-term prognosis in this high-risk group.