Similar delayed thrombocytosis has been reported after coronary bypass surgery.28 IL-6-mediated acute phase stimulation of thrombopoietin could be involved.29 As platelets of patients with CTEPH are highly active,10 the reactive postoperative thrombocytosis may further aggravate the thrombotic state. This evidence concerns the gene THPO and chronic thromboembolic pulmonary hypertension.