ECG of the Week – 28th November 2016 – Interpretation

The following ECG’s are from a 62 yr old female who presented with chest and epigastric pain. The first ECG was performed by the patient’s GP and the second ECG on arrival in the Emergency Department. Her pain was ongoing at the time of both ECG’s and she has a past medical history of hypertension, obesity and T2DM.




ECG from GP
Click to enlarge

Key features:

  • Rate 96 bpm
  • Regular sinus rhythm
  • Normal Axis
  • Normal Interval
  • Normal ST Segments
  • Biphasic / Inverted T wave in lead III

ECG on arrival ED
Click to enlarge

Compared with earlier ECG there is new:

  • Right axis deviation – new compared with above
  • Leads aVR & lead I complete inversion i.e. negative P wave / QRS complex / T wave
  • Flat aVR with morphology very different to V1
  • Other features unchanged – rate, rhythm, intervals, ST segments


Interpretation:

  • Multiple features suggesting RA / LA lead reversal
    • Complete inversion of leads aVR and I 
    • New axis change between serial ECG’s


Remember RA / LA reversal results in:

  • Inversion of lead I
  • Leads II & III swap places
  • Leads aVR & aVL swap places

What happened ?


This all seemed very straight forward until we reviewed the patient and found all the leads to be in the correct position !!
Remember ECG’s are complicated machines with multiple connections and just because the one connection with the patient appears to be correct doesn’t mean there isn’t a problem elsewhere. So we removed the ECG machine from the situation, the patient was completed disconnected from the usual machine and a new recording was performed on a portable ECG machine, i.e everything in the process after the patient was replaced. The following ECG is below:

ECG repeated on different ECG machine
Click to enlarge

Comparing with the prior ECG’s we can see resolution of the complete lead inversion and axis change seen in the second ECG with the overall morphology similar to the ECG performed at the GPs. I suspect the change in appearance of aVL between the 1st and 3rd ECG reflects both patient and lead positioning during ECG recording.
It turned out the culprit was a damaged cable connection between the patient leads and ECG monitor unit !!

References / Further Reading

Life in the Fast Lane

Textbook

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.

ECG of the Week – 28th November 2016 – Interpretation

The following ECG’s are from a 62 yr old female who presented with chest and epigastric pain. The first ECG was performed by the patient’s GP and the second ECG on arrival in the Emergency Department. Her pain was ongoing at the time of both ECG’s and she has a past medical history of hypertension, obesity and T2DM.




ECG from GP
Click to enlarge

Key features:

  • Rate 96 bpm
  • Regular sinus rhythm
  • Normal Axis
  • Normal Interval
  • Normal ST Segments
  • Biphasic / Inverted T wave in lead III

ECG on arrival ED
Click to enlarge

Compared with earlier ECG there is new:

  • Right axis deviation – new compared with above
  • Leads aVR & lead I complete inversion i.e. negative P wave / QRS complex / T wave
  • Flat aVR with morphology very different to V1
  • Other features unchanged – rate, rhythm, intervals, ST segments


Interpretation:

  • Multiple features suggesting RA / LA lead reversal
    • Complete inversion of leads aVR and I 
    • New axis change between serial ECG’s


Remember RA / LA reversal results in:

  • Inversion of lead I
  • Leads II & III swap places
  • Leads aVR & aVL swap places

What happened ?


This all seemed very straight forward until we reviewed the patient and found all the leads to be in the correct position !!
Remember ECG’s are complicated machines with multiple connections and just because the one connection with the patient appears to be correct doesn’t mean there isn’t a problem elsewhere. So we removed the ECG machine from the situation, the patient was completed disconnected from the usual machine and a new recording was performed on a portable ECG machine, i.e everything in the process after the patient was replaced. The following ECG is below:

ECG repeated on different ECG machine
Click to enlarge

Comparing with the prior ECG’s we can see resolution of the complete lead inversion and axis change seen in the second ECG with the overall morphology similar to the ECG performed at the GPs. I suspect the change in appearance of aVL between the 1st and 3rd ECG reflects both patient and lead positioning during ECG recording.
It turned out the culprit was a damaged cable connection between the patient leads and ECG monitor unit !!

References / Further Reading

Life in the Fast Lane

Textbook

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.

ECG of the Week – 28th November 2016

The following ECG’s are from a 62 yr old female who presented with chest and epigastric pain. The first ECG was performed by the patient’s GP and the second ECG on arrival in the Emergency Department. Her pain was ongoing at the time of both ECG’s and she has a past medical history of hypertension, obesity and T2DM.





