Methods

We retrospectively evaluated 2,825 consecutive patients with acute STEMI who were admitted to the emergency department of the Siyami Ersek Thoracic and Cardiovascular Surgery Center (Istanbul, Turkey) and underwent urgent cardiac catheterization from October 2003 to January 2009.

The patients were enrolled in the study if they fulfilled the following criteria: (1) they had presented within 12 hours from the onset of symptoms (typically, chest pain lasting for >30 minutes), (2) they had ST-segment elevation ≥2 mm in ≥2 contiguous electrocardiographic leads or new onset of complete left bundle-branch block, and (3) they had primary PCI (angioplasty and/or stent deployment). Of the 2,825 total patients, 1,201 were excluded because they did not satisfy these criteria. Patients with cardiogenic shock at admission (n = 66); those with active infections, systemic inflammatory disease, known liver, hematologic, or malignant disease, congestive heart failure, end-stage renal disease (glomerular filtration rate <15 ml/min/1.73 m ² ), or missing or unavailable bilirubin values (n = 967); and those who did not undergo PCI (n = 181, 96 underwent emergent coronary artery bypass grafting and 85 were deemed suitable for medical treatment) were excluded. After these exclusions were accounted for, the final study population consisted of 1,624 patients. All primary PCI procedures were performed in high-volume (>3,000 PCIs/year) tertiary healthcare centers by experienced experts performing >75 PCIs/year. The hospital’s ethics committee approved the study protocol.

The cardiovascular risk factors were ascertained from a review of the medical records. The angina-to-reperfusion time and door-to-balloon time were also determined. The follow-up data were obtained from the hospital records or by interviewing (directly or by telephone) the patients, their families, or their personal physicians. The fasting blood samples were taken on the morning after PCI. The TB and direct bilirubin and other biochemistry parameters were measured using standard methods (the reference range for TB in our laboratory is 0.1 to 1.2 mg/dl). A 12-lead electrocardiogram was recorded for each patient immediately after hospital admission. In addition, the MI type was recorded from the electrocardiogram.

All patients received chewable aspirin (300 mg, unless contraindicated) and oral clopidogrel (300-mg loading dose) before coronary angiography. The patients’ angiographic data were evaluated from the catheter laboratory records. Emergency coronary angiography was performed using the percutaneous femoral approach. The infarct-related artery was graded according to the Thrombolysis In Myocardial Infarction classification. Heparin (100 U/kg) was administered when the coronary anatomy was first assessed. The use of tirofiban was left to the discretion of the operator. After angioplasty, all patients were admitted to the coronary care unit; 100 mg aspirin, 75 mg clopidogrel, and statins were continued in all patients. Successful primary PCI was defined as residual stenosis <50% and Thrombolysis In Myocardial Infarction grade 3 flow after the procedure.

Hypertension was defined as the previous use of antihypertensive medications, systolic pressure >140 mm Hg, or diastolic pressure >90 mm Hg in ≥2 separate measurements. Diabetes mellitus was defined as a previous diagnosis, if a patient followed a diet or used antidiabetic medicines, or a fasting venous blood glucose level of 126 mg/dl in 2 separate measurements in previously untreated patients. Hypercholesterolemia was defined as total cholesterol ≥200 mg/dl. Anemia was defined as a baseline hemoglobin concentration <13 and 12 mg/dl in men and women, respectively. Contrast-induced nephropathy was defined as an increase in the serum creatinine level ≥0.5 mg/dl or ≥25% from baseline within 72 hours of administration of radiocontrast. The patients were also evaluated according to the Killip clinical examination classification. The glomerular filtration rate on admission was estimated using the simplified Modification of Diet in Renal Disease equation. A quantitative assessment of the left ventricular systolic function was performed using the modified biplane Simpson’s method to calculate the left ventricular ejection fraction.

Cardiogenic shock was defined as marked and persistent (>30 minutes) hypotension with systolic arterial pressure <80 mm Hg with signs of hypoperfusion because of left ventricular dysfunction, right ventricular infarction, and mechanical complications. Advanced heart failure was defined as a New York Heart Association classification of at least III. Acute stent thrombosis was defined as total occlusion on the angiogram. Cardiovascular mortality was defined as unexplained sudden death, death from acute MI, heart failure, and arrhythmia. Reinfarction was defined as an elevation of the serum creatine kinase-MB enzyme levels by twice the upper limit of normal and ST-segment re-elevation. Major adverse cardiac events were defined as cardiovascular mortality, reinfarction, or repeat target vessel revascularization.

