Circulation Journal
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Print ISSN : 1346-9843
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Multicenter Cohort Study of Acute Myocardial Infarction in Korea　– Interim Analysis of the Korea Acute Myocardial Infarction Registry-National Institutes of Health Registry –
Ju Han Kim, Shung-Chull Chae, Dong Joo Oh, Hyo-Soo Kim, Young Jo Kim, Youngkeun Ahn, Myeong Chan Cho, Chong Jin Kim, Jung-Han Yoon, Hyun-Young Park, Myung Ho Jeong, Korea Acute Myocardial Infarction-National Institutes of Health Registry Investigators
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キーワード: Multicenter study, Myocardial infarction, Research design
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論文ID: CJ-16-0061

この記事には本公開記事があります。
The final version of this article is now available: Vol. 80 (2016), No. 6 pp. 1427-1436
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Abstract

Background: The Korea Acute Myocardial Infarction Registry (KAMIR)-National Institutes of Health (NIH) registry has the aim of evaluating the clinical characteristics, management, and long-term outcomes of patients with acute myocardial infarction (AMI) in Korea.

Methods and Results: Patients hospitalized for AMI in 20 tertiary university hospitals in Korea have been enrolled since November 2011. The study is expected to complete the scheduled enrollment of approximately 13,000 patients in October 2015, and follow-up duration is up to 5 years for each patient. As of October 2015, an interim analysis of 13,623 subjects was performed to understand the baseline clinical profiles of the study population. The mean age was 64.1 years; 73.5% were male; and 48.2% were diagnosed with ST-segment elevation AMI. Hypertension is a leading cause of AMI in Korea (51.2%), followed by smoking (38.5%) and diabetes mellitus (28.6%). Percutaneous coronary intervention was performed in 87.4% and its success rate was very high (99.4%). In-hospital, 1-year, and 2-year mortality rates were 3.9%, 4.3%, and 8.6%, respectively. The rates of major adverse cardiac events at 1 and 2 years were 9.6% and 18.8%, respectively.

Conclusions: This analysis demonstrated the clinical characteristics of Korean AMI patients in comparison with those of other countries. It is necessary to develop guidelines for Asian populations to further improve their prognosis.

Acute myocardial infarction (AMI) is a leading cause of death around the world.1,2 In Korea, as in other developed countries, the incidence of AMI has increased over several decades. It is important to prevent the occurrence of AMI, and to manage the patients for a long time after surviving an AMI. To improve the prognosis, we needed to investigate the risk factors, clinical features, use of medications, and procedural findings of AMI in Korean patients. The Korea Acute Myocardial Infarction Registry (KAMIR) was launched for this purpose by the Korean Society of Cardiology in 2005.3–7 However, there were some limitations in the KAMIR, including lack of long-term follow-up, despite a great expansion in the number of enrollments. Therefore, there has been a systematic effort to develop a national registry funded by the National Institutes of Health (NIH) for better understanding of AMI in Korea. The authors have established this registry to identify the overall clinical features, current treatment strategies, and prognosis of patients with AMI in Korea and to compare this registry with those from other countries.

Methods

Objectives of the Registry

The KAMIR-NIH registry (http://www.kamir.or.kr) is a prospective, open, observational, and on-line registry with a multicenter cohort study that is currently ongoing. The registry protocols of KAMIR-NIH were verified and approved by the institutional review board of each participating center. Patients with a diagnosis of AMI at presentation to hospital have been enrolled and followed up continuously. The aims of the KAMIR-NIH are as follows: (1) to collect data on baseline clinical characteristics, current treatment patterns, and short- and long-term patient outcomes; (2) to analyze the prognostic factors of AMI; and (3) to improve the long-term prognosis of individual patients.

Patients

Patients hospitalized for AMI from 20 tertiary university hospitals capable of percutaneous coronary intervention (PCI) have been consecutively enrolled since November 2011 throughout Korea. The planned enrollment of approximately 13,000 patients is expected to be complete in October 2015, with follow-up through 2018. AMI is defined as cardiomyocyte necrosis in a clinical setting consistent with acute myocardial ischemia.8 AMI was diagnosed by the characteristic presentation, serial changes on ECG suggesting infarction, and an increase in cardiac markers, preferably cardiac troponins, with at least one value above the 99th percentile of the upper reference limit. ST-segment elevation MI (STEMI) was defined as new ST elevation in ≥2 contiguous leads, measuring >0.2 mV in leads V1–3 or 0.1 mV in all other leads, or a new left bundle branch block on 12-lead ECG with a concomitant increase in troponin-I or -T.

