In some congestive heart failure cases why does the upper extremities swell and not the lower. ?

Dependent edema: In congestive heart failure, the parts of the body lowest will swell. Usually that means the ankles. Arm swelling might occur if someone lays flat and dangles their arms lower. It may also occur if there is an internal blockage in the return of blood flow from the upper body to the heart (superior vena cava syndrome).

Unlikely!: The venous back pressure is elevated throughout and usually the arms seem less swollen since they are not as dependent( hanging down) as the legs.