The Figure shows a spectrum of patients with persistent AFib of varying durations (<2, 2-6, and >6 weeks) prior to undergoing cardioversion [29] The teal, dark blue, and purple bars show left atrial function (measured as % A-wave filling) immediately, at 24 hours, and 1 week post-cardioversion, respectively.  As seen in the Figure, the longer a patient has been in persistent AFib prior to cardioversion (moving left to right on the X-axis), the less likely that cardioversion will successfully restore normal atrial function, no matter how long after cardioversion (immediately, 24 hours, 1 week) atrial function is assessed.

Reiffel JA. Am J Med 2013; 126: 00-00.