What's the difference between an ICD and a CRT-D?

An ICD can have one or two wires, called leads, depending on what your heart needs. One lead goes in the right ventricle, and if you need a second lead, it will be placed in the right atrium. A CRT-D system adds a third, attaching a lead to the left ventricle so it can help both sides beat in synch and thus pump more efficiently. If you've experienced heart failure, you'll most likely get a CRT-D.