2.1

Demographic, hemodynamic and laboratory data

Patients’ demographic data such as age, gender, body mass index, history of hypertension, history of diabetes mellitus, history of hyperlipidemia, history of chronic kidney disease defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m ² , family history of coronary artery disease (CAD), smoking status, use of β-blocker, previous percutaneous coronary intervention (PCI), previous coronary artery bypass grafting (CABG), and previous myocardial infarction were recorded. TIMI risk score was calculated and classified into three groups: low risk (0–2), intermediate risk (3–4), and high risk (5–7). Systolic blood pressure, diastolic blood pressure, and heart rate were recorded upon arrival to our hospital and SI was calculated. In addition, Killip class on admission was recorded.

Laboratory data on admission including white blood cell count, hemoglobin level, and eGFR were recorded. Cardiac troponin I was measured using the second-generation VITROS® troponin I assay (Ortho-Clinical Diagnostics Inc., NJ, USA). The upper limit of normal for cardiac troponin I was 0.034 μg/L, which represented the 99th percentile reference value.

Transthoracic echocardiography was performed in a standard manner during hospitalization. Left ventricular ejection fraction was obtained using either the Teichholz or biplane Simpson’s method.

2.2

Coronary angiography

All patients underwent cardiac catheterization within 5 days of presentation. An independent cardiologist blinded to the clinical data reviewed all coronary angiography, and the assessment was compared to the primary assessment by the treating cardiologist. In the event of a discrepancy between the assessments, a third investigator made the final interpretation. Revascularization procedures including PCI and CABG were performed at the discretion of the treating physician. Obstructive CAD was defined as stenosis greater than or equal to 50% in the left main coronary artery and 70% in any other epicardial coronary arteries. In addition, coronary blood flow was graded according to TIMI criteria .

2.3

End points.

The primary end point was in-hospital mortality. The secondary end point was cardiogenic shock, defined as sustained systolic blood pressure less than 90 mmHg requiring either vasopressors or inotropes without other identifiable causes of shock status, such as sepsis or hypovolemia.

2.4

Statistic analyses.

In our present study, elevated SI was defined as SI ≧ 0.7 consistent with previous studies of STEMI populations . Patients were divided into those with SI ≧ 0.7 and those with SI < 0.7. In addition, a subgroup analysis was performed after excluding patients who presented with systolic blood pressure < 90 mmHg.

Data was expressed as either a number (percentage) or median (interquartile range). Continuous variables were compared using the Wilcoxon rank sum test. Dichotomous variables were compared using the chi-squared test or Fisher’s exact test. Two-sided p values < 0.05 were considered statistically significant. All statistical analyses were performed using R software (version 3.0.1).

2.1

Demographic, hemodynamic and laboratory data

Patients’ demographic data such as age, gender, body mass index, history of hypertension, history of diabetes mellitus, history of hyperlipidemia, history of chronic kidney disease defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m ² , family history of coronary artery disease (CAD), smoking status, use of β-blocker, previous percutaneous coronary intervention (PCI), previous coronary artery bypass grafting (CABG), and previous myocardial infarction were recorded. TIMI risk score was calculated and classified into three groups: low risk (0–2), intermediate risk (3–4), and high risk (5–7). Systolic blood pressure, diastolic blood pressure, and heart rate were recorded upon arrival to our hospital and SI was calculated. In addition, Killip class on admission was recorded.

Laboratory data on admission including white blood cell count, hemoglobin level, and eGFR were recorded. Cardiac troponin I was measured using the second-generation VITROS® troponin I assay (Ortho-Clinical Diagnostics Inc., NJ, USA). The upper limit of normal for cardiac troponin I was 0.034 μg/L, which represented the 99th percentile reference value.

Transthoracic echocardiography was performed in a standard manner during hospitalization. Left ventricular ejection fraction was obtained using either the Teichholz or biplane Simpson’s method.

2.2

Coronary angiography

All patients underwent cardiac catheterization within 5 days of presentation. An independent cardiologist blinded to the clinical data reviewed all coronary angiography, and the assessment was compared to the primary assessment by the treating cardiologist. In the event of a discrepancy between the assessments, a third investigator made the final interpretation. Revascularization procedures including PCI and CABG were performed at the discretion of the treating physician. Obstructive CAD was defined as stenosis greater than or equal to 50% in the left main coronary artery and 70% in any other epicardial coronary arteries. In addition, coronary blood flow was graded according to TIMI criteria .

2.3

End points.

The primary end point was in-hospital mortality. The secondary end point was cardiogenic shock, defined as sustained systolic blood pressure less than 90 mmHg requiring either vasopressors or inotropes without other identifiable causes of shock status, such as sepsis or hypovolemia.

2.4

Statistic analyses.

In our present study, elevated SI was defined as SI ≧ 0.7 consistent with previous studies of STEMI populations . Patients were divided into those with SI ≧ 0.7 and those with SI < 0.7. In addition, a subgroup analysis was performed after excluding patients who presented with systolic blood pressure < 90 mmHg.

Data was expressed as either a number (percentage) or median (interquartile range). Continuous variables were compared using the Wilcoxon rank sum test. Dichotomous variables were compared using the chi-squared test or Fisher’s exact test. Two-sided p values < 0.05 were considered statistically significant. All statistical analyses were performed using R software (version 3.0.1).