(Re-posting because I put the answer with the wrong question)
Cardiac nurses and doctors are focusing on heart disease. As a general rule, doctors provide opinions and diagnosis while nurses provide aid and physical treatment. Typically nurses will have more contact with patients than doctors, and they are responsible for carrying out tasks (drawing blood, setting up IVs) rather than making decisions. But the role of nurses varies greatly depending on the types of nurse (check out the following posts):
To add to the above answer, as nurses we do spend much more time with the patients, and we are essentially the eyes and ears of the health care team. We assess and monitor our patients for changes, and use the information to create care plans for the patient's needs. We speak and work with the doctors to find the right types of care. Nurses do make quite a few decisions on a daily basis, but we are not diagnosing or prescribing as emmawilson said. Carrying out physical tasks is just a tiny part of what a nurse does, and many of the tasks we do carry out that have been ordered by a physician are being ordered because of a nurse's observation of a patient condition. This is why team work is so important. We are all looking at the same problem and trying to fix it or care for it, but we are just looking at it from different angles so as much information as possible can be used to benefit the patients the most.