Malnutrition is a relevant prognostic factor in cardiovascular disease. However, it has not been studied in adults with CHD and Fontan circulation.

Retrospective, single-centre cohort study including all consecutive adults with Fontan circulation. Objectives: 1. To evaluate the prevalence of malnutrition, defined according to Controlling Nutritional Status score, which includes albumin, lymphocytes, and cholesterol and 2. To assess its utility as a prognostic marker.

We included 93 patients (55.9% male) with a mean age of 32.7 ± 8.3 years. After a median follow-up of 5.5 years (interquartile range 2.2 – 10.6), 14 patients met the combined primary outcome of death or heart transplant (15.1%). Moderate or severe malnutrition (Controlling Nutritional Status score ≥ 5) was detected in 18.3%. Overweight was found in 21.5% of patients, obesity in 4.3%, and low weight in 8.6%, with no significant differences in malnutrition parameters across weight categories. Patients with malnutrition had worse functional capacity (58.8% in New York Heart Association—NYHA-class III–IV, vs. 33.3% in patients without malnutrition, p = 0.05).

In univariate analysis, malnutrition was associated with a worse prognosis (death or heart transplant) with a hazard ratio of 3.7 (95% confidence interval 1.3 to 10.7, p = 0.01). In the adjusted model including cyanosis, functional class, and protein-losing enteropathy, malnutrition did not reach statistical significance (p = 0.81).

Malnutrition as defined by Controlling Nutritional Status score is common in adults with Fontan circulation and represents a strong prognostic marker. Controlling Nutritional Status scale could be used in Fontan patients as a simple tool to identify a high-risk population.