A pediatrician is a doctor who specializes in the regular care of children, as well as the diagnosis and treatment of illness in children. Young patients are often more complicated to treat because they are still growing and developing.
While pediatricians may sub-specialize in specific therapy areas like oncology, surgery, ophthalmology, and anesthesiology, in general, pediatricians provide services like vaccinations, health exams, and treatment of common ailments and injuries. In addition, pediatricians are trained to handle the complex emotional and behavioral issues faced by children, especially during puberty.
Pediatricians normally see their patients from birth until the age of 18, although some may agree to treat patients into their early 20s, if requested.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.
These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.
In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.

Pediatric cardiologists are pediatricians with additional, specialized, training in the heart health of your children. When infants are born with congenital heart disease or abnormal hearts, pediatric cardiologists get involved as soon as possible — sometimes before the child is even born.
Through specific testing, they can diagnose the problem and care for the child throughout their treatment, which could range from medication to surgery and transplants. Other heart conditions they treat include arrhythmias, heart murmurs, holes in the heart and viral infections that affect blood flow.

While cardiologists diagnose and treat all types of heart disease, electrophysiologists have extended education in rhythmic disorders, also known as cardiac arrhythmia or an irregular heartbeat. An electrophysiologist typically works closely with a cardiologist and together they can treat arrhythmia, help you prevent blood clots, or restore and control a normal heart rate.
They can also provide information on medications and devices — such as a pacemaker or an implantable defibrillator — used to control an abnormal heart rate. When it come to treating arrhythmias, there are both invasive and non-invasive treatment options and an electrophysiologist can help you decide which is right for you.

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.