Apparatus and methods are described including a blood pump that includes an axial shaft configured for insertion into, and rotation within, a subject's body. The blood pump also includes an impeller, which includes a proximal bushing disposed over the axial shaft, a distal bushing disposed over the axial shaft distally from the proximal bushing, and one or more blades. Each of the blades includes a single inner helical elongate element, a single outer helical elongate element, and a film of material extending between the inner helical elongate element and the outer helical elongate element. The blades are proximally coupled to the proximal bushing and distally coupled to the distal bushing such that, as the axial shaft rotates, the blades rotate, thereby pumping blood of the subject. Other applications are also described.

Apparatus and methods are described including a blood pump that includes an axial shaft configured for insertion into, and rotation within, a subject's body. The blood pump also includes an impeller, which includes a proximal bushing disposed over the axial shaft, a distal bushing disposed over the axial shaft distally from the proximal bushing, and one or more blades. Each of the blades includes a single inner helical elongate element, a single outer helical elongate element, and a film of material extending between the inner helical elongate element and the outer helical elongate element. The blades are proximally coupled to the proximal bushing and distally coupled to the distal bushing such that, as the axial shaft rotates, the blades rotate, thereby pumping blood of the subject. Other applications are also described.

A system and method of increasing the pumping efficiency of an individual's heart, wherein an actual pumping efficiency is compared to an optimal pumping efficiency to determine a force assist profile. A cardiac assist device is created that will apply the force assist profile to the heart. The cardiac assist device is surgically inserted in vivo to physically affect the heart. The cardiac assist device has an outer shell and at least one inflatable membrane that passes over the ventricles of the heart, wherein the inflatable membrane is inflated and deflated in accordance with a pressure profile provided by a pneumatic pump. The outer shell embodies outer shell strain characteristics. Each inflatable membrane embodies membrane strain characteristics. The force assist profile is a function of the outer shell strain characteristics, the membrane strain characteristics, and the pressure profile.

A system and method of increasing the pumping efficiency of an individual's heart, wherein an actual pumping efficiency is compared to an optimal pumping efficiency to determine a force assist profile. A cardiac assist device is created that will apply the force assist profile to the heart. The cardiac assist device is surgically inserted in vivo to physically affect the heart. The cardiac assist device has an outer shell and at least one inflatable membrane that passes over the ventricles of the heart, wherein the inflatable membrane is inflated and deflated in accordance with a pressure profile provided by a pneumatic pump. The outer shell embodies outer shell strain characteristics. Each inflatable membrane embodies membrane strain characteristics. The force assist profile is a function of the outer shell strain characteristics, the membrane strain characteristics, and the pressure profile.