A man in his 60s with a seemingly mechanical fall and subsequent seizure. Until the ECG.

Written by Pendell Meyers

A man in his 60s is brought in to the ED by EMS for a fall witnessed by his wife, followed by multiple episodes of seizure like activity. Initially the history sounded like a mechanical fall. EMS reported normal vitals with the exception of "periods of bradycardia." The patient received multiple doses of benzodiazepines for possible seizure activity and arrived altered at the ED. 

He was intubated soon after arrival for airway protection in the setting of multiple seizure like episodes and very depressed mental status.

Here is his initial ED ECG:

What do you think?

Initially this ECG was misread as atrial fibrillation.

Instead, it is sinus tachycardia at approximately 100 bpm with second degree type 1 (wenckebach) AV block. Atrial fibrillation results in an irregularly irregular rhythm, whereas this rhythm is regularly irregular, displaying "grouped beating" in which the QRS complexes come in groups of three.

Pearl: any regularly irregular rhythm started as a regular rhythm, but then encountered either dropped (AV blocks) or added beats (PACs, PJCs, PVCs).

I do not see any evidence of OMI or hyperkalemia, both of which are very important causes of bradycardia to be identified on the ECG.

AV block was not initially noticed, and the history and potential seizure activity caused team to focus on neuroimaging and seizure workup.

Some time later, the doctor was called emergently to the bedside for a "change in the monitor", and this ECG was recorded:

Nothing but P waves! There are sinus P waves at about 100 bpm with complete AV block, and no underlying escape rhythm, resulting in ventricular asystole. In other words, cardiac arrest. 

Ideally, of course, we would not have captured a 10 second ECG of this, because we should have started CPR and intervened by pacing, but here it is!

Similarly: 

Ventricular fibrillation on a 12-lead ECG

Transcutaneous pacing was performed with successful capture.

A transvenous pacemaker was placed.

An ECG was recorded with transvenous pacing:

Potassium was normal. ACS was ruled out.

There was never any further witnessed seizure activity.

The patient received a permanent pacemaker and recovered.

Learning Points:

Syncope and seizure are sometimes very hard to distinguish. Sometimes cardiac syncope results in hypoxemic and/or cardiac arrest-related seizures. Both conditions require an ECG to look for any findings of cardiac dysrhythmias.

See this case:

What do you think of this elderly man with "possible seizure"?

Cardiac syncope with any degree of AV block is concerning that the patient could have experienced a deeper degree AV block as the cause of their syncope, and that such an even will recur.

ED providers must be facile with transcutaneous and transvenous pacing.

Hyperkalemia and RCA OMI are two of the most important causes of bradydysrhythmias to look for on the ECG.

See this case also: 

A New Seizure in a Healthy 20-something

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MY Comment, by KEN GRAUER, MD (3/14/2022):

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Insightful case presented by Dr. Meyers — with the important lesson that seizure-like activity is not always a neurologic problem.  It can be cardiac.

• As per Dr. Meyers — the 2nd ECG in today's case showed persistence of an atrial rate at ~90/minute, but no ventricular activity. Terminology varies for this type of rhythm — but my preference is to call this sudden, abrupt loss of ventricular activity as Ventricular Standstill rather than a manifestation of AV block.
• A case report by Adegoke (Paroxysmal Ventricular Standstill: Am Case Rep 21:e924381, 2020) — is similar to today's case in its presentation of seizure activity as a result of an episode of ventricular standstill. Adegoke makes the points that: i) More than 20% of epileptics are misdiagnosed (some of these misdiagnoses being of cardiac etiology); ii) Ventricular standstill for more than 16 seconds may result in seizure activity; and, iii) Although ventricular standstill is most often seen in patients with underlying structural heart disease — it can occur de novo in patients without a pre-existing cardiac condition.

The initial ECG in today's case was misdiagnosed as AFib (Atrial Fibrillation). I wanted to expand on Dr. Meyers explanation of this arrhythmia. For clarity — I've reproduced this initial tracing in Figure-1.

 

QUESTION: 

• WHY was the rhythm in Figure-1 misdiagnosed?

ANSWER:

A systematic approach was not followed.