Data Collection

Written informed consent was given by each patient. If patients were unable to give consent because of disease severity, informed consent was obtained from a relative or legal representative. Data were collected by the attending physician with the assistance of a trained clinical research coordinator, via a web-based case report form in the Clinical Data Management System (iCReaT) of the Korea NIH. The KAMIR-NIH registry documented all consecutive variables and values at baseline admission of patients with AMI in Korea. The cardiovascular risk factors (hypertension, diabetes mellitus, dyslipidemia, smoking, and family history of coronary artery disease) and other comorbidities were identified. The baseline data included the initial presentation and laboratory results at the emergency department. During the in-hospital period, events including all-cause death, cardiac death, and any complications related to AMI were recorded. After discharge, all major adverse cardiac events (MACE) including cardiac death, MI, repeat PCI (target lesion or target vessel revascularization, or non-target vessel revascularization), stent thrombosis, or coronary bypass graft, and all events of non-cardiac death, cerebrovascular accident, and re-hospitalization because of heart failure were recorded at 6, 12, 24, and 36 months. The follow-up results of echocardiography, laboratory studies, and prescribed medications were also recorded at 12, 24, and 36 months. The follow-up data were collected from the patients by attending physicians and the web-based case report forms were completed. If the patients did not visit the hospitals, the outcome data were assessed by telephone interview.

Study Management

The registry is governed and managed by a committee consisting of healthcare professionals with expertise in AMI. The committee designed the study protocol and case report forms. The committee supervises all activities related to publications from the aggregate database. The present study is funded by the Korea NIH.

Statistical Methods and Sample Size Determination

Determination of Sample Size and Study Power For determination of sample size, we selected the timeliness of reperfusion therapy as a representative index. From the previous KAMIR data set, a total of 10,950 (53%) patients were diagnosed with STEMI and underwent PCI. Among these patients, 47% were untimely (>90 min) [Pr(x=1)]. The mortality rate of patients who experienced appropriate reperfusion therapy (≤90 min), was 7% within 1 year [Pr(y=1/x=0)]. We presumed that the odds ratio (OR) of death in 1 year because of delayed reperfusion therapy was 1.3, which minimally expected 80% of the OR of 1.57 in a previous study.9 To observe >80% power and an alpha of 0.05, we needed a sample size of 6,293 calculated by StudySize software (ver. 2.0.4; CreosStat HB, Sweden). In addition, we presumed that the rate of follow-up loss was approximately 10%, requiring a total of 6,923 STEMI patients. Therefore, a total of 13,000 AMI patients were planned to be enrolled in this study, because the proportion of STEMI was 53%. We estimated that a total of 3,000 AMI patients would be annually enrolled from 20 centers, and that we might need 4 years to complete this cohort study.

Statistical Analysis For continuous variables, the data are expressed as the mean±standard deviation or as the median with an interquartile range using unpaired t-test or Mann-Whitney rank-sum test. For categorical variables, the data are expressed as counts and percentage and analyzed by the Chi-square (or Fisher’s exact) test. Cumulative 2-year MACE-, cardiac death-, and repeat PCI-free survival curves were constructed from Kaplan-Meier survival analyses and compared using log-rank test. All analyses were two-tailed, with clinical significance defined as P<0.05. Statistical analysis was performed using SPSS, version 21.0 for Windows (SPSS-PC, Chicago, IL, USA) and R, version 3.2.2.

Results

A total of 13,623 Korean patients with AMI were enrolled in this study until October 2015. We excluded patients whose clinical data were incomplete for interim analyses. A total of 12,956 patients were enrolled at 20 hospitals around Korea.

Demographics and Baseline Clinical Characteristics

The clinical characteristics of the patients in KAMIR-NIH are shown in Table 1, and they are compared with other AMI registries including GRACE,10 SCAAR,11 NRMI,12 MINAP,13 and SWEDEHEART/RIKS-HIA.13 The mean age was 64.1 years and 73.5% were male. Less than half of the patients (48.2%) were diagnosed as STEMI. Among the risk factors for ischemic heart disease, hypertension was the most common comorbidity (51.2%), followed by smoking (38.5%), diabetes mellitus (28.6%), dyslipidemia (11.2%), previous MI (8.1%), family history (6.3%), and cerebrovascular accident (6.2%). In Table 2, we compare the baseline characteristics according to the diagnosis: STEMI vs. non-STEMI (NSTEMI). STEMI patients were younger (62.8±12.8 years vs. 65.1±12.4 years, P<0.001), male-predominant (77.7% vs. 70.6%, P<0.001), and more obese (body mass index 24.1±3.4 kg/m2 vs. 23.9±3.5 kg/m2, P=0.012) than NSTEMI patients. Although most of the patients with STEMI (90.8%) complained of chest pain, only 19.9% utilized the emergency medical service in Korea. Hypertension (54.8% vs. 47.0%, P<0.001), diabetes mellitus (32.0% vs. 24.8%, P<0.001), dyslipidemia (11.8% vs. 10.6%, P=0.022), cerebrovascular accident (7.5% vs. 4.8%, P<0.001), and heart failure (2.3% vs. 0.9%, P<0.001) were more frequent in patients with NSTEMI than STEMI. Only smoking was more frequent in STEMI patients (43.9% vs. 34.4%, P<0.001). STEMI patients had a higher Killip class (22.8% vs. 20.2%, P<0.001) and a higher proportion of significant atrioventricular block (1.4% vs. 0.6%, P<0.001).

