This is an interesting ECG for showing students AV sequential pacing and also ventricular tachycardia. The unusual thing about this ECG is that the V Tach starts at the time the machine begins recording the precordial leads. This particular ECG machine shows a slight "gap" at the lead change, so we don't see the actual start of the V Tach. Both rhythms have wide QRS complexes. The pacemaker is pacing the right ventricle, so you will see a wide QRS with a leftward axis, as the impulse spreads up and leftward toward the left ventricle. The V Tach portion is, of course, limited to the precordial leads, so we cannot plot the frontal plane axis. But, it meets many of the accepted criteria for ventricular tachycardia, including: very wide QRS, negative QRS in Lead V6, absence of RBBB or LBBB pattern. For more on recognizing V Tach in a WCT, go to Ask the Expert at this LINK.
This is also a very good example of how the interpretation by the machine can be wrong. Always read the ECG yourself!