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Monday, 24 September 2012

LBBB full discussion

#ECGclass case 11

Below is the ECG of a 62yrs lady who complains of dizzy spells and palpitations.
Examination is entirely normal.
She is not on any medication and has no significant past medical history.

What does this ECG show?



Answer: Left Bundle Branch Block.

Note the widened QRS complex. 

P-waves are present (agree, not clearly seen, because of baseline interference). 
P-waves are usually seen best in V1, so if you are unsure, always check this lead closely. (That said, in the ECG above I think they are clearest in V3 and V4).

Note how all the ST segments, are deflected in an opposite direction the the associated QRS. This is one of the criteria for LBBB.

LBBB makes any further interpretation of the ECG impossible.

This is quite possibly incidental to her symptoms. It would be helpful to look back through her notes to see if any older ECG's confirm whether or not this is long standing LBBB. 
If it is a recent change, then investigations for a possible underlying cause may be necessary. 

Causes of LBBB:
  • Coronary and Hypertensive Heart Disease
  • Aortic Stenosis
  • Idiopathic degenerative disease
  • Congestive Heart Failure
  • Pericarditis or Myocarditis
  • Cardiomyopathy and Myocarditis
  • Cardiac Surgery
  • Anteroseptal MI
  • Syphilitic, Rheumatic and congenital disease
  • Cardiac Tumours

Discussion:

Normal Conduction pathways

Assuming the conduction impulse starts as normal in the Sino-atrial node, and travels through the atria to the Atrio-Ventricular node, it should arrived safely at the Bundle of His.  From there, it should travel down the Left and Right Bundle Branches and into the Purkinje fibres within the ventricles, without delay.
Any delay in conduction, in either the Left or Right Bundle Branch, will give rise to a widened QRS complex. (Normal width is 1.5 to 2.5 small squares, or 0.06 - 0.11 seconds).  
This is then known as Left Bundle Branch Block (LBBB), or Right Bundle Branch block (RBBB). A QRS complex of 3 small squares, or more, is considered broad.

In any Bundle branch block, the P waves and PR intervals should remain normal, and constant.
(I say this because another cause of QRS widening, is if the depolarisation occurs within the ventricular muscle itself. In these circumstances, a P-wave would not be present. Sometimes called a 'ventricular escape rhythm').

If LBBB and RBBB occur together, this is a complete heart block (same outcome as when the block is within the Bundle of His itself).

Any block/delay in the Left Bundle Branch is seen most clearly in the leads that face the left ventricle. Those leads are V5 and V6 and lead I.

Defintion of LBBB:
  • QRS >/= 120ms
  • No secondary R wave in lead v1                                
  • No Q waves in the lateral leads (I, aVL and v5+6)
  • The ST changes are deflected opposite (discordant) to the dominant QRS complex. 
  • The T wave changes are in the same direction as the ST segments (ie. Opposite to QRS)
  • ST elevation in leads v1-4
  • T wave inversion in leads I and aVL
Other criteria of LBBB:
  • Rhythm must be supraventricular (i.e. conduction arises from atria: P-waves seen, and normal)
  • RsR waveform should be present in Lead I.
  • RsR waveform is also seen in V6.  (Coupled with a QS or rS in V1 this gives rise to the "W-L-M" waveform formation)

RBBB - I will cover RBBB in more detail another time. But for now, just remember that the QRS will once be again be wide. As the leads looking directly at the Right Bundle branch, are leads V1 and V2, it is in these leads that the RsR pattern will be most prominent. i.e. "M -(R) -W" formation.
RBBB makes further ECG interpretation difficult, but as the Right bundle branch is supplying a smaller muscle mass than the left, the ECG changes are less pronounced than with LBBB. 
LBBB electrical changes are so profound, that any further interpretation of the ECG is impossible.


LBBB and chest pain

So what about LBBB and ACS / STEMI's?

Given the abnormal appearance of the ST segments in LBBB (elevated in V1-4), What happens if this patient presents with chest pain?

Imagine this lady returns to see you in an urgent appointment the following month. She is complaining of prolonged chest pain at rest, for several hours. She has no past history of, or risk factors for, IHD, and her symptoms sound very much like acid reflux. Examination is normal and she looks clinically stable.

If this lady presents with chest pain, how will you know if the ST elevation is significant? 


This is a difficult problem.  LBBB makes any ST segment analysis very tricky!

