Identify whether all the elements of negligence are present and, if so, who or what entity will be sued successfully:
A male patient who is obese, fifty, has a positive family history for cardiovascular disease, a 20 pack year history of smoking, presents to the ER with shortness of breath, radiating substernal chest pain, and diaphoresis (sweating), is examined by the ER doctor who orders EKG, enzyme study, places patient on oxygen, does a stethoscope examination, and, after a proper and thorough exam, concludes the patient is not having a heart attack and sends patient home where he promptly suffers cardiac arrest and dies.