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Figure 4 Left panels. Increase in APD90 induced by d,l-sotalol 10–5 M (open symbols) and 10–4M (solid symbols) as a function of PCL in (A) endomyocardial biopsies of unaffected (n = 7; circle) and affected dogs (n = 8; triangle; #, n = 7) and (B) Purkinje fibers of unaffected (n = 6); circle) and affected dogs (n = 5; triangle). In the affected group, the number of experimental data decreased to 3 at PCL = 4,000 ms under sotalol 10–5 and 10–4 M and to 4 at PCL = 2,000 ms under sotalol 10–4 M because of the occurrence of early afterdepolarizations or triggered activity. Right panels. (C) Typical action potentials recorded in endomyocardial biopsies of an unaffected dogs (bottom) and an affected dog (top) under control conditions (C) and in presence of d,l-sotalol 10–5 M (10–5) and 10–4 M (10–4) at PCL = 1,000 ms. Vertical bar, 50 mV; horizontal bar, 100 ms. (D) Typical action potentials recorded from Purkinje fibers of an unaffected dog (bottom) and an affected dog (top) in the presence of d,l-sotalol 10–4 M at PCL = 8,000 ms. Vertical bar, 50 mV; horizontal bar, 2 s. APD = action potential duration; PCL = pacing cycle length.
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