Underutilization of Hospital-based Cardiac Rehabilitation after Acute Myocardial Infarction in Korea

Ischemic heart disease (IHD) is one of the most burdensome chronic diseases in Korea.1 With an improvement in survival after IHD,2 more efforts are being channeled towards secondary prevention.3 Cardiac rehabilitation (CR), an aspect of secondary prevention program, is highly recommended after IHD in national clinical practice guidelines,4, 5, 6 (based on the evidence of CR) for improving clinical outcomes.7, 8, 9 Nevertheless, CR participation rate after IHD has been low and shows disparities between countries10 and individuals on account of various barriers.11 According to a global report based on the responses of experts in CR from countries in 2017, and IHD burdens report from the Institute for Health Metrics and Evaluation, CR was available in only half of all countries, and the number of CR facilities for patients with IHD was insufficient in Korea.12, 13 The number of incident IHD cases per year per CR facility in Korea was 22, higher than the median value among countries worldwide (n = 21) and the mean of the Organization for Economic Cooperation and Development countries (n = 17).12

In Korea, CR was primarily introduced around the late 1990s. There has been expert- and government-led efforts to promote CR. Regional cardiocerebrovascular centers have been established since 2009, and a total of 14 centers are being operated to improve the quality of cardiovascular treatment, including CR. CR services after IHD have been reimbursed as medical treatment benefits since February 2017. Despite these efforts, the rate of CR participation remains low in the hospitals actively delivering CR (14%–35%).11 Nationwide CR participation rates are expected to be lower, considering the insufficient number of CR facilities12; however, this has not been estimated in Korea. Understanding the current status of nationwide CR use may be an important first step to establish an effective strategy towards the promotion of CR in Korea.

Therefore, this study was designed to measure the nationwide hospital-based CR participation rate, the current numbers of hospitals delivering CR services among patients after acute myocardial infarction (AMI), and the insufficiency in the number of CR facilities in Korea compared to those of other high-income countries. The Korean National Health Insurance Service (NHIS) database from 2017 was used, because only claim codes starting from February 2017 could be identified. Similarly, the risk factors for CR nonparticipation after AMI were identified in hospitals considered as actively delivering CR.

Despite the recommendations accentuating the role of CR in AMI patients,4, 5, 6 only 1.5% of these patients participated in the CR program in Korea. There was geographical variance in participation, ranging from 0.0% to 6.4%. The relatively high AMI incidence obtained in this study compared to that of the Statistics Korea18 and a range of 71.4%–73.1% accuracy of the operational definition for diagnosing AMI16 could have resulted in the underestimation of the participation rate. Nevertheless, even considering these limitations, the participation rate of 1.5% was remarkably lower than that of Europe (30%–50%)19 and the United States (10.3%–16.3%).20 According to our calculation, the CR density in Korea was about 10. This means that approximately 234 more CR facilities should be established to cover the annual incidence of AMI.

In hospitals with > 10 CR participants, the CR participation rate was similarly insufficient (9.5%). This suggests that efforts are required to promote CR participation even in actively-operating CR facilities; the identification of CR barriers is important to plan effective promotion strategies. This study showed a markedly lower CR participation in patients with old age, female sex, and rural residence, in line with the results of previous studies.21, 22, 23 The reasons for inadequate CR participation among these populations are multifactorial.24, 25 Proposed explanations for low participation in elderly patients include inadequate physician referral, comorbidity-associated mobility issues, and transportation issues.26 Poor CR participation in females might be attributed to insufficient physician referral, more familial responsibilities, and less spare time to attend CR programs.27 Self-reliant rural attitudes and low accessibility to medical facilities might have contributed to poor CR participation among rural residents.28 To overcome these issues, strategies should be implemented, including automated referral systems, improved awareness of CR, flexible therapy hours, and alternative CR delivery models such as home- and community-based CR.24, 29

In this study, no difference was observed between the participants and the nonparticipants with regard to income status; this is different from previous studies that revealed higher income earning patients attend CR more in Europe30 and the United States.31 One possible explanation for the unobserved difference is the decreased economic burden of CR due to its coverage by the National Health Insurance in Korea. Another possible explanation is that high income earning patients are more likely to be economically active with insufficient time to participate32; this can offset the beneficial effects of high income on CR participation. Therefore, further study is required to clarify the effect of socioeconomic status on CR participation in Korea. Similarly, CCI was not a significant factor in previous studies investigating CR barriers.23, 33, 34 However, the fewer comorbidities group (the group with the lowest CCI ranging between 0–4) participated least often in this study; this could be due to the less motivation and fewer needs of these patients, which could have resulted in nonparticipation in CR.11, 35 In addition, CCI is determined by the number of comorbid diseases, and this may not directly reflect the patient's physical or cardiac function, which are important factors for CR participation.36 Therefore, a further study including variables such as cardiorespiratory fitness level or ejection fraction is needed.

In this study, only a limited number of potential barriers were retrospectively investigated. Nevertheless, various CR barriers have been reported in the literature21, 37, 38 and they may differently affect CR participation depending on the particular clinical situation in each hospital or region. Therefore, efforts to identify CR barriers in each region and planning effective CR promotion strategies according to identified barriers are required.39

There are several limitations to this study. First, the diagnosis of AMI was operationally defined using medical claim records. In a previous study, this method has been known to have an accuracy ranging between 71.4%–73.1% and fair-to-good reliability.16 Nevertheless, there are possibilities of false exclusion or inclusion. Second, national CR density was calculated using the median capacity of Korean hospital-based CR facility participating in a previous global survey.12 Most of the hospitals used in the estimation of the CR capacity were tertiary or general hospitals that probably had larger CR capacity, and the CR density may have been underestimated. In addition, the distance from a CR facility to a patient's home is an important influencing factor for CR participation27 that was not considered. For example, a CR facility with a large capacity could be situated extremely far from the patient's home; therefore, the required number of CR facilities based on CR density in this study could have been equally underestimated. Third, there could be mismatch between procedure, benefits, and claim record. Because the period of index admission in this study was the transition period of the change in benefits type for CR, there is a possibility of incomplete reimbursement for any reason. Therefore, follow-up research until the post-transitional period is important. Fourth, other known factors that affect participation in CR, including physician referral pattern, the ability to drive, and education level, were not evaluated.21, 23 Further comprehensive studies should be performed to evaluate CR barriers. Fifth, indication for CR was confined to AMI in this study. Current indications for CR are broader, including other cardiovascular diseases such as unstable angina, valvular heart disease, heart failure, and peripheral arterial diseases.5, 6, 40, 41 Therefore, the possibility of unrevealed demand for CR exists. Further studies, including these group of patients, are needed. Finally, this is the initial report of CR utilization (in the period of CR utilization) in Korea. Three more regional cardiocerebrovascular centers were installed in 2019, and more hospitals may provide CR at this time. Therefore, a follow-up study is required.

In conclusion, hospital-based CR participation rate after AMI was only 1.5% nationally, and the overall supply was insufficient in Korea, despite coverage by the National Health Insurance, compared to CR use in other high-income countries. To overcome these problems, more CR facilities and effective strategies to overcome CR barriers are required. Therefore, a follow-up study with a more comprehensive evaluation of barriers to CR is needed in the future.