Cardiologists are doctors who specialize in the diagnosis, prevention and treatment of conditions related to the heart and blood vessels. A patient may be referred to a cardiologist if he experiences symptoms like chest pains, shortness of breath, dizziness, or high blood pressure. The physician will then evaluate your symptoms, take your health and family history and your weight. The cardiologist may order additional diagnostic tests, such as an echocardiogram, X-ray or blood tests. If necessary, the cardiologist may also call for a cardiac catheterization - a procedure in which a small tube is inserted into or near the heart that can take pictures of the heart's activity, or relieve blockage. Once determining whether there is a heart condition, a cardiologist will treat a patient through cholesterol management, cardiac rehabilitation, and fitness. If surgical intervention is required, like open-heart surgery, a cardiologist will make that determination, but a cardiothoracic surgeon will perform the procedure.