Table 1. Clinical Characteristics of Patients With Acute MI in Korea Compared With Other Registries
  KMAIR-NIH KAMIR5 GRACE10 SCAAR11 NRMI12 MINAP13 SWEDEHEART/
RIKS-HIA13
Region South Korea South Korea Europe,
America		 Sweden US UK Sweden
Time period Nov 2011–
Oct 2015		 Nov 2005–
Oct 2010		 2004–2007 Jan 2003–
Dec 2004		 1994–2006 Jan 2004–
Dec 2010		 Jan 2004–
Dec 2010
Sample size 13,624 27,852 28,449 19,771 542,008 391,077 119,786
Follow-up rate (%) 97.1* NA 89.8 95.2 NA NA NA
Follow-up duration 525.6 days 231.6 days 2 years 3 years NA NA NA
Demographics
　Mean or median age (years) 64.1 63.2 65.0 65.7 64.0 69.5 71.2
　Male (%) 73.5 75.0 68.4 72.0 59.0 65.2 63.7
Comorbidities (%)
　Hypertension 51.2 45.9 64.7 44.5 52.3 47.3 45.2
　DM 28.6 24.6 25.2 18.1 22.4 17.6 22.7
　Dyslipidemia 11.2 9.5 53.0 NA 28.0 NA NA
　Smoking 38.5 62.8 59.8 20.4 31.3 29.5 23.3
　Previous MI 8.1 11.1 30.3 37.4 NA 18.3 22.4
　Family history of CAD 6.3 7.9 NA NA 28.0 NA NA
　CVA 6.2 5.6 NA 6.0 NA 8.5 10.1
　HF 1.8 1.1 8.8 7.4 NA 5.3 9.7
Vital signs
　SBP (mmHg) 129.9 126.8 NA NA 147.0 139.0 145.0
　DBP (mmHg) 78.4 78.0 NA NA NA NA NA
　Pulse rate (/min) 78.7 76.4 NA NA 86.0 79.0 78.0
STEMI (%) 48.2 56.6 35.9 22.6 41.8 40.3 32.1
Multivessel disease (%) 54.3 52.7 NA 50.0 NA NA NA
Culprit artery (%)
　LM 2.3 1.2 NA 1.3 NA NA NA
　LAD 46.7 52.7 NA 44.7 NA NA NA
　LCX 17.5 9.5 NA 21.5 NA NA NA
　RCA 33.7 36.6 NA 28.8 NA NA NA
PCI rate (%) 87.4 84.2 NA NA 64.0 39.7 87.9
DES (%) 96.9 91.1 NA 30.5 NA NA NA
PCI success rate (%) 99.4 99.0 NA NA NA NA NA
In-hospital mortality (%) 3.9 2.0 NA NA 8.0 10.6 7.7
1-year mortality (%) 4.3 3.1 NA NA NA NA NA
2-year mortality (%) 8.6 NA 5.7 NA NA NA NA
3-year mortality (%) NA NA NA 7.2 NA NA NA

*Rate of follow-up at 6 months. CAD, coronary artery disease; CVA, cerebrovascular accident; DBP, diastolic blood pressure; DES, drug eluting stents; DM, diabetes mellitus; GRACE, the Global Registry of Acute Coronary Events; HF, heart failure; KAMIR, Korea Acute Myocardial Infarction Registry; LAD, left anterior descending artery; LCX, left circumflex artery; LM, left main; MI, myocardial infarction; MINAP, Myocardial Ischaemia National Audit Project; NA, not available; NIH, National Institutes of Health; NRMI, National Registry of Myocardial Infarction; PCI, percutaneous coronary intervention; RCA, right coronary artery; SBP, systolic blood pressure; SCAAR, Swedish Coronary Angiography and Angioplasty Registry; STEMI, ST-segment elevation myocardial infarction; SWEDEHEART/RIKS-HIA, Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies/Register of Information and Knowledge about Swedish Heart Intensive care Admissions; UK, United Kingdom; US, United States.

