We consecutively selected 5,074 patients with AMI who underwent successful PCI from November 2005 to June 2007 and had 1-year follow-up data in the KAMIR. Among them, patients with a history of DM, regardless of whether they received treatment, were assigned to the DM group (n = 1,412) and those without a history of DM were assigned to the non-DM group (n = 3,662).

The KAMIR is a prospective, multicenter, observational, online registry that can be used to evaluate epidemiology, current management, and clinical outcomes in Korean patients with AMI and improve care for AMI patients. Data, including baseline clinical and angiographic characteristics as well as clinical outcomes, were collected by a specialized study coordinator at each center using a standardized case report form. AMI was diagnosed by characteristic clinical presentation, serial changes on electrocardiogram (ECG) suggesting infarction, and increases in cardiac enzymes [6]. The diagnosis of ST-segment elevated myocardial infarction (STEMI) was based on a suggestive history with an ST elevation of 2 mm in two precordial leads, an ST elevation of 1 mm in two limb leads, or a new left branch bundle block on 12-lead ECG with a concomitant increase in troponin-I or -T to the 99th percentile of the upper reference limit.

Emergent or early invasive treatments were determined based on the status of the patients with AMI according to the clinical decision of the operators. Primary PCI was defined as angioplasty and/or stenting as quickly as possible in patients with STEMI. Early invasive treatment was defined as angioplasty and/or stenting within 24 hours of admission in patients with non-STEMI. Coronary angiography was performed by transfemoral or transradial approaches. Conventional heparin was infused during the procedure to maintain an activated clotting time of at least 250 seconds. Stents were implanted in cases in which significant coronary artery stenosis was present following balloon angioplasty. The type of stent was decided by the operator. Successful revascularization was defined as a target vessel at the treatment site that had achieved angiographic residual stenosis of < 30% following balloon angioplasty or implantation of stents in the presence of thrombolysis in myocardial infarction (TIMI) antegrade 3 flow. Antiplatelet agents were administered to all patients prior to intervention, including 300 mg aspirin and 300-600 mg clopidogrel. After the intervention, 100 mg aspirin was recommended as a treatment for life and 75 mg clopidogrel was administered for at least 1 year. Other medical treatments, including angiotensin converting enzyme inhibitors (ACEis) or angiotensin II receptor blockers (ARBs), beta-blockers, calcium channel blockers, and lipid-lowering agents were also used based on the standard treatment regimen for patients with AMI according to the physician's decision.

The primary endpoint was in-hospital and 1-year mortality of patients with AMI with and without DM. The secondary endpoint was 1-year major adverse cardiac events (MACE) defined as the composite of cardiac death, nonfatal MI, target lesion revascularization (TLR), target vessel revascularization (TVR), and coronary artery bypass graft. Cardiac death was defined as any death with an undetermined cause and a definitive noncardiac origin. TLR or TVR was defined as any percutaneous coronary revascularization performed on a treated lesion or vessel. Hypertension was defined as a history of hypertension or antihypertensive medication use. A current smoker was defined as someone who reported smoking cigarettes during the past 30 days. Dyslipidemia was defined as a diagnosis previously made by a physician or treatment with lipid-lowering medications. Baseline creatinine clearance was calculated using the Cockcroft-Gault formula considering age, gender, and body weight.

Continuous variables are expressed as mean ± SD, and categorical variables are expressed as frequencies. The analysis of continuous variables was performed using Student's t test and that of categorical variables was performed using the chi-square or Fisher's exact tests. Multiple logistic regression and Cox proportional regression analyses were conducted to identify the independent predictors of in-hospital and 1-year mortality. Variables entered into the multivariate models were age, gender, creatinine clearance, history of hypertension, DM, dyslipidemia, ischemic heart disease, current smoker, left ventricular ejection fraction (LVEF), ACC/AHA B₂ or C lesions, Killip class on admission, multivessel disease, STEMI or non-STEMI, concomitant medications, and stent type. All statistical analyses were performed using SPSS version 15.0 (SPSS Inc., Chicago, IL, USA). All statistical tests were two-tailed, and a p value < 0.05 was considered statistically significant.

