Dual antiplatelet therapy has a key role in a prevention of thrombosis of treated artery in patients undergoing percutaneous transluminal angioplasty (PTA). Weak therapeutic response and presence of residual platelet activity is related to high risk for stent thrombosis and it is well in known in coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI). However there are few data on the association between a different entity of platelet inhibition on antiplatelet treatment and clinical outcomes in patients with peripheral artery disease (PAD). The aim of this study was to evaluate the degree of on-treatment platelet reactivity, and its association with ischemic and hemorrhagic adverse events at follow up in PAD patients undergoing PTA.

This is a single-center observational cohort study. All together 450 patients undergoing and elective PTA (both with and without stenting) who are going to be refereed to the Clinic for Vascular and Endovascular Surgery (based on the previous experience) during the two year period (January 1st 2020 and January 1st 2022) are planned to be involved in this study. All interventions will be performed according to the current standards and the type of the endovascular procedure will be at the discretion of operator. All patients will receive at the day of treatment 300mg of Aspirin and 300mg of Clopidogrel. The day after the procedure platelet function will be assessed by "point-of-care" impedance aggregometry test using the Multiplate analyzer. According to the manufacturer proposition, resistancy on Aspirin will be defined as arachidonic acid receptor (ASPI) value < 600 and ASPI/thrombin receptor activating peptide (TRAP) < 0.5, and for Clopidogrel adenosine diphosphate (ADP) < 500 and ADP/TRAP < 0.5 . After that patients will receive dual antiplatelet therapy (Aspirin 100mg and Clopidogrel 75mg) in the six months period. Follow-up examinations will be scheduled on 1, 6 and 12 months after the intervention. Adherence to antiplatelet treatment will assessed during scheduled or unscheduled examinations. Statistical analysis will be performed using the software package SPSS 20 (SPSS Inc., Chicago, Il, USA). Categorical data will be represented as numbers and percentages. Chi-square test or Fisher exact test as appropriate will be used to compare categorical data. Continuous variables will be represented as mean ± standard deviation and as median and interquartile range, depending on the normality of data. Student's t test or Mann-Whitney U test as appropriate will be used to compare two population groups. We will then assess the ability of ASPI and ADP values to distinguish between patients with and without clinical event at 6 months follow up by receiver-operating characteristic (ROC) curve analysis and the optimal cut-off ASPI and ADP values will be determined by estimating the value resulting in the maximum sum of sensitivity and specificity (area under the curve - AUC). Kaplan-Meier curves with log-rank test will be used to assess difference in the time-to-event end-points. A multivariable Cox proportional hazard model adjusted for clinical and laboratory variables will be performed to evaluate the independent contribution of platelet hyper- or hypo-reactivity to the outcomes. A P-values <0.05 will be considered statistically significant.

Inclusion Criteria:

- all patients treated due to PAD with PTA with/without stenting of aorto-iliac, femoro-popliteal and crural disease at the mentioned time period with critical limb ischemia (CLI) or intermittent claudication (IC)

Exclusion Criteria:

• younger that 18 and older than 85
• contraindications for Aspirin and Clopidogrel use
• thrombocytopenia (<100 x 10⁹/l)
• thrombocytosis (>450 x 10⁹/l)
• kidney insufficiency (stage 4 and 5)
• more severe anemia (Hgb < 100 g/l)
• severe hepatic disorder
• congestive heart failure
• known hemorrhagic disorder
• known malignant disease
• previous use of drugs with known anti-thrombocyte mechanism of action (dipyridamole, NSAID)
• use oral anticoagulant therapy
• use of corticosteroids
• use of drugs that are metabolized threw CYP3A4 (like erythromycin and rifampicin)

All patients treated at the Clinic for Vascular and Endovascular Surgery, Clinical Center of Serbia, Belgrade due to PAD (critical limb ischemia {CLI} or intermittent claudication {IC}) with PTA with/without stenting of aorto-iliac, femoro-popliteal and crural disease between January 1st 2020 and January 1st 2022

to be available on request for now