Here’s a fascinating, and scary, video of an implanted automatic defibrillator in action.

20 year-old Belgian soccer player, Anthony Van Loo, collapsed during a match. Blogging over at MedPage Today, electrophysiologist Dr. Wes analyzes the subsequent video, giving a precise play-by-play, so to speak, of when the defibrillator kicked in, likely restoring the arrhythmia into a normal heart rhythm.

As for the cause, Dr. Wes has got you covered: “In young people, the cause of these life-threatening arrhythmias include right ventricular dysplasia, catecholamine-induced ventricular tachycardia, idiopathic cardiomyopathy, and long QT syndrome . . . At maximum output, a defibrillator can deliver about 830 volts in a tenth of a second to restore the heart rhythm back to normal.”

Take a look at the video yourself: