Early- and late-term clinical outcome and their predictors in patients with ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction

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Abstract

Backgrounds

The disparity between ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) remains controversial. We compared clinical outcomes and prognostic factors between STEMI and NSTEMI using large-scale registry data.

Methods

We recruited 28,421 patients with STEMI (n = 16,607) and NSTEMI (n = 11,814) between November 2005 and April 2010 from a nationwide registry in Korea. We performed landmark analysis of cardiac death, recurrent acute myocardial infarction (re-AMI), revascularization, and major adverse cardiac events (MACE) at 30 days (early term) and 1 year (late term) after admission.

Results

Patients with NSTEMI had a greater number of co-morbidities than STEMI patients. Early term MACE (6.9% vs. 4.5%, p < 0.001) and cardiac death (6.1% vs. 3.7%, p < 0.001) were higher in STEMI patients. However, late-term MACE (8.0% vs. 9.1%, p = 0.007), cardiac death (1.9% vs. 2.6%, p = 0.001), and re-AMI (0.6% vs. 1.3%, p < 0.001) were lower in the STEMI group. The independent predictors of cardiac death were old age, renal dysfunction, LV dysfunction, Killip class, post-thrombolysis in myocardial infarction (TIMI) flow, and major bleeding in both groups. Female gender, previous ischemic heart disease, diabetes, current smoking, multivessel disease, and body mass index were MI type- or time-dependent predictors.

Conclusion

The STEMI group displayed poor early term clinical outcome, whereas the NSTEMI group displayed poor late-term clinical outcome. The STEMI and NSTEMI groups had different predictor profiles for cardiac death, suggesting that different strategies are required for improving the late-term outcome of STEMI and NSTEMI patients.

Introduction

Acute myocardial infarction (AMI) is a major cause of death and disability worldwide, and the prevalence is rising in developing countries. AMI can be clinically categorized as non-ST elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI) according to the presenting electrocardiogram (ECG) [1]. The proportion of patients diagnosed with NSTEMI increased significantly after the introduction of the troponin assay, whereas the proportion diagnosed with STEMI decreased [2]. According to previous studies, the short-term and long-term mortalities of AMI have been declining, and this decline has generally been attributed to closer adherence to the current guidelines for AMI management [2], [3], [4].

The main pathogenesis of acute coronary syndrome is the disruption or erosion of an atherosclerotic plaque and a subsequent cascade of thrombosis, which decreases coronary blood flow. Although STEMI and NSTEMI have a similar pathogenesis, their treatment strategies are different, and their prognosis differs [3], [4]. STEMI occurs when there is a transmural infarction of the myocardium due to total occlusion of a coronary artery, which requires emergent percutaneous coronary intervention (PCI) or thrombolysis for treatment. However, NSTEMI occurs when there is a partial occlusion of the coronary arteries without transmural infarction. NSTEMI occurs when there is collateral flow to the territory of a completely occluded culprit artery. Similar baseline clinical angiographic characteristics have been reported in many studies [5], [6], [7]. Although the worse short-term mortality associated with STEMI is well known, the differences in long-term mortality between STEMI and NSTEMI patients have been controversial [8], [9], [10]. The predictors of early mortality are well established, but the predictors of late-term mortality (especially in 30-day survivors) are neither well established nor separately categorized [10], [11], [12], [13], [14].

The objective of this study is to evaluate (1) the differences in early (≤ 30 days) and late-term (31 days to 1 year) clinical outcomes and (2) the differences in the independent risk factors between STEMI and NSTEMI patients using data from the nationwide registry of the Korea Working Group of Myocardial Infarction.

Section snippets

Administration of AMI registry

In Korea, efforts have been made to collect nationwide data and to standardize the clinical practice regarding AMI. Part of that effort has been the Korean Acute Myocardial Infarction Registry (KAMIR), a nationwide registry that collected data from November 2005 to January 2008 and its successor, the Korean Registry of Myocardial Infarction (KorMI), which collected data from January 2008 to July 2010. Both these registries were supported by the Korean Working Group of Acute Myocardial

Patient characteristics

Fig. 1 describes the study scheme. Among 29,199 subjects from the 2 databases, the data of 28,421 patients with AMI were extracted for this study: 16,607 with STEMI and 11,814 with NSTEMI. The median follow-up duration was 214 days (range, 0–730 days). The proportion of patients with STEMI was greater than the proportion of patients with NSTEMI, but the proportion of NSTEMI increased since the beginning of registration.

Patients with NSTEMI were older and more likely to be women. Patients with

Discussion

In this multicenter prospective observation study, we found that the rates of early term MACE and cardiac mortality were higher in patients with STEMI than in patients with NSTEMI, whereas the rates for late-term MACE, cardiac mortality, and re-AMI risk were lower in patients with STEMI than in patients with NSTEMI. However, these higher late-term events in patients with NSTEMI were associated with different patient characteristics and angiographic findings. Age, gender, low BMI, renal

Conclusions

We found that STEMI was associated with a higher risk of early term clinical events even after multivariate adjustment, whereas NSTEMI patients displayed a higher risk of late-term clinical events, which was not significant after adjustment. Patients with STEMI and NSTEMI have different risk factor profiles, which should be adequately managed to improve long-term outcome, especially in patients with NSTEMI.

Acknowledgment

KAMIR was carried out with the support of the Korean Circulation Society (KCS) in the memorandum of the 50th anniversary KCS. This study was supported by grant number 02-2011-056 from the SNUBH Research Fund and National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A2A2A02012821 and 2012M3A9C7050140).

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