The impact of dominant ventricle morphology and additional ventricular chamber size on clinical outcomes in patients with Fontan circulation

Objectives: The functional roles of ventricular dominance and the presence of an additional ventricular chamber (AVC) after Fontan operation are still uncertain. This is a clinical study to assess and correlate such anatomical features to late clinical outcomes. Methods Fontan patients who underwent cardiac magnetic resonance imaging (CMRI) and cardiopulmonary exercise test (CPET) in the previous 3 years were retrospectively reviewed. Clinical, CMRI, and CPET data from the last follow-up were analyzed to assess any correlation between AVC size and ventricular morphology. Results Fifty patients were analyzed: left/right dominance was 29/21, with a median age of 20 years (interquartile range:16–26). Median follow-up after the Fontan operation was 16 years (interquartile range:4–42). NYHA class III-IV was present in 3 cases (6%), 4 patients (8%) underwent Fontan conversion surgery, and 2 (4%) were listed for heart transplantation. Two patients (4%) died at follow-up. Statistical analysis showed that the AVC was larger (> 20ml/m2) in the right dominant ventricles (p = 0.01), which were also associated with a higher incidence of postoperative low-cardiac output syndrome (p = 0.043). Left ventricular dominance was associated with a better ejection fraction (p = 0.04), less extent of late gadolinium enhancement (p = 0.022), higher METs (p = 0.01), and pVO2 (p = 0.033). A larger AVC was associated with a higher need for postoperative ECMO support (p = 0.007), but it did not influence functional parameters at CMRI or CPET. Conclusions In Fontan patients, left ventricular dominance correlated to better functional outcomes. Conversely, a larger AVC which is more frequent with right ventricular dominance can affect negatively the early post-Fontan course.