A–fib

:  atrial fibrillation A-fib occurs when the top chambers of the heart, responsible for bringing blood back from the rest of the body, start to flutter.—Forbes, 13 July 2009 Individuals who walked two to three miles per hour … had a 32 percent lower risk of developing AFib, whereas those who walked more than three miles per hour (moderate pace) lowered their risk by 41 percent.—Food & Fitness Advisor, Nov. 2008