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Wednesday, 20 March 2013

RBBB - Case 27

#ECG Class is an educational blog which runs alongside Twitter.
A new ECG "quizz" is launched most Monday evenings, in term time. 

Cases are generally aimed at Primary Care.  All scenarios are completely fictitious, but based on commonly occurring presentations in General Practice. 
This is an educational site, intended for healthcare professionals and shouldn't be construed as patient advice. 

Please use the Hashtag #ECGclass on Twitter, if you want to ask the patient any questions, or request any further investigations. Alternatively, please join in discussion and leave comments below.

Remember there are no right or wrong answers!  

ECG interpretation is often open to debate, and will usually evolve and change as new information becomes available.  Everyone's opinion is valid, and useful for others, as the evolution process takes place.  Together we will try and form an interpretation based on the trace, and information, we have in front of us.  Don't worry if you disagree - shout up and share your thoughts - the diagnosis is often arguable on the basis of a 12 lead trace, and may only become more obvious when a longer rhythm strip is available. 

Please feel free to join in, but most important of all, have fun! :-)

#ECGclass case 27


Back to the wonderful world of everyday-GP-land tonight.

A 19 yr old man comes to see you in surgery. He's worried about some short-lived palpitations he had in the early hours of Sunday morning.

He's usually fit and well with no significant family history of IHD, or sudden unexplained death. He is on no medication. On further questioning he admits the palpitations were an isolated episode after a rather 'heavy' night of alcohol, caffeinated energy drinks, smoking.  He denies any use of recreational drugs.

After a thorough history and examination, you are completely happy that this was lifestyle induced, and educate him appropriately. You reassure him that no further investigations are necessary, but to call you again if problematic symptoms return.

He appears to remain anxious and unconvinced, and doesn't seem to want to leave.

What now? 

Do you:
a) Smile, stand up and open the door for him? 
b) Turn back to your computer and sip your coffee, waiting patiently for him to leave?
c) Explore his concerns?





Update 1

OK. You are feeling benevolent, so you opt for c.

He tells you that he is in the process of applying to the RAF as he hopes to be a fighter jet pilot. He's worried that these recent symptoms may mean something more sinister, which may need 'dealing' with before he attends for his interview/medical.  He asks if he could have 'a heart trace or something'.

Do you :
a) Agree to his request and book him for an ECG? (It goes against your clinical judgement, but if it will help reassure him - it's going to be normal after all...).
Or, 
b) Do you stand your clinical ground and offer more firm reassurance? (if the RAF are interested, surely it's up to them to investigate)





Update 2

You do the ECG, and this is what you get:


Is it normal?


Check:
Rate:  Atrial (P-wave rate) and Ventricular (Q-wave rate)?
Pwaves: Present? Regular? Consistent?
PR Interval: consistent?
QRS:normal shape? size? Duration? Consistently preceeded by a P wave?
ST segments - Are they isoelectric?
QT interval - is it normal duration?




Q1. Does this man's ECG fulfil this definition for sinus rhythm?
       (Check the definition of sinus rhythm if you are unsure).


Q2. What about the QRS - does it look normal? Is the duration normal?
       (see normal interval values if need)


Final Update/Full Discussion.




I would pass this as a 'normal' ECG.

The rate (approx 54bpm) is a bit slow to be defined as sinus rhythm (SR = 60-100bpm) so we would have to call it a sinus bradycardia.
The P waves are regular and consistent, and each P wave is followed by a QRS.
The PR interval is constant and normal  (normal PR interval is 3-5 small squares).
The ST segments, and QT interval, are also normal.


What about the QRS?

Unfortunately it may be a bit tricky to see clearly on this digital reproduction, but there is a slight 'blip' in the QRS conduction. This is seen most clearly in the inferior leads, aVL, and perhaps V1.  However, despite this, the QRS isn't broad enough to class this a Bundle Branch Block.

Normal conduction through the ventricles is very fast (0.12 secs - under 3 small squares).  In order to diagnose a complete Bundle Branch Block, there has to be some delay in conduction through the ventricles. ie. The QRS complex will be widened to > 0.12secs ( 3 or more small squares).

Some may class this as an "incomplete" Bundle Branch Block - but even so, the rest of BBB criteria aren't really met. Nor is the QRS wide enough to qualify as a more non-specific intraventricular conduction delay. (Intraventricular conduction delay is suggested if a widened QRS is seen, but without the morphological features of LBBB or RBBB).

So - Coupled with his presenting symptoms, I would pass this a normal ECG in a healthy adult. I don't think any further investigations are warranted.

But what will the RAF say?
I have no idea.
If their expert occupational physicians feel that this warrants further specialist investigations on occupational grounds, they will arrange the necessary.  Thoughts/comments welcome please!