NICE Chest pain of recent onset guidelines (2010) state:

"Follow local protocols for people with a resting 12-lead ECG showing regional ST-segment elevation, or presumed new onset LBBB consistent with acute STEMI, until a firm diagnosis is made"

This seems very sensible! In view of this we may not have to deal with this dilemma in GP-land....unless of course we are in a very rural location, with secondary care services a long ambulance journey away. 

So for the benefit of rural GP's and Paramedics, we have the Scarbossa criteria to assess likelihood of STEMI. Scores are added up to a mximum of 10. where Scarbossa score = 10, the patient has 100% liklihood they are having an MI.


Chest Pain Assessment in LBBB using the Scarbossa Score

In Summary, scores  are attributed as follows:


In the ECG example above, her Scarbossa score = 0, making the likelihood of this being an MI very low (16%)....but not impossible!

Below are examples of a Scarbossa score 7,  and a Scarbossa score 10 .


Sacrbossa Score = 7
Probability of MI= 96%

Scarbossa Score = 10
Probability of MI = 100%

Hopefully, you can see how the above two ECG's with LBBB, vary for the example in case 11.
This is difficult, and advanced stuff. 
Unless you are very satisfied clinically, that this is not ischaemic pain, the err on the side of caution, and follow standard chest pain pathways. 

Tah Dah! 
There you go. All you ever need to know, and more, about LBBB.  
Thank you. :-)
hw/LBBB/2012



#ECGclass Case11 - Questions 1- 3


#ECGclass Case 11.
Below is the ECG of a 62yrs lady who complains of dizzy spells and palpitations.
Examination is entirely normal.
She is not on any medication and has no significant past medical history.

Q1. What does this ECG show?



Answer:

Left Bundle Branch Block.

Note the widened QRS complex. 

P-waves are present (agree, not clearly seen, because of baseline interference). 
P-waves are usually seen best in V1, so if you are unsure, always check this lead closely. (That said, in the ECG above I think they are clearest in V3 and V4).

Note how all the ST segments, are deflected in an opposite direction the the associated QRS. This is one of the criteria for LBBB.

LBBB makes any further interpretation of the ECG impossible.

This is quite possibly incidental to her symptoms. It would be helpful to look back through her notes to see if any older ECG's confirm whether or not this is long standing LBBB. 
If it is a recent change, then investigations for a possible underlying cause may be necessary. 


Q2. Can you list the causes of LBBB?


Causes of LBBB:
  • Coronary and Hypertensive Heart Disease
  • Aortic Stenosis
  • Idiopathic degenerative disease
  • Congestive Heart Failure
  • Pericarditis or Myocarditis
  • Cardiomyopathy and Myocarditis
  • Cardiac Surgery
  • Anteroseptal MI
  • Syphilitic, Rheumatic and congenital disease
  • Cardiac Tumours

Discussion:

Normal Conduction pathways

Assuming the conduction impulse starts as normal in the Sino-atrial node, and travels through the atria to the Atrio-Ventricular node, it should arrived safely at the Bundle of His.  From there, it should travel down the Left and Right Bundle Branches and into the Purkinje fibres within the ventricles, without delay.
Any delay in conduction, in either the Left or Right Bundle Branch, will give rise to a widened QRS complex. (Normal width is 1.5 to 2.5 small squares, or 0.06 - 0.11 seconds).  
This is then known as Left Bundle Branch Block (LBBB), or Right Bundle Branch block (RBBB). A QRS complex of 3 small squares, or more, is considered broad.

In any Bundle branch block, the P waves and PR intervals should remain normal, and constant.
(I say this because another cause of QRS widening, is if the depolarisation occurs within the ventricular muscle itself. In these circumstances, a P-wave would not be present. Sometimes called a 'ventricular escape rhythm').

If LBBB and RBBB occur together, this is a complete heart block (same outcome as when the block is within the Bundle of His itself).

Any block/delay in the Left Bundle Branch is seen most clearly in the leads that face the left ventricle. Those leads are V5 and V6 and lead I.

Defintion of LBBB:
  • QRS >/= 120ms
  • No secondary R wave in lead v1                                
  • No Q waves in the lateral leads (I, aVL and v5+6)
  • The ST changes are deflected opposite (discordant) to the dominant QRS complex. 
  • The T wave changes are in the same direction as the ST segments (ie. Opposite to QRS)
  • ST elevation in leads v1-4
  • T wave inversion in leads I and aVL
Other criteria of LBBB:
  • Rhythm must be supraventricular (i.e. conduction arises from atria: P-waves seen, and normal)
  • RsR waveform should be present in Lead I.
  • RsR waveform is also seen in V6.  (Coupled with a QS or rS in V1 this gives rise to the "W-L-M" waveform formation)

RBBB - I will cover RBBB in more detail another time. But for now, just remember that the QRS will once be again be wide. As the leads looking directly at the Right Bundle branch, are leads V1 and V2, it is in these leads that the RsR pattern will be most prominent. i.e. "M -(R) -W" formation.
RBBB makes further ECG interpretation difficult, but as the Right bundle branch is supplying a smaller muscle mass than the left, the ECG changes are less pronounced than with LBBB. 
LBBB electrical changes are so profound, that any further interpretation of the ECG is impossible.