Table 2. Comparison of Baseline Characteristics of Patients With Diagnosis of STEMI and NSTEMI
  STEMI
(n=6,246)		 NSTEMI
(n=6,710)		 P value
Age (years) 62.8±12.8 65.1±12.4 <0.001
Sex (%)     <0.001
　Male 4,853 (77.7) 4,738 (70.6)  
　Female 1,393 (22.3) 1,972 (29.4)  
Height (cm) 165.4±8.4 163.8±8.7 <0.001
Weight (cm) 66.2±12.0 64.5±12.1 <0.001
BMI (kg/m2) 24.1±3.4 23.9±3.5 0.012
AC (cm) 87.7±8.9 87.4±9.0 0.270
Symptoms
　Chest pain 5,673 (90.8) 5,500 (82.0) <0.001
　Dyspnea 1,261 (20.2) 1,800 (26.8) <0.001
　Previous angina 1,346 (21.5) 1,973 (29.4) <0.001
First medical contact     <0.001
　PCI center 1,758 (28.1) 2,437 (36.3)  
　Non-PCI center 3,248 (52.0) 3,547 (52.9)  
　EMS 1,240 (19.9) 726 (10.8)  
Previous history
　MI 370 (5.9) 645 (9.6) <0.001
　PCI 518 (8.3) 926 (13.8) <0.001
　CABG 25 (0.4) 94 (1.4) <0.001
Risk factors
　Hypertension 2,935 (47.0) 3,677 (54.8) <0.001
　DM 1,551 (24.8) 2,149 (32.0) <0.001
　Smoking 2,744 (43.9) 2,305 (34.4) <0.001
　Dyslipidemia 659 (10.6) 794 (11.8) 0.022
　Family history 380 (6.1) 444 (6.6) 0.228
　CVA 302 (4.8) 502 (7.5) <0.001
　HF 56 (0.9) 155 (2.3) <0.001
Physical findings
　SBP (mmHg) 125.3±31.9 134.3±28.2 <0.001
　DBP (mmHg) 76.5±20.1 80.4±16.7 <0.001
　Heart rate (beats/min) 76.9±20.7 80.1±18.6 <0.001
Killip class     <0.001
　I 4,801 (77.2) 5,340 (79.8)  
　II–IV 1,445 (22.8) 1,370 (20.2)  
ECG findings
　Sinus rhythm 5,308 (85.0) 5,896 (87.9) <0.001
　AV block (II/III) 89 (1.4) 38 (0.6) <0.001
　AF/AFL 340 (5.4) 348 (5.2) 0.540
　VT/VF 88 (1.4) 51 (0.8) <0.001

Data given as number (%) or mean±SD. AC, abdominal circumference; AF, atrial fibrillation; AFL, atrial flutter; AV, atrioventricular; BMI, body mass index; CABG, coronary artery bypass graft; DBP, diastolic blood pressure; ECG, electrocardiogram; EMS, emergency medical service; NSTEMI, non-STEMI; SD, standard deviation; VF, ventricular fibrillation; VT, ventricular tachycardia. Other abbreviations as in Table 1.

Baseline Laboratory and Echocardiographic Findings

As shown in Table 3, the mean white blood cell count was higher (11,500±4,200/mm3 vs. 9,600±5,000/mm3, P<0.001) and the proportion of lymphocyte count (25.3±14.3% vs. 24.0±11.8%, P<0.001) was higher in patients with STEMI. Although the mean level of glucose at presentation was higher in STEMI patients (178.3±81.8 mg/dl vs. 161.8±82.1 mg/dl, P<0.001), there was no significant difference in hemoglobin A1c levels (6.5%±1.5% vs. 6.5±1.5%, P=0.069). Patients with STEMI had higher levels of total cholesterol (180.6±46.1 mg/dl vs. 175.0±46.4 mg/dl, P<0.001), triglyceride (139.8±124.5 mg/dl vs. 128.9±114.9 mg/dl, P<0.001), and low-density lipoprotein (LDL) cholesterol (113.8±38.7 mg/dl vs. 109.6±39.6 mg/dl, P<0.001) than patients with NSTEMI. The mean left ventricular ejection fraction at presentation was lower in STEMI patients (50.1±10.4% vs. 53.5±11.7%, P<0.001).

