Percutaneous coronary intervention (PCI) is an essential treatment modality for coronary artery disease and its indication and application have been widened along with its technical advancement. While many related studies have been done in Korea, there is paucity of descriptive data representing national status of the procedure. There are studies in United States using nation-wide sample1) or community-based population2) reporting descriptive data. In Korea, a recent study3) using 2006–2010 database of Health Insurance Review and Assessment Service reported descriptive data regarding the status of coronary revascularization, which estimated procedure rate in 2010 as 131/100,000 person-years (123.4 for PCI only). However, this study has limitations such as lack of long-term outcome except in-hospital mortality and relative restricted duration of follow-up.

The objective of this study is to report descriptive data representing national status of PCI using National Health Insurance Service-National Sample Cohort (NHIS-NSC) 2002–2013 provided by National Health Insurance Service Data Sharing Service (http://nhiss.nhis.or.kr/bd/ab/bdaba015lv.do) including mortality data.

Though this is not the first study to report the Korean status regarding PCI, it provides additional information which the previous Korean study3) lacks. In this study, the trend of PCI during the year 2002–2013 was shown. Increasing in the number of procedures was evident and the procedure rate was more than tripled during this period while the rate of CABG was stationary. Recent report from Korean PCI registry5) from 93 hospitals reported descriptive statistics based on 2014 cohort but without information for long-term trend.

In United States, a study utilizing the Nationwide Inpatients Sample database reported that the rate for PCI increased to more than three times from 1988 to 2001 (80.3 to 244 per 100,000/person-years)6) Another study1) investigated coronary revascularization trends in the US during 2001–2008 period, which reported that there was 14% decrease in the annual rate of coronary revascularizations and the decrease was mostly explained by 39% decrease in CABG and PCI rate changed minimally (2% decrease). Further study investigated data during 2007–2011 reported decrease of annual PCI rate by 27.7% (p=0.03) and this decrease was mostly due to the decrease in PCI utilization for stable coronary artery disease.7)

In contrast to the US, annual PCI rate in Korea showed increasing trend at least until the year 2013. Increasing trend of PCI seems to be largely due to increase in the incidence of IHD, which can be estimated by the increase of admission for IHD. However, considering that the proportion of cases underwent PCI among the total admission for IHD significantly increased (from 50.6% in 2002 to 61.5% in 2013, p for trend <0.001) and the proportion of primary PCI among all PCI cases remained the same, increased elective procedure probably for stable angina may be an important factor contributed to the increasing trend. While invasive strategy including PCI is a standard treatment in acute coronary syndrome,8) its benefit in patients with stable angina is not conclusive probably because of the influence of highly effective preventive medical therapy.9) Further study is warranted to ensure whether increasing use of elective PCI for stable coronary disease is well-justified.

While the increasing trend in both total admission for IHD and PCI was evident, there was a ‘notch’ during 2008–2010 and also temporary interruption of increasing trend in the number of hospitals performing PCI in 2009, while there is no such finding in the trend of the annual rate of primary PCI (Figure 1 and Table 4). While the cause for this finding is uncertain, a possible explanation, though only speculative, is that the association with the global financial crisis. Financial crisis of 2008 began with a crisis in the subprime mortgage in the US and developed into an international banking crisis with the collapse of Lehman Brothers on September 2008.10) This financial crisis followed by a global economic downturn and also had impact on the Korean economy resulted in reduced gross domestic product and private consumption during 2008–2010.11) In Canada, Pilote et al.12) reported inequities in access to cardiac procedures after AMI, i.e., patients in low SES were less likely to undergo cardiac catheterization compared to those in high SES (men: 33%; compared with 47%; women: 18%; compared with 47%), even under universal health insurance coverage. The economic downturn of the period may influence the decision for PCI, especially elective procedures, both in individual and hospital levels, though this is only a speculation based on indirect evidences.

There was clear increasing trend in the number of hospitals performing PCI along with the increase of total number of PCI and also the proportion of smaller hospitals increased. Proportion of the PCI's done in the hospitals with less than 500 beds were only 7% in 2002 and increased to 27.5% in 2013. Similar findings were observed in a US study that a significant increase in the proportion of PCI's at centers without on-site cardiac surgery (from 1.8% to 12.7%) during the period of 2003–2012.13)

In our PCI cohort, regions of hospitals were largely insignificant as a predictor of mortality except Jeju region which showed lower mortality (Table 6). This is probably related to the disease severity of patients but further analysis was impossible due to the lack of data on clinical information. Presence of hypertension was associated with lower mortality, probably because hypertension was defined by the use of antihypertensive medication and represented well-treated group. Low personal SES is apparently associated with poor prognosis, which is consistent with previous epidemiological studies.14)15)

This study has several limitations. Because the study cohort is a retrospective cohort based on the National Health Insurance database, there are lack or insufficiencies in the clinical information such as: 1) comorbidities and especially its severity, 2) clinical events outside the range of the follow-up period, 3) clinical characteristics such as hypertension, diabetes and/or dyslipidemia and its changes over time. While some of them could be obtained from ICD codes in the insurance claims, significant over- or under-diagnoses is not avoidable because the diagnosis should be based on the ICD codes for outpatient visit. Also there might be some inaccuracy in the diagnosis of IHD and myocardial infarction. However, diagnosis of IHD and myocardial infarction was defined by ICD codes for admission, which is known to have less errors compared to outpatient setting.16)17)

In conclusion, annual procedure rate of PCI increased more than three times during 2002–2013 period and also the number of hospitals which performed PCI. SES, either personal or national, has a significant effect on the patients' prognosis and national trend of health care. These findings should be considered in prediction of further trend and policy making.