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AV Sequential Pacing to Ventricular Tachycardia

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!

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