Introduction: Several studies have reported high residual platelet activity (measured using platelet aggregation tests) in patients treated with clopidogrel depending on the grade of drug biotransformation in liver via cytochrome P450 system. (1-3) It is also known that this high on-treatment activity as well as clinical outcomes may be improved by increasing clopidogrel dose. We report the results of a group of patients who have completed 1-year follow-up and who were included in a randomized clinical trial investigating efficacy and safety of individualized P2Y12 receptor antagonists treatment based on aggregometry tests versus fixed dose ticagrelor regimen in patients after acute myocardial infarction with ST-segment elevation (STEMI).

Patients and Methods: We analyzed the data of 51 consecutive patients (9 female, mean age 58.9 years) treated for STEMI. During the first month after STEMI all the patients were treated using fixed dose ticagrelor with aspirin. Afterwards the patients were randomized into two groups. First group continued with the aforementioned therapy during one-year period. Patients in the second group were switched from ticagrelor to clopidogrel and treated during the one-year period by individualizing clopidogrel dose based on aggregometry tests using Multiplate^® analyzer. Primary outcome was the incidence of major cardiovascular events (cardiovascular death, myocardial infarction, stroke and repeat revascularization). Secondary (safety) outcome was the incidence of minor and major bleeding defined using BARC classification.

Results: During one-year follow-up we haven’t observed primary outcome or major bleeding event. We found statistically significantly lower incidence of minor bleeding in the group of patients treated with individualized P2Y12 antagonists dose tailoring (p=0.027) which transfers to 4.8 times higher chance of having minor bleeding while treated with fixed dose ticagrelor in comparison to patients treated with individualized approach (OR 4.8; 95% CI 1.118 to 20.611; p=0.035).

Conclusion: These results show that individualized P2Y12 antagonists treatment using aggregometry tests may represent equally effective but safer treatment approach in comparison to fixed dose ticagrelor regimen in patients after STEMI.