That's the answer to your description's question: before or on the 51st ball drawn. But since your heading asks a slightly different question, I'll also answer your heading's question, which is just before 51 balls.
Looking for the definition of AFIS? Find out what is the full meaning of AFIS on Abbreviations.com! 'Automated Fingerprint Identification System' is one option -- get in to view more @ The Web's largest and most authoritative acronyms and abbreviations resource.
Atrial fibrillation (AFib) is a heart rhythm abnormality caused by a problem with the heart's electrical system. Normally, the heart's electricity flows from the top chambers (atria) to the bottom chambers (ventricles), causing the normal contraction.