Do you know when you get checked by a cardiologist, what do they check for?

Various conditions: A broad range of conditions that affect the heart, including rhythm problems, blockage sin the arteries that feed the heart, valve diseases, and decreased heart muscle function.

Plenty: History and physical very important. Depending on symptoms or physical findings they may check for structural heart problems, arrhythmias, blockages, heart failure with a few other tests if necessary. If they find something wrong they will guide you to improve it or treat the problems. I hope this helps as your question is quite open ended.