Table 3. Baseline Laboratory and Echocardiographic Findings in Patients With Diagnosis of STEMI and NSTEMI
  STEMI
(n=6,246)		 NSTEMI
(n=6,710)		 P value
Laboratory findings
　WBC (/mm3) 11,500±4,200 9,600±5,000 <0.001
　　Neutrophils (%) 66.3±16.3 66.6±14.1 0.350
　　Lymphocytes (%) 25.3±14.3 24.0±11.8 <0.001
　Hemoglobin (g/dl) 14.2±3.4 13.4±2.2 <0.001
　Platelets (×1,000/mm3) 236.1±68.3 229.1±68.6 <0.001
　Glucose (mg/dl) 178.3±81.8 161.8±82.1 <0.001
　Creatinine (mg/dl) 1.0±0.8 1.2±2.9 <0.001
　Total cholesterol (mg/dl) 180.6±46.1 175.0±46.4 <0.001
　Triglyceride (mg/dl) 139.8±124.5 128.9±114.9 <0.001
　HDL-C (mg/dl) 42.6±12.3 43.1±12.7 0.054
　LDL-C (mg/dl) 113.8±38.7 109.6±39.6 <0.001
　CK-MB (ng/ml) 166.4±189.6 58.5±115.4 <0.001
　Troponin-I (ng/ml) 80.4±396.3 22.1±54.4 <0.001
　NT-proBNP (pg/ml) 1,693.8±4,889.2 3,491.2±7,360.7 <0.001
　hs-CRP (mg/dl) 1.6±12.8 5.6±234.0 0.295
　HbA1c (%) 6.5±1.5 6.5±1.5 0.069
　Aspirin reaction units 456.8±76.3 462.5±72.6 0.042
　P2Y12 reaction units 182.2±108.7 218.1±108.2 <0.001
Echocardiographic findings
　LVEF (%) 50.1±10.4 53.5±11.7 <0.001
　RWMI 1.5±0.4 1.4±0.4 <0.001
　LVESD (mm) 35.2±8.2 34.8±8.6 0.034
　LVEDD (mm) 49.6±6.4 49.8±6.9 0.089
　LVESV (ml) 48.3±23.0 47.0±27.3 0.046
　LVEDV(ml) 95.3±47.6 94.7±36.3 0.572

Data expressed as mean±SD. CK-MB, creatine kinase-MB; Hb, hemoglobin; HDL-C, high-density lipoprotein cholesterol; hs-CRP, high-sensitivity C-reactive protein; LDL-C, low-density lipoprotein cholesterol; NT-proBNP, N-terminal pro B-type natriuretic peptide; LVEDD, left ventricular end-diastolic diameter; LVEDV, left ventricular end-diastolic volume; LVEF, left ventricular ejection fraction; LVESD, left ventricular endsystolic diameter; LVESV, left ventricular endsystolic volume; RWMI, regional wall motion index; WBCC, white blood cell count. Other abbreviations as in Tables 1,2.

Comparison of the Medications Prescribed During Hospitalization

The medications prescribed during hospitalization of the STEMI and NSTEMI patients are shown in Table 4. In Korea, almost all patients are treated with aspirin whether they are diagnosed as STEMI (99.6%) or NSTEMI (99.4%). Clopidogrel was more frequently prescribed for NSTEMI patients (82.4% vs. 74.8%, P<0.001), whereas prasugrel and ticagrelor were more often used for STEMI patients (14.4% vs. 9.6%, P<0.001 and 21.5% vs. 18.0%, P<0.001, respectively). Beta-blockers and renin-angiotensin-aldosterone system blockers were used in approximately 80% of all patients. Angiotensin-converting enzyme inhibitors were used in 51.6% of STEMI patients and 40.7% of NSTEMI patients. Angiotensin II receptor blockers were also used in one-third of all patients: 26.2% of STEMI and 35.9% of NSTEMI. Almost all patients (90%) were prescribed a stain whether they were diagnosed as STEMI or NSTEMI.

Table 4. Comparison of the Medications Prescribed During Hospitalization of Patients With Diagnosis of STEMI and NSTEMI
  STEMI
(n=6,246)		 NSTEMI
(n=6,710)		 P value
Antiplatelet agents*
　Aspirin 6,223 (99.6) 6,670 (99.4) 0.082
　Clopidogrel 4,674 (74.8) 5,527 (82.4) <0.001
　Cilostazol 685 (11.0) 693 (10.3) 0.250
　Prasugrel 898 (14.4) 645 (9.6) <0.001
　Ticagrelor 1,342 (21.5) 1,208 (18.0) <0.001
β-blockers 5,169 (82.8) 5,304 (79.0) <0.001
ACEIs 3,223 (51.6) 2,747 (40.9) <0.001
ARBs 1,639 (26.2) 2,408 (35.9) <0.001
CCBs 257 (4.1) 797 (11.9) <0.001
Statin 5,622 (90.0) 6,008 (89.5) 0.392
Omega-3 fatty acid 214 (3.4) 161 (2.4) 0.001
Oral hypoglycemic agents 1,041 (16.7) 1,302 (19.4) <0.001

Data expressed as number (%). *All cases of patients using any antiplatelet agent at loading or maintenance dose are included. ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin II receptor blocker; CCB, calcium-channel blocker. Other abbreviations as in Tables 1,2.