Regardless of the system you choose to use — Once you have ensured that your patient is hemodynamically stable — there are 5 Parameters that need to be assessed for the interpretation of any cardiac arrhythmia. These 5 Parameters can be conveniently remembered by the saying, "Watch your Ps, Qs and the 3Rs". Focus your attention on the long lead II rhythm strip — and LOOK for:

• The presence of P waves (or other sign of atrial activity).
• QRS width.
• The 3Rs = Rate and Regularity of the rhythm — and — if P waves are present, are these P waves Related to neighboring QRS complexes?

 

Figure-1: The initial ECG in today's case.

With a little practice — assessment of the Ps, Qs, 3Rs takes no more than seconds. For clarity — I've isolated the long lead II rhythm strip from the initial tracing in today's case in Figure-2. I'll emphasize the following:

• I have found the simple act of labeling P waves to be tremendously helpful in facilitating recognition of complex arrhythmia mechanisms (RED arrows in Figure-2).
• Using calipers saves time and greatly increases the accuracy of your interpretation. You become instantly smarter once you start using calipers.
• 
  
• The rhythm in Figure-2 can not be AFib — because there are P waves! It admittedly is sometimes difficult to determine if the atrial rhythm is or is not regular throughout the tracing, especially when some P waves are partially (or totally) hidden within the QRS or ST-T wave (as is the case in Figure-2). That said — setting your calipers to the P-P interval defined by 2 deflections that you know are P waves (such as the P wave before and after beat #2) allows you to "walk out" regular atrial activity throughout the entire rhythm strip (RED arrows).
• As per Dr. Meyers — although the rhythm in Figure-2 is not regular — it is regularly irregular (ie, there is group beating). Group beating is sometimes most easily recognized by standing back a little bit from the tracing. Although there are many potential causes of group beating (including atrial bigeminy or trigeminy) — I always strongly consider the possibility of AV Wenckebach whenever I see group beating.
• There is "perfect" group beating in Figure-2 (ie, beats #2,3,4 — 5,6,7 — 8,9,10 — and 11,12,13 making up 4 similar-looking 3-beat groups). It's good to realize that group beating with AV Wenckebach will not always be as uniform as seen in Figure-2 (ie, you may see a mixture of 2-beat, 3-beat and/or 4-beat groupings).
• Another clue to AV Wenckebach is to look to see if there are PR intervals that repeat. This is usually easiest to see by looking just in front of the QRS complex that ends each of the short pauses (ie, in front of beats #2, 5, 8, 11 and 14). The fact that the long PR interval preceding beats #2,5,8,11 and 14 stays the same confirms that these P waves are conducting (and strongly suggests the reason for group beating is AV Wenckebach).
• The narrow QRS and the presence of 1st-degree AV block for the 1st beat in each of the groups are 2 additional findings in support of AV Wenckebach.

Figure-2: I've numbered the beats and labeled P waves in the long lead II rhythm strip (See text).

For clarity — I illustrate the mechanism for today's rhythm in the laddergram I've drawn in Figure-3:

• The laddergram demonstrates that the rhythm is 2nd-Degree AV Block, Mobitz Type I ( = AV Wenckebach). Because the PR interval of conducting beats is so prolonged — it could be easy to overlook this rhythm diagnosis IF one failed to use a systematic approach.
• Laddergrams are a wonderful tool for illustrating the mechanism of complex rhythms. It is EASY to learn how to read laddergrams. Learning to draw laddergrams takes a bit more time and practice. (For those interested — Please see the references I provide below).
• 
  
• P.S.: Of the 2nd-degree AV blocks — it is Mobitz II that poses significant risk of developing prolonged ventricular pauses. The Mobitz I (AV Wenckebach) form that was seen in today's case would not be expected to result in the sudden onset of ventricular standstill that was seen in today's patient ...

Figure-3: Laddergram illustrating the mechanism in today's case.

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How to Draw a Laddergram (Step-by-Step Demonstration) 

• See ECG Blog #69 — for a Step-by-Step description on drawing a Laddergram.
• See ECG Blog #188 — for a brief ECG Video review on the basics of what a Laddergram is — with LINKS at the bottom of the page to more than 50 ECG blog posts in which I review illustrative laddergrams.
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• CLICK HERE — to DOWNLOAD my Free PowerPoint Laddergram STENCIL for your use as desired.

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