Left atrial hypertrophy is best diagnosed in V1 - if have 1 x1mm then it's LAH.
Q waves are no longer physiologic if they are >1/3 of the height of the R wave. However, the most sensitive way of telling if there is an inferior infarct is to see if the Q wave has reached 0.04secs in width. Only the Q wave in III is allowed to exceed these limits of 0.03 and 1/3 of the R wave.
V1- the significance of ST elevation there is RV infarct if no V2 elevation, else septal infarct if there is V2 elevation. You confirm this by doing right chest leads.
Pericarditis - the only leads that fail to show ST elevation are those in which the QRS is predominantly negative - AVR, AVL, III, V1.
However, the specific sign is that the PR segment gets depressed - you can tell it's depressed by comparing it to the TP segment just in front of it. This is said to be due to atrial injury.
The things that tell you it is early repolarization are that the R and T waves tend to be tall, there is early transition, a terminal slur in the QRS praecordially.
One that I'm sure you've stuffed up before is the RBBB. There are two types of RBBB - just RBBB - and RBBB with infarction. You tell the latter by looking at V1-3 to see if there are Q waves, and then looking at the ST segment to see if it is elevated. Neither should be the case!
The ST elevation means that there is either an acute infarct or a large akinetic region.
You've messed this one up before - before you say there is Wenckebach, have a look between the QRS and T wave for P waves. If they're there then this is CHB, and there is a junctional escape.
If you see a bifascicular block then look for the anterior MI that is causing it.
If see ST depression in V1 think of acute posterior MI.
Excluding RVH as the cause of a prominent R in V1 - should see a deep S wave laterally if there is RVH. So, what you see is in v4-6 there is never a situation of R dominance - it's a VERY late transition!
The other thing to do in whatever lead you see your P wave best is to look for a second P wave on the other side of the QRS. If you see one then there is 2:1 block. But it has to occur every time - if you only see it once then this is just a blocked PAC. The differential for when you see this is typical atrial flutter that has been slowed by anti-arrhythmics - the way you tell this is to then look at the inferior leads- if you see three negative defelections with no flat bits in between in AVF, then this is flutter.
-A mistake you've already made is not looking for the RAE in II once you've seen the LAE in V1.
- PR depression in association with LAE is due to depolarization of a large atrium.
- The last thing you do on your examination is check for hypoelectrolytaemia (ca, mg, k) and hypothyroidism or hypothermia - this causes long QT (little - long). You have to look for the END of the T wave, not its highest point. You can actually differentiate between these- low K produces a long T wave (and a U wave to give the impression that it's even longer), and low Ca produces a long ST segment.
Along with looking at the QT you therefore cast a glance at one of the T waves to make sure that it is not sharp and symmetrical, because that means HIGH potassium.
The rule for >1/2 of the R-R interval only works when the heart rate is >80bpm.
- what to do when you get a paced rhythm?
Some basic rules are:
- a big spike means an old (unipolar) system.
- two spikes means "an AV sequential pacemaker"
- spikes should never be seen anywhere but in front of a complex - if they are seen elsewhere then this is undersensing, and undersensing is lead fracture till proven otherwise.
- spikes should always be completed by a complex - if they are not then this is failure of capture - and this complex should always be the same - if it is not then there is fusion.
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