Existence of bistability and correlation with arrhythmogenesis in sheep atria

This experimental study investigates the response of sheep atria to periodic pacing. In 23 trials over 6 animals, a window of bistability was observed wherein for a range of pacing periods the atria responded 1:1 or 2:1 depending on whether pacing period was increasing or decreasing. In 18 trials, non-paced activations were also observed. In 17 of those 18 trials, the non-paced activations occurred at pacing periods within or no more than 30 ms away from the window of bistability. These results suggest bistability exists in cardiac tissue and is correlated with arrhythmogenesis.