Heart failure (HF) is the leading cause of death among adults with congenital heart disease (ACHD)1. Although survival in patients with univentricular circulation has significantly improved over the last decades, these patients remain highly susceptible to HF due to a broad range of mechanisms that go beyond classical systolic and diastolic dysfunction2. They constitute a particularly challenging population to manage, as medical therapy has scarce evidence, and both mechanical circulatory support and heart or combined transplantation are technically complex and associated with substantial risk.
In a recent article3, Catalano et al. analyse characteristics, survival and health care costs of ACHD patients with single ventricle physiology (SV-ACHD) who were admitted to hospital due to HF and compare them with patients with acquired HF. Using retrospective data from 2016-2021 taken from the National Inpatient Sample (NIS) database, they extract a remarkably large cohort of 28,402,843 HF admissions with a considerable number of 3,375 SV-ACHD admissions (0.01% of total). Other ACHD diagnoses were excluded.
Median age at hospital admission was 34 years in the SV-ACHD group, compared with 73 years in the acquired HF group. Indeed, 88.1% of patients with acquired HF were 55 years or older, while 89.1% of SV-ACHD were younger than 55 years. As expected, basal characteristics differed: SV patients had higher rates of coagulopathy, liver disease and valvular heart disease; while acquired HF patients exhibited a higher prevalence of traditional cardiovascular risk factors including hypertension, diabetes, obesity, chronic pulmonary disease and chronic kidney disease. Crude absolute mortality was similar between groups (5.7% in acquired HF vs 5.8% in SV). However, on multivariable analysis adjusted by age, demographics, hospital characteristics and comorbidities, SV-ACHD patients had a higher risk of in-hospital death with a hazard ratio of 1.88 (CI 1.21- 2.91). In addition, SV-ACHD patients were more likely to present with cardiogenic shock, had prolonged length of stay, and increased hospital costs. It's interesting how, despite anatomical complexity for mechanical support and higher surgical risk for transplantation, SV-ACHD patients were more likely to receive advanced therapies, likely reflecting their young age. Other factors associated with mortality risk included age, comorbidities, cerebrovascular disease, coagulopathy, severe liver disease, severe renal failure, and weight loss. Analysing temporal trends, mortality seemed to improve over time. Even though the study period is too short to draw definitive conclusions, we can be optimistic as mortality seems also lower when compared with data from the previous decade.
Caution is warranted when interpreting these large database-based studies, as bias may be present. The study authors acknowledge several important limitations, mainly derived from the use of administrative coding, which may lead to misclassification, precludes assessment of long-term survival following admission, and prevents analysis of readmission patterns, with a risk of counting an individual patient multiple times for multiple admissions. Furthermore, the type of palliation is not described. We can assume that most SV patients in the United States have undergone Fontan-type palliation, but other anatomies may coexist with their own characteristics and prognostic implications4.
Despite these limitations, the study provides a comprehensive picture of the population with SV-ACHD hospitalized for HF and offers concrete data on mortality, advanced therapies use, length of stay and hospital costs. Importantly, it underscores the relevance of HF as a reason for admission and cause of mortality among SV-ACHD patients, putting the focus on this unique and increasingly prevalent population. Nevertheless, many questions and uncertainties arise and optimal management of these patients remains a challenge. These findings should be a call to action in such a young population, given the substantial personal, social and economic impact. Occasionally, HF decompensations in SV-ACHD have reversible causes, such as arrhythmias or Fontan pathway stenosis or obstruction, and targeted interventions can be effective. For the rest of the cases, HF reflects a complex interplay of pulmonary vascular disease, systolic and diastolic dysfunction, and lymphatic abnormalities. In these cases, HF can be an ominous marker of Fontan circulation failure and should prompt early consideration of advances therapies.
In summary, SV-ACHD patients admitted for HF experience a higher risk of in-hospital mortality when adjusted for age and clinical factors, have increased risk of procedure utilization and increased total costs when compared with patients with acquired HF.