PACEMAKERS

The normal pacemaker appearance is:
1. Broad R waves in I and AVL...because the impulse heads towards the left from the paced RV.
2. Broad QS waves in II, III and AVF...because the impulse heads upwards from the paced apex.
3. QS waves in leads V1-V5 with V6 also showing a dominant S wave, but a small r beforehand.

SO, EVERYTHING IS DOWN, EXCEPT FOR AVL AND I.

4. It is normal to have fusion beats and pseudo-fusion beats.
Fusion= spike but the QRS complex is only a little broad (occurs when the sinus rate and pacemaker rate are virtually the same).
Pseudo-fusion= spike but the QRS complex is narrow (occurs when the ventricle is still in its absolute refractory period).



When you see a pacemaker that doesn't look like it's a LBBB, the options are:

1. It's high lead placement - this makes V1 and V2 look like AVR and AVL respectively. You will still see that the limb leads have a superior axis.

2. It's lead reversal, such that leads V4-6 are placed in V1-3 position.

3. It's a BiV pacemaker, because BiV's can be placed in the coronary sinus if the sinus is big enough. You will see 2 ventricular spikes and may have an atrial spike because you want to control the rate and so block the patient's sinus rate with anti-arrhythmics.

4. It's LV pacing from a perforated septum. You know that the LV is being activated first because lead I is isoelectric.