Heart failure (HF) is a disease of epidemic proportions. Hospitalization accounts for the largest expenditure for care; annual costs are estimated to be $27.9 billion per year, about 3% of the total national health care budget.^1,2 and ³ In-hospital mortality ranges from 2% to 20% and 90-day recidivism in those discharged directly from the emergency department (ED) has been reported to be 61%.^4,5 Current guidelines for disposition are based on little or no empirical evidence.^6,7 and ⁸ As a direct result of the high-risk features of these patients and a lack of disposition guidance, the emergency physician’s triage decisions are historically conservative; more than 80% of ED patients with acute decompensated heart failure (ADHF) are admitted to the hospital.⁹ It has been suggested that poor ED risk stratification, particularly overestimation of disease severity, is the fundamental cause of the overutilization of limited in-hospital resources for this rapidly growing patient population.¹⁰

A novel approach for ADHF is necessary to decrease the relative burden of this disease. Despite recent advances in diagnostic and therapeutic measures for HF, the admission rate has remained largely unchanged. The observation unit (OU) presents an opportunity for further risk stratification and treatment for up to 24 hours to better delineate the need for admission. Using the OU to avoid hospital admission (average cost $5,456 per admission³) in just a small percentage of patients is likely to have a profound effect on health care expenditures.

The evaluation and disposition of ED patients with ADHF resembles the approach to chest pain in the 1980s, prior to the advent of chest pain centers. As a result of extensive research over the last 2 decades, we have experienced a dramatic paradigm shift in ED chest pain patients: from a high proportion of admitted patients to a rapid OU protocol allowing further risk stratification and safe, early discharge.^11,12 and ¹³ Preliminary research suggests a similar approach to ADHF may yield similar results.^14,15

It has been suggested that appropriate candidates for the OU are those who have an expectation of (a) hospital stays less than 48 hours, (b) no diagnosis traditionally requiring hospitalization, (c) no procedure requiring hospitalization, and (d) no probability of death.¹⁶ Due to the multiple comorbidities of ADHF patients, identifying a cohort that will fulfill these criteria is inherently difficult. However, excluding subjects with high-risk features,^{5,17,18,19,20,21,22} and ²³ as well as including subjects identified as proper candidates from previous OU research,^15,24 and ²⁵ lends some guidance in patient selection. Our OU protocol is a collaborative effort between the Department of Emergency Medicine and the Division of Cardiology at the University of Cincinnati. Inclusion and exclusion criteria were selected based on a review of previously derived retrospective risk data and an OU protocol, so as to identify what current practice suggests is a low- to moderate-risk patient (Table 3-1).^{5,15,17,18,19,20,21,22} and ²³