TBX5 and atrial fibrillation: To examine whether dantrolene has antiarrhythmic effects on spontaneous depolarizations induced by TBX5 insufficiency, we conducted simulations in which Jleak was blocked by 80% (Hom-Tbx5-dantrolene) to mimic the treatment with dantrolene (10 μM) in left human atrial cardiomyocytes from patients with AF (Fig. 5(d)).