The parameter of interest in the study population was the mean platelet volume (MPV), and the main objective of the research was to identify a possible relationship between MPV and several variables—biological (NT-proBNP, presepsin, red cell distribution width (RDW)), electrocardiographic (atrial fibrillation (AFib) rhythm, sinus rhythm (SR)), and echocardiographic (left ventricle ejection fraction (LVEF), left atrial (LA) diameter, left ventricle (LV) diameter, pulmonary hypertension (PH)). Here, NPPB is linked to pulmonary arterial hypertension.