Figure 7.

Pacing to induce proarrhythmia after administration of moxifloxacin. Three ECG leads (II, AVR and LL) are shown. After administration of 2 followed by 8 mg kg⁻¹ moxifloxacin, the QT interval is 630 ms at a CL of the idioventricular rhythm of 1654 ms. A programmed electrical stimulation (PES) was performed, resulting in 8 beats with a CL of 500 ms, followed by a beat after 1200 ms and an extra beat after 400 ms. The extra beat was paced close to the refractory period as evidenced by the broad R wave. Neither this nor any other stimulation protocol lead to arrhythmias. Note, however, the different T-wave morphologies of the nonpaced beats before and after the stimulation protocol. Furthermore, a tendency towards T-wave alternans can be observed during pacing with a CL of 500 ms. Horizontal scale bar, 1 s.