I call this the "calculus of the cardiologist":
Heart procedures = big money
More procedures = more big money
You do the math. If you do more procedures, you get more money. 
What if your patients don't need more procedures? That's easy. You lower the bar on reasons to do procedures. You scare the pants off people and lead them to think that all heart disease or questions about heart disease are potentially life-threatening. You could even appear to be doing the patient a big favor. "My Lord! This is potentially dangerous. We need to perform a procedure without delay!"
There are incentives beyond direct cash payment. A patient of mine today showed me a memo to employees in his company that showed why certain hospitals are targeted for care. The criteria for choosing centers was based on number of procedures performed. In other words, the more procedures performed at a hospital, the more procedures will be directed there. Of course, this makes sense at some level. More procedures can also mean greater skill.
But have we lost sight of the fact that the mission is not more procedures and more money, but to get rid of a disease? If the intensity of effort devoted to heart procedures were re-directed to early detection, prevention, and reversal of disease, we'd have half the hospitals we now have. We'd also chop a huge chunk out of the national healthcare budget.