Background: Unstable Angina (UA) is a common subset of Acute Coronary Syndrome (ACS) and presents as atypical chest pain without the presence of cardiac biomarkers. It accounts for nearly 550,000 hospital admissions each year in the United States [1]. Management of UA can vary depending on the physician and/or intensity of symptoms. Prior studies have shown that 30-day readmissions for ACS is as high as 34.3% [2]. Given such a high 30-day readmission rate for ACS, we sought to specifically analyze risk factors for 30-day readmission for UA over a five year period.

Methods: We utilized Agency of Healthcare Research and Quality’s (AHRQ) 2010-2014 Nationwide Readmission Database which includes 70.5 Million discharges across 22 states to identify admissions with a principal diagnosis of unstable angina with ICD-9 codes 411.1, 411.81 or 411.89. Applicable admissions were all adults (age >= 18) from January 1 to November 30 of each respective year. Patients who died during index admission and those with missing covariates were excluded. Readmissions that were either all-cause or related to Unstable Angina within 30-days of an index admission were analyzed with p-values < 0.05 considered statistically significant. Predictors for readmission were determined using a multivariable logistic regression model.

Results: A total of 50,067 patients were admitted for UA. There were 5,615 readmissions (11.21%) within 30 days of the index admission. Predictors of readmission were weekend admissions (Odds Ratio [OR] 1.06, 95% Confidence Interval [CI] 0.99-1.14), discharged Against Medical Advice (OR 2.20, 95% CI 1.98-2.46), discharged to home health care (OR 1.84, CI 1.64-2.06), Age 18-65 (OR 1.24, CI 1.14-1.36), length of stay between 7 to 14 days (OR 1.69, CI 1.49-1.94), male gender (OR 1.32, CI 1.25-1.40), and the presence of the comorbidities obesity (OR 1.04, CI 0.96-1.12) or Chronic Kidney Disease (OR 1.79, CI 1.66-1.92).

Conclusions: Unstable angina has an 11% 30-day readmission rate. Identification of risk factors for readmission may allow for the development of interventions to decrease the rate of readmissions. Prior studies have concluded early angiography (within 48 hours) for Non-ST Elevation Myocardial Infarction (NSTEMI) and UA had lower 30-day readmission rates (10.4%) [3]. Future studies are needed to analyze if early angiography truly makes a difference in the 30-day readmission rate for patients within the UA subset.