Cardiologists are doctors who specialize in treating illnesses and conditions that affect the heart. The heart is an intricate and vital organ, and cardiologists need years of training, plus further specialization. The four types of cardiologists are non-invasive, non-interventional, interventional and electrophysiology. Each type provides a particular kind of care and treatment for the heart patient.

Non-Invasive Cardiologist

A non-invasive cardiologist examines patients and orders tests, such as a stress test or electrocardiogram, to diagnose, treat and prevent heart problems. Patients see this doctor in his office. The results of the tests and exams show whether the patient can be treated with medication and lifestyle changes. If surgery is needed, the patient is transferred to another doctor.

Non-Interventional Cardiologist

This cardiologist performs the same exams and tests as the non-invasive cardiologist, except that she also can perform minor operations. One example is catherization, which locates blocked arteries in the heart. The non-interventional cardiologist is limited to these operations. Some of these surgeries are done in the office, some in a hospital. If the cardiologist finds a blockage, she refers the patient to an interventional cardiologist.

Interventional Cardiologist

This cardiologist undergoes one to three years of additional training after the three-year residency, and can perform more advanced surgeries. These include valve repairs, atheroectomy (plaque removal), balloon angioplasty and mesh stent placement to relieve blockages. Most of an interventional cardiologist's time is spent in the hospital, with some office hours for follow-up and consultation.

Electrophysiology Cardiologist

This cardiologist studies the electrical stimulus to the heart, looking for irregular heartbeats and other problems that could cause cardiac arrest. She performs tests such as an echocardiogram, a painless, non-invasive test that uses sound waves to view an image of the heart. Electrophysiology cardiologists perform surgeries to install pacemakers and defibrillators and prescribe drug therapies, among other treatments, to reduce the incidence of heart failure.