Challenging Rhythms in 12yo — MIS-C Case Report

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Review of ECG Rhythms — MIS-C Case Report (9/16/2024):

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What follows below are my first impressions of the ECG rhythms sent to me from the Case Report by Dimah Jarmakani et al — of a 12-year old boy with MIS-C (Multisystem Inflammatory Syndrome in Children).

• For full discussion of the case — CLICK HERE — 
• User-friend link = tinyurl.com/KG-Blog-MIS-C —

CASE Overview (by Dr. Jarmakani):

A 12-year-old boy was admitted to our hospital with severe myocardial dysfunction and chaotic rhythm with tachy- and bradycardic arrhythmias. What follows are the ECG tracings of our patient:

• ECGs #1 and #2 were performed on the 2nd and 4th hospital days, respectively — at which time the patient had severe myocardial dysfunction. 
• ECGs #3,4,5,6 were done one week later — at which time the patient began to respond to the medical treatment, with recovery of myocardial function. 

We requested assistance from Dr. Grauer for interpretation of the ECG tracings, This is his response to us: 

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My impressions of representative tracings from this case:

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ECG #1:

Figure-1: ECG #1 is from the 2nd hospital day.

MY Thoughts on ECG #1:

This clearly is a challenging series of arrhythmias — obtained from this acutely ill 12-year old boy with MIS-C:

• I put limb leads and chest leads from this first tracing togeter (these tracings were sequentially recorded). Note that this tracing was recorded at half standardization. 
• The rhythm is highly variable. The RED arrow looks like a sinus P wave in front of beat #2. We really do not see more sinus P waves in this ECG #1 — but having glanced ahead at ECG #2, there clearly are sinus-appearing P waves in this next tracing (below) — so I’ll suppose that the RED arrow in front of beat #2 in ECG #1 is a sinus P wave (or possibly a P wave from another atrial focus).
• Given that this RED arrow P wave is pointed — I think we are seeing the opposite picture under each of the YELLOW arrows! I therefore suspect these YELLOW arrows highlight the location of retrograde conduction from ventricular beats.
• QRS morphology of beats #3,4; 6,7; 9,10; 12,13 and 15 shows marked right axis with an rS in lead I — and qR pattern in leads III,aVF.
• Unfortunately — we do not know for certain which beats in the limb leads correspond to which beats in the chest leads — but my guess is that beats #3,4; 6,7; 9,10; 12,13 and 15 with LPHB-like conduction — correspond to the RBBB-like beats in lead V1 of the chest leads. These beats are very wide and not preceded by P waves — so I think these are all PVCs (with a bunch of ventricular couplets) — and with the YELLOW-arrow retrograde conduction. RBBB-LPHB-like conduction suggest these may be fascicular beats from the left anterior hemifascicle (although the QRS is wider than fascicular beats usually are).
• In the chest leads of ECG #1 — we also see a LBBB-like etiology for beats #6 and 13 in the chest leads. It is hard to say if these are PVCs from another ventricular focus (though their close resemblance to LBBB conduction suggests to me that they may be supraventricular beats with aberration).
• I think the BLUE arrows in ECG #1 represent conducted beats from a different atrial focus (ie, these P waves being negative or not well seen in lead II — but better seen in other leads).

BOTTOM Line for ECG #1: 

• As interesting as the above details are — I do not think this matters clinically. The overall rhythm is chaotic — which is not necessarily unexpected given the history of an acutely ill 12-year with severe dilated cardiomyopathy on Echo. 
• I’d guess the overall rhythm is sinus, perhaps with a wandering atrial pacemaker and very frequent ventricular ectopy with multiple couplets. 
• The rhythm is not MAT — because pure MAT should show a different-shape P waves with every beat, which is not what we see here. That said — there is a spectrum of disorders with sinus rhythm and PACs at one end — and true MAT at the other end. This rhythm fits somewhere in between these 2 ends of this spectrum — and it is readily explained by the severe, acute illness of this child.
• As to interpretation of the 12-lead ECG itself — in both ECG #1 (and because of the scarcity of normally conducted beats in this initial tracing — I looked ahead at ECG #2 ) — the diffuse T wave inversion in inferior and all chest leads may be consistent with acute myocarditis as another component of the patient's MIS-C.

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ECG #2:

Figure-2: ECG #2 is from the 4th hospital day.

MY Thoughts on ECG #2:

Once again — the limb leads and chest leads are not simultaneously recorded. As noted in the Figure legends — ECG #2 was recorded on the patient's 4th hospital day (or 2 days after ECG #1 was recorded).

• NOTE: ECG #2 was recorded with double standardization!
• Even accounting for double standardization — sinus P waves in lead II (RED arrows) are tall and peaked, consistent with RAA (which is consistent with this patient’s underlying heart disease).
• After 2 sinus beats — we see junctional escape at a slow escape rate at ~40/minute. This is followed by 2 more sinus beats, and then another slow junctional escape beat.
• Given the young age of this patient — rather than SSS (Sick Sinus Syndrome) — I'd suspect some other underlying (and hopefully "fixable" ) cause of these rhythms, such as rate-slowing medication, electrolyte disturbance or hypoxemia.
• I suspect that best treatment for the rhythm disturbances seen thus far will be treatment of this patient’s underlying heart disease — which is easier said than done. In the meantime, a pacemaker may be needed if the rhythm slows further.

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ECG #3:

Figure-3: ECG #3 — obtained 1 week later during recovery.

MY Thoughts on ECGs #3,4,5,6:

The final 4 tracings in this case report were all recorded ~1 week later, as the patient was recovering. (Note that ECGs #3,4,5 are recorded at double standardization — while ECG #6 is recorded at normal standardization).

• The "good news" — is that overall the patient is improving clinically! That said — the rhythm remains chaotic. There definitely are periods of bradycardia (for which temporary pacing may be needed). There is an underlying sinus rhythm — with the “theme” being that there are lots of ectopics, including many different PAC shapes (therefore multiple PAC sites) and some PVCs.
• Overall — I think this rhythm “acts” like MAT. By strict definition — each P wave should change in shape with “true MAT” — and that does not quite happen, since there are periods of sinus rhythm. But as mentioned earlier — there is a “spectrum” of supraventricular arrhythmias — and sinus rhythm with lots of different looking PACs as we see here “acts” clinically like MAT. This type of rhythm may be seen with a very “sick” patient (as is the case here) — and/or with hypoxemia, electrolyte disorders, heart failure.
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• BOTTOM Line: It’s hard to be sure of every single beat on these rhythm strips — but determination of what each beat is, is not important. Instead — it is the “theme” that counts — which as I describe above, seems to be a highly variable series of arrhythmias that act clinically like MAT + PVCs — for which best treatment is support and a goal of optimizing treatment of this patient's heart failure (with possible component of acute myocarditis).

ECG #3:

• There is marked sinus bradycardia and arrhythmia. 
• Beat #4 is a PAC (Note that the P looks different in leads III and aVL). 
• Beat #5 is junctional escape (the sinus P in front of beat 5 has a PR too short to conduct!)

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ECG #4:

Figure-4: ECG #4 — obtained 1 week later during recovery.

ECG #4:

• Beats #1 and 2 are sinus conducted.
• Beats #3 and 6 look like PVCs. 
• Since the QRS is different and we see retrograde P waves — I think beats #4,5,9,11,13,15,17 are PVCs. 
• The other beats are PACs with different-looking P waves. 
• The fixed coupling for beats #4,5,9,11,13,15,17 supports these being PVCs.

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ECG #5:

Figure-5:  ECG #5 — obtained 1 week later during recovery.

ECG #5:

• Now that we know that the pointed P waves in lead II are the sinus beats — we can identify the P waves in front of beats #2, 6,7,8,9 as being sinus P waves. 
• Once again — the P in front of #6 is too short to conduct, so this is junctional escape. 
• After beat #9 — we see ventricular bigeminy with retrograde P waves (albeit with changing P wave morphology in front of supraventricular beats #11,13,15).

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ECG #6:

Figure-6: ECG-6 — obtained 1 week later during recovery.

ECG #6: 

• The first 6 beats show sinus bradycardia.
• I cannot tell for certain if the “dip” under the BLUE line is a PAC that then conducts with aberration — or if the last beat is a PVC.