Mechanic vs Heart Surgon

A mechanic was removing a cylinder head from the motor of a Harley motorcycle when he spotted a well-known cardiologist in his shop. The cardiologist was there waiting for the service manager to come take a look as his bike when the mechanic shouted across the garage 'Hey Doc, want to take a look as this?' The cardiologist a bit surprised, walked over to where the mechanic was working on the motorcycle. The mechanic straightened up, wiped his hands on a rag and asked, 'So Doc look at this engine. I open it's heart, take the valves out, repair any damage, and then put them back in. When I finish, it works just like new. So how come I make $39,000 a year and you get the big bucks ($1,700,000) when you and I are doing basically the same work?' The cardiologist paused, smiled and leaned over, then whispered to the mechanic: 'Try doing it with the engine running!'