Chest Pain and LBBB


So what about ACS / STEMI's in the presence of a LBBB?


Given the abnormal appearance of the ST segments in LBBB (elevated ST segments in V1-4), what happens if this patient presents with chest pain?

Imagine this lady returns to see you in an urgent appointment the following month. She is complaining of prolonged chest pain at rest, for several hours. She has no past history of, or risk factors for, IHD, and her symptoms sound very much like acid reflux. Examination is normal and she looks clinically stable.


Q 3.   If this lady had presented with chest pain. How would you know if the ST elevation is significant? 



When you've had a go,  you'll find the full discussion on the next blog!

Tuesday, 18 September 2012

Ischaemia secondary to Severe Aortic Stenosis - Case 10


#ECGclass Case 10

This 49yr old man presents to his GP with a 6 month history of chest pain.
Sometimes this is triggered by exertion, sometimes at rest. It can be prolonged, often lasting several hours and on occasions, all weekend.
He considers himself fit and active, so he light-heartedly dismisses his symptoms, and works through his 'mild' discomfort, which is very localised in the left upper chest, without radiation. He has no arm pain, no dizziness, and no breathlessness. He has only presented under duress from his wife.

He is a non smoker, with no risk factors for IHD and not on any medication. His BP is normal, as always. However, you do hear a systolic heart murmur at the left sternal edge.

You obtain an ECG below:

What now?

Discussion.

Widespread T-wave inversion with chest pain at rest. 

It wouldn't be wrong to admit this man, on the basis of his rest pain, and ECG changes. Given his dismissive nature, he may take some persuading, but with rest symptoms he is at risk.  You can't reassure him that nothing adverse will happen if he stays at home.

At very least, it should prompt an urgent referral to the RACPC.  In the meantime he should be started on aspirin/beta-blocker and a statin and given GTN/999 advice. The referral should include his ECG and make note of the murmur. (Note: Not all RACPC are set up with ECHO facilities, so if this information is included in the referral, an "ECHO on arrival" request can be made by the clinician receiving the referral).

In this case, an ECHO confirmed severe Aortic stenosis. As such, an  ETT is contraindicated.
He needs same day admission for monitoring, and an in-patient work up for diagnostic cardiac catheterisation.

It's not uncommon to see marked LVH with prolonged severe Aortic stenosis. The above ECG shows no voltage criteria for LVH, and we know he is normotensive.

Below is another example of severe AS, this time, causing the typical 'strain' pattern seen with LVH:

Note the similarities in the two ECG's. However, in this second example, there is gross voltage criteria for LVH (fulfilled in Leads I, aVL, V1-6). There is widespread T-wave depression, and typical of LVH,  T-wave inversion in the leads which face the left ventricle (i.e. leads I, aVL, v4-6).

T-wave inversion is also seen in leads V2 and V3.  This is suggestive of other pathology, such as co-existing coronary disease.

Lesson - Don't let the stoical nature of patients disarm you! :-) 

HW/ECGclass/sept2012


Monday, 17 September 2012

#ECGclass Quizz Case 10

#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 and theoretical, 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 10

This 49yr old man presents to his GP with a 6 month history of chest pain.
Sometimes this is triggered by exertion, sometimes at rest. It can be prolonged, often lasting several hours and on occasions, all weekend.

He considers himself fit and active, so he light-heartedly dismisses his symptoms. His job involves heavy labour, but he 'works through' his mild discomfort, which is very localised in the left upper chest, without radiation. He only came to see you, under duress, from his wife.
Other than this, he feels great.
He has no arm pain, no dizziness, and no breathlessness.

He is a non smoker, with no risk factors for IHD, and is not on any medication. His BP is normal, as always. However, you do hear a systolic heart murmur at the left sternal edge.

You obtain an ECG below:


What now?

He's sitting in front of you, feeling 'great' and looking clinically well.  At the time of his consultation/ECG, he is pain free, but he admits the pains can come and go several times a day.

