That altered autonomic nerve activity is not the entire explanation for the influence of sleep apnea in AF occurrence was shown in a study of sleep apnea in a rat model of obesity.309 Obstructive apnea promoted AF induction in obese rats much more than in lean rats, with only partial protection (<50%) by autonomic blockade. On the other hand, obstructive episodes caused LA dilation that was enhanced in obese rats by obesity-associated left-ventricular diastolic dysfunction. Prevention of LA dilation fully prevented apnea-associated AF. In this model, neither obstructive apnea nor obesity was enough to cause significant AF vulnerability; the interaction appeared necessary to cause the degree of LA dilation needed to allow for AF induction.