ECG from GP
Click to enlarge

ECG on arrival ED
Click to enlarge



Things to think about

  • What are the key ECG features in each ECG ?

ECG of the Week – 21st November 2016 – Interpretation

This ECG is from an 89 yr old female who presented with abdominal pain and fever. She has a PPM in-situ and a history of ischaemic cardiac disease.




Click to enlarge

Rate:

  • 72 bpm

Rhythm:

  • Intrinsic atrial activity
  • Ventricular paced rhythm
    • Complexes #1-10, #12 
    • All preceded by v-pacing spike – see below for more information
  • Sinus / native ventricular complex
    • Complex #11

Axis:

  • Left Axis Deviation

Intervals paced complexes (#1-10, #12)

  • PR – Variable (160-200ms)
  • QRS – Variably prolonged (100-160ms)

Intervals sinus complex (#11)

  • PR – Normal (140ms)
  • QRS – Normal (100ms)

Additional:

  • Variable QRS morphology of paced complexes
    • Complexes #1-4,6,9,12 all have similar morphology
    • Complexes #5,7,8 preceded by pacing spike but morphology similar to native complex (#11) best appreciated in rhythm strip
  • ST Depression and deep T wave inversion in native QRS complex #11
  • Morphology of QRS in leads V1-2 not typical for LBBB with Rsr’ in v2

Key features of interest:

  • Lack of typical LBBB pattern in leads V1-2 with RSR pattern in lead V2
    • This can be seen in cases of pacing lead malposition or migration but can also be seen in appropriate RV pacing – see below for a detailed explaination
  • Deep T wave inversion in the native (non-paced) QRS complex seen in the lateral leads
  • Variable QRS morphology of the paced complexes
    • Due to variable fusion of native and paced QRS complexes

Is RBBB morphology during right ventricular pacing always due to pacing lead malposition ?

The short answer to this is no. There are cases in which an RBBB morphology can occur with appropriate right ventricular apical pacing.

For an example of RBBB morphology associated with lead malposition check out this case here.

Features which may assist in differentiating between lead malposition and correct placement are:

  • Frontal plane axis between 0 and -90 degrees and;
  • Precordial transition point before lead V3

And / or:

  • Repositioning of leads V1-2 one interspace lower with resolution of RBBB features

In this ECG the frontal plane axis is between 0 and -90 deg with a precordial transition from positive to negative QRS between leads V2-3. These features support correct RV lead placement rather than lead migration and may be seen with inappropriate ECG lead positioning.

I would recommend the following freely available papers which both include a review of RBBB morphology during right ventricular pacing.

  • Erdogan O, Aksu F. Right bundle branch block pattern during right ventricular permanent pacing: Is it safe or not? Indian Pacing Electrophysiol J. 2007 Aug 1;7(3):187-91. PMID: 17684578   Full text here
  • Almehairi M, Baranchuk. Right Bundle Branch Block Morphology During Apical Right Ventricular Pacing. The Journal of Innovations in Cardiac Rhythm Management, 4 (2013), 1303–1304. Full text here


What about the native QRS in leads V4-6

The broad differentials for the changes on the native complex are:

  • ACS
  • Structural Heart Disease
  • Cardiac T-wave Memory

T-wave memory is an interesting phenomenon that could explain the marked T wave changes seen on the non-paced complex on this ECG. It results in transient T wave changes following a period of abnormal ventricular conduction e.g. ventricular tachycardia, paced rhythms, intermittent bundle branch block or aberrant conduction. 
The following paper by Vakil that is freely available (linked to below) that contains a nice overview of T-wave memory, proposed mechanisms, and a case example.
The deep T wave inversion on this ECG correspond to the leads in which a negative QRS was seen in the patients paced ECG a finding consistent with T-wave memory. 

  • Vakil K, Gandhi S, Abidi KS, et al. Deep T-Wave Inversions: Cardiac Ischemia or Memory? JCvD 2014;2(2):116-118. Full text here.

Pseudo-fusion

Complexes #5,7,8 are all proceeded by a pacing spike but have a QRS morphology similar to native sinus complex. This is due to pseudo-fusion which occurs when the pacing rate and native sinus rate are close together. This is a benign condition but does result in unnecessary pacemaker activity. 

We have another example of pseudo-fusion here:

You can find a nice overview of pseudo-fusion and fusion beats in paced rhythms here:


References / Further Reading

Textbook

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.