The present invention provides an in vivo device for improving diastolic function of the heart, comprising: at least one elastic component that may be operatively connected to the external surface of the left or right ventricle of the heart by means of connecting elements, wherein said elastic component comprises essentially longitudinal members arranged such that the lateral separation therebetween may be increased or decreased in response to elastic deformation of said elastic component, and wherein said essentially longitudinal members are arranged such that said elastic component is curved in both the vertical and horizontal planes, such that its inner surface may be adapted to the curvature of the external ventricular surface of the heart, such that said elastic component is capable of exerting both radially outward expansive and tangentially-directed forces on the external surface of the cardiac ventricle.
