This question comes up from time to time, sometimes in the midst of a serious discussion but more often than not as part of a lighthearted conversation. It often gets disputed when cardiologists and neurologists get together! In fact, I remember wondering about it as a child watching the Wizard of Oz!
Certainly the brain is much more complicated than the heart. In fact, the brain is simply an amazing organ. To say that we have barely scratched the surface of our understanding of the brain is an understatement. Even with the incredible advancements in research over the last 50 years, we still have a very limited understanding of the brain and the its workings. I never cease to be amazed at the ability of the brain to control functions that we take for granted, things as simple as walking and movement.
The heart on the other hand is a much simpler organ. Its complexity pretty much pales in comparison to the brain. It has one very straightforward job to do, and that is to pump blood. Nevertheless, the heart is pretty amazing in its own special way. In fact, I never cease to be amazed every time I look at a beating heart. To think we have an organ inside that never stops pumping, never takes a break and can continue on for 80 or even 100 years in some cases is truly amazing.
When you get down to the question of which is more important, obviously they both are. In fact, I think it's probably a useless argument to try to rank one above the other. In fact, it may be useless to try to rank any organ in the body above another - we need them all!
Another way to argue the question might be the following: Which one can you live without? Well, technically speaking, your body can still be alive without a brain. On the other hand, it's pretty difficult for your body to be alive without a heart. In either circumstance, the quality of life is pretty poor without one or the other!
Interestingly, technology has advanced to the point in the last 15 years or so that truly artificial hearts do exist. Artificial hearts have been implanted in adults for some time, and recently the first total artificial heart was successfully used in a pediatric patient for 160 days until he was able to receive a living heart transplant. An example of a totally artificial heart is shown in the picture on the right.
So, as a cardiologist, I'd certainly like to think of the heart as more important than the brain, but this is probably not really the case! Certainly we are nowhere near a brain transplant or a totally artificial brain!