That's very interesting, thank you. The idea of them using a ball with rattles in it takes a bit away from the amazement that I was feeling but not much...it's still incredibly impressive that they are able to do this.
The type of injury you refer to is known as blunt cardiac trauma, and it is becoming more commonplace (or at least the diagnosis is). It is happening more and more here in the USA in baseball, and can cause a heart arrhythmia, an infarction (heart attack) even in children, or even a torn aorta (blunt aortic trauma) which is frequently fatal.. So it's best to keep your eye on that ball :-)
Next year the Cricket World Cup will be held in the West Indies. If you get a chance to watch I am sure you will find it an interesting game. The one day game is very fast.