Optical Mapping of Atrial Electrophysiological and Calcium Handling Abnormalities in a Rat Model of Sterile Pericarditis

Postoperative atrial fibrillation (POAF) frequently arises after cardiac surgery and is associated with atrial inflammation and remodeling. The sterile pericarditis (SP) model reproduces this condition in rats, providing a valuable platform to investigate inflammation-induced atrial electrophysiology. This protocol describes the preparation of Langendorff-perfused rat hearts after SP induction and the use of simultaneous dual optical mapping to record transmembrane voltage and calcium transients. Hearts are stained with the voltage-sensitive dye RH237 and the calcium indicator Rhod-2 AM, while contractility is suppressed using blebbistatin to minimize motion artifacts. High-speed imaging enables spatiotemporal mapping of atrial action potentials and calcium dynamics during controlled pacing protocols. Quantitative parameters include action potential duration, conduction velocity, calcium transient duration, time to peak, and alternans magnitude. The method allows precise assessment of atrial conduction heterogeneity, electro-calcium coupling, and arrhythmia vulnerability under inflammatory stress. This visualized approach provides a reproducible and versatile platform for studying POAF mechanisms and testing pharmacological or genetic interventions that target atrial remodeling.