Fig. 4

Pacing-induced atrial fibrillation (AF) in high-fat (HFa) and high-fructose/cholesterol (HFr) diet-fed rats. a Representative optical membrane action potential (AP) and calcium transient (CaT) recordings in control, HFa, and HFr diet-fed rats under consecutive S1 pacing. b Representative AP and CaT traces in control, HFa, and HFr diet-fed rats under consecutive S1 pacing followed by a premature beat of S2. c Short run of atrial arrhythmias of one representative HFr diet-fed rat induced by S1 pacing protocol. Notably, the third S1 pacing beat caused the functional conduction block at a distal site, leading to the activation of reentry circle of the right atrial appendage (RAA). d Focal discharges of one representative RAA induced by S1 pacing in one HFa diet-fed rat. The isochronal map indicates that the pacing site was in the lower edge of the RAA, whereas repetitive ectopic beats arose from the central region, subsequently spreading to surrounding tissue in the RAA followed by the consecutive S1 pacing