A, Original, representative, L-type Ca2+ currents (ICaL) recorded from atrial myocytes isolated just prior to cardiac surgery (CS), from a patient in post-CS sinus rhythm, SR (□) and from a patient in post (3 day)-CS AF (■). Superimposed currents shown were evoked by voltage pulses (100 ms, 0.33 Hz, −40 mV holding potential), increasing in 10 mV steps between −30 and +40 mV. B and C, Histograms of peak ICaL density (at +10 mV) and increase in peak ICaL density by 0.05 μM isoproterenol (ISO), respectively, in atrial myocytes from patients in post-CS sinus rhythm (P-CS SR, □) and post-CS AF (P-CS AF, ■). Values are mean±SE. In (B), n=279 cells, 86 patients for P-CS SR, and 62 cells, 19 patients for P-CS AF (3 day). In (C), n=56 cells, 22 patients for P-CS SR, and 23 cells, 12 patients for P-CS AF (7 day). NS=not significant.