The study population was divided into tertiles according to the TB values. High TB (group 1, n = 450) was defined as a value in the third tertile (>0.9 mg/dl) and low TB (group 2, n = 1,174), as a value in the lower 2 tertiles (≤0.90 mg/dl). Qualitative variables are expressed as percentages and quantitative variables as the mean ± SD. A comparison of the parametric values between the 2 groups was performed using a 2-tailed Student’s t test. Categorical variables were compared by the likelihood ratio, chi-square test, or Fisher’s exact test. A backward stepwise multivariate logistic regression analysis, which included variables with p <0.1, was performed to identify independent predictors of in-hospital death. The cumulative survival curve for long-term cardiovascular mortality was constructed using the Kaplan-Meier method, with differences assessed using log-rank tests. A p value <0.05 was considered statistically significant. All statistical studies were performed using the SPSS program, version 15.0 (SPSS, Chicago, Illinois).

Results

Of the 1,624 patients, 1,174 were in the low TB group (mean age 56.8 ± 11.6 years, 80% men) and 450 were in the high TB group (mean age 56.9 ± 11.8 years, 90% men). The baseline characteristics of the 2 groups are summarized in Table 1 . More patients were men in the high TB group and their Killip classes were higher (class 2/3) at admission than those of patients in the low TB group. The incidence of contrast-induced nephropathy was greater in the high TB group than in the low TB group.

The laboratory data of the patients are listed in Table 2 . The serum TB and direct bilirubin level was 0.59 ± 0.19 mg/dl and 0.15 ± 0.13 mg/dl in the low TB group and 1.37 ± 0.74 mg/dl and 0.33 ± 0.31 mg/dl in the high TB group (p <0.001), respectively. Patients with a high TB level had significantly greater levels of peak creatine kinase-MB and hemoglobin and a lower level of total cholesterol. Anemia on admission was greater in the low TB group than in the high TB group.

Angiographic and procedural characteristics are listed in Table 3 . In the high TB group, significantly greater rates of procedural failure, relatively wide stent diameters, and lower post-PCI left ventricular ejection fractions were observed. Culprit lesions in bypass graft were more frequent in the high TB group.

The in-hospital adverse outcomes after primary PCI are listed in Table 4 . The in-hospital mortality rate was relatively greater in the high TB group than in the low TB group (4% vs 1.5%, p = 0.003). Major adverse cardiac events were more frequent in the high TB group than in the low TB group (11% vs 6%, p = 0.04). Cardiopulmonary resuscitation, advanced heart failure, inotrope use, cardiogenic shock necessitating an intra-aortic balloon pump, and serious ventricular arrhythmia were noted more often in the high TB group than in the low TB group.

Table 4

In-hospital cardiac events and complications

Variable	Low Serum TB (n = 1,174)	High Serum TB (n = 450)	p Value
In-hospital mortality	18 (1.5%)	18 (4%)	0.003
Reinfarction	25 (2%)	12 (3%)	0.52
Target vessel revascularization	58 (5%)	26 (6%)	0.49
Major adverse cardiac events	74 (6%)	51 (11%)	0.04
Stroke	6 (1%)	5 (1%)	0.19
Cardiopulmonary resuscitation	25 (2%)	21 (5%)	0.006
Renal failure requiring dialysis	7 (1%)	4 (1%)	0.52
Serious ventricular arrhythmia	33 (3%)	22 (5%)	0.03
Advanced heart failure	143 (12%)	77 (17%)	0.009
Inotrope use	65 (6%)	45 (10%)	0.001
New atrial fibrillation	15 (1%)	6 (1%)	0.93
Intra-aortic balloon pump/cardiogenic shock	22 (2%)	21 (5%)	0.002
Complete atrioventricular block requiring transient pacemaker	35 (3%)	18 (4%)	0.3
Gastrointestinal bleeding	11 (1%)	2 (0.4%)	0.32
Acute thrombosis	11 (1%)	6 (1%)	0.48
Transfusion requirement	48 (4%)	16 (4%)	0.62

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