Abstract: A heart pump for the circulation of blood outside of the body of a living subject is described. The pump permits to slow up the speed of the flow of the blood during the circulation outside of the body for the purpose of making determinations of hematochemical parameters of the blood by means of well known apparatuses. The pump comprises a body made of rigid material which is divided in the interior by means of separation plates into three chambers. The first and the last chambers simulate the function of the heart valve while the central chamber simulates the function of a ventricle. A flexible conduit is disposed in the interior of the pump. Blood circulates in the flexible conduit which extends in a rectilinear manner or wound spirally in the interior of the chambers which are completely filled up with incompressible fluid. The peristaltic action of the heart is simulated by means comprising pistons which are staggered and which act in correspondence to each chamber.