To the Editor We read with great interest the article by Agarwal et al1 regarding national trends in heart failure hospitalizations and readmissions from 2010 to 2017. The authors found that the primary heart failure hospitalization declined from 2010 to 2014, followed by an increase from 2014 to 2017. However, it is important to note that 2014 is the time when Medicaid was expanded in many states under the Affordable Care Act.2 Therefore, it is possible that the observed trend could be explained by Medicaid expansions. Indeed, the data the authors provided showed that an increase in hospitalizations was observed mainly among Medicaid beneficiaries (Table 21), supporting this hypothesis. If the data allow, it would be informative to see whether the trends differ between states that expanded Medicaid compared with those that did not. If the research question is to investigate the underlying mechanisms as to why we are observing such trends, we believe the quasi-experimental designs, such as a difference-in-difference (DID) design or event study design, using residents of nonexpansion states as the control may be appropriate. Similarly, it is important to note that the US Centers for Medicare & Medicaid Services introduced the Hospital Readmissions Reduction Program (HRRP) in October 2012, which financially penalizes hospitals with higher-than-expected readmission rates for selected conditions, including heart failure. Although evidence is mixed, prior studies have found that the HRRP may be effective in reducing the readmission rates, and this may affect the observed trends.3,4 Given the overall trends may be confounded by the introduction of Medicaid expansions (in some states) and HRRP (introduced nationally), we believe that it may be informative if authors could disentangle the underlying national trends from the effect of policies (Medicaid expansions and HRRP) that were introduced during the study period.