Patient with stable ischaemic heart disease and essential thrombocythemia in Invasive Cardiology Laboratory -- role of the automated systems for estimation of platelet aggregation. A case of a 63-year-old male patient with essential thrombocythemia and coronary artery disease is presented. The patient underwent elective coronary angiography and subsequent angioplasty of the intermediate branch. The procedure was complicated by a massive thrombosis of the right coronary artery. Tirofiban and subsequent stenting relieved anginal symptoms. Next, platelet activity was monitored using the platelet function analyser PFA-100 which enabled optimisation of the antiplatelet agent dosages. The usefulness of this device in the catheterisation laboratory is discussed.