Background: Dyslipidemia is one of the risk factor of coronary artery disease but there have been reports showing paradoxical effect of LDL cholesterol (LDL-C) level which lower LDL-C level at the time of diagnosis of patients with acute coronary syndrome was associated with higher 1-year mortality. However, this relationship has not been established in Thai patients.

Objective: To evaluate LDL-C and 1-year all-cause mortality rate after acute ST-elevation myocardial infarction (STEMI) in Thailand.

Materials and Methods: The present study was a retrospective study of 1,542 consecutive patients with STEMI from 1999 to 2015 whom underwent percutaneous coronary intervention (PCI) either primary PCI or rescue PCI at a tertiary care hospital in Thailand. Patients were classified into 4 groups according to their initial LDL-C level: <70 (group 1), 70-99 (group 2), 100-129 (group 3) and ≥130 mg/dl (group 4). The primary end point was a 1-year all-cause mortality rate. T-test, Chi-square and survival time analysis were used to analyze.

Results: The rates of 1-year all-cause mortality were 23.0%, 21.2%, 12.3% and 9.2% in group 1, group 2, group 3 and group 4, respectively. Comparing with group 4, the hazard ratio (HR) was 2.72 (95 % confidence interval [CI] 1.62-4.57; P<0.001) for group 1, HR 2.45 (95% CI 1.64-3.66; p<0.001) for group 2 and HR 1.35 (95% CI 0.89-2.06; p=0.153) for group 3. In multivariate analysis, the predictors of 1-year all-cause mortality were Killip class IV (HR 2.40, 95% CI 1.78-3.25; p<0.001), cardiopulmonary resuscitation (HR 2.25, CI 1.64-3.09; p<0.001), left ventricular ejection fraction ≤40% (HR 2.07, 95% CI 1.57-2.72; p<0.001), culprit lesion at left main (HR 1.78, 95% CI 1.13-2.81; p=0.024), creatinine >1.5 mg/dl (HR 1.77, 95% CI 1.32-2.38; p<0.001), but not the LDL-C level (p=0.732)

Conclusion: In this single center experience, lower LDL-C level at time of diagnosis of STEMI was associated with higher 1-year all-cause mortality but the effect was not shown after multivariate analysis. This represent LDL-C was not the risk factor to predict 1-year all-cause mortality in STEMI but there were other factors that associated with the outcome. LDL-C was independent risk marker.

Keywords: LDL cholesterol, STEMI, 1-year mortality rate