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Understanding atrial fibrillation (AF) requires integrated understanding of ionic currents and Ca²⁺ transport in remodeled human atrium, but appropriate models are limited.

To study AF, we developed a new human atrial action potential (AP) model, derived from atrial experimental results and our human ventricular myocyte model.

Atria versus ventricles have lower I_K1, resulting in more depolarized resting membrane potential (≈7 mV). We used higher I_to,fast density in atrium, removed I_to,slow, and included an atrial-specific I_Kur. I_NCX and I_NaK densities were reduced in atrial versus ventricular myocytes according to experimental results. SERCA function was altered to reproduce human atrial myocyte Ca²⁺ transients. To simulate chronic AF, we reduced I_CaL, I_to, I_Kur and SERCA, and increased I_K1,I_Ks and I_NCX. We also investigated the link between Kv1.5 …