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

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).

In this retrospective study, we grouped 1,198 STEMI patients into tertiles (T) based on platelet count on admission: T1 = 102-206 [10⁹ platelets/L] (n = 402), T2 = 207-259 [10⁹ platelets/L] (n = 396), and T3 = 260-921 [10⁹ platelets/L] (n = 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 (p = 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 (p = 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, p = 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, p = 0.02; T3: HR = 3.55, 95% CI = 1.23-9.78, p = 0.01) compared with T2. At 5 years, all-cause mortality remained numerically higher in the T1 and T3.

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