Association of baseline platelet count with all-cause mortality after acute myocardial infarction

We sought to evaluate baseline platelet count as a prognostic indicator in patients with acute myocardial infarction (AMI).

Data of 13,085 patients with AMI were retrieved from a prospective nationwide AMI registry from November 2011 to December 2015. Using Cox hazards models, cumulative risks for adverse outcomes were compared among patients with baseline platelet count of less than 150 K/µL (lowest quartile), 150 to 249 K/µL, 250 to 349 K/µL (reference) and equal to or greater than 350 K/µL (higher quartile). The primary outcome of interest was all-cause mortality. Secondary outcomes included myocardial infarction, re-hospitalisation for heart failure, and stroke.

During a median follow-up of 2.1 years, a steep U-shaped association was observed for the occurrence of all-cause mortality (p for non-linearity <0.001). For stroke, a similar U-shaped curve was also seen (p for non-linearity = 0.095). After multiple adjustments, the lowest and higher quartiles of baseline platelet count were positively associated with all-cause mortality (adjusted hazard ratio: 2.120; 95% confidence interval: 1.345-3.341; p = 0.001, and adjusted hazard ratio: 1.642; 95% confidence interval: 0.957-2.817; p = 0.072, respectively). Similar results were observed in sensitivity analyses even after excluding patients with age ≥75 years or patients with heart failure.

In patients with AMI, baseline platelet count demonstrated a U-shaped association with an increased risk of all-cause mortality at two years. If validated, these findings suggest that baseline platelet count could serve as a preferred prognostic marker in AMI due to its low cost and universal availability.