Introduction: Heart failure (HF) is a significant cause of morbidity and mortality in the United States, contributing to approximately 1 in 8 deaths. Individuals with end-stage HF (eHF) experience debilitating symptoms leading to poor quality of life (QoL). We aimed to identify arrhythmias contributing to poor QoL and mortality in the inpatient setting. Hypothesis: The burden of arrhythmias in eHF may be overwhelming and a significant predictor of mortality. Understanding this may help proffer clinical management and improve outcomes. Methods: We used the ICD-10 code for eHF (I5084) from the National Inpatient Sample (NIS) (2016-2020) to identify all patients with eHF. We used a multivariate logistic regression model to adjust for confounders and estimate the mortality probability in each arrhythmia cohort. Our primary outcome was in-hospital mortality risk in each group. A p-value of 0.05 was deemed significant. Results: There were 22703 hospitalizations with eHF (mean age 67 years ±16), 66.5% (15091) were men, 59% (13018) were Caucasians, 27.2% (6017) were Blacks, 8.7% (1924) were Hispanics and 2.9% (505) Asians. Of these, 50.4% (11434) had atrial fibrillation (AFIB), 5.3% (1201) supraventricular tachycardia (SVT), 2.6% (586) ventricular fibrillation (VFIB), 1.6% (372) complete heart block (AVB3), and 0.4% (85) type 2 degree block (AVB2). All subgroups had independent associations with mortality, and VFIB was the highest predictor; adjusted odds ratio (aOR) 5.8 (4.6-7.1, p<0.0001), AFIB 4.3 (3.9-4.5, p<0.0001), SVT 1.9 (1.6-2.4, p<0.0001), AVB3 1.8 (1.3-2.4, p<0.0001), and AVB2 1.3 (0.6-3.0, p=0.5). Conclusion: Our analysis revealed that a high percentage of the in-hospital population with end-stage heart failure is burdened with atrial fibrillation. Ventricular fibrillation, atrial fibrillation, supraventricular tachycardia, and complete heart block all carried independent mortality risk, with ventricular fibrillation having the highest risk. Proactive management of arrhythmias in this population is warranted.