Atrial fibrillation in a BSE case. ECG of a 55 month-old cow (D114) orally dosed at 6 months of age with 100 g BSE brainstem homogenate. The QRS complexes are normally shaped but the R-R intervals are completely irregular, sometimes greater than two previous intervals, with irregular movements of the baseline (flutter waves). Mean heart rate 83 beats per minute. The ECG appeared normal with regular R-R intervals 46 days earlier.