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, often referred to as afib, is an irregular heartbeat, a rapid heartbeat, or a quivering of the upper chambers of the heart, called the atria. Atrial fibrillation is due to a malfunction in the heart's electrical system, and is the most common heart irregularity, or cardiac arrhythmia. For more detail about how the heart works and what happens to the heart when it is in atrial fibrillation, see About the Heart.