Risk variants at 4q25 do not modify the L-type calcium current in isolated human atrial myocytes. (A) I_Ca recordings from patients that had normal variants (black traces) or at least one risk variant (grey traces) in the absence of presence of AF. The mean I_Ca is shown below each trace. (B) Superimposed normalized I_Ca traces (top panel) and the fast time constant for I_Ca inactivation (bottom). (C) I_Ca recordings at different test potentials (top) in myocytes from patients carrying a risk variant, one of them with AF and one without AF (no AF). Current–voltage curves for each patient group (bottom). *indicates a significant difference between AF-patients and those with No AF. (D) I_Ca tracings recorded with different pre-potentials (top) in myocytes from patients without AF with a normal or a risk variant at 4q25. The voltage for half-maximal I_Ca inactivation is shown below. The number of patients is indicated for each data set in parentheses and P-values for comparisons are given above (in B) or below graphs (in A and D).