It may not be the reason a person decides to become a cardiologist, but fame is a possibility. Many doctors, especially those working at teaching hospitals, conduct research throughout their careers. If a cardiologist creates a new treatment protocol and uses it with great success on their patients, you're likely to see it on the news, read about it in the paper, and maybe even get to attend the book signing.
Could you be the kind of famous cardiologist that sends a murmur through an entire crowd? Talk about your self-sustaining business.
While that kind of public influence isn't typical, being influential among your peers and patients within a geographical area is common. Top cardiologists, particularly those associated with the best teaching hospitals, will draw patients from 100 miles away or more.