Figure 1.

(a–e) Examples of Lead II ECGs recorded at (a) baseline (−10 min), then (b) 1 min, (c) 5 min, (d) 10 min and (e) 15 min after starting drug administration in a rabbit receiving phenylephrine and clofilium. These examples illustrate drug-induced QT prolongation and slowing of the heart rate. When U waves were present these were included in measurement of the QT interval. In (d, e), clear U waves can be seen and are indicated by arrows. (f) An example of arrhythmias recorded towards the end of the second cycle of drug administration in the same rabbit. At the beginning of the recording there is bigeminy, then a three-beat salvo and an episode of TdP, which spontaneously reverted to sinus rhythm.