Too much endurance exercise bad for the heart?

I was intending to blog about this study on the cardiac effects of extreme endurance sport, but Dr. John beat me to it and has a great commentary on his blog. The article from the European Heart Journal agrees with prior studies that extreme endurance sport can cause heart dysfunction in the short term, which usually recovers completely. The new finding is that for extremes of endurance performace, some permanent damage may occur. The study is not conclusive, and we cannot forget that regular exercise is an excellent way to reduce your risk of dying. It is possible, however, that running an ultra every weekend might be a bit too much for the ticker.