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Wednesday, 18 March 2015

Spring term 1 - Working through and abnormal ECG - Full discussion

Spring Term - Case 1

This delightful 84yrs old man comes to see you in surgery. 

Amongst other things, he mentions some chest pains. His symptoms are a bit vague and non-specific. He’s been having them for 6yrs. They don’t sound cardiac, but you know him well, and know he has a history of IHD.

He’s not a fit man, but on the other hand, he’s not clinically unwell today. 
He seems much the same as usual. A long with his known IHD and CKD5, he’s also pretty immobile from his osteoarthritis and obesity. 
He seems a bit breathless today, as usual.

You think  this could be anything! 

He has a lot of potential problems. You note from his recent annual review blood checks, that he has chronic stable anaemia (Hb10.5ish for many yrs) secondary to his CKD. His renal function is poor but stable (eGFR is 10-12).

You decide it might be wise to get an ECG whilst you consider how best to take this forward. 

The practice nurse pops it back in front of you: 

Now what shall you do?
Are you any the wiser?

Lets look at the ECG methodically and see if it helps. 
All ECG’s can be analysed with a few simple methodical rules. 
If in doubt, just describe what you see. 

Q1.  Is this a regular or irregular rhythm?

Q2.  What is the rate of this ECG?

Q3.  Are there any P waves?


  • Are they obvious? Perhaps hidden in other waves? Or simply non-existent? 
  • If you can see them - how do they appear (Morphology? Orientation? Size?) 
  • Do they have a consistent appearance? 
  • Do they have a consistent relationship with the QRS?

Q4.    Considering the QRS complexes: 

  • Are they consistent in all leads? 
  • What about their orientation?
  • What is the duration of the QRS complex?
A normal QRS complex should be no wider than 1 and half to 2 and half    squares (0.06 – 0.11 seconds). 

Q5.   What is the cardic Axis here?  Is there any axis deviation?

Q6.   What are the common causes of Left Axis Deviation (LAD). 


Always comment - Is this a regular or an irregular rhythm?

It’s regular. 
Best seen by studying the QRS complexes in long lead II in this case.

(If there is no rhythm strip on a 12 lead ECG, you may only have 3 complexes to study. If so, regularity can be very difficult/impossible to determine).


The rate has already been calculated for you at 52bpm. 

If not a quick ready reckoner is as follows:

For regular rhythms: Rate = 300 divided the number of large squares between 2 complexes.

For irregular rhythms: Rate = The number of complexes in 30 large squares (ie 6 seconds) multiplied by 10


I can just to say see P waves in the chest leads v1-6 but they are subtle! 
Because of poor quality baseline, I can’t see them in the limb leads or rhythm strip. 
(It may be impossible to see on your social media device – may need to zoom in or print a large copy)

Cheats tip
If you’re not sure about seeing complexes or waves – repeat the ECG with the ‘gain’ increased to magnify the complexes. This is the second ECG I took on this man...
How many of you noticed the comment on the top right corner of the ECG:  “non-standard lead gain”?  ;)  

Always comment on this if you see in in an assessment!

On his original ECG I couldn’t be sure if he had P-waves or not. 

If there were no P-waves, then this would be a ventricular escape rhythm ie. No atrial activity seen, and the ventricles have helpfully responded by setting up their own pacemaker focus somewhere within them.

Of the few P-waves we can see, their shape is uniformly round. They appear to be upright in V1 but possibly inverted in v2-6. Not important for purposes of this lesson. 

The P-waves we can see, appear to have a consistent relationship with the following QRS complexes, HOWEVER, this is prolonged...
The normal PR interval (start of P wave to the first deflection of the QRS complex) should be 3-5 small squares (0.11 to 0.20 seconds). In this case the PR interval is between 8-9 small squares. (>0.32 seconds)


Well done so far!

QRS Complexes.

Now we need to study the QRS complexes.
We’ve already decided they are regular.
We can’t really comment on the size, because we now know that the gain has been increased. So there’s no point thinking about LVH on this ECG.

We can consider their shape, and the Cardiac Axis. 

What is the duration of the QRS complex?

A normal QRS complex should be no wider than 1 and half to 2 and half small squares (0.06 – 0.11 seconds. 

In a heart with a healthy conduction system, once the impulse passes through the AV node, it travels through bundle of His, and down the Left and Right Bundle branches. As long as there is no delay in this conduction, this gives rise to a narrow QRS complex (less than 3 small squares).
If, however, after the impulse reaches the Bundle of His, there is any delay in the conduction, through either the Left or Right bundle branch, then the QRS complex will be widened.

LBBB usually gives rise to a wider QRS complex than RBBB. 

In LBBB, the width of the QRS is > 120ms (more than 3 small squares) 
Whereas, in RBBB it is often ≤ small squares.

LBBB = Left chest leads (I, V5 and V6) show RSR pattern (remember: WiLLiaM
RBBB = Right chest leads (V1 and 2) show RSR pattern. (remember MaRRoW)

If we go back to the ECG in this case, we notice that the QRS complexes are slightly broad, with RBBB formation.


But, that’ s not all....

If you have successfully worked out the cardiac axis, you will also see that there is

Left Axis Deviation here. RBBB alone would not normally alter the cardiac axis.

Common causes of LAD are:

1. Left ventricular Hypertrophy 

2. Inferior MI
3. May be normal varinat in obesity or stocky body 

He is of slim build and from his original ECG (with standard gain) I can confirm there was no voltage criteria for LVH. Those certainly look like deep pathological Q waves in the inferior leads (but don't forget about the increased gain). 

We know something is going wrong in his conductive tissue.

In the normal conducting system, the Left Bundle branch divides into two – the Anterior fascicle, and the Posterior fascicle. If both fascicles are blocked, then it becomes a full LBBB, but if only one fascicle is blocked, this is known as a “Hemiblock” or “Fasicular” block.

A Left Anterior Hemiblock (Left fasicular block), will always cause a LAD.
If you ever see RBBB + LAD, on an ECG, then you almost certainly have a LEFT ANTERIOR HEMIBLOCK.

So this 84yrs man has: 

  2. RBBB 

In fact, he is relying entirely on his small posterior fascicle, of the left bundle branch for ventricular conduction. If that fails him, he’s in trouble.

Unsurprisingly, an ECHO revealed severely reduced LV systolic function. 

He needs a full cardiology assessment and consideration for pacing.

The End.

Well done to those of you who got this far!  :)

Hope you found this helpful.