Introduction: Recently resistance to an acetylsalicylic acid (ASA) administration has been a frequently mentioned problem. However, to identify ASA nonresponsive patients (ASA resistance) is difficult and common examination procedures can contain important preanalytic, analytic and postanalytic mistakes. Recently a possibility to use aggregometry after induction with cationic propyl gallate (CPG) has been discussed in this context; it´s a robust, highly sensitive, and specific method for ASA resistance estimates. We asked ourselves following questions during our work: Goal: a) Experience patients with acute coronary syndrome (ACS) ASA resistance more often than healthy volunteers?; b) Are aggregation values in both patients with different metabolic homeostasis disorders and patients with risk factors for atherosclerotic complications different?; c) Change results of measured aggregation induced by CPG in patients treated with identical ASA therapy during a several years long monitoring; respectively are patients assessed differently during the monitoring?; d) Is it possible to use one-shot aggregation assessment following CPG to estimate ASA resistance or is it necessary to repeat the examinations?; e) Is recurrence of ACS complications more frequent during two years of monitoring of patients with ACS history resistant to 100 mg doses of ASA per day? Method: 103 patients of an average age 69 were assessed. All of them suffered from ACS without ST segment elevations and were treated conservatively; in addition to it all of them were treated with 100 mg ASA/day. They were assessed at the onset of ACS and after 3, 12 and 24 months. The examination consisted of taking patient history, clinical examination, BMI determination, laboratory test for cholesterol, HDL, LDL, triacylglycerols, and glucose, and of an aggregation of thrombocytes assessment under standard conditions (spontaneous and after CPG induction). Results and conclusion: a) ASA resistance is more frequent in patients with ACS compared to healthy volunteers (45 % to 6 %, p < 0,001). b) Patients with type II DM, smokers, patients with low HDL cholesterol levels or high triacylglycerols levels are ASA resistant more often (< 0,05). c) Results of measured aggregation of thrombocytes don’t change during administration of the identical dose of 100 mg ASA/day during 2 years of monitoring. Respondents usually are assessed identically during monitoring (responsive/ASA nonresponsive). d) ASA resistance can be estimated from one-shot aggregation assessment following induction with CPG. e) Two years after diagnosing the ASA resistance a percentage of cardiovascular complications recurrence is higher in patients with history of ACS (p < 0,001). One-shot assessments of the CPG induced thrombocytes aggregation and the spontaneous aggregation are sensitive in 81 % of patients with ACS history and specific in 100 % of patients at risk of recurrence of cardiovascular complications. If these results are confirmed it could lead to a change in interventions in patients with ASA resistance proved by this method.

        Key words: Aggregation of thrombocytes - Aggregometers - CPG - Acute coronary syndrome - ASA resistanc