All heart pumps damage the blood. So far we've not found a way to pump blood without causing damage due to various factors, sheer, pressure, heat, etc.
Impellers are particularly bad. Alternatives that use flexible membranes are better but still not perfect. Abiomed and Ventriflo both had pumps that use a flexible membrane. Abiomed had the first TAH (total artificial heart) to be implanted.
There are also other problems with blood pumps, such as stasis areas where blood can stagnate causing issues like thrombosis. These can be caused by valves or other issues in the flow path.
People on blood pumps need blood thinners and anticoagulants which can cause their own problems long term.
Impellers are particularly bad. Alternatives that use flexible membranes are better but still not perfect. Abiomed and Ventriflo both had pumps that use a flexible membrane. Abiomed had the first TAH (total artificial heart) to be implanted.
There are also other problems with blood pumps, such as stasis areas where blood can stagnate causing issues like thrombosis. These can be caused by valves or other issues in the flow path.
People on blood pumps need blood thinners and anticoagulants which can cause their own problems long term.
Source: 15 years of working on blood pumps.