Cardiopulmonary exercise testing in Fontan patients: unmasking the secret of Super-Fontans

Abstract Background Exercise capacity is usually reduced in Fontan patients, however there a subset of patients who have normal exercise and better outcomes, the “Super-Fontans”. The aim this study was to characterize cohort undergoing cardiopulmonary testing (CPET) identify predictors functional capacity. Methods Single center retrospective analysis consecutive aged >10 years old underwent CPET, between March 2018 May 2021. Peak respiratory exchange ratio1.05 defined maximal CPET. VO2 (pVO2) as percentage its predicted value used reference stratify tertiles. Patients 3rd tertile, with pVO2 superior 75%, were considered good-performers. Blood tests transthoracic echocardiogram (TTE) performed on same day. Additional data collected from electronic charts. Results In total, 49 included (mean age 19±7 old, 67% male) intra or extracardiac conduit implanted mean 12±7 prior most common primary diagnoses tricuspid/pulmonary atresia (43%), followed by unbalanced complete AV septal defect (14%) double inlet left ventricle (14%). 12 had systemic right ventricle. All, except 5 preserved systolic ventricular function 37% moderate severe regurgitation. majority hemoglobin levels (median 15.6 g/dL), hepatic enzymes total bilirubin 0.8 mg/dL), renal creatinine mg/dL) low NT-proBNP 122 pg/mL). All median %VO2 at VT1 57% peak 66±14% predicted. Most (69%) showed limitation due cardiovascular cause, O2 desaturation, present 22% CPETs. completion not associated (p=0.6). good-performer group comprised 13 (27%), all sinus rhythm, which 10 physically active. Compared remainder, higher (18.7 vs. 14.6, p=0.01) VT2 (25.9 22.1, p=0.02), both mL/kg/min. Also, heart rate (% predicted) (90 81, p=0.03) subgroup – fig.1. Conversely, differences TTE parameters (GLS valve regurgitation) blood biomarkers statistically significant. On multivariable analysis, no single variable Conclusion our cohort, capacity, largely dysfunction. However, “Super-Fontans” stood out they anaerobic threshold illustrating their physical condition. These findings highlight role regular activity cornerstone for Funding Acknowledgement Type funding sources: None.