See a great web resource ECGpedia.org Conduction Delays for a simple and clear definitions of Bundle Branch blocks - complete and incomplete -  and Intraventricular conduction delays.


Incomplete RBBB
Here's an example of a  more obvious "Incomplete RBBB":


Note the morphological features of RBBB (seen RsR in V1), but the QRS complex is not quite wide enough to diagnoses RBBB (is just under 0.12 secs).

If the same man presented with this ECG and the same history - would that have altered your management? 

It shouldn't have. This ECG might be seen in normal healthy hearts, and clinically his symptoms sound more suggestive of benign palpitations/tachycardia, secondary to lifestyle triggers.


Complete RBBB
Here on the other hand is a full blown RBBB with widened QRS:



In summary

In Right and Left Bundle branch blocks, or  any Intraventricular conduction delay, the QRS complex will be widened.

An RsR pattern ('M' shape) is usually seen most prominently in the lead looking directly at that bundle branch: 
RBBB = RsR most prominent in V1/V2 
LBBB = RsR most prominent in Leads I and V6.

Usually, The R' (2nd R wave) is larger than the R (1st R defection) - giving a very distorted M shape.

An incomplete RBBB may be seen in normal healthy hearts. 
Likewise LBBB may be a normal variant in the elderly, but should raise suspicion of other things if seen in a younger person.



Learning Points:

  • RBBB can be a finding normal in healthy hearts.
  • Go with your clinical judgement 
  • Have the confidence of your conviction to state the ECG is within acceptable normal limits.  


Thank you. :)






7 comments:

  1. Another helpful case. I wld still like to know the dangers if any of more detailed assessment in current climate. If this case was my son, would not be satisfied without echocardiogram +/- 24h ecg. Unless you can show me NNT/NNH for NOT doing the tests.

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  2. Thanks David. I can't quote figures but will see what I can source.

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  3. There are 3 situations to consider:

    1. Incomplete RBBB. Not uncommon finding in young fit individuals - managed essentially as such and not a bar to aircrew entry.

    2. Complete RBBB (0.2-0.4% of aircrew). Now becomes interesting. On the whole - benign - but most Air Forces will organise echo either on entry/selection or if 'acquired' during career (which was the situation I spoke to Heather about in my Harrier pilot at Wittering! Thanks for remembering Heather!) This is to exclude structural problem with resultant BBB.

    3. LBBB (up to 0.1% or aviators) - completely different kettle of fish. Usually in older aircrew (35-40+) - association with CAD and HT means - must be investigated. Different AF have different ways, but MSCT etc are included. I am a but distant now from my Av Med to comment on current Ix techniques but it probably won't be far off NICE risk stratification and then Ix from there.

    The risks are not just the BBB but obviously - potential for prolonged QT intervals, CAD and acute incapacitation thereof. The environmnet in which you are asking these young men and women to operate is high G/Hot/Vibration+/Noise/Potential for relative hypoxia - list goes on. Plus - you are entrusting sev millions of £ or $ of kit. There is a large pool of applicants - so AFs can be selective.

    Hope that frames this. There are plenty papers out there on BBB in aviation.

    Victor

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  4. Thanks Victor - a really useful summary which helps us all understand the implications. Appreciate you taking the time to add this information. H.

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  5. No probs Heather. The other thing to consider, which David highlighted is parental concerns - won't be the first time, nor the last, that Air Marshal Biggles wants to see his son or daughter replicate his outstanding 4000 hours single seat fast-jet. I can't say I've been there personally, but I have heard former RAF colleagues tell some real tales of 'pressure' from high ranking parents - who can also bring pressure to bear on high ranking medical officers.... reality of Service life :) That's why I mentioned the signing of the entry paperwork. Yes, the decision ultimately is that of the RAF Medical Board - but always worth asking what the candidates parents for a living - would probably have been one of my first questions when exploring his concerns (!) :)

    Victor

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  6. Entirely normal ECG in a young fit individual, sinus brady at that rate is of no concern. Energy drinks should come with a health warning, we often have young people presenting to A&E after a night on the vodka and redbull with palpitations. The majority have succeeded in provoking AF or SVT or other atrial tachy on a wild night out and have no underlying pathology. One must remain mindful of the implications of over analysing ECGs (particularly easy from an ECG as there is so many normal variants). Giving someone with a normal ECG a label can have repercussions on their psychological wellbeing, career, life insurance etc.

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  7. Thank you Sam. I agree completely. You make some very valid points. Whilst clinicians have an important role in diagnosing illness, they also have an equally important role in diagnosing normality. Making a firm negative diagnosis can be far more difficult than making a positive one. It takes a bold and confident clinician, but is necessary to avoid the ongoing psychological morbidity associated with over-investigation.
    A frustratingly common example seen by me, is A&E discharge letters which state : "Non-cardiac chest pain. Refer RACPC". What? :-)

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