When you've had a go,  you'll find the full discussion on the next blog!

Tuesday, 11 September 2012

Voltage Criteria for LVH - case 9


#ECGclass Quizz case 9                                                    

This 56yrs lady attends for a well-woman BP check.  After 3 repeated measurements, a minute apart, her mean BP is 146/90 so the Practice nurse decides to do an ECG, in accordance with the practice protocol. 
        Image courtesy of www.frca.co.uk 

What is your impression?
Does she need any further investigations?

This ECG is compatible with Left Ventricular Hypertrophy (LVH).  
It shows voltage criteria for LVH, in leads I and  aVL.  
As no other criteria for LVH are met, it is often better to say “This ECG meets the voltage criteria for LVH”, rather than diagnose hypertrophy.

In accordance with latest NICE Hypertension Guidelines, you may want to offer this lady an ambulatory BP monitoring (ABPM), or Home BP monitoring (HBPM), for confirmation of diagnosis. Her CVD risk, and any target organ damage, should also be assessed.  
Whether she turns out to have Stage 1, or Stage 2, Hypertension on the basis of her ABPM, her LVH will certainly sway you towards a lower threshold to treat. 
Unless it is likely to change your management plan, an ECHO is not necessarily required to confirm diagnosis of LVH. 
(See 2011 NICE CG127 Hypertension Guidelines for care management pathways).   


Discussion
The main purpose of showing this ECG is to discuss the various voltage criteria for LVH. 
Don't just look at the chest leads! 
Interestingly, there is no one universally agreed criteria for diagnosis of LVH by ECG.  A few of the more commonly accepted ones are listed below. 

A normal Left ventricular wall is 9-11mm thick. Larger than this is defined as LVH, and can only be diagnosed by ECHO measurement. Various ‘voltage criteria’ seen on ECG, however, can be suggestive of LVH.

The Left ventricle is represented by leads v5 and v6, so in LVH, we expect the ‘R’ waveforms to be enlarged/tall in these leads.  (Conversely, we expect the ‘S’ waves to be deep in the right ventricular leads, that is V1 and v2).

Suggested voltage criteria for LVH include:
  • ·      The sum of the S wave in v1 or v2, PLUS the R wave in v5 or 6 35mm,   OR,
  •     The sum of the deepest S wave +  the tallest R wave  > 40m
  • ·      Any single, R or S, wave in leads v1-v6  45mm
  • ·      The R wave in aVL   11mm
  • ·      The R wave in lead I 12mm
  • ·      The R wave in aVF 20mm
Generally speaking, the predictive value of the voltage criteria is cumulative. i.e. The more voltage criteria met, the greater the likelihood of LVH.

In the ECG above, the precordial leads do not meet the voltage criteria for LVH (arguably borderline, I admit, at 35mm).

Many clinicians are aware of the R and S wave criteria in the precordial (chest) leads, but this can be dependent on body habitus. The chest leads placed on a  tall, thin man, with little adipose tissue, are in close proximity to the heart so naturally, the waveform amplitude in the chest leads will be large.   The limb leads, being less affected by body habitus, are often more reliable in these individuals.  
Voltage criteria for LVH in V1-V6 alone, in a tall thin person, without other cause for concern, it not necessarily and indication for an ECHO. 

If a patient with LVH criteria on ECG is hypertensive, then arguably, an ECHO is only helpful if it will alter your threshold for treatment. If you plan to treat anyway, an ECHO is of dubious further value. 

Likewise, with an ECG suggestive of LVH in a normotensive person, an ECHO would only be indicated if a) Body habitus didn't explain the amplitude, or b) There was other signs/symptoms of concern (Possible HOCM? or Aortic Stenosis?)


Strain pattern
When LVH is associated with other pathology, such as hypertension or aortic stenosis, a 'strain pattern' is often seen:
  • ·      ST depression + flipped asymmetric T wave
  • ·      ST elevation + upright asymmetric T wave
  • ·      The strain pattern is greatest in the lead with the tallest/deepest QRS complex.  (seen in Lead 1 in example above).

Thank you.  :-)


HW/sept2012/#ecgclass


Monday, 10 September 2012

#ECG class Case 9


#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 and theoretical, 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 9                                                 

This 56yrs lady attends for a well-woman BP check.  
After 3 repeated measurements, a minute apart, her mean BP is 146/92. 
In accordance with the practice BP protocol, the practice nurse arranges an ECG:

Image courtesy of www.frca.co.uk

What is your impression?
Does she need any further investigations?

When you've had a go,  you'll find the full discussion on the next blog!