The cardiac muscle has intercalated disk that allows rapid transmission of the impulse. This will allow the cardiac muscle to have a coordinated way. The heart muscle has pacemaker that will spread the signal in regular time. The transmission of impulse is also controlled by a few checkpoint like the bundle of his to make the signal to the Purkinje fiber of left and right ventricle at the same time.
The wastes would build up in your blood, and can cause serious damage. You can also have serious infections and pain if your kidney is not functioning properly.