Question: What causes an abnormal heart rhythm?
Answer :There are multiple causes of arrhythmias. One can be born with abnormalities, either genetic or anatomic abnormalities, that can cause an arrhythmia. A very common one is called the Wolf-Parkinson-White syndrome, where there's an extra conducting system in the heart that can cause rapid heartbeats. And we can generally cure that by a procedure called ablation: we put a catheter, a long skinny wire, inside the heart, find where that extra pathway is and we can then eliminate it.
There are other congenital causes that are due to abnormal electrolytes, that is the potassium or the calcium or the sodium that flow in and the out of the cells, that can be responsible for abnormal heartbeats.
Then there are a whole set of acquired abnormalities. For example, a heart attack can produce arrhythmias. That's due to the lack of blood flow to the heart, and that ischemic event -- the lack of blood flow -- can cause arrhythmias. Or, the scar that may result from the heart attack after healing can cause arrhythmias as well.
The common electrophysiologic mechanism -- that is, what happens inside the heart -- is what's called reentry. Now, picture the interstate highway and you're driving your car down the interstate and there's a cloverleaf exit off into town. And you take that exit and go into town. Now, suppose that cloverleaf exit, instead of going into town came back on to the interstate. So you take the cloverleaf exit, you get back on the interstate, you take the exit back on the interstate, and you would then reenter in that fashion. That can, on the heart muscle, due to a scar or something like that, can cause heart rhythm abnormalities -- arrhythmias -- due to reentry. There are other causes as well, but that's the most common.