Studying patients with acute myocardial infarction undergoing primary percutaneous coronary intervention has found that cytomegalovirus-seropositive patients demonstrated a greater fall in the concentration of terminally differentiated CD8 effector memory T cells in peripheral blood during the first 30 minutes of reperfusion compared with cytomegalovirus-seronegative patients. This evidence concerns the gene CD8A and myocardial infarction.