Basal and hypokalemic QT intervals, Q-Pend intervals, and electromechanical window values determined during steady-state pacing and extrasystolic stimulations in guinea-pig and rabbit hearts.

All parameters are given in ms. S1-evoked values were measured during LV epicardial pacing at a cycle length of 250 ms in guinea-pig hearts, and at 350 ms in rabbit hearts. Basal S2-evoked values were measured upon extrasystolic excitation with a coupling interval exceeding ERP by 5 ms. In hypokalemia, S2-evoked values were measured at the shortest effective coupling interval producing no tachyarrhythmia (Guinea-pig: S1–S2 = 105±2 ms; Rabbit: S1–S2 = 124±8 ms).*P#P2-beat vs. basal S1-beat.