Value of increasing ECG gain with possible AF

Value of increasing ECG gain with possible AF.
(A) Lead V1 and lead II rhythm strips show an irregularly irregular rhythm. At first glance, the rhythm looks like AF with moderate ventricular response.
(B) However, when the gain is increased twofold, it is now apparent that there are P waves preceding each QRS (*). Some P waves (eg, the 1^st, 2^nd, 6^th, 7^th, 8^th, 9^th, and 14^th) appear to be sinus P waves, while the 3^rd, 4^th, 5^th, 10^th, 11^th, 12^th, and 13^th P waves appear to be nonsinus, suggesting frequent atrial premature complexes. In this case, magnification of the ECG tracing facilitates recognition of a common AF mimic that could be associated with a preliminary ECG machine interpretation of AF.