Coronary Angiographic and Procedural Findings

As shown in Table 1 and Table 5, coronary angiography was performed in almost all the patients, but more commonly in the patients with STEMI (99.3% vs. 97.5%, P<0.001). The overall rate of PCI in all patients was 87.4%: 96.7% of STEMI and 82.9% of NSTEMI. The procedural success rate of was very high, regardless of the diagnosis (98.5% in STEMI; 98.9% in NSTEMI; P=0.088). The transfemoral approach was used more frequently than the transradial approach in STEMI patients (74.2% vs. 25.2%, P<0.001). The rate of using drug-eluting stents (DES) was 97.0% among STEMI patients and 96.9% among NSTEMI, and the details were not different between groups. The most common diseased vessel was the left descending artery (46.7%), followed by the right coronary artery (33.7%), left circumflex artery (17.5%), and left main stem (2.3%). Multivessel disease was present in 46.7% of STEMI and 52.1% of NSTEMI patients. During the index procedure, 17.4% of STEMI and 18.2% of NSTEMI patients were examined by intravascular ultrasound.

Table 5. Baseline Coronary Angiographic Findings and Procedural Characteristics in STEMI and NSTEMI Patients
  STEMI
(n=6,246)		 NSTEMI
(n=6,710)		 P value
Coronary angiography (%) 6,202 (99.3) 6,539 (97.5) <0.001
PCI (%) 6,038 (96.7) 5,560 (82.9) <0.001
Vascular access route (%)     <0.001
　Transradial approach 1,524 (25.2) 2,774 (49.8)  
　Transfemoral approach 4,484 (74.2) 2,699 (48.5)  
　Both 34 (0.6) 92 (1.7)  
No. of involved vessels (%)
　No significant stenosis 64 (1.0) 442 (6.8) <0.001
　1 3,243 (52.3) 2,688 (41.1) <0.001
　2 1,729 (27.9) 1,818 (27.8) 0.940
　3 975 (15.4) 1,217 (18.6) <0.001
　LM complex 179 (2.9) 338 (5.2) <0.001
　LM isolated 30 (0.5) 36 (0.6) 0.688
Target lesion location (%)
　LAD 3,081 (51.0) 2,338 (42.0) <0.001
　LCX 570 (9.4) 1,459 (26.2) <0.001
　RCA 2,303 (38.1) 1,612 (28.9) <0.001
　LM 96 (1.6) 172 (3.1) <0.001
ACC/AHA type (%)
　A 47 (0.8) 108 (1.9) <0.001
　B1/B2 2,711 (45.2) 2,955 (53.3) <0.001
　C 3,234 (54.0) 2,476 (44.7) <0.001
Preprocedural TIMI flow 0 (%) 3,816 (63.7) 1,594 (28.8) <0.001
Postprocedural TIMI flow 3 (%) 5,747 (95.5) 5,418 (97.7) <0.001
Stent type (%)
　Bare-metal stent 180 (3.0) 170 (3.1) 0.868
　Paclitaxel-eluting stent 7 (0.1) 7 (0.1) 1.000
　Sirolimus-eluting stent 66 (1.1) 74 (1.3) 0.283
　Zotarolimus-eluting stent 1,269 (21.0) 1,147 (20.6) 0.585
　Everolimus-eluting stent 2,728 (45.2) 2,508 (45.1) 0.874
　Biolimus-eluting stent 1,041 (17.3) 957 (17.2) 0.947
　Other DES 358 (5.9) 231 (4.2) <0.001
Stent length (mm) 25.1±7.1 24.6±7.6 0.001
Stent diameter (mm) 3.2±0.4 3.1±0.4 <0.001
Multivessel PCI (%) 860 (14.3) 1,507 (27.2) <0.001
Staged PCI (%) 689 (11.4) 384 (6.9) <0.001
PCI success rate (%) 5,996 (99.4) 5,526 (99.5) 0.247
Additional testing
　IVUS 1,087 (17.4) 1,222 (18.2) 0.239
　FFR 37 (0.6) 116 (1.7) <0.001
　OCT 124 (2.0) 148 (2.2) 0.416

Data expressed as number (%) or mean±SD. ACC/AHA, American College of Cardiology/American Heart Association; FFR, fractional flow reserve; IVUS, intravascular ultrasound; OCT, optical coherence tomography; TIMI, Thrombolysis In Myocardial Infarction. Other abbreviations as in Tables 1,2.

In-Hospital and Post-Discharge Outcomes

As shown in Table 6, approximately 20% of all patients experienced complications: 24.9% of STEMI and 15.9% of NSTEMI patients. The most common complication was cardiogenic shock (8.4%), followed by newly developed heart failure (4.8%), atrial fibrillation (3.3%), and minor bleeding (3.0%). Overall in-hospital mortality was 3.9%: 5.1% in STEMI and 2.6% in NSTEMI patients. The most common cause of in-hospital death was pump failure (2.6%). After discharge, the median of follow-up period was 525.6 days, and the composite rates of MACE at 6 months, 12 months, and 24 months were 4.4%, 9.6%, and 18.8%, respectively (Figure). The rates of cardiac death, non-cardiac-death, MI, and repeat PCI at 24 months were 5.2%, 3.4%, 4.5%, and 9.0%, respectively. During 2 years, 6.8% of all patients were readmitted for heart failure.

