VWF and acute coronary syndrome: Two main types of thrombi were observed in patients with acute coronary syndromes, white and red.6 Histology indicated that white thrombi from patients with ST-segment–elevation MI (STEMI) were mainly composed of fibrin, whereas red thrombi were mainly composed of RBCs.7 Thrombi from patients with STEMI that are resistant to fibrinolysis are characterized by dense fibrin and higher contents of platelets and VWF (von Willebrand factor).8 These studies highlight how fibrin contribution to thrombi varies between disorders and may impact disease progression and outcome.