A method of determining endothelial dependent vasoactivity of a subject, the method is effected by recording pressure-related signals of a plurality of locations adjacent to at least one blood vessel; extracting at least one parameter from the pressure-related signals; and using the at least one parameter to determine a change of at least one characteristic of the at least one blood vessel, the change being representative of endothelial functioning; thereby determining the endothelial dependent vasoactivity of the subject.