30-Day unplanned readmission rates, causes and outcomes of patients hospitalized for acute coronary syndrome based on the trial participation status

Background: This study aimed to investigate the association between index trial participation status and 30-day unplanned readmission rates, causes, and outcomes in acute coronary syndrome (ACS) patients. Methods: The National Readmission Database was analysed for all index hospitalizations with a principal diagnosis of ACS between October 2015 to November 2019, stratified by index trial participation status (International Classification of Diseases – 10th edition code: Z00.6). The 30-day unplanned readmission rates, causes and outcomes were analysed, including the assessment of factors associated with readmission. Multivariable regression analyses were reported as adjusted odds ratios (aOR) with 95 % confidence intervals (95 % CI). All analyses were weighted and utilized hierarchical multi-level organization. Results: A total of 2,066,328 cases with a principal diagnosis of ACS were included in the study, of which there were 4061 trial participants (0.2 %) and 189,240 (9.2 %) cases experienced unplanned 30-day readmission. Rates of unplanned 30-day readmission were similar between trial participants and non-participants (9.8 % vs. 9.2 %, p = 0.16). Consistently, after multivariable adjustment, there was no significant association between trial participation and unplanned 30-day readmissions (aOR 0.96, 95 % CI 0.86–1.07, p = 0.45). Compared with trial participants, the majority of readmissions in non-participants were related to cardiovascular conditions (55.2 % vs. 46.7 %, p = 0.005, respectively). There was no significant difference in all-cause mortality (5.5 % vs. 4.6 %, p = 0.368, respectively), but trial participants were more likely to develop major bleeding (3.5 % vs. 2.1 %, p = 0.044), ischemic stroke (4.0 % vs. 2.1 %, p = 0.008) and haemorrhagic stroke (2.0 % vs. 0.6 %, p < 0.001) at readmissions. Conclusion: Overall rates of unplanned 30-day readmissions after ACS are similar between trial participants and non-participants, but non-participation in trials was associated with a higher likelihood of cardiovascular readmission.