Fig 3. Effects of dofetilide and quinidine on the restitution of JTpeak and JTend intervals.

JTpeak (panels A and B) and JTend (panels E and F) intervals were measured on ECG at variable pacing rates, both at baseline and upon drug infusion, and plotted as a function of preceding diastolic interval (DI). The JTpeak and JTend restitution (rest) curves were differentiated in order to determine the maximum restitution slope value attained at the shortest DI (panels C, D, G, and H). Drug effects on the JTpeak vs. JTend difference in the maximum restitution slope are shown in panel I (dofetilide) and panel J (quinidine). *P<0.05 vs. basal value (in panels I and J).