It's no use pumping a dry well.

涸进汲水，无济于事。

The injured muscle may not be able to pump blood as well, and its rhythm might be thrown off.

此外，受损的心肌可能无法泵出血液，而且心脏节律也可能紊乱。

That can be created by heart failure, blood backing up into the lungs from the heart 'cause the heart isn't pumping well.

这可能是由心力衰竭造成的，血液从心脏回流到肺部，因为心脏的泵送不畅。