Abstract Body (Do not enter title and authors here): Introduction: The prevalence of heart failure (HF) among U.S. patients (pts) with Fontan physiology is poorly defined, with estimates generally derived from single centers. We leveraged a 7-state administrative dataset—the largest single ventricle (SV) cohort to date—to estimate HF prevalence across the lifespan and its associated comorbidities.

Methods: This is a study from the CDC-funded STAR1 registry of CHD pts ages 0-45. All ICD diagnostic/procedural codes from 2010-2019 were collected. SV pts ≥5 yrs (presumed post-Fontan) were identified via ICD-9/10 codes associated with SV physiology and Fontan palliation. HF of any type was identified via ICD9/10 query. To depict HF burden over the lifespan (Figure 1), HF prevalence was calculated per 5-year age range via the following: total number of pts with HF coded in an encounter for that age range divided by the total number of pts at risk in that age range.

Results: Of the 4,753 Fontan pts identified, 2,836 (60%) were 5-17 years old (yo), 1,358 (28%) were 18-30 yo and 559 (12%) were ≥31 yo at first encounter. Diagnoses included hypoplastic left heart in 1,752 (37%), tricuspid atresia in 1,945 (41%), and SV not otherwise specified in 1,056 (22%), of which 36%, 41% and 46% were adults, respectively; 168 SV patients were >45 yo by end of the surveillance period. Overall, 1,401 (29%) had a diagnosis of HF at any time. HF prevalence increased over the lifespan, ranging from 8.3% in patients 5-9 yo to 58.3% of pts ≥45 yo (Figure 1). HF patients had higher rates of cardiac and non-cardiac comorbidities than their non-HF peers (Table 1). Traditional modifiable cardiovascular risk factors, including hypertension, hyperlipidemia, smoking, and diabetes, were significantly higher among pts with HF across all ages. Heart transplant occurred in 22% of all HF pts (occurring in 30% of 5-17 yo, 16% of ≥ 31 yo, p < 0.05) vs. 0.2% in non-HF pts. 231 (16%) of HF pts died (mortality rate 184 deaths/10,000 person-years) vs. 81 deaths among 3,352 (2%) pts without HF (mortality rate 28 deaths/10,000 person-years, p < 0.05).

Conclusions: In the largest Fontan cohort studied to date, ~1/3 were diagnosed with HF at any time, with steady increase to >50% after age 45. The HF cohort had a significantly higher burden of comorbid disease, including potentially targetable risk factors. This emphasizes the need for close surveillance and early diagnosis in this complex patient population.