The aim of this study is to test the potentially protective role of myonectin in patients with a first episode of ST elevation myocardial infarction (MI) treated with primary percutaneous coronary intervention (PCI).

The main questions which are assumed to be answered after study completion:

1. Does higher myonectin concentration influence the in-hospital and 30-day course of the first ST-elevation MI in patients treated with primary coronary angioplasty
2. Is there a relationship between the serum myonectin concentration, related to patient's nutritional status and physical activity with the patient's physical activity declared as usually before the coronary event occurrence, the cardiac biomarkers level, and myocardial and skeletal muscle mass determined in order to objectify the relationship of physical activity before the infarction with 30-day and one-year mortality, and the other primary and secondary outcomes measured at 12-month visit, e.g. the extent of myocardial infarction,
3. Is there a relationship between the baseline concentration of myonectin and troponin with the control of atherosclerosis risk factors, declared physical activity and parameters of body composition, outcome of treadmill exercise test, values of echocardiographic parameters and myonectin concentration 12 months after a cardiovascular incident

Myonectin or Complement C1q Tumor Necrosis Factor - Related Protein 15 (CTRP15) is a cytokine secreted by skeletal muscle. The participation of myonectin in the regulation of lipid homeostasis in the liver and adipose tissue has been proven. The concentration of myonectin depends on the nutritional status of the organism, it decreases during fasting and increases after feeding. In studies on mice, a protective effect of high concentrations of myonectin on the course of myocardial infarction was observed. The effect of regular physical exercise on the concentration of myonectin in the serum was also demonstrated. Abnormal function of myokines, including myonectin, has also been linked to sarcopenia, which significantly negatively affects the prognosis of patients with heart failure.

Potentially protective properties of myonectin in the case of ischemia-reperfusion injury in the course of myocardial infarction have not been studied in humans so far.

Myonectin may become a potentially useful prognostic indicator of the severity of myocardial infarction. It may also potentially become a target for a new cardioprotective therapy in patients with acute myocardial ischaemia.

Inclusion Criteria:

• symptoms of acute coronary syndrome
• acute ST segment elevation in two or more leads in ECG
• primary PCI

Exclusion Criteria:

• pregnancy
• patients unconscious, with altered consciousness or not able to cooperate
• cardiogenic shock
• significant physical effort within 24 hours before onset of MI
• active infection at admission, intramuscular injection
• myocardial infarction in patient's medical history
• heart failure New York Heart Association (NYHA) class III - IV in patient's medical history
• renal failure (chronic kidney disease, CKD) with glomerular filtration rate (GFR) < 30ml/min
• history of malignant neoplasms in the last 5 years
• patients incapacitated, active soldiers, imprisoned or related with investigators

All patients admitted to the study site with a diagnosis of STEMI treated with primary PCI who consent to follow-up during the scheduled enrollment window.