Abstract: A heart support device for circulatory assistance is disclosed. The device (2) comprises a chamber body (4) comprising an outer wall and defining an internal volume (Vx) configured to receive a volume of fluid. The chamber body (4) comprises an outlet opening (8) at its proximal end (4a), the outlet opening (8) being in fluid communication with an exterior volume in which the chamber body (4) is disposed. The outer wall of the chamber body (4) is configured to alternately collapse and expand between a first configuration in which the internal volume Vx=V1 and a second configuration in which the internal volume Vx=V2, wherein Vi is larger than V2, and thereby pump the fluid through the outlet opening (8). The cross-sectional internal diameter of the outlet opening (8) is less than a maximum cross-sectional internal diameter of the chamber body (4).