Abstract Body (Do not enter title and authors here): Background: COVID-19 has led to significant global morbidity and mortality. Its impact on patients with hypertrophic cardiomyopathy (HCM) remains unclear.

Aim: To evaluate the impact of COVID-19 infection on the readmission rate and associated outcomes in patients with HCM.

Methods: In a retrospective study using the 2020 National Readmission Database, we collected data on patients with HCM who were admitted with the principal diagnosis of COVID-19. The primary outcome was the all-cause 30-day readmission rate. Secondary outcomes were common causes of readmission, in-hospital mortality, and resource utilization.

Results: In 2020, a total of 1503 patients with HCM (mean age 67 years, 49% female) were hospitalized for COVID-19. Among them, 1216 (80.9%) were discharged alive and 180 (14.8%) were readmitted within 30 days. In-hospital mortality for readmissions remained relatively unchanged compared with index admissions (15.4% vs 19.0%, P=.34; Table 1). The most common cause of readmission was COVID-19 infection (38%), followed by other infections (11%) and acute kidney injury (4%). The most common cardiac cause for readmission was paroxysmal atrial fibrillation (2%). The mean length of stay for readmissions was relatively similar to the index admission (7.8 vs 9.9 days, P=.43). The mean hospital charge associated with readmission was $84,976 (total hospital charges were $15.2 million). The mean hospital cost associated with readmissions was $24,603 (total hospital costs were $4.4 million). A higher Charlson comorbidity index score was the main independent predictor of higher readmission rates.

Conclusions: This study highlights the significant burden of COVID-19 on patients with HCM. Despite efforts to reduce readmission rates, a considerable percentage of patients experienced readmission within 30 days, largely attributed to COVID-19 infection. Close follow-up after discharge could prevent such readmission and the associated high mortality rates.