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Figure 2 Action potential duration (APD₉₀) and left ventricular peak (+)dP/dt in steady state pacing experiments. As cycle length increased, action potential duration progressively increased in all three states. After sotalol, the APD was significantly longer than that seen during the baseline state and with esmolol (*p < 0.001; p < 0.001 for interaction). Left ventricular peak (+)dP/dt was higher with sotalol than it was with esmolol (significant at cycle lengths above 400 ms [*p < 0.001; p < 0.001 for interaction]); moreover, the inverse relation between peak (+)dP/dt and cycle length (seen in baseline and esmolol states) was abolished by sotalol.