Mean age was higher in the DM group than in the non-DM group. Female gender, history of hypertension, dyslipidemia, previous ischemic heart disease, and diagnosis of non-STEMI were more prevalent in the DM group. However, male gender, current smoker, and diagnosis of STEMI were more prevalent in the non-DM group. LVEF and creatinine clearance were lower in the DM group. However, no differences in concomitant medications except calcium channel blockers were observed between the two groups. Table 1 shows the baseline clinical characteristics, concomitant medications, and laboratory findings of the two groups.

In the baseline angiographic and procedural characteristics, single-vessel disease was more prevalent in the non-DM group than in the DM group. However, three-vessel disease or left main coronary artery disease were more prevalent in the DM group, whereas preprocedural TIMI antegrade 0 flow rates were more common in the non-DM group and postprocedural TIMI antegrade flow rates did not differ between the two groups. TAXUS stents (Boston Scientific Co., Natick, MA, USA) were used more commonly in the non-DM group, whereas Cypher stents (Cordis, Johnson & Johnson, Miami Lakes, FL, USA) were used more commonly in the DM group. The stent diameter of the target lesion was smaller, and the total number of implanted stents was more numerous, in the DM group than in the non-DM group (Table 2).

The DM group had a significantly higher incidence of in-hospital mortality than the non-DM group (4.6% vs. 2.8%, p = 0.002).

Approximately 92% of all hospital survivors were available for the 1-year clinical follow-up, during which the DM group had significantly higher incidences of total mortality (5.0% vs. 2.5%, p < 0.001), cardiac death (3.4% vs. 1.4%, p < 0.001), and MACE (12.0% vs. 8.7%, p = 0.001) than did the non-DM group (Table 3).

Subgroup analyses showed that the incidence of in-hospital mortality in the DM group was significantly higher than in non-DM patients with STEMI (6.2% vs. 3.5%, p = 0.001), but no difference in in-hospital mortality was observed between the two groups in patients with non-STEMI (2.4% vs. 1.6%, p = 0.164). However, the incidence of 1-year mortality in the DM group was higher than that of non-DM patients with both STEMI and non-STEMI (4.6% vs. 2.7%, p = 0.010 in STEMI; 5.5% vs. 2.1%, p < 0.001 in non-STEMI).

A Kaplan-Meier survival analysis revealed that the DM group had significantly lower 1-year survival rates than the non-DM group (95.2% vs. 97.7%, p < 0.001) (Fig. 1).

The independent predictors of in-hospital mortality by multiple logistic regression analysis were Killip III or IV class on admission, use of ACEis or ARBs, LVEF, creatinine clearance, and STEMI, whereas DM was not an independent predictor of in-hospital mortality (hazard ratio, 1.386; 95% confidence interval, 0.810 to 2.374; p = 0.234). However, independent predictors of 1-year mortality included Killip class on admission, age, LVEF, creatinine clearance, balloon angioplasty, use of bare metal stents, multivessel disease, female gender, current smoker, and history of DM (Table 4).

Many limitations of our study should be noted. First, this was a multicenter prospective observational registry study and not a randomized controlled trial. Second, we only included patients with AMI who underwent successful revascularization and excluded those who received medical treatment including thrombolytic therapy. Therefore, we could not evaluate the impact of DM in patients with AMI. Third, because a follow-up coronary angiography was performed in only approximately 43% of all patients, we may have underestimated the incidence of repeated PCI and MACE.

In conclusions, DM was more highly associated with 1-year mortality than in-hospital mortality in patients with AMI who underwent successful PCI. This suggests that patients with AMI and DM who undergo successful PCI may require further intensive treatment and continuous attention.