Table 6. In-Hospital Complications and Mortality of Patients With Diagnosis of STEMI and NSTEMI
  STEMI
(n=6,246)		 NSTEMI
(n=6,710)		 P value
Complications 1,553 (24.9) 1,069 (15.9) <0.001
　Cardiogenic shock 747 (12.0) 340 (5.1) <0.001
　Newly developed HF 257 (4.1) 322 (4.8) 0.066
　Recurrent ischemia 67 (1.1) 42 (0.6) 0.007
　Stent thrombosis 32 (0.5) 10 (0.1) 0.001
　Cerebral infarction 36 (0.6) 45 (0.7) 0.570
　Cerebral hemorrhage 10 (0.2) 6 (0.1) 0.141
　Significant Hb decrease 74 (1.2) 74 (1.1) 0.722
　Minor bleeding 188 (3.0) 194 (2.9) 0.728
　AV block 187 (3.0) 48 (0.7) <0.001
　VT 341 (5.5) 106 (1.6) <0.001
　VF 183 (2.9) 58 (0.9) <0.001
　Atrial fibrillation 230 (3.7) 195 (2.9) 0.015
　Acute kidney injury 56 (0.9) 67 (1.0) 0.612
　Sepsis 39 (0.6) 43 (0.6) 0.994
　Multi-organ failure 55 (0.9) 39 (0.6) 0.057
In-hospital mortality 316 (5.1) 176 (2.6) <0.001
　Cardiac death 278 (4.5) 137 (2.0) <0.001
　　Pump failure 224 (3.6) 111 (1.7) <0.001
　　Mechanical complications 25 (0.4) 12 (0.2) 0.022
　　Arrhythmia 6 (0.1) 6 (0.1) 1.000
　　Other 23 (0.4) 8 (0.1) 0.001
　Non-cardiac death 39 (0.6) 39 (0.6) 0.838
　　Multi-organ failure 16 (0.3) 15 (0.2) 0.624
　　Bleeding 5 (0.1) 3 (0.1) 0.868
　　Sepsis 6 (0.1) 12 (0.2) 0.382
　　Others 12 (0.2) 9 (0.1) 1.000

Data expressed as number (%). Abbreviations as in Tables 2,3.

Figure.

Clinical outcomes after discharge. Kaplan-Meier survival curves for (A) major adverse cardiac events (MACE), (B) cardiac death and (C) repeat percutaneous coronary intervention (PCI). CVA, cerebrovascular accident; HF, heart failure.

Discussion

The KAMIR-NIH is an extending and expanding study that is a successor of the previous KAMIR registry. The KAMIR was developed for the prevention and management of AMI in Korea3,6,7 and this interim analysis of the cohort study had some valuable findings of AMI in an Asian population. The Korean patients had different clinical profiles in comparison with those from Western countries. First of all, the proportion of STEMI was still high in Korea. Among Korean AMI patients, STEMI decreased from 56.6% of KAMIR to 48.2% of KAMIR-NIH. Hypertension was the most common risk factor in Korean patients with AMI, as in other registries. Interestingly, compared with the previous KAMIR registry, KAMIR-NIH showed a decrease in the prevalence of smoking in Korea, reflecting a national effort for cessation of smoking over the decade. The prevalence of diabetes mellitus was higher, and the prevalence of dyslipidemia and previous MI was lower than in other countries. On subgroup analysis, NSTEMI patients had higher rates of comorbidities, except smoking. The prevalence of diabetes mellitus has rapidly increased, especially in aging countries.14 Diabetes mellitus is related to greater endothelial dysfunction,15 inflammatory processes,16 and greater atherosclerosis burden, with more diffuse and more multivessel disease.14 These result in a higher prevalence of multivessel disease, which might be associated with poor prognosis. In contrast, the patients with STEMI were younger than those with NTSEMI, and they less frequently had comorbidities. This discrepancy was consistent with a previous analysis of the KAMIR registry,6 and more frequent comorbidities in NSTEMI patients might result from the decrepit old subjects. In addition, NSTEMI would be caused by insidious atherosclerosis rather than sudden interruption of coronary blood flow by plaque rupture, followed by rapid progression of atherothrombosis.5 Because our interim analysis demonstrated an increase in NSTEMI, the need for treatment strategies for multivessel disease may be commonly encountered in the current clinical setting.

The KAMIR-NIH showed unique laboratory and echocardiographic findings. Levels of LDL-cholesterol were higher and levels of P2Y12 reaction units (PRU) were lower. As already mentioned, the prevalence of dyslipidemia was lower in this cohort study, compared with other registries. However, the levels of LDL-cholesterol were high in both STEMI and in NSTEMI patients. For secondary prevention after AMI, efforts should be made to lower the level of LDL-cholesterol.17 The previous guidelines recommend LDL-cholesterol goals of either <70 mg/dl or ≥50% reduction from baseline,18,19 or no specific target.20 The previous KAMIR study results supported the strategy of reducing of LDL-cholesterol ≥50% from baseline.17,21 Recently, the Improved Reduction of Outcomes: Vytorin Efficacy International Trial (IMRPOVE-IT) study proposed that lower is better, and the role of non-statin lipid-lowering agents for improving cardiovascular outcomes.22 In this clinical setting, the newer KAMIR-NIH registry will investigate the target of LDL-cholesterol and the effect of non-statin agents in an Asian population. The previous studies suggested that clopidogrel resistance develops with higher levels of PRU in Korea.23,24 Although the mean level of PRU was below the cut-off value for clopidogrel resistance in both STEMI and NSTEMI patients, the newer P2Y12 inhibitors, prasugrel and ticagrelor, were used frequently during hospitalization. In the near future the KAMIR-NIH registry will provide data on antiplatelet agent switching.

In Korea, most patients with AMI undergo coronary angiography, and are treated by PCI rather than fibrinolysis or coronary artery bypass graft surgery. There are 98 PCI centers in Korea, the population of which is approximately 51 million, and many AMI patients in Korea may have access to the highly experienced PCI centers certificated by the Korean Society of Interventional Cardiology (PCI >100 cases/year). The medical insurance covers the cost of PCI including coronary stents. Therefore, the KAMIR-NIH included almost all angiographic and procedural findings of AMI patients, and the authors are convinced that high-quality data were collected, with a high procedural success rate of 99.4%. Unlike the Western registries, approximately 97% of Korean AMI patients received DES. DES are superior to bare-metal stents in terms of lower rates of target lesion revascularization, but have similar safety outcomes as bare-metal stents.7,25,26 The difference between KAMIR-NIH and KAMIR was that only 1% of AMI patients in KAMIR-NIH had 1st-generation DES. Thus, we should focus on 2nd-generation DES or newer DES for real-world practice. In addition, as mentioned before, we found several differences in the characteristics of Korean AMI patients compared with Western populations. The current clinical guidelines for AMI, whether established by a European or American society, are based on Western populations. We propose that new Asian guidelines reflecting these discrepancies are required for the “real world”.

In this study, in-hospital complications and mortality were compared between STEMI and NSTEMI patients. A trend of poor prognosis in STEMI patients was observed. In-hospital mortality was 5.1%, and 24.9% experienced more than 1 periprocedural complications. Because pump failure was the most common cause of cardiac death in both STEMI and NSTEMI patients, it is important to reduce total ischemic time to improve prognosis. After discharge, the rates of MACE, including cardiac death, non-cardiac death, MI, and repeat PCI, continued to be high during 24 months, and a large proportion of the MACE was repeat PCI. The KAMIR score was developed for risk stratification and prediction of 1-year mortality using 6 independent variables: age, Killip class, serum creatinine, in-hospital PCI, left ventricular ejection fraction, and admission glucose.27,28 This scoring system should be validated with the newer KAMIR-NIH data, and modified appropriately for prediction of long-term clinical outcomes. Additionally, 6.8% of AMI patients were readmitted for heart failure. The symptoms of heart failure are directly related to quality of life, which may thus need to be included as a subjective factor in the newer risk model for assessment of post-AMI outcomes.29

Study Limitations

First, it is important to control the quality of follow-up data of ongoing prospective cohort studies. Registry data requires high follow-up and response rates to yield reliable data that can be applied in clinical practice. Second, it was difficult to reflect and update the most recent changes in managing AMI during the follow-up period. Third, the authors need to expand and extend the data for improving clinical effect, especially maintaining long-term follow-up.

In conclusion, an interim analysis of the KAMIR-NIH registry revealed that AMI is a still challenging medical problem associated with high in-hospital mortality and poor long-term clinical outcomes in Korea. There are several differences in the clinical profiles, baseline characteristics, risk factors, management and prognosis of AMI patients in Korea in comparison with other Western AMI registries. Therefore, further research into the prevention and management of AMI is needed for better clinical outcomes, taking into account regional heterogeneity. Ultimately, guidelines for Asian individuals with AMI should be established.

Acknowledgments

This study was performed with the support of the Korean Circulation Society (KCS) as a memorandum of the 50th Anniversary of the KCS. This study was sponsored by the National Institute of Health, Republic of Korea. This research was supported by a fund (2013-E63005-02) by Research of Korea Centers for Disease Control and Prevention.

References
 
© 2016 THE JAPANESE CIRCULATION SOCIETY
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