ECG of the Week: ECG of the Week - 24th June 2013

This ECG is from a 29 year old female.
She presents to your ED complaining of palpitations and an episode of chest tightness. The chest tightness lasted 45 minutes and was associated with nausea and dizziness. She has a history of pericarditis as a teenager and gives a long history of intermittent palpitations.
She was pain free when this ECG was performed with normal vital signs.

Click to enlarge

Rate:

72 bpm mean ventricular rate

Rhythm:

Sinus
Possible Regularly irregular

2 Complexes --> Pause --> 3 Complexes --> Pause

Axis:

Normal (~65 deg)

Intervals:

PR - Normal but variable (~150-190ms)
QRS - Normal (80ms)
QT - 360ms

Segments:

Minor ST depression leads II, III, aVF

Additional:

8th Complex - P wave merges with preceding T wave
Subtle changes in P wave morphology throughout
Slight P-P and P-R interval lengthening preceding pause

Does not support an SA Exit Block pattern
Group beating but without Wenckebach pattern

Interpretation:

Likely high right atrial Premature Atrial Complexes (PACs)

This would explain the similar P wave morphology throughout the ECG
Beats post PAC related pause can be symptomatic due to an increased stroke volume

What happened ?

The patient was admitted under cardiology for further investigation.

She was discharged following a normal ECHO, serially normal troponins, normal electrolytes, negative D-dimer, and normal thyroid function.

I don’t know if her ECGs remained similar to the one we have or whether they became ‘more regular’ during her in-pt stay.

Comments on this week's ECG

Thanks to Dr Ken Grauer (@ekgpress) of ECG Interpretation blog for sharing his expert thoughts on this ECG, they can be found here and are pasted below.

Interesting case & tracing. First task in the history will be to assess the likelihood that the "chest tightness" might be coronary disease. Chances of this would seem to be slight given: i) age of patient; ii) duration of tightness and associated nausea & dizziness - but I'd want to attain some level of comfort that she doesn't have CAD before proceeding.

I assume recent Echo has at some point been done (given prior history of pericarditis and longterm symptoms) - as this would help to rule out underlying structural heart disease.
My "guess" is that "palpitations" is the main problem - with perhaps some component (primary or secondary) of anxiety (many folks with longterm cardiac palpitations eventually develop some anxiety from palpitations ... ). The "good news" - is that studies of patients who present primarily with palpitations as the chief complaint reveal overall GOOD long term prognosis (albeit frequent recurrence of symptoms).
Regarding this ECG - it is irregular in what appears to be a pattern. There are groups of beats - but not with Wenckebach features (no decreasing R-R within groups). This doesn't fit for either SA or AV Wenckebach ... KEY to evaluation is P wave morphology - as I suspect she has sinus rhythm with frequent PACs (atrial bigeminy inparts). P wave morphology with PACs will ideally be different than sinus P wave morphology - although if the atrial site of the PAC is close to the SA node, this may be less evident. We just do NOT see enough of the rhythm to tell IF P wave morphology is changing for the early beats. It looks like it MIGHT be changing (in V1,V2,V3) - though not really for the other P waves. The pattern is too regularly irregular for sinus arrhythmia - so if not PACs, I'm not sure what this could be ... The rest of the 12-lead is unremarkable.
That said - priorities for patients with palpitations thought to be due to ectopics are to look for extracardiac/exacerbating factors - which might include caffeine, other drugs (cocaine, adhd meds, otc sympathomimetics), alcohol, ischemia, electrolyte disorders, psychological stress, etc - and that's where I'd focus. Some patients respond well to low-dose beta-blockers - and I'd probably empirically consider that here.

Also thanks to Dr Rahul Goswami (@Rahul_Goswami_), a man I've been fortunate enough to work with, for his ongoing support of our ECG nerdiness. Go and check out his blog at Emergence Phenomena, for more EM FOAM goodness.

References / Further Reading

Life in the Fast Lane