The impact of smoking on post-clopidogrel platelet reactivity in patients with acute myocardial infarction

Background and Objectives

Smoking increases inhibition of clopidogrel-induced platelet reactivity in patients undergoing elective coronary stenting. However, an association between pre-admission smoking (PS) and post-clopidogrel platelet reactivity in patients with acute myocardial infarction (AMI) has not been determined.

Subjects and Methods

Study cohorts were recruited from a pool of patients at our hospital who were undergoing coronary stenting for AMI (n=134). Immediately after arrival at the emergency room (ER), all patients received a 600 mg loading dose of clopidogrel followed by a maintenance dose of 75 mg/day. Platelet aggregation was measured with light transmittance aggregometry (LTA) after addition of 5 or 20 µmol/L adenosine diphosphate (ADP).

Results

Maximal platelet aggregation (Agg_max) was lower in PS patients after 5 µmol/L ADP (43.6±15.7% vs. 48.4±12.5%, p=0.096) and 20 µmol/L ADP stimuli (56.2±15.6% vs. 61.3±11.6%, p=0.073) compared with non-smoking (NS) patients. However, there were no differences in 5 µmol/L (42.6±16.3% vs. 43.8±15.6%, p=0.776) and 20 µmol/L ADP-induced Agg_max (54.8±14.3% vs. 56.5±15.9%, p=0.692) between PS patients <0.5 pack/day and ≥0.5 pack/day. Although more PS patients met the criteria for low post-clopidogrel platelet reactivity (LPPR) (≤37%; the lowest quartile of 5 µmol/L ADP-induced Agg_max) than NS patients (30.9% vs. 13.5%, p=0.048), advancing age was the only independent predictor of LPPR {odds ratio (OR) 0.960, 95% confidence interval (CI) 0.929 to 0.993, p=0.019}.

Conclusion

PS is significantly not associated with decreased residual platelet reactivity in AMI patients.

Differences in Clinical Outcomes Between Patients With ST-Elevation Versus Non-ST-Elevation Acute Myocardial Infarction in Korea

In Korea, the incidence of acute myocardial infarction has been increasing rapidly. Twelve-month clinical outcomes for 13,133 patients with acute myocardial infarction enrolled in the nationwide prospective Korea Acute Myocardial Infarction Registry study were analyzed according to the presence or absence of ST-segment elevation. Patients with ST-segment elevation myocardial infarction (STEMI) were younger, more likely to be men and smokers, and had poorer left ventricular function with a higher incidence of cardiac death compared to patients with non-ST-segment elevation myocardial infarction (NSTEMI). NSTEMI patients had a higher prevalence of 3-vessel and left main coronary artery disease with complex lesions, and were more likely to have co-morbidities. The in-hospital and 1-month survival rates were higher in NSTEMI patients than in STEMI patients. However, 12-month survival rates was not different between the two groups. In conclusion, NSTEMI patients have worse clinical outcomes than STEMI patients, and therefore should be treated more intensively during clinical follow-up.