Abstract Body (Do not enter title and authors here): Background
Heart failure (HF) is a significant public health concern, affecting approximately 6.2 million adults in the United States, with high mortality and readmission rates. Cardiac rehabilitation (CR) programs have been widely recognized as a crucial component of HF management, aiming to improve physical function, reduce symptoms, and enhance quality of life. Despite the established benefits of CR, there is a need to understand the trends in mortality and readmission rates among HF patients participating in these programs. We aim to analyze mortality and 30-day readmission rate trends among heart failure patients undergoing cardiac rehabilitation from 2017 to 2020 using NRD data.

Hypothesis
We hypothesize a significant downward trend in mortality rates and significant yearly variation in 30-day readmission rates among heart failure patients undergoing cardiac rehabilitation.

Methods
We analyzed NRD data from 2017 to 2020, including patients with ICD-10 codes I50 (heart failure) and Z5189 (cardiac rehabilitation). Trend analyses were performed using Ordinary Least Squares (OLS) regression for mortality rates and the Cochrane-Armitage test for binary data. Multivariate regression adjusted for age, sex, and comorbidities. Statistical analyses were conducted using STATA version 18.

Results
From 2017 to 2020, annual mortality rates were 6.9% (95% CI: 0.95% to 12.85%), 5.5% (95% CI: 0.47% to 10.52%), 4.6% (95% CI: -0.51% to 9.68%), and 1.9% (95% CI: -1.90% to 5.74%), respectively. The mean age was 78 years, with 54% were female. OLS regression showed a significant downward trend in mortality (p = 0.025), while the Cochrane-Armitage test did not (p = 0.998). Multivariate regression also indicated a downward trend, though individual predictors were insignificant (p=0.576). For 30-day readmission rates from 2017 to 2020, annual margins were 21.5% (2017), 21.7% (2018), 18.0% (2019), and 34.3% (2020), showing significant yearly variation.

Conclusion
Despite the varying range of 30-day readmission within the years of interest, there seems to be a significant downward trend in mortality for heart failure patients who underwent cardiac rehabilitation. Further studies are required to corroborate these findings as understanding CR program outcomes can help identify improvement areas, guide resource allocation, and inform healthcare policy decisions.