Fluid seals for catheter pump motor assembly

A catheter pump system comprising:

• a shaft assembly;
• an impeller coupled with a distal portion of the shaft assembly;
• a motor assembly that imparts rotation on the impeller through the shaft assembly, the motor assembly comprising a motor that rotates the shaft assembly, the shaft assembly comprising an output shaft portion through the motor, the output shaft portion comprising a motor lumen;
• a fluid pathway for supplying a fluid from outside the body, the fluid pathway conveying at least a portion of the supplied fluid proximally during operation of the catheter pump system;
• and
• a seal disposed between the motor assembly and the impeller, the seal configured to impede the fluid from the fluid pathway from entering the motor assembly at least about an outer periphery of the shaft assembly.

A method of operating a pump, the pump comprising an impeller and a motor assembly comprising a motor coupled with the impeller, the method comprising:

• rotating a shaft assembly with the motor to impart rotation to the impeller;
• directing fluid into the pump from outside the body, at least a portion of the fluid flowing back proximally along a fluid pathway between the impeller and the motor assembly;
• and
• impeding the fluid from entering the motor assembly at least about an outer periphery of the shaft assembly with a seal, the seal comprising an opening through which a portion of the shaft assembly extends.