A cardiologist is a heart doctor. He or she is the one to visit if you feel a tightness in your chest and shortness of breath. We know that the suffix -ologist refers to someone who studies some area. To that, we add cardio-, which comes from the Greek kardia, meaning heart, and we get someone who studies the heart.. The actual study of the heart is called cardiology, with cardiologist coming along a few years later.