LBBB AMI

The Sgarbossa criteria can be simplified:
- if see ST elevation in V4-6 of 1mm then that's 5 points
- if see ST depression in V1-3 of 1mm then that's 3points
- if see massive ST elevation in V1-3 (5mm) then that's 2 points...and because this is often seen, you need to get "3" points to be said to have an MI.

Also, you should never have qR complexes in leads V5-6, I, AVL, and interestingly in II, III and AVF.

Then there are 2 eponymous signs:
Cabrera: notching of the ascending part of the S in V3/4
Chapman: notching of the ascending part of the R in V5/6

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.

Fused-looking beats

This is an example of a fusion beat from a sinus beat and a junctional ectopic.

When VE's don't lead to a fully compensatory pause

The rule is that VE's lead to a fully compensatory pause (from the R before to the R after is 2x the usual R-R interval) and that SVE's lead to a less-than-compensatory pause.

What leads to a more-than-compensatory pause?
When you have a VE followed by a sinus pause and a junctional escape.

When you have both narrow and wide complexes in the same rhythm strip

This is the one that I hate the most, but it's really not that hard.

The pearl is to look at the coupling interval between two narrow complex beats. And then to look at the coupling interval between a narrow complex beat and a wide complex beat. If it's smaller, then the wide complex is aberrant conduction. If it's larger, then you have an accelerated idioventricular rhythm that is ignoring the sinus or atrial pacemaker that was originally driving the ventricle.

That's it. The only two possibilities.

LVH in the presence of RBBB

The way to diagnose this is to ignore the praecordial leads. Instead, use the limb leads:
AVL>10
RI + SIII >25

Some suggestive findings are:
LAA
LAD (though if have this then the voltage threshhold for AVL is higher).

Poor R wave progression

The differential for old anteroseptal MI is:

1. Emphysema - you see low R wave voltages V1-3 but also an R prime in V1 and V2 (because of the lateral S waves), a vertical axis and RAA.

2. Lead placement

3. LVH/HCM because the tall R waves laterally mean that there will be negative vectors septally..