Baseline Platelet Count Predicts Infarct Size and Mortality after Acute Myocardial Infarction.

Introduction:  Platelets greatly contribute to cardiovascular diseases. We sought to explore the association of platelet counts with infarct size and outcome in patients presenting with acute ST-segment elevation MI (STEMI) treated with primary percutaneous coronary intervention (PPCI).

Methods And Results:  In this retrospective study, we grouped 1,198 STEMI patients into tertiles (T) based on platelet count on admission: T1 = 102-206 [10 platelets/L] ( = 402), T2 = 207-259 [10 platelets/L] ( = 396), and T3 = 260-921 [10 platelets/L] ( = 400). Primary endpoint was 1-year all-cause mortality. Patients with highest platelet counts on admission showed the greatest area at risk and infarct size: area at risk (median) was 22.0% (interquartile range [IQR]: 12.0-39.8%) in T1, 21.0% (IQR: 11.0-37.1%) in T2, and 26.0% (IQR: 14.9-45.0%) of the left ventricle in T3 ( = 0.003); final infarct sizes after 7 to 14 days were as follows: 10.0% (IQR: 2.0-21.0%) in T1, 9.0% (IQR: 2.0-20.7%) in T2, and 12.0% (IQR: 3.0-27.3%) of the left ventricle in T3 ( = 0.015) as serial imaging revealed. At 1 year, 16 all-cause deaths occurred in T1, 5 in T2, and 22 in T3 (log-rank test,  = 0.006). After adjustment, T1 and T3 were associated with all-cause 1-year mortality (T1: hazard ratio [HR] = 3.40, 95% confidence interval [CI] = 1.23-9.54,  = 0.02; T3: HR = 3.55, 95% CI = 1.23-9.78,  = 0.01) compared with T2. At 5 years, all-cause mortality remained numerically higher in the T1 and T3.

Conclusions:  In patients with STEMI undergoing PPCI, low and high blood platelet levels on admission were associated with increased long-term mortality (Fig. 1).