A cardiologist is a medical doctor who studies and treats diseases and conditions of the cardiovascular system — the heart and blood vessels — including heart rhythm disorders, coronary artery disease, heart attacks, heart defects and infections, and related disorders. A cardiologist is a healthcare provider who can treat chest pain, high blood pressure and heart failure, as well as problems with your heart valves, blood vessels and other heart and vascular issues. They can order tests like electrocardiograms, echocardiograms and CTs (computed tomography